Patent Description:
Related Art: The discussion of any work, publications, sales, or activity anywhere in this submission, including in any documents submitted with this application, shall not be taken as an admission that any such work constitutes prior art. The discussion of any activity, work, or publication herein is not an admission that such activity, work, or publication existed or was known in any particular jurisdiction.

Biosimilars are therapeutics similar to but not identical to existing innovator or reference products. Unlike the case for small molecule drugs, biosimilars are not merely generic versions of original products. Conventional generics are considered to be therapeutically and molecularly equivalent to their originators. This is simply not the case with biosimilars, which are complex, three-dimensional biomolecules, whose heterogeneity and dependence upon production in living cells makes them quite different from classical drugs. The structures and functional activities of bio-therapeutics are exquisitely sensitive to their environments. The intended structure of a therapeutic is maintained by a delicate balance of factors, including concentration of the protein, control of post-translational modifications, pH as well as co-solutes in the formulation, and production/purification schemes (<NPL>). As such, biopharmaceutical structure must be prudently maintained, for if not held in check, undesirable and adverse pharmacological consequences can arise.

Adverse drug reactions (ADR) of biopharmaceuticals are typically attributed to exaggerated pharmacology as well as immunological reactions. The range of patient ADR's extends from symptomatic irritation to morbidity and death. While the etiology for some ADR's may be traced to patient pharmacogenomic sensitivity, many are attributed to intrinsic properties of the therapeutic, which has resulted in morbid and fatal patient consequences and substantial financial loss to the biotherapeutic industry (<NPL>). As such, the occurrence of catastrophic ADR's has exemplified the need for improved analytics for the development and quality control of biopharmaceuticals.

In order to minimize ADR's and to facilitate the development of biosimilars, the FDA, the Center for Drug Evaluation and Research, and the Center for Biologics Evaluation and Research have issued guidelines that stress the use of state-of-the art technology for evaluating protein higher order structure (HOS) (<NPL>). HOS analysis involves the determination of the tertiary and quaternary structure and associated conformation of a given biomolecule. Such biomolecules include protein and protein conjugates which may or may not be considered to be a biotherapeutic agent. Although a variety of HOS analytics exist today, their inadequacies to reliably predict biotherapeutic efficacy and safety has been brought into question, establishing the unmet need for new and improved HOS analytics (<NPL>).

A technique to address the unmet need for HOS analysis is irreversible protein hydroxylation, in combination with mass spectrometry (MS), (<NPL>). This process has been coined hydroxyl radical protein foot-printing (HRPF). A variety of techniques have been used to perform HRPF. Perhaps the most widely used approach relies upon fast photochemical oxidation of proteins (FPOP) that generates hydroxyl (OH) radicals from hydrogen peroxide (H<NUM>O<NUM>) using a single, high fluence, short pulse of UV light. The reaction of OH radicals and solvent exposed amino acids typically results in net insertion of one oxygen atom into the amino acid. OH radicals are short-lived, and when generated by a brief UV pulse, reactions between amino acids and radicals may be completed before any conformation change by the labeled protein can occur (<NPL>). The mass spectra of the peptide products of enzyme digestion show various levels of oxidation marked by peak shifts of 16Da, 32Da, 48Da, etc. This information can be used to deduce which of the peptides are located on the exterior of the HOS and, thus, lead to greater understanding of the HOS.

A technical limitation of FPOP HRPF that deleteriously impacts comparative studies stems from the reaction of OH radicals with non-analyte components in the sample, such as buffer constituents, incipient solutes, and extraneous biologicals. Variability in the rate of background scavenging causes trial-to-trial irreproducibility, which has limited comparative studies (<NPL>). While OH radicals are excellent probes of protein topography, they also react with many compounds found in analytical preparations. Competition between analyte protein and background scavengers for free OH radicals exists, making it desirable to measure the effective concentration of radical available to oxidize a target protein to ensure reproducible results. In photochemistry, effective radical concentration is measured using a radical dosimeter internal standard. Ideally, a dosimeter would have: a simple relationship between effective radical concentration and dosimeter response; a simple, rapid, and non-destructive measurement means; and be unreactive to most proteins.

Prior art teaches radical dosimetry as performed using spiked peptide internal standards (<NPL>; <NPL>. ), or a UV absorbing internal standard, such as adenine, added to the buffer and assessed in a post-labeling manner (<NPL>. In peptide radical dosimetry, labeled peptide and target protein are subsequently analyzed using LC-MS (with optional proteolysis) to assess the relative ratio of oxidized peptide to that of the target protein. Should the desired peptide to protein oxidation ratio not be achieved, the entire experiment is repeated adjusting the concentration of H<NUM>O<NUM> dependent upon the need to either increase or decrease effective OH radical load. For adenine dosimetry, the effective change in adenine UV absorbance is determined upon completion of the labeling process, and the ratio of the achieved vs target adenine UV absorbance change is determined. The H<NUM>O<NUM> concentration is subsequently varied in accordance with the desired change in UV absorbance. Both of these approaches are performed after labeling has been completed and do not enable real-time adjustment of effective OH radical load, consuming precious sample and needlessly wasting investigator time.

<CIT> and <CIT> teach systems and methods by which to perform radical dosimetry in real-time, as biologicals are labeled during the FPOP HRPF process. While creating a real-time means to adjust and compensate for variation in background scavenging, the systems and method taught in these applications requires the addition of an extrinsic internal standard dosimeter to the biological mixture. Under some conditions, the extrinsic internal standard may cause artifactual changes in biomolecular higher order structure, and as such, be incompatible for the desired goal of providing a facile means of characterizing nascent higher order structure of biologicals.

<CIT> describes a device and methodologies by which commonly used biological buffer systems can be employed as radical dosimeter internal standards. The photometric properties of some commonly employed biological buffers are altered in a predictable manner upon OH radical attack. As such, these buffers can be employed as radical dosimeter internal standards, eliminating the need to add extrinsic reagents, and as the solvating properties of these buffers are well established to stabilize nascent configurations of biomolecules, they do not alter biological higher order structure.

The afore noted art describes devices and means by which to perform HRPF radical dosimetry while labeling proteins or biopharmaceuticals in vitro. However, the practice of applying the results of in vitro structural experiments to authentic in vivo behavior has been brought into question (<NPL>). Because of shortcomings of in vitro HRPF, there has been recent interest and desire to extend the use of HRPF to intact whole cells in an in vivo manner. For example, <CIT> describes a means and methodology by which in vivo HRPF can be performed. Briefly, a plurality of fused-silica capillary tubes and microfluidic fittings are used to support the mixing of buffer suspended cells with H<NUM>O<NUM>. As taught, H<NUM>O<NUM> is rapidly taken up by the cells without causing cellular disruption, inducing apoptosis, or precipitating cell death. However, the systems and methods taught still result in a variety of shortcomings.

<CIT> discloses devices and methodologies for flash photo-oxidation of proteins to determine their higher order biomolecular structure.

<CIT> discloses a system for the fast photo-chemical oxidation of proteins and the like using a UV/fluorescence detector system for measuring the amount of radical generated in the sample mixture. A photoreactive reagent mixture comprising hydrogen peroxide and Alexa Fluor dosimeter reagent and a sample is pushed through a path of a laser beam in a capillary reaction cell and into the sample holding loop. The sample is pushed through the capillary reaction cell without laser pulse and into the loop with the UV/fluorescence detector. The fluorescence of the AlexaFluor dosimeter will be measured in this detector to measure the amount of available hydroxyl radical generated in the FPOP process.

<CIT> suggests a flow assembly for cells comprising a first flow path configured to receive a plurality of cells, a second flow path configured to receive a buffer, and a third flow path configured to receive the plurality of cells and the buffer. The plurality of cells is in a single-file orientation and the buffer generally surrounds the single-file orientation of the plurality of cells when being in the third flow path.

Disclosed embodiments include systems and methods that addresses the above noted shortcomings of present day in vitro HRPF by providing the means for real-time, in vivo measurement of effective hydroxyl radical concentration and adjustment for unwanted background scavenging using the photometric properties of an in vivo radical dosimeter internal standard; the means by which cellular singulation and partitioning can be assessed and reproducibly controlled; as well as a means to determine the arrival time of a cell into an HRPF photolysis zone.

Disclosed embodiments are directed to systems and methods for the analysis of protein higher order structure comprising improved embodiments to perform in-vivo flash photo-oxidation of proteins enabling advanced hydroxyl radical protein foot-printing. Disclosed embodiments provide an in-line, in vivo radical dosimetry system wherein closed-loop control is established between the flash photolysis system and dosimeter to control irradiance of the flash photolysis system in response to measured changes in the photometric properties of an intra-cellular, internal standard radical dosimeter.

In some embodiments, the disclosure includes an in-line, in vivo radical dosimetry system wherein closed-loop control is established between an automated, in-line microfluidic mixing system and dosimeter to control the concentration of H<NUM>O<NUM> in response to measured changes in the photometric properties of an intra-cellular, internal standard radical dosimeter.

In some embodiments, the disclosure includes an in-line, in vivo radical dosimetry system wherein closed-loop control is established between the flash photolysis system and dosimeter to control irradiance of the flash photolysis system in response to measured changes in the photometric properties of an intracellular internal standard radical dosimeter, for which OH radicals are created by the photolysis of intracellular H<NUM>O<NUM>.

In some embodiments, the disclosure includes an in-line, in vivo radical dosimetry system wherein closed-loop control is established between the flash photolysis system and dosimeter to control irradiance of the flash photolysis system in response to measured changes in the photometric properties of an intracellular internal standard radical dosimeter, for which OH radicals are created from water using photo-catalytic metal oxides, external of the cell.

In some embodiments, the disclosure includes an in-line, in vivo radical dosimetry system wherein closed-loop control is established between the flash photolysis system and dosimeter to control irradiance of the flash photolysis system in response to measured changes in the photometric properties of an intracellular internal standard radical dosimeter, for which OH radicals are created from water using photo-catalytic metal oxides, internal to the cell.

In some embodiments, using an in vivo, in-line radical dosimetry system, the disclosure includes methods of producing labeled biomolecules for analysis comprising: (<NUM>) mixing cells with a biological buffer, internal standard radical dosimeter that is ultimately taken up by the cell, and other required labeling reagents, (<NUM>) introducing said cells into an optical dosimetry zone, (<NUM>) determining the nascent photometric properties of said cells, (<NUM>) photo-irradiating said cells in an optical photolysis zone with at least one burst of UV irradiation, (<NUM>) determining the change in photometric properties for said cells after photo-irradiation, and (<NUM>) adjusting the spectral irradiance of the UV source light in accordance with the change in radical dosimeter photometric property.

In some embodiments, using an in vivo, in-line radical dosimetry system, this disclosure includes methods of producing labeled biomolecules for analysis comprising: (<NUM>) mixing cells with a biological buffer, internal standard radical dosimeter that is ultimately taken up by the cell, and other required labeling reagents, (<NUM>) introducing said cells into an optical dosimetry zone, (<NUM>) determining the nascent photometric properties of said cells, (<NUM>) photo-irradiating said cells within an optical photolysis zone with at least one burst of UV irradiation, (<NUM>) determining the change in photometric properties for said cells after photo-irradiation, and (<NUM>) adjusting the concentration of H<NUM>O<NUM> using an in-line, microfluidic mixer in accordance with the change in radical dosimeter photometric property.

In some embodiments, using an in vivo, in-line radical dosimetry system, the disclosure includes methods of producing labeled biomolecules for analysis comprising: (<NUM>) mixing said cells with a biological buffer, internal standard radical dosimeter that is ultimately taken up by the cells, and metal-oxide photo-catalyst, (<NUM>) introducing said cells into an optical dosimetry zone, (<NUM>) determining the nascent photometric properties of said cells, (<NUM>) photo-irradiating said cells in an optical photolysis zone with at least one burst of UV irradiation, (<NUM>) determining the change in photometric properties of said cells after photo-irradiation, and (<NUM>) adjusting the spectral irradiance of the UV source light in accordance with the change in radical dosimeter photometric property.

In some embodiments, using an in vivo, in-line radical dosimetry system, the disclosure includes methods of producing labeled biomolecules for analysis comprising: (<NUM>) mixing cells with a biological buffer and internal standard radical dosimeter that is ultimately taken up by the cell, (<NUM>) introducing said cells into an optical dosimetry zone, (<NUM>) detecting the arrival and presence of said cells cell by monitoring the intensity of scattered light exiting the dosimetry zone, (<NUM>) determining the elapsed time between the arrival of consecutive cells, (<NUM>) determining the cell isolation volume per the product of the elapsed time and net buffer flow rate, and (<NUM>) adjusting the sheath flow and buffer flow parameters to achieve a desired cell isolation volume.

In some embodiments, using an in vivo, in-line radical dosimetry system, the disclosure includes methods of producing labeled biomolecules for analysis comprising: (<NUM>) mixing cells with a biological buffer and internal standard radical dosimeter that is ultimately taken up by the cell, (<NUM>) introducing said cells into an optical dosimetry zone, (<NUM>) detecting the arrival and presence of a cell by monitoring the intensity of scattered light exiting the dosimetry zone, (<NUM>) determining the net flow rate for said arriving cell, (<NUM>) determining the interconnect volume that extends from the photolysis zone and the dosimetry zone, (<NUM>) determining the transit time required for said cell to travel from the photolysis zone to the dosimetry zone, (<NUM>) determining the photolysis zone arrival time for said cell, and (<NUM>) triggering the photolysis system at such time when all subsequent cells arrive at the photolysis zone.

Following the production of labeled biomolecules other methods, such as mass spectrometry or electrophoresis, may be used to identify labeled peptides and deduce information regarding higher order structures of biomolecules in vivo.

Disclosed embodiments include an analysis system comprising: a sample introduction system configured to provide intact biological entities to a photolysis zone, the biological entities being isolated from each other in a focused sheath flow; a photolysis light source configured to generate light to generate hydroxide radicals from a source of hydroxide radicals; a photolysis zone configured to receive the sheath flow and the light so as to oxidize an internal standard and so as to oxidize biological compounds of the biological entities in vivo; a dosimetry zone configured to receive the biological entities from the photolysis zone, to detect presence of the biological entities using a scattered light detector and to detect oxidation of the internal standard using a fluorescence detector; control logic configured to determine that a target concentration of hydroxide radicals was generated for each of the biological entities and to adjust operation of the photolysis zone to meet the target concentration of hydroxide radicals; and a reservoir configured to receive the biological entities including the oxidized biological compounds.

Disclosed embodiments include a method of oxidizing biomolecules within an intact cell, the method comprising: introducing a sample mixture containing at least one cell into a photolysis zone, a source of hydroxide radicals and a dosimeter internal standard into a photolysis zone of a flash photolysis system; providing light to generate the hydroxide radicals from the source of hydroxide radicals, the hydroxide radicals being configured to oxidize biomolecules within the at least one cell; waiting an optionally predetermined time for the at least one cell to reach a dosimetry zone of a radical dosimeter configured to detect a photometric property of the dosimeter internal standard resulting from reaction of the dosimeter internal standard and the hydroxide radicals, wherein the at least one cell is detectable within a dosimetry zone of the radical dosimeter by light scattering; measuring a photometric property of the dosimeter internal standard using the radical dosimeter, while the at least once cell is within the dosimetry zone; determining that a target level of hydroxide radicals was not generated based on the measured photometric property of the dosimeter internal standard; and adjusting a concentration of hydroxide radicals within the photolysis zone by adjusting at least one of: <NUM>) an amount of light provided to the photolysis zone, <NUM>) a concentration of the source of hydroxide radicals, <NUM>) a flow rate of the at least once cell within the photolysis zone, or <NUM>) adjusting a time of providing the light to the photolysis zone.

A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the disclosure are utilized. Further, the above objects and advantages of the disclosure will become readily apparent to those skilled in the art from reading the following description of exemplary embodiments when considered in the light of the accompanying figures that incorporate features of the present disclosure.

Any of the methods described herein can according to specific embodiments further make use of any one or more of the following of which:.

Devices and methods are provided for the analysis of biomolecular higher order structure that is accomplished by selective labeling of solvent exposed molecular groups, as catalyzed by in vivo fast photo-oxidation with real-time monitoring and control of effective OH radical concentration. Moreover, devices and methods are provided for the analysis of biomolecular higher order structure that is accomplished by in vivo fast photo-oxidation with real-time monitoring and control of in vivo species isolation volume and subsequent flash photolysis. The devices and methods can be applicable to a variety of in vivo embodiments that are photometrically translucent or transparent such as but not limited to: eukaryotic cells, prokaryotic cells, bacteria, intra-cellular viruses, virions, virus-like particles, single-cell organisms, eukaryotic tissues, and multi-cellular organisms. While the present disclosure refers to cells for illustrative purposes, such reference is not restrictive, and it is understood that such references are inherently applicable to any and all photometrically translucent or transparent in vivo biological or, in an example not part of the present invention, non-biological entities.

The devices and methods can be applicable to a variety of research fields, such as: general protein biochemistry; diagnostics research; infectious disease research; biopharmaceutical research and development; antibody research and development; biosimilar development; therapeutic antibody research and development; small molecule drug research and development; and development of other therapeutic compounds and materials. Moreover, the devices and methods can be applicable to a variety of research analyses such as: protein-ligand interaction analysis; protein-protein interaction analysis; protein-DNA interactions; protein-RNA interactions; protein-fusion product analysis; protein conformation and conformational change analysis; cell-cell interactions; virus-cell interactions; small drug molecule mode of action analysis; biopharmaceutical mode of action analysis; antibody-antigen analysis; protein epitope mapping; protein paratope mapping; and chemical reaction monitoring.

The device can receive cells for subsequent chemical labeling via a step-wise introduction of cells by manually pipetting the cells into appropriate micro-centrifuge tubes or microplates that are placed into the system's sample introduction assembly. Alternatively, the device can be hyphenated with and receive cells directly from other separation and analysis instruments such as but not limited those which perform selective cell sorting, cell counting, and cell isolation from tissue.

This section provides a general overview of the flash photolysis instrument with in-line, in vivo radical dosimeter that uses the photometric properties of an internal standard dosimeter to assess and ultimately control in vivo effective OH radical concentration. Moreover, this section provides a general overview of the present disclosure that uses the photometric properties of an in vivo embodiment to assess isolation volume and to control precise triggering of the flash photolysis system at such time when the in vivo embodiment arrives at the system's photolysis zone. A detailed description of each sub-assembly is provided elsewhere herein. Moreover, methods that describe the interplay of these subassemblies are provided to enable understanding of typical instrument operation.

Disclosed embodiments include a flash photolysis system <NUM>, as illustrated in <FIG>. Flash photolysis system <NUM> is configured to oxidize sample cells in real-time to achieve in vivo radical dosimetry. In vivo analytes (i.e. cells) are introduced via the sample introduction system <NUM>. Cells in suspension can be presented using small volume micro-centrifuge tubes or by using multi-well microtiter plates as readily available from Eppendorf (Hamburg, Germany). Microfluidic circuitry is configured for cellular aspiration, mixing with H<NUM>O<NUM>, cellular hydrodynamic focusing using a sheath flow apparatus, transportation to photolysis and dosimetry zones, as well as the transportation and deposition of labeled cells. In some embodiments, sample introduction system <NUM> is configured to provide intact biological entities to a photolysis zone (e.g., photolysis zone <NUM>, the biological entities being isolated from each other in a focused sheath flow. The sheath flow is typically configured to isolate the biological entities from each other. For example using proper conditions, the biological entities are separated from each other by regular intervals.

Photo-oxidation occurs within the photolysis zone <NUM>. In some embodiments, a photolysis zone <NUM> is comprised of a fused silica capillary as available from Polymicro Technologies - Molex (Phoenix, AZ, USA). Typical capillary internal diameter can range from <NUM> micrometers to <NUM>. Typical wall thickness can range from <NUM> - <NUM> micrometers. In some embodiments, opto-fluidic chips are fabricated using a variety of techniques such as lithography assisted wet chemical etching, dry reactive ion etching, and laser ablation micro-structuring that create microfluidic channels within a quartz substrate. In some embodiments, opto-fluidic chips are fabricated by embossing fluidic channels within a plastic substrate, where formed fluidic channels transport sample into optically transparent cells created by sealing optically transparent windows to regions where the plastic substrate has been removed. Exemplary plastic substrates include but are not limited to: polycarbonate, polyethylene, polyether-ether-ketone, cyclic olefin polymer, cyclic olefin copolymer, polytetrafluorethene, Kalrez®, and polychlorotrifluoroethylene. Fluidic and optical channel internal diameters can range from but are not limited to <NUM> to <NUM>. In some embodiments, fluidic and optical channels can have different internal diameters to ideally match disparate requirements of fluid transfer, fluid mixing, hydrodynamic focusing, and optical coupling. Moreover, the opto-fluidic chip can contain an optical wave-guiding structure, such as an integral optical fiber, monolithic waveguide, liquid core waveguide, or evanescent guiding means using metal oxides, rare-earth metals, or grating structures. In another embodiment at least one sample contacting surface of the photolysis cell is coated with a photocatalytic metal oxide, such as TiO<NUM>. For some photocatalytic metal-oxide formulations, photolysis can be initiated using long UV (wavelength > <NUM>) or visible light. For these embodiments, capillaries and opto-fluidic chips can be fabricated using various varieties of glass, such as BK-<NUM> or Borofloat® <NUM> (Schott AG, Germany), in lieu of fused silica or quartz. In another embodiment, quartz or glass opto-fluidic cells comprise a resonance structure to support resonance and/or multi-pass incident photon collision with suspended cells, dissolved reactants, such as but not limited to H<NUM>O<NUM>, suspended metal-oxide nanoparticles, or immobilized metal oxide films upon at least one sample contacting surface.

The photolysis zone <NUM> receives suspended cells from the sample introduction system <NUM> via a microfluidic path <NUM>. After processing, photo-irradiated cells within the photolysis zone <NUM> are transferred into the radical dosimeter <NUM>. The photolysis zone <NUM> is in optical communication with the flash photolysis light <NUM>. Flash photolysis light <NUM> is an example of a photolysis light source configured to generate light to generate hydroxide radicals within photolysis zone <NUM> from a source of hydroxide radicals. The photolysis zone <NUM> is configured to receive the sheath flow including biological entities, to receive the light from flash photolysis light <NUM> so as to oxidize the dosimeter internal standard so as to oxidize biological compounds of the biological entities in vivo. For example, peptides comprising amino acids may be oxidized in the photolysis zone <NUM>.

The photolysis zone <NUM>, flash photolysis light <NUM> and radical dosimeter <NUM> comprise a flash photolysis system. The flash photolysis system is comprised of: a plasma flash lamp or other appropriate light source such as an excimer laser, a solid state laser, or laser diode; and associated light collection/transmission optics to match the requirements of the light transmission means to the photolysis zone.

The radical dosimeter <NUM> is configured to receive fluid and suspended cells from the photolysis zone <NUM>, or in examples not part of the present invention, the radical dosimeter <NUM> is incorporated into the photolysis zone <NUM> by employing an orthogonal optical path. A variety of photometric detection schemes may be employed by the radical dosimeter to monitor the associated photometric properties of the dosimeter internal standard. In some embodiments, the dosimeter internal standard can be an extraneous additive that is spiked into the biological sample. In some embodiments, the intrinsic photometric properties of a biological buffer system, once taken up by the cell, may serve as an intrinsic dosimeter internal standard. By "intrinsic" or "intrinsic to a buffer" it is meant that the internal standard is one of the chemical species that provides the buffering property. The buffer is optionally a physiologically compatible buffer configured to maintain the cells at a physiological pH or ion concentration. In some embodiments, the internal standard is configured to become fluorescent as a result of the light received from flash photolysis light received in photolysis zone <NUM>. For example, the dosimeter internal standard may increase fluorescence by factors of at least <NUM>, <NUM> or <NUM> times upon reaction with hydroxide radical, in various embodiments.

Photometric detection schemes include but are not limited to: fluorescence, photometric absorbance, refractive index detection, light scatter detection, and luminescence. In some embodiments, the photometric detection scheme comprises a fluorescence detector employing ultra violet (UV) photo-excitation source to create UV fluorescence or emission. In some embodiments, the fluorescence detector employs a UV excitation source to create visible fluorescence or emission. In some embodiments, the fluorescence detector employs a visible excitation source to create visible fluorescence or emission. In some embodiments, the fluorescence detector also includes an integral light scatter detector.

The control electronics <NUM> functions to: provide direct current (DC) drive voltage, derived from laboratory alternating current (AC) power sources, to peripheral assemblies; provide analog and digital control signals to peripheral devices; receive analog or digital information from peripheral devices; provide ADC and digital to analog conversion (DAC) functions; and provide data to and receive commands from the instrument controller <NUM>. In a typical embodiment, the control electronics assembly comprises a motor controller that interfaces with motors located within the sample introduction-collection system <NUM>. Moreover, the control electronics assembly in such embodiments may contain a universal serial bus (USB) hub for digital communication with the instrument controller <NUM>.

The instrument controller <NUM> functions to provide process control for various instrument peripheral devices while receiving status and data information from these devices in digital format. In some embodiments, the instrument controller <NUM> runs a software control program with two main modules: a low level, multi-threaded module for instrument component control and a high level user interface (UI) module. In some embodiments, the control electronics <NUM> comprises an embedded microprocessor that provides low level instrument component control while communicating with a high level UI control program of the instrument <NUM> via a USB or wireless interface.

Together instrument controller <NUM>, control electronics <NUM> and various interconnections represent control logic configured to control flash photolysis system <NUM>. This control logic can be configured to perform steps of any of the methods disclosed herein. For example, in some embodiments, control logic is configured to determine that a target concentration of hydroxide radicals was generated for each biological entity. This target concentration is optionally selected to assure that that an oxidation reaction of cell constituents has sufficient oxidizing agent to go near a desired level of completion.

The control logic may further be configured to manage the feedback loop that includes adjusting conditions in the photolysis zone <NUM> to meet the target concentration of hydroxide radicals. The conditions in the photolysis zone <NUM> may be adjusted by, for example, changing a concentration of a source of hydroxide radicals, changing a flow rate in the sample introduction system <NUM>, changing an amount of light received from the photolysis light source <NUM>, changing a time at which the light is received from the photolysis light source, changing a separation distance/volume of isolated cells, and/or the like. By changing conditions in the photolysis zone <NUM>, control logic can provide feedback to sample introduction system <NUM> and/or the photolysis light source <NUM> based on analysis of a first cell to improve analysis of a second cell.

In some embodiments, control logic is configured to normalize a quantitation of oxidized and/or identified peptides from a cell based on a fluorescence signal from the internal standard within the dosimetry zone <NUM>. This allows comparison of results from different experiments using different instances of flash photolysis system <NUM>.

The control logic is optionally further configured to determine a time the photolysis light is received by cells in the photolysis zone <NUM> and/or to determine a time period between which isolated cells enter the photolysis zone <NUM>. These determinations may be based on detection of fluorescence and/or scattered light in the dosimetry zone <NUM> and may be controlled by adjusting flow rates and/or volumes in sample introduction system <NUM>.

The control logic is optionally further configured to control flow of cells to labeled cell reservoir <NUM> and analyzer <NUM>. For example, the control logic may be configured to control flow of cells such that ruptured cells are diverted from a particular container of labeled cell reservoir <NUM>, or such that different oxidized cells are placed in different compartments over a function of time. In some embodiments, control logic is configured to use an analyte signal from analyzer <NUM> to control any aspect of flash photolysis system <NUM>.

Instrument controller <NUM> and control electronics <NUM> are optionally combined into a single device.

<FIG> illustrates further details of the flash photolysis system <NUM> of <FIG> Flash photolysis system <NUM> is used for cell introduction, cell processing, and processed cell collection. Cells to be processed are suspended/placed in buffer and stored in reservoir <NUM>. In some embodiments the cells have been previously incubated with a buffer containing an extrinsic and/or intrinsic radical dosimeter internal standard. This incubation allows the internal standard to enter the interior (absorbed) and/or be adsorbed onto the surface of the cells. In some embodiments, the buffer includes compounds that act inherently as an intrinsic in vivo internal standard to perform radical dosimetry. Under microprocessor control (e.g., control electronics <NUM> and/or Instrument controller <NUM>, syringe pump <NUM> aspirates cells from reservoir <NUM> and pumps them into mixer <NUM>. The elements <NUM>-<NUM> and <NUM> are optionally part of sample introduction system <NUM>.

H<NUM>O<NUM> is stored in reservoir <NUM>. Under microprocessor control, syringe pump <NUM> aspirates H<NUM>O<NUM> from reservoir <NUM> and pumps the aspirated H<NUM>O<NUM> into mixer <NUM>. The aqueous concentration of H<NUM>O<NUM> in reservoir <NUM> is selected so that at the desired net flow rate for pumps <NUM> and <NUM> and the effective desired final concentration of H<NUM>O<NUM> are achieved. Exemplary H<NUM>O<NUM> concentration range from, but are not restricted to, <NUM> - <NUM>. Exemplary net flow rates after mixer <NUM> range from, but are not restricted to, <NUM> - <NUM> uL/min. H<NUM>O<NUM> is an example of a source of hydroxide radicals, which is added to the cells (or other biological entities) by sample introduction system <NUM>.

Sheath buffer is stored in reservoir <NUM>. Under microprocessor control, syringe pump <NUM> aspirates sheath buffer from reservoir <NUM> and pumps the sheath buffer into hydrodynamic focusing mixer <NUM>. Cells mixed with H<NUM>O<NUM> are pumped from mixer <NUM> into the hydrodynamic focusing mixer <NUM> by the combined pumping action of pumps <NUM> and <NUM>. Subsequently, sheath buffer functions to hydro-dynamically focus the cells, creating a single-file array of cells, each isolated by a given volume of sheath buffer. The single-file array of cells is created by constricting the flow from mixer <NUM> to the extent that a diameter of the flow is similar to the diameter of the cells. Exemplary sheath buffer flow rates range from, but are not restricted to, <NUM> - <NUM> uL/min.

After single-file cell isolation, by the combined pumping of syringe pumps <NUM>, <NUM>, and <NUM>, cells are shuttled into photolysis zone <NUM>, where they may be irradiated by the flash photolysis light <NUM>. After flowing through the photolysis zone <NUM>, cells can be pumped into the dosimetry zone <NUM> which is part of radical dosimeter <NUM>, wherein photometric properties of the cells can be measured. Dosimetry zone <NUM> is configured to detect oxidation of the internal standard using, for example, a fluorescence detector. Dosimetry zone <NUM> is also configured to detect presence of the cells (or other entities) within the dosimetry zone <NUM> using a detector configured to detect light scattering. This scattered light detector is optionally also configured to determine if the cell is intact. For example, the scattered light detector and associated instrument control logic may be configured to distinguish between cells that are intact, cells that are disrupted, and cells that are stuck together. In some embodiments, radical dosimeter <NUM> includes both dosimetry zone <NUM> and photolysis zone <NUM>. Dosimetry zone <NUM> includes photolysis zone <NUM>. The photometric properties measured can include, but are not restricted to, photometric fluorescence and/or photometric absorbance. After leaving the dosimetry zone <NUM>, suspended cells are optionally pumped into and collected in a labeled cell reservoir <NUM>. Real-time measurements made in Dosimetry zone <NUM> allow for a feedback loop in which photolysis conditions can be modified to assure that a desired amount of H<NUM>O<NUM> production occurs and a desired amount of in vitro or in vivo analyte oxidation.

During initial operation of the system, a base-line measurement of the cell's photometric property is optionally taken. The baseline measurement is performed for the introduced cell without any photolysis. Once the baseline measurement is made, photolysis proceeds and once the (one or more) photo-exposed cells enter the dosimetry zone, the photometric property of the photo-exposed cells are assessed. In some embodiments, labeled cell reservoir <NUM> contains more than one fluid storage compartment. For example, labeled cell reservoir <NUM> may include several compartments or wells in which oxidized biological compounds may be selectively placed. In some embodiments, different aliquots of the output of dosimetry zone are placed in different compartments based on fluorescence and/or light scattering measurements made in dosimetry zone <NUM>. In one compartment, non-photo-exposed cells that flowed through the system during the baseline measurement process are collected. In another compartment, photo-exposed intact cells are collected. In another compartment cells that were found not to be intact may be placed. Photo-exposed (e.g., oxidized cells) may be placed in different compartments as a function of time in order to perform time-based experiments, such as kinetic studies. The compartments may be "sample wells," lengths of capillary, channels, and/or the like.

From labeled cell reservoir <NUM> collected samples are optionally analyzed using analyzer <NUM>. Analyzer <NUM> is configured to perform chemical analysis of the samples. For example, Analyzer <NUM> may be configured to identify peptides, carbohydrates, metals, nucleic acids, lipids, and/or amino acids oxidized in the photolysis zone <NUM>. Analyzer <NUM> may include, for example, a mass spectrometer, scintillator, electrophoresis device, chromatograph, and/or any other device configured to separate and/or identify sample constituents based on radioactivity, mass, charge, size, or other chemical property. In some embodiments, analyzer <NUM> is configured to detect isotopic or radio isotopic labels within cells or other biological entities and optionally to identify if the components including such labels have been oxidized. In some embodiments, analyzer <NUM> is configured to measure a ratio of oxidized/non-oxidized concentrations of a particular component. In some embodiments, analyzer <NUM> is "in-line" with labeled cell reservoir <NUM> and thus configured to receive and analyze samples in real-time. For example, labeled cell reservoir <NUM> may include a capillary configured to provide sample directly to an input of a mass spectrometer.

<FIG> illustrates methods <NUM> for in vivo cell labeling, according to disclosed embodiments.

In an optional add internal standard step <NUM>, the dosimeter internal standard is added to the cells or other entities to be analyzed. The internal standard may be intrinsic to a buffer with which the cells are mixed or added. The cells may be left in contact with the internal standard for a time such that the internal standard has time to be absorbed into the interior of the cells and/or be adsorbed on to surfaces of the cells. After this time the internal standard may be washed from the cells in a wash cells step <NUM>. Steps <NUM> and <NUM> leave the internal standard that was absorbed in or adsorbed to the cells, while leaving the surrounding fluid practically devoid of internal standard. These two steps improve the accuracy of the measurement of the internal standard by reducing the background of internal standard not bound to the cells. Step <NUM> is optional where, for example, the cells already include a dosimeter internal standard.

In introduce step <NUM> one or more first cells are introduced into the flash photolysis system using sample introduction system <NUM>. As noted elsewhere, the introduced cells may have added a dosimeter internal standard. For example, the cells may have been placed in a buffer including an intrinsic internal standard that we adsorbed onto a surface of the cells or absorbed into the interior of the cells. After the cells have received the internal standard, they may then be placed in a solution having minimal constituents capable of being oxidized by H<NUM>O<NUM>. This results in the internal standard being associated with the cells but not the surrounding solution.

In an optional measure step <NUM>, the first introduced cell(s) containing intrinsic or extrinsic dosimeter internal standard are measured in an un-irradiated state (i.e., not yet oxidized using photolysis) to assess their nascent photometric properties. This initial assessment serves as the baseline measurement against which subsequent photometric property measurements can be compared.

In an irradiate step <NUM>, an introduced cell (or cells) is irradiated in the photolysis zone <NUM>. The irradiated cell can be the first introduced cell or a second introduced cell. In a measure step <NUM> one or more photometric properties of the irradiated cell(s) are measured using radical dosimeter <NUM>. The measurements made in step <NUM> can be compared with those made in step <NUM> to determine an effective H<NUM>O<NUM> concentration and an extent to which photolysis induced oxidation of biomolecules has occurred. In embodiments where the dosimeter internal standard is primarily associated (absorbed & adsorbed) with the cells, the measured photolysis induced oxidation represents a quantitative measurement of in vivo oxidation of the biomolecules of the cells.

In assess step <NUM>, the measured changes in photometric properties are used as a surrogate to access the effective OH radical concentration and thereby the completeness of oxidation reactions with target (in vivo) biomolecules. In a decision step <NUM>, it is determined if a target OH radical concentration has been achieved. If the determination is TRUE, then the method proceeds to good result step <NUM> in which the photolysis conditions are considered satisfactory, the oxidation process is continued on additional cells and subsequent irradiated cells are ultimately collected and analyzed as illustrated in <FIG>. Good result step <NUM> optionally includes analysis of the cells using analyzer <NUM> and use of results from analyzer <NUM> to determine properties of the cells, such as kinetics, three-dimensional protein structure, molecular interaction cites, and/or the like. If the determination is FALSE, then the method proceeds to adjust step <NUM> in which photolysis system fluence and/or H<NUM>O<NUM> concentration is varied and the method of <FIG> is repeated for additional cells to assess the new level of OH radical yield resulting from the adjusted parameters. In some embodiments the method <NUM> is manually operated by a user. In some embodiments, all or part of the method <NUM> is automated under microprocessor control using instrument controller <NUM> or control electronics <NUM>. The method may be repeated until a desired level of OH radical yield and/or biomolecule oxidation is achieved. Measure step <NUM> may or may not be performed for every cycle of the method.

Disclosed embodiments include in vivo Radical Dosimetry Using Intracellular Fluorescent Indicators of Oxidative Reactions. A technical limitation of fast photochemical oxidation of proteins (FPOP) hydroxy radical protein foot-printing (HRPF) arises from the reaction of OH radicals with background or non-analyte components in the sample, such as buffer constituents, extraneous proteins, cellular structures, and incipient solutes. Variability in the degree of background scavenging causes trial-to-trial irreproducibility, which has limited comparative studies (<NPL>). While OH radicals are excellent probes of protein topography, they also react with many compounds found in analytical preparations. Competition between target protein and background scavengers for free OH radicals exists. As such, to obtain reproducible results it is desirable to measure the effective concentration of available hydroxyl radical to oxidize the target protein or proteins and to accordingly adjust total hydroxyl radical production. For in vivo HRPF, radical dosimetry is optionally performed by monitoring only changes in effective OH radical load that occur within the cell, and in some cases preferentially occur within specific cellular organelles.

In photochemistry, effective radical concentration is measured using a radical dosimeter, such as radical dosimeter <NUM>. Ideally, a dosimeter would have: a simple relationship between effective radical concentration and dosimeter response; a simple, rapid, and non-destructive measurement means; and be unreactive to most proteins. In one approach the use of radical dosimetry for the assessment of background scavenging for in vitro systems includes methods of determining free OH radical concentration by measuring the absorbance change of adenine. This approach includes an off-line method of collecting photo-exposed adenine and associated analyte protein, where flow is diverted from a capillary photolysis cell and is directed to an off-line UV detector. This approach consumes substantial product (several microliters) and requires much time to generate sufficient volume to transport the sample and to perform UV absorbance measurements. Other approaches include methods to perform in vitro radical dosimetry in real-time, as biologicals are labeled during the FPOP HRPF process. In these approaches, a photometric detection scheme is applied to the flowing stream of analyte in order to detect changes in the optical properties of a dosimeter internal standard. Particular description is given to the use of adenine as a dosimeter internal standard that is added to the analytical sample as an exogenous or extrinsic component. Moreover, these approaches include methods in which labeling parameters may be altered in real-time to achieve desired levels of effective OH radical concentration and associated labeling efficiency, and methods by which effective OH radical yield can be controlled by varying the fluence and/or spectral irradiance of a plasma flash lamp source in addition to dithering H<NUM>O<NUM> concentration. See, for example, <CIT>, <CIT> and International Application <CIT>.

While the above approaches teach in vitro methods by which to perform off-line and in-line closed loop radical dosimetry to improve the reproducibility of in vitro HRPF, they fail to address the requirements for in vivo HRPF. For in vivo HRPF to be effective, each cell are preferably photo-irradiated only once with a short burst of UV irradiation, employing typical pulse widths on the order of <NUM> - <NUM>,<NUM> nanoseconds. Further, for in-line, in vivo radical dosimetry to be most useful, photometric measurements should be taken in a way such that a single cell or a given quantity of cells are consistently probed to enable comparative measurements. As such, a flowing stream of cells should be created in a precise manner that provides a predictable amount of isolation volume that segregates each cell in its single-file array, and enables precise and predictable temporal delivery of each cell, or a given number of cells, to photolysis and dosimetry zones. It is also desirable to separate, for both measurement and collection, those cells that have been irradiated from those that have not.

In vivo HRPF greatly benefits from the assessment of the effective intracellular OH radical concentration. Accordingly, in vivo radical dosimetry benefits when a dosimeter internal standard (intrinsic or extrinsic) only (or predominantly) present within the cell and not in the extracellular fluid. Dependent upon cell type, intracellular volumes range from <NUM> to <NUM> nL. The typical working concentration for an internal standard radical dosimeter is on the order of <NUM> - <NUM>. As such, the effective amount of intracellular dosimeter ranges from <NUM> picomole to <NUM> nanomole, substantially challenging photometric detection. Under such constraints, photometric absorbance detection will very likely fail to provide sufficient analytical sensitivity to accurately and precisely determine the change of photometric absorbance of an intracellular radical dosimeter upon the introduction of OH radicals. The latter is attributed to the fact that photometric absorbance detection functions by detecting changes in transmitted light of sample when probed by incident light. For solute concentrations below <NUM>, the resultant photometric change in transmitted light becomes measurably indistinct and effectively insignificant when compared to the original intensity of incident light.

Unlike photometric absorbance detection, photometric fluorescence detection functions by detecting small changes of light on a dark background, as detected light is only generated when a fluorescent moiety is illuminated using the appropriate wavelength of excitation light that is prohibited from striking the fluorescence detector. As such, fluorescence detection is on the order of <NUM>,<NUM> - <NUM>,<NUM> times more sensitive than absorbance detection, and has been successfully applied to imaging and photometric measurements of single cells. For the purpose of radical dosimetry using an internal standard, an ideal fluorescence dosimeter would have: a simple relationship between effective radical concentration and fluorescence response; be unreactive to cellular constituents and biomolecular complement; and not fluoresce unless attacked by oxidative chemistry. There is a preponderance of literature that describes fluorescence moieties that could be used for in vivo dosimetry; however the vast majority of these compounds are inherently fluorescent. Under such conditions, the use of inherently fluorescent radical dosimeters to detect effective OH radical concentration would be dependent upon detecting the loss of fluorescence upon OH radical attack. As such, these fluorescent probes would provide limited sensitivity akin to that of photometric absorbance, as once again detection would be limited by searching for small changes in light intensity upon a large background.

In disclosed embodiments, using an intrinsic or extrinsic, intracellular radical dosimeter internal standard, the effective concentration of generated OH radicals can be assessed by comparing the difference in fluorescence signal for irradiated and non-irradiated cells. During protocol development, the measured change in dosimeter fluorescence is compared with in vivo HRPF empirical results to determine the ideal effective OH radical concentration for subsequent experiments. Once a metric for dosimeter fluorescence signal change has been established, the variability in measured dosimeter fluorescence change for all subsequent experiments performed using similar cells and microfluidic conditions can be leveraged as a way to monitor changes in background scavenging. Once background scavenging has been assessed, corrections can be applied to compensate for trial to trial variability as illustrated in <FIG>. In some methods, photo-irradiance can be altered proportionally with changes in back-ground scavenging. Irradiance can be increased to compensate for increased levels of scavenging or decreased to address decreased levels of scavenging. In some methods, the concentration of H<NUM>O<NUM> can be proportionally adjusted to address variation in intracellular scavenging. In another methods, the measured abundance of the oxidized species, as detected by mass spectrometry or some other detection scheme such as but not limited to isoelectric focusing electrophoresis, in two or more different trials could be normalized between runs by multiplying said response by a normalization factor derived from the ratio of fluorescence signal change for the different trials.

Exemplary extrinsic fluorescent radical dosimeter internal standards are illustrated table <NUM> of <FIG>. The internal standards listed in <FIG> are intended to be illustrative and not restrictive in scope, as other internal standards will become obvious in light of the teachings presented here to those of ordinary skill in the art. The dosimeter internal standards listed in <FIG> exhibit low inherent fluorescence, and are transformed into fluorescent species upon oxidative attack, and that transformation process is dependent upon the kinetics of oxidative attack, which in turn is dependent upon the yield or concentration of oxidative species. Moreover, all of these internal standards when added to nutrient buffer for cell suspensions or incubated cell lines are readily taken up by said cells. Prior to in vivo HRPF, cells are isolated from their original nutritive buffer by the process of dialyses, buffer exchange, or centrifugation, and then re-suspended in a buffer devoid of dosimeter. During the in vivo HRPF process, cells are mixed with HzOz just prior to photolysis. H<NUM>O<NUM> is rapidly and readily taken up by the cells, and when UV photo-irradiated as taught herein, photo-lysed into OH radicals, which rapidly attack intracellular components, including the fluorescent radical dosimeter. Upon oxidation, the radical dosimeters listed in <FIG> become brilliantly fluorescent when irradiated with the appropriate excitation wavelength as shown, and the net change in measured fluorescence is dependent upon the effective yield of OH radicals. The fluorescence emission wavelength for each species is also listed.

For some in vivo HRPF studies, it is desirable to analyze the biological complement and bio-physiology of cell organelles, such as the nucleus, when studying DNA replication or DNA-mRNA transcription, or mitochondria, when studying cellular energetics and respiration. Under such circumstances, the use of an in vivo dosimeter internal standard that preferentially compartmentalizes into said organelles is useful and enabling. One such in vivo dosimeter is CellROX® Green, as available from ThermoFisher (USA). CellROX Green preferentially localizes in the nucleus and mitochondria of eukaryotic cells.

As illustrated in <FIG>, some embodiments include an integrated photometric fluorescence and light scatter detector <NUM> for in vivo HRPF radical dosimetry. <FIG> depicts the salient optical componentry for an integrated photometric fluorescence and light scatter detector <NUM> for use in in vivo HRPF radical dosimetry. This integrated device provides at least, but not limited to, two basic functions: <NUM>) it provides a system by which fluorescence signal may be generated and detected for an intracellular, internal standard, fluorescence radical dosimeter; and <NUM>) it provides a system by which to detect the entrance of an in vivo entity into the dosimeter zone <NUM>, count the number of in vivo entities that enter the dosimeter zone <NUM> within a designated time period, determine the size of said in vivo entity or entities, and determine the residence time of a single in vivo entity within the dosimetry zone <NUM>.

Fluorescence detector theory of operation is as follows. Excitation light <NUM> is provided by a high flux, narrow band-width solid state UV source <NUM> such as a UV light emitting diode (LED), as available from Q-Photonics (Ann Arbor, MI) or a compact, solid state laser, as available from Thorlabs (Newton, NJ). Typical output power can range from but limited to <NUM> - <NUM> mW, and typical bandwidth can range from but not limited to <NUM> to <NUM>. The wavelength of UV source <NUM> is selected to be an appropriate choice for the excitation wavelength of the employed in vivo internal standard radical dosimeter. A focusing lens assembly <NUM> is used to focus excitation light to a narrow beam waste on the order of <NUM> - <NUM>µmeters within the center of the dosimetry zone <NUM>, creating the probed dosimetry zone. Excitation light is directed to strike the dosimetry zone <NUM> that may contain an in vivo entity or entities, by dichroic mirror <NUM>. Dichroic mirror <NUM> preferentially reflects light of the excitation wavelength while simultaneously being transparent for light of longer wavelength, such as that of the fluorescence emission light <NUM>. Fluorescence emission light <NUM> is collimated using collimator <NUM>. After collimation, emission light can be optionally filtered by notch filter <NUM>, to selectively transmit light of the appropriate emission wavelength. Notch filter <NUM> may be required as collected emission light may be comprised of both fluorescence light as well as a small amount of original excitation light that transmits through dichroic mirror <NUM>, which was created by the back-scatter of excitation light incident to cell optical surfaces and probed contents. Emission light is directed to ultimately strike fluorescence/emission photodetector <NUM>, which serves to measure the intensity of the fluorescence/emission light. Photodetector <NUM> may comprise a UV responsive silicon photodiode such as the S1336-8BQ silicon photodiode available from Hamamatsu (Hamamatsu City, Japan). Alternatively, photodetector <NUM> may comprise a compact photo-multiplier tube (PMT) such as Micro PMT assembly H12400 available from Hamamatsu. Photodetector <NUM> output current is processed by a current to voltage (I to V) convertor to provide a voltage that is proportional to incident emission light intensity <NUM>. Photodetector <NUM> output voltage is transmitted to control electronics <NUM>, where an analog to digital converter (ADC) creates a digital signal that is ultimately transmitted to the instrument controller <NUM> where fluorescence calculations are performed.

Light scatter detector theory of operation is as follows. Excitation light <NUM> from UV source <NUM> is focused by lens <NUM> and reflected by dichroic mirror <NUM> to enter dosimetry zone <NUM>. Upon incidence with an in vivo entity located within the probed region of the dosimetry zone <NUM>, incident excitation light <NUM> is elastically scattered. Due to the size difference between the incident excitation wavelength (nm) and in vivo entity size (µm), the scattered light <NUM> is preferentially detected orthogonally with respect to the incident excitation light. Scattered light <NUM> is collimated by collimator <NUM> and ultimately strikes scatter photodetector <NUM>. For a given excitation light intensity, the measured intensity of scattered light will be proportional to the size and number of in vivo entities located within the dosimetry zone <NUM> probed volume. As scattered light detection is being performed in an orthogonal direction with respect to incident excitation light, measured back-ground scatter, in the absence of in vivo entities, attributed to elastic and inelastic scatter of probed volume contents, as well as elastic scatter from radical dosimeter <NUM> optical surfaces are extraordinarily low, creating a very low background signal.

Scatter Photodetector <NUM> may comprise a UV responsive silicon photodiode such as the S1336-8BQ silicon photodiode available from Hamamatsu (Hamamatsu City, Japan). Alternatively, photodetector may comprise a compact photo-multiplier tube (PMT) such as Micro PMT assembly H12400 available from Hamamatsu. Scatter photodetector <NUM> output current is processed by a current to voltage (I to V) convertor to provide a voltage that is proportional to incident scatter light <NUM>. Photodetector <NUM>) output voltage is transmitted to control electronics <NUM>, where an analog to digital converter (ADC) creates a digital signal that is ultimately transmitted to the instrument controller <NUM> where light scatter calculations are performed.

Disclosed embodiments include methods of determining and controlling cell-to-cell isolation volume to enable reproducible in vivo radical dosimetry. For in vivo HRPF radical dosimetry to be effectively implemented, photometric measurements of an internal standard radical dosimeter should be performed when the in vivo entity or entities are present within the dosimetry zone, to enable meaningful comparative measurements that represent differences in cell-to-cell, intracellular radical dosimeter response.

<FIG> depicts methods <NUM> of determining and controlling cell-to-cell isolation volume using the described disclosure herein that further enables the detection of in vivo entities within the dosimetry zone. In an introduce cell step <NUM>, a single file array of cells is formed as described elsewhere herein, and introduced into mixer <NUM> from which it flows into dosimetry zone <NUM>. In a detect first cell step <NUM> a signal from Scatter photodetector <NUM> is monitored to detect the arrival time of said first cell into the dosimetry zone <NUM>. Upon the entrance of a cell or other in vivo biological entity within the dosimetry zone, the intensity of scattered excitation light <NUM> increases in accordance with the in vivo entity size and number of in vivo entities within the probed region. In a detect second cell step <NUM> the process described above is used to detect the arrival time of a second cell into the dosimetry zone <NUM>. The net flow rate for the system is calculated <NUM> by summing the pumping speeds of syringe pump <NUM>, syringe pump <NUM>, and syringe pump <NUM>. The flow rate can be reduced to the point where the time between detection of the first cell and the cell is long enough to reduce the probability that two cells will be in the dosimetry zone <NUM> at the same time. This achieves single cell isolation in which the conditions allow the irradiation and oxidation of one cell at a time.

In a calculate cell isolation volume step <NUM>, the cell-to-cell isolation volume is determined by multiplying the arrival time difference between the first and second cells by the net flow rate <NUM>. If the empirically determined cell isolation volume deviates by less than +/- <NUM>% (or some other predetermined limits) from the desired isolation volume (which is directly related to a separation distance and separation time), then the system proceeds to label additional cells without further adjustment in a proceed step <NUM>. Proceed step <NUM> optionally includes the methods illustrated in <FIG>. Optionally, should the empirically determined cell isolation volume deviate by greater than +/- <NUM>%, sheath flow syringe pump <NUM> pumping speed is altered, in an adjust sheath flow rate step <NUM>, to achieve the desired cell isolation target volume <NUM> and the determination process repeated <NUM> until target cell isolation volume is achieved.

Various embodiments include systems and method for detecting the presence of in vivo entities within dosimetry zone <NUM>. The detected time of entry and exit of an in vivo entity within the dosimetry zone may be used to determine the data acquisition period for photometrically determining intracellular dosimeter internal standard radical response. Upon entrance into the dosimetry zone <NUM>, the in vivo entity causes a rapid rise in the intensity of scattered light as detected by scatter photodetector <NUM>. Concordantly, upon in vivo entity exit, the intensity of scattered light as detected by scatter photodetector <NUM> precipitously drops. The time difference between the rise and drop of scattered light intensity represents the dosimetry zone dwell period of the in vivo entity, e.g. cell. During the dwell period, light intensity values as detected by emission photo-detector <NUM> are summed and/or integrated to determine the net dosimetry signal for the in vivo entity of interest. By employing this approach, photometric dosimetry may be performed by detecting signals that arise from intracellular and/or extracellular photometric signals, while rejecting any inherent background signal that arises from the extracellular fluid for regions devoid of in vivo entities. As such, the majority of the measured photometric signal will be comprised of that which arises from intracellular components, as the background single for extracellular fluid is, by experimental design, substantially lower than that of intracellular fluid, and measurements are exclusively taken in the presence of an in vivo entity or entities.

Some embodiments include systems and methods for determining the viability of in vivo entities. For a given in vivo entity, scattered light intensity will be proportional to the size and number of in vivo entities present within dosimetry zone <NUM> during photometric assessment. Using the methodology disclosed herein, means to effectively ensure a constant arrival rate of in vivo entities within the dosimetry zone is described. Under such circumstances, the number of in vivo entities for each data acquisition period can be constantly controlled, rendering the variation in measured scattered light to be vastly dependent upon changes in in vivo entity size. Changes of in vivo entity size can be attributed to inherent morphological variation or can be indicative of artifactual alteration in cellular/species morphology, which may be indicative of cellular disruption, cell death, or cellular apoptosis. As the inherent goal of in vivo HRPF is to assess biomolecular complement HOS under viable conditions, it is desirable to detect and signal the presence of inviable processes and/or conditions. Disclosed embodiments described herein provide systems and methods to detect the potential harm to in vivo moieties that may arise from the HRPF protocol, and as such provides a means by which in vivo HOS analysis can be performed for viable and not disrupted in vivo entities. For example, a disrupted cell or the presence of more than one cell within the dosimetry zone <NUM> at the same time can be detected based on the measured light scattering. These detected entities under these circumstances may be separated from entities that were not irradiated under these conditions and discarded.

Disclosed embodiments include systems and methods for triggering the flash photolysis light 103in sync with arrival of an in vivo entity into the photolysis zone <NUM>. In vivo HRPF ideally includes determining and quantitating the presence of an in vivo entity within the photolysis zone in order to reliably irradiate said entity or entities in a reproducible manner and to photo-catalytically create a reproducible, intracellular OH radical load.

<FIG> depicts methods <NUM> of determining the arrival of an in vivo entity into the photolysis zone <NUM>, while providing systems and methods by which the flash photolysis light <NUM> is precisely triggered to flash upon the arrival of the in vivo entity into said photolysis zone. In an introduce cell step <NUM> a single file array of cells is formed as described elsewhere herein, and a first cell is introduced into photolysis zone <NUM>. In a detect step <NUM> the output signal of scatter photodetector <NUM> is monitored to detect the arrival time of said first cell into the dosimetry zone <NUM>. Upon the entrance of a cell or other in vivo entity within the dosimetry zone <NUM>, the intensity of scattered light increases in accordance with the in vivo entity size and number of in vivo entities within the probed region. This increase is detected by scatter photodetector <NUM>. In a determine net flow rate step <NUM>, the net flow rate for the system is calculated by summing the pumping speeds of syringe pump <NUM>, syringe pump <NUM>, and syringe pump <NUM>. In a determine interconnect volume step <NUM>, as a direct manifestation of the microfluidic system design, the interconnect volume that extends from the photolysis zone and the dosimetry zone is determined and remains constant during the in vivo HRPF process. In a determine transit time step <NUM>, the transit time required for an in vivo entity to travel from the photolysis zone <NUM> to the dosimetry zone <NUM> is calculated by dividing the interconnect volume by the net flow rate. In a determine photolysis zone arrival time step <NUM>, the photolysis zone arrival time is calculated by determining the difference of the dosimetry zone arrival time and the photolysis zone to dosimetry zone transit time. In a trigger step <NUM>, for subsequent cells or in vivo entities, the photolysis system is triggered to flash at the determined photolysis zone arrival time or a consistent interval thereafter. In a continue process step <NUM>, the process proceeds and additional labeled cells are deposited within labeled cell reservoir <NUM> until a target number of cells has been processed.

While the teachings herein describe particular utility of detection signals that arise from light scatter photodetector <NUM> and fluorescence/emission photodetector <NUM>, it will be obvious to those of ordinary skill in the art that the afore said detectors could be used for the purpose of detecting in vivo entity arrival into the dosimetry zone <NUM> or for the purpose of predicting the arrival of an in vivo entity into the photolysis zone <NUM> by a plurality of undescribed combinations or means. For example, signals generated at fluorescence/emission photodetector <NUM> could be summed in temporal coherence with those from light scatter photodetector <NUM> to improve the overall sensitivity to detect the presence of an in vivo entity within the dosimetry zone. As such, the methodologies described herein are intended to be exemplary and not restrictive in scope.

Disclosed embodiments include systems and methods of calibrating a closed-loop control radical dosimetry system. In these embodiments, the closed-loop control radical dosimetry system comprises calibration logic that is used to predict the required change in optical fluence or hydrogen peroxide concentration in response to measured radical dosimeter photometric fluorescence change. The calibration function is empirically determined through a plurality of measurements for which a known or control mixture of supporting buffer, in vivo entity, and radical dosimeter are treated with a single flash of light for each distinct control aliquot at a various fluence or H<NUM>O<NUM> concentration levels. In an exemplary embodiment, a software routine running in either the low level instrument control or high level user interface programs (e.g., control electronics <NUM> and/or instrument controller <NUM>), generates a look-up table or curve fit that describes the measured change in dosimeter photometric fluorescence at each fluence or H<NUM>O<NUM> concentration, allowing for the creation of a mathematical expression, or calibration function, that describes the relationship between applied fluence and/or H<NUM>O<NUM> concentration and measured dosimeter fluorescence change for a single flash exposure. In another embodiment, the look-up table and subsequent calibration function is manually generated by the user employing fluorescence change values for each flash voltage value and/or H<NUM>O<NUM> concentration.

During in vivo HRPF processing, background hydroxyl radical scavenging is assessed via dosimetry. The measured change in dosimeter photometric fluorescence is compared to a user specified targeted change. When the measured dosimeter value deviates by > +/- <NUM>% from the target value, the applied fluence or H<NUM>O<NUM> concentration is altered to achieve the targeted change of measured dosimeter absorbance. The above calibration function is used to predict the required change in fluence or H<NUM>O<NUM> concentration.

Disclosed embodiments include post-analytical normalization of labeled product abundance. In these embodiments, spectral irradiance and/or H<NUM>O<NUM> concentration is altered to adjust for unwanted changes in background scavenging of OH radicals and, as such, represents a pre-analytical or pre-data processing scheme of correction. It is also possible to apply scavenging correction to acquired HRPF data in a post-analytical or data processing manner. During post-analytical correction, the measured abundance of the oxidized species for an experimental trial, as detected by mass spectrometry or some other detection scheme such as but not limited to isoelectric focusing electrophoresis, is normalized by multiplying said response by a normalization factor derived from the ratio of dosimeter fluorescence change determined between the experimental trial and reference trial. Specifically, the normalization factor is the ratio of the measured dosimeter fluorescence change of the experimental trial divided by the measured dosimeter fluorescence change of the reference trial. Alternatively, the normalization factor could comprise the ratio of the measured dosimeter fluorescence change of the reference trial divided by the experimental trial. In this manner, for example, the ion current for a given protein mass spectrometry (MS) measurement or peptide single MS or tandem MS measurement could be adjusted by multiplying said ion current value by the determined normalization factor. The application of pre-analytical and post-analytical normalization schemes are not mutually exclusive, and could be employed alternatively or in tandem to achieve higher levels of compensation than achievable otherwise. In one embodiment, post-analytical normalization is applied to data acquired from in vivo HRPF experiments performed under the control of pre-analytical scavenging correction.

In vivo Radical Dosimetry System for Hydroxyl Radical Protein Foot-Printing have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the scope of the appended claims. The inventive subject matter, therefore, is not to be restricted except in the disclosure. Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be presented or utilized, or combined with other elements, components, or steps that are not expressly referenced.

While biological cells are used herein to illustrate disclosed embodiments, in alternative embodiments, the "cells" may be replaced, in any examples, by other entities such as biological entities, viruses, multi-cellular organisms (e.g., fungi, spores, nanobes, molds, algae, nematodes, amoeba, protozoa, Trichoplax adhaerens or yeasts).

The logic discussed herein can include electronic circuits, hardware, firmware, and/or software store on a non-transient computer readable medium.

Claim 1:
An analysis system (<NUM>, <NUM>) comprising:
a photolysis zone (<NUM>),
a sample introduction system (<NUM>) configured to provide intact biological entities to the photolysis zone (<NUM>), the biological entities being isolated from each other in a focused sheath flow;
a photolysis light source (<NUM>) configured to generate light to generate hydroxide radicals within the photolysis zone (<NUM>) from a source of hydroxide radicals;
the photolysis zone (<NUM>) being configured to receive the sheath flow including the biological entities and the light of the photolysis light source (<NUM>) so as to oxidize a dosimeter internal standard and so as to oxidize biological compounds of the biological entities in vivo,
a radical dosimeter (<NUM>) comprising a dosimetry zone (<NUM>) and a fluorescence/emission photodetector (<NUM>), wherein
the dosimetry zone (<NUM>) is configured to receive the biological entities from the photolysis zone (<NUM>), and wherein the fluorescence/ emission photodetector (<NUM>) is configured to detect oxidation of the dosimeter internal standard, resulting from reaction of the dosimeter internal standard and the hydroxide radicals, within the dosimetry zone;
control logic (<NUM>, <NUM>) configured to determine based on the detected oxidation of the dosimeter internal standard if a target concentration of hydroxide radicals was generated for each of the biological entities and, when it is determined that the target concentration of hydroxide radicals was not generated for each of the biological entities, to control the sample introduction system (<NUM>) and/or the photolysis light source (<NUM>) to adjust conditions of the photolysis zone (<NUM>) to meet the target concentration of hydroxide radicals; and
a reservoir (<NUM>) configured to receive the biological entities including the oxidized biological compounds, characterized in that
the radical dosimeter (<NUM>) further comprises a scattered light detector (<NUM>),
wherein the scattered light detector (<NUM>) is configured to detect presence of the biological entities within the dosimetry zone (<NUM>).