Patent Description:
In life sciences, it may be necessary to measure the viscosity of liquid samples comprising protein. High confidence in these viscosity measurements is often critical to the research being performed and the development of therapeutic protein products. The cone and plate method is commonly used to measure the viscosity in these situations. The cone and plate method is a dynamic viscosity measurement method that measures the viscosity of a sample based on varied applied rotational shear stress and shear rates. The cone and plate method is appreciated by those with ordinary skill in the art as generally being highly precise and accurate. Other methods of viscosity measurement, e.g., Rheosense Initium and Malvern Viscosizer, may also be used.

The process of moving liquids with the application of acoustic signals is known as Acoustic Droplet Ejection (ADE). Further details about ADE are discussed in <NPL>. <CIT> discloses methods of ejecting droplets containing a non-Newtonian fluid by an acoustic droplet ejector can include applying a tone burst of focused acoustic energy to a fluid reservoir containing a non-Newtonian fluid at sufficient amplitude to effect droplet ejection according to a tone burst pattern. <CIT> relates to the efficient transport of a small volume of fluid, such as may be required by mass spectrometers and other devices configured to process and/or analyze small samples of biomolecular fluids, such transport involves nozzleless acoustic ejection.

Any "embodiment" or "example" which is disclosed in the description but not covered by the claims should be considered as presented for illustrative purpose only. One aspect of the present disclosure provides a method including (a) positioning the liquid sample of the protein in a first location of an acoustic liquid handler; (b) applying, using the acoustic liquid handler, one or more first acoustic signals until a specified amount of the liquid sample has been transferred from the first location to a second location of the acoustic liquid handler; and (c) determining the viscosity of the liquid sample based on (i) a number of the one or more first acoustic signals required to transfer the specified amount of the sample from the first location to the second location and (ii) a set of parameters of the first acoustic signal. Additionally or alternatively, the viscosity may be determined based on any of (i) SubEject Power(dB) required to transfer the specified amount of the sample to the second location, (ii) SubEjectAmp(Volt) required to transfer the specified amount of the sample to the second location, (iii) New EjectAmp(Volt) required to transfer the specified amount of the sample to the second location, (iv) New EjectAmp+ThreshdB(Volt) required to transfer the specified amount of the sample to the second location, and/or (v) Power Difference(Volt) required to transfer the specified amount of the sample to the second location.

Another aspect of the present disclosure provides a method including (a) positioning the sample of the protein in a first location of an acoustic liquid handler; (b) iteratively applying, using the acoustic liquid handler, one or more acoustic signals to the sample in the first location until it is determined that a specified amount of sample has been transferred from the first location to the second location; and (c) determining the viscosity of the sample based on a number of iterations required to transfer the specified amount of the sample to the second location. Additionally or alternatively, the viscosity may be determined based on SubEject Power(dB), SubEjectAmp(Volt), New EjectAmp(Volt), a sum of New EjectAmp+ThreshdB(Volt), or Power Difference(Volt) required to transfer the specified amount of the sample to the second location.

Another aspect of the present disclosure is an acoustic liquid handler. The acoustic liquid handler has a first location with one or more wells adapted to receive a sample. The acoustic liquid handler is configured to apply one or more first acoustic signals to the sample in the first location until a specified amount of the sample has been transferred from the first location to a second location of the acoustic liquid handler. The acoustic liquid handler has a controller configured to determine the viscosity of the sample based on a number of first acoustic signals required to transfer the specified amount of the sample from the first location to the second location. Additionally or alternatively, the viscosity may be determined based on SubEject Power(dB) required to transfer the specified amount of the sample to the second location, SubEjectAmp(Volt) required to transfer the specified amount of the sample to the second location, New EjectAmp(Volt) required to transfer the specified amount of the sample to the second location, New EjectAmp+ThreshdB(Volt) required to transfer the specified amount of the sample to the second location, or Power Difference(Volt) required to transfer the specified amount of the sample to the second location.

In further accordance with any one or more of the foregoing aspects, the method and/or the acoustic liquid handler may further include any one or more of the following preferred forms.

In some forms, the specified amount of the sample to be transferred is all or substantially all of the sample.

In some forms, the specified amount of the sample to be transferred is a minimum amount of the sample required to create a displacement along one or more axes of a meniscus of a portion of the sample remaining in the first location.

In some forms, the controller is configured to measure an amount of the sample transferred using a fluid measurement technique.

In some forms, the controller is configured to determine the viscosity of the sample based on the set of parameters of the first acoustic signal.

In some forms, the parameters include at least two of a frequency, a power, an amplitude, a wavelength, a bandwidth, and a period.

In some forms, the one or more first acoustic signals each have a frequency in the range of <NUM> to <NUM>, such as <NUM> to <NUM> or <NUM> to <NUM>. In some forms, the one or more first acoustic signals each have a power in the range of <NUM> dB to <NUM> dB, such as <NUM> - <NUM> dB or <NUM> - <NUM> dB. In some forms, the controller is configured to vary a set of parameters of the acoustic liquid handler until the specified amount of sample has been transferred.

In some forms, the controller is configured to iteratively increase the frequency of the first acoustic signal.

In some forms, the controller is configured to iteratively increase the frequency of the first acoustic signals by no more than <NUM> or no more than <NUM> per iteration.

In some forms the controller determines whether the specified amount of the sample has been transferred.

In some forms, the controller determines whether the specified amount of the sample has been transferred by: applying one or more second acoustic signals to a first portion of the sample not transferred from the first location; determining an amount of the first portion of the sample not transferred based on the application of the one or more second acoustic signals; determining an amount of a second portion of the sample transferred based on the determination of the amount of the first portion of the sample not transferred; and comparing the amount of the second portion and/or first portion of the sample to the specified amount of the sample to be transferred.

In some forms, the amount of the first portion of the sample not transferred is determined based on an impression that forms on a meniscus of the first portion of the sample not transferred responsive to the application of the one or more second acoustic signals.

In some forms, the sample has a volume of at least <NUM>µL and no more than <NUM>µL.

In some forms, the sample has a volume of approximately <NUM>µL.

In some forms, the first location is a first well of a source plate removably disposed in the acoustic liquid handler and the second location is a first well of a destination plate removably disposed in the acoustic liquid handler, wherein the first well of the destination plate is inverted with respect to the first well of the source plate.

In some forms, the controller determines the viscosity of the sample by comparing the number of the one or more acoustic signals to a predetermined relationship between the number of the one or more first acoustic signals and the viscosity for the set of parameters of the one or more first acoustic signals. For example, in some forms, the controller is calibrated based on a predetermined relationship between viscosity for a standard or known substance (e.g. cone-plate derived cP) and the number of first acoustic signals required to transfer the specified amount of the standard or known substance (e.g., acoustic iterations). In some forms, the controller may be calibrated based on a predetermined relationship between viscosity for a standard or known substance (e.g. cone-plate derived cP) and SubEject Power(dB) required to transfer the specified amount of the standard or known substance, SubEjectAmp(Volt) required to transfer the standard or known substance, New EjectAmp(Volt) required to transfer the specified amount of the standard or known substance, New EjectAmp+ThreshdB(Volt) required to transfer the specified amount of the standard or known substance, and/or Power Difference(Volt) required to transfer the specified amount of the standard or known substance. The calibrated controller may be used to determine the viscosity of one or more samples, including samples of unknown composition and/or unknown viscosity. The one or more samples may be different from each other. The determinations of viscosity for the one or more samples may be made without further calibration of the controller.

In some forms, the controller updates the predetermined relationship for the set of parameters based on the number of the one or more first acoustic signals and the determined viscosity of the sample.

In some forms, a mass spectrometry apparatus configured to generate mass spectrometric data from the sample, optionally wherein the one or more first acoustic signals are configured to transfer the sample or a portion thereof to the mass spectrometry apparatus.

In some forms, the mass spectrometry data are generated using electrospray ionization, atmospheric pressure ionization, atmospheric pressure chemical ionization, atmospheric matrix-assisted laser desorption/ionization, wherein said viscosity may be determined concurrently with said mass spectrometry data.

In some forms, an analytical device to perform an analysis on the sample, optionally wherein the one or more first acoustic signals transfer the sample to the analytical device from the first and/or second location.

In some forms, the analytical device comprises a mass spectrometer, a liquid chromatography device, a spectrophotometric device, a glycan analysis device, an infrared detector, a fluorescence plate reader, or combinations thereof.

In some forms, the acoustic liquid handler is configured to determine whether the sample is within specification or defective based on the measured viscosity of the sample. A specification refers to one or more specified parameters indicating the acceptability of the sample when the characteristics of the sample (e.g., viscosity) fall within the specified parameters. If the characteristics of the sample do not fall within the specified parameters, the sample may be considered defective.

In some forms, the method and/or acoustic liquid handler may be performed on at least <NUM> additional samples within two hours.

The figures described below depict various aspects of the system and methods disclosed herein. It should be understood that each figure depicts an embodiment of a particular aspect of the disclosed system and methods, and that each of the figures is intended to accord with a possible embodiment thereof. Further, whenever possible, the following description refers to the reference numerals included in the following figures, in which features depicted in multiple figures are designated with consistent reference numerals.

As discussed above, it may be necessary to measure the viscosity of liquid samples comprising protein. Because very small amounts (e.g., volumes) of liquid samples (in some instances, as little as <NUM>µL) are often of interest in research, it may be necessary to measure the viscosity of those very small amounts of liquid samples of protein. Conventional viscosity measurement techniques, however, present disadvantages, for example in terms of throughput, speed, and sample consumption.

For example, the conventional cone and plate viscosity measurement method discussed above typically requires <NUM>µL of a liquid sample to produce an accurate viscosity measurement. Therefore, when less than <NUM>µL of the liquid sample is available, the cone and plate method may be inoperable or inaccurate for measuring the viscosity of the liquid sample. The cone and plate method is also a destructive measurement method in that the liquid sample is typically difficult or impossible to recover after the completion of the viscosity measurement. This is because the cone and plate method measurement process comprises spinning the liquid sample with a rotating cone while tracking rotational shear stress and shear rates to determine viscosity. The result of the rotation of the cone is that the liquid sample is spun into a puddle on the plate with a high surface-area-to-volume ratio. Some of the liquid sample may spin off the plate and into other areas or components of the cone and plate testing machine. And even if the liquid sample can be recovered, it is likely that the fidelity of the liquid sample will be affected (for example, by contamination and/or damage to the sample) and the recovered liquid sample will be unsuitable for use in future research. Thus, even when more than <NUM>µL of the liquid sample is available, the destructive nature of the cone and plate method may destroy all of, or a substantial portion of, the liquid sample in the measurement process. The destruction of all of, or a substantial portion of, the liquid sample consumes limited resources, and inhibits the repeatability of the research. Another problem is that the conventional cone and plate method is a manual method. Thus while the cone and plate method can provide measurements with a high degree of accuracy, this only happens when performed under ideal operation. If the operator does not utilize proper techniques when performing the cone and plate method, the measured viscosity of the liquid sample can be skewed, presenting challenges in assay-to-assay comparisons.

Other methods of viscosity measurement of small liquid samples present problems as well. For example, the Rheosense Initium method has not demonstrated high accuracy and precision for highly viscous liquid samples, requires an approximate range of viscosity to be known prior to the measurement to function as intended, and does not take into account shear rates. As another example, the Malvern Viscosizer method also uses glycerol standards and also does not take into account shear rates. Moreover, the Rheosense Initium instrument and the Malvern Viscosizer instrument each are serial instruments (which run one sample at a time), and are subject to capillary clogging, which can entail enhanced cleaning and drying procedures (it is noted that residual liquid in the capillaries of these instruments can dilute a sample and skew viscosity readings). The enhanced cleaning and drying procedures can lead to run times of over one hour per sample.

The present disclosure aims to reduce these problems by providing a highly accurate and precise method and system for determining the viscosity of a liquid sample of a protein using an acoustic liquid handler that moves the liquid sample from a first location to a second location. The method and system non-destructively determine viscosity of smaller amounts of the liquid sample than measurable by conventional methods such as the cone and plate method. In fact, the disclosed method and system may be used to accurately determine the viscosity of a liquid sample with as little as <NUM>µL of the liquid sample. Moreover, because the disclosed method and system are non-destructive, the liquid sample may be recovered from the second location without affecting the fidelity of the liquid sample. Therefore, the liquid sample may be reused, maintaining the repeatability of the research and conserving resources. For example, after the determination of viscosity, the liquid sample may be used for additional analysis such as for additional analytics such as, but not limited to high throughput dynamic light scattering viscosity (See <NPL>), and colloidal stability measurements (See <NPL>), biotherapeutic high molecular weight analysis by size exclusion chromatography (See <NPL>) and high throughput mass spectrometric analytics (See <NPL>). The disclosed method and system is also substantially, if not entirely, automated such that performance is not dependent on operator technique. The automated method and system are also significantly faster than the cone and plate method, producing results on the timescale of seconds per liquid sample rather than minutes per liquid sample (as required for the cone and plate method).

<FIG> illustrates one example of a system <NUM> for determining a viscosity of a liquid sample of a protein constructed in accordance with the teachings of the present disclosure. As illustrated in <FIG>, the system <NUM> includes an acoustic liquid handler <NUM> having a first location <NUM> adapted to receive the liquid sample and a second location <NUM> adapted to receive the liquid sample from the first location <NUM>. As will be discussed in greater detail below, the acoustic liquid handler <NUM> is configured to apply one or more first acoustic signals to the liquid sample in the first location <NUM> until a specified amount of the sample has been transferred from the first location <NUM> to the second location <NUM>. The system <NUM> is in turn configured to determine the viscosity of the sample based on a number of the one or more first acoustic signals required to transfer the specified amount of the sample from the first location <NUM> to the second location <NUM>.

The acoustic liquid handler <NUM> illustrated in <FIG> is a standalone scientific instrument such as the Echo <NUM> Acoustic Liquid Handler manufactured by Labcyte or the ATS-<NUM> instrument manufactured by EDC Biosystems, though in other examples, the acoustic liquid handler <NUM> may be incorporated into a broader scientific instrument. The acoustic liquid handler <NUM> generally uses the ADE process of applying ultrasonic pulses to eject droplets of the liquid sample, allowing for contactless and highly-precise transfer of small amounts of the liquid sample from the first location <NUM> to the second location <NUM>. The acoustic liquid handler <NUM> may be used to transfer small amounts (e.g., small volumes) of the liquid sample that are in the range of, for example, milliliters, microliters, nanoliters, picoliters, or other small volumes or amounts of the liquid sample. While in this example the acoustic liquid handler <NUM> is used in connection with samples of proteins such as therapeutic proteins, the acoustic liquid handler <NUM> may instead be used to determine the viscosity of samples of nucleic acids (such as DNA and/or RNA), surfactants, serums, cell cultures, or other liquid samples of interest. Examples of therapeutic proteins include an antibody (such as a monoclonal antibody), an antigen-binding antibody fragment, an antibody protein product, a hormone, a growth factor, a cytokine, a cell-surface receptor or a ligand thereof, a fusion protein, a chimeric protein, a PEGylated protein, a peptide, a protein fragment or a conjugate comprising a protein (for example an antibody-drug conjugate or antibody-nucleic acid conjugate). Antibody protein products include those based on the full antibody structure and those that mimic antibody fragments which retain full antigen-binding capacity, e.g., scFvs, Fabs and VHH/VH. Examples of antibody protein products include, without limitation a single chain antibody (SCA); a nanobody; a bispecific T cell engager molecule; a diabody; a triabody; a tetrabody; and multispecific antibodies (such as bispecific antibodies or trispecific antibodies). In some embodiments, the antibody protein product comprises or consists of a bispecific T cell engager (BiTE®) molecule. BiTE® molecules refer to engineered bispecific antibody protein product formats See <NPL>). They comprise the fusion of two single-chain variable fragments (scFvs) of different antibodies, or amino acid sequences from four different genes, on a single peptide chain, typically of about <NUM> kilodaltons. One of the scFvs binds to T cells via the CD3 receptor, and the other to a tumor cell via a tumor specific molecule.

In this example, the first location <NUM> is a plate or tray having a plurality of wells that facilitate a high-throughput liquid transfer of the sample. More particularly, the first location <NUM> is a plate having <NUM> wells each configured to receive a portion of the sample. Alternatively, the plate may have <NUM> wells, <NUM> wells, <NUM> wells, or any other number of wells for high-throughput liquid transfer. In other examples, the first location <NUM> may be a single well. In yet other examples, the plate of the first location <NUM> may be replaced by any one of one or more jars, beakers, troughs, pens, flasks, test tubes, cylinders, burettes, microfluidic or nanofluidic array, or any other suitable receptacles for holding the liquid sample. In this example, the plate that defines the first location <NUM> is removable from the acoustic liquid handler <NUM> to allow for convenient dispensing of the liquid sample into the well or wells of the first location <NUM>. The plate can in turn be loaded into the acoustic liquid handler <NUM> in preparation for ADE operation of the acoustic liquid handler <NUM>. In other examples, however, the plate (or other component defining the first location <NUM>) can be an integral part of the acoustic liquid handler <NUM>.

As also illustrated in <FIG>, the second location <NUM> is inverted with respect to the first location <NUM> and positioned above the first location <NUM>. The liquid samples transferred from the first location <NUM> into the second location may be held in the second location due to the surface tension of the liquid sample, or any other suitable method of holding the liquid sample in the second location such as the use of an electric field. In other examples, however, the second location <NUM> can be positioned differently relative to the first location <NUM>.

Reference is now made to <FIG> and <FIG>, which depict an interior portion of the acoustic liquid handler <NUM> as well as an acoustic signal emitter <NUM> and a controller <NUM> for determining the viscosity of a liquid sample <NUM> of protein in the first location <NUM>. As discussed above, the amount of the liquid sample <NUM> needed to determine the viscosity using the system <NUM> is a small volume. For example, the volume of the liquid sample <NUM> may, for example, be no more than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>µL of the sample, or some other suitable volume or other amount of the liquid sample <NUM>.

Reference is now made to <FIG> and <FIG>, which depict an interior portion of the acoustic liquid handler <NUM> as well as an acoustic signal emitter <NUM> and a controller <NUM> for determining the viscosity of a liquid sample <NUM> comprising protein in the first location <NUM>. It is noted that the depicted liquid sample <NUM> may comprise one or more samples, any of which may have the same or different viscosity than another sample. As discussed above, the amount of the liquid sample <NUM> needed to determine the viscosity using the system <NUM> is a small volume. For example, the volume of the liquid sample <NUM> may, for example, be no more than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>µL of the sample, or some other suitable volume or other amount of the liquid sample <NUM>.

The acoustic liquid handler <NUM> is configured to apply one or more first acoustic signals to the liquid sample in the first location <NUM> via the acoustic signal emitter <NUM>. The acoustic signal emitter <NUM> focuses each of the first acoustic signals on the surface of the liquid sample in the wells of the plate of the first location <NUM>, causing a mound (which may be referred to as a "displacement") to form on the surface of the liquid sample and a droplet to eject from the liquid sample in the first location <NUM> into a second location <NUM>. The volume of the ejected droplet may be determined based on a set of parameters of the first acoustic signals. The parameters may include one or more of frequency, a power, an amplitude, a wavelength, a bandwidth, a period, or other parameters.

More specifically, as depicted in <FIG>, the acoustic signal emitter <NUM> applies one or more acoustic signals <NUM> to the liquid sample <NUM> contained in a leftmost well of the wells of the plate defining the first location <NUM>, thereby producing a mound <NUM> and ejecting a droplet <NUM> upwards into a leftmost well of the wells of the plate defining the second location <NUM>. It will be appreciated that the other wells of the first location <NUM> contain additional samples from the liquid sample <NUM>, any of which may comprise more of the same sample (for example, to run a sample in duplicate, triplicate, etc.), and/or a different sample (for example, comprising a different protein, concentration, and/or formulation ingredients). The acoustic signal emitter <NUM> is depicted with a rightward arrow to indicate that after the specified amount of the liquid sample <NUM> has been ejected from the leftmost well of the wells of the first location <NUM> and into the leftmost well of the wells of the second location <NUM>, the acoustic signal emitter <NUM> will move rightward to similarly apply one or more acoustic signals <NUM> to each liquid sample contained in each respective well of the other wells of the first location <NUM>. While <FIG> only depicts a single row of wells for each of the first location <NUM> and second location <NUM>, it is worth noting that there can be multiple rows laid out over a grid, or some other arrangement, as shown in the depiction of the first location <NUM> and the second location <NUM> in <FIG>.

In this example, the controller <NUM> is located remotely from but communicatively connected to the acoustic liquid handler <NUM>. In other examples, however, the controller <NUM> may be part of or located proximate to the acoustic liquid handler <NUM>. As illustrated in <FIG>, the controller <NUM> generally includes a processor <NUM>, a memory <NUM>, a communications interface <NUM>, and computing logic <NUM>. One of ordinary skill in the art will appreciate that the controller <NUM> can also include additional components, such as, for example, analog-digital converters, digital-analog converters, amplifiers, sensors, and gauges, which are not explicitly depicted herein. Optionally, the controller <NUM> is calibrated based on a predetermined relationship between viscosity for a standard such as a known substance (e.g., cone-plate derived cP viscosity of the standard) and the number of first acoustic signals required to transfer a specified amount of the standard (e.g., iterations). The linear fit in <FIG> with R<NUM> values of <NUM> - <NUM> suggests that the controller <NUM> can be reliably calibrated based on the relationship between viscosity and the number of first acoustic signals, including for the determination of viscosity for samples of unknown viscosity and/or composition. The calibrated controller <NUM> may be used to determine the viscosity of one or more samples, including samples of unknown composition and/or viscosity. The calibrated controller <NUM> may determine the viscosity of the one or more samples without further calibration. In some examples, the calibration is based on a linear relationship between viscosity for a standard or known substance and the number of first acoustic signals required to transfer a specified amount of the standard or known substance. In some examples, the calibration is based on a determined mathematical relationship between viscosity for a standard or known substance and the number of first acoustic signals required to transfer a specified amount of the standard or known substance, which mathematical relationship may be linear or non-linear. In some examples, the calibration is based on a linear relationship between viscosity for a standard or known substance and any of (i) number of first acoustic signals required to transfer a specified amount of the standard or known substance, (ii) SubEject Power(dB) required to transfer a specified amount of the standard or known substance, (iii) SubEjectAmp(Volt) required to transfer a specified amount of the standard or known substance, (iv) New EjectAmp(Volt) required to transfer a specified amount of the standard or known substance, (v) New EjectAmp+ThreshdB(Volt) required to transfer a specified amount of the standard or known substance, or (vi) Power Difference(Volt) required to transfer a specified amount of the standard or known substance.

The processor <NUM> may be a general processor, a digital signal processor, ASIC, field programmable gate array, graphics processing unit, analog circuit, digital circuit, or any other known or later developed processor. The processor <NUM> operates pursuant to instructions in the memory <NUM>. The memory <NUM> may be a volatile memory or a non-volatile memory. The memory <NUM> may include one or more of a read-only memory (ROM), random-access memory (RAM), a flash memory, an electronic erasable program read-only memory (EEPROM), or other type of memory. The memory <NUM> may include an optical, magnetic (hard drive), or any other form of data storage device.

The communications interface <NUM>, which may be, for example, a HART® interface, a FOUNDATION™ fieldbus interface, a PROFIBUS® interface, or some other port or interface, is provided to enable or facilitate electronic communication between the acoustic liquid handler <NUM> (e.g., the acoustic signal emitter <NUM>) and the controller <NUM> and between any other components of the system <NUM>. This electronic communication may occur via any known communication protocol, such as, for example, the HART® communication protocol, the FOUNDATION™ fieldbus communication protocol, the PROFIBUS® communication protocol, or any other suitable communication protocol.

The logic <NUM> includes one or more routines and/or one or more sub-routines, embodied as computer-readable instructions stored on the memory <NUM>. The controller <NUM>, particularly the processor <NUM> thereof, can execute the logic <NUM> to cause the processor <NUM> to perform actions related to the operation (e.g., control, adjustment), maintenance, diagnosis, and/or troubleshooting of the acoustic liquid handler <NUM> and any components interior to the acoustic liquid handler <NUM> (e.g., the acoustic signal emitter <NUM>), as will be described in greater detail below.

More particularly, the controller <NUM> is generally configured to control the operation of the acoustic signal emitter <NUM>. In particular, the controller <NUM> is configured to provide instructions to the acoustic signal emitter <NUM> to (i) emit one or more acoustic signals <NUM> of a set of parameters towards a first well in the first location <NUM> until the specified amount of the liquid sample <NUM> in that first well is transferred to the second location <NUM>, and (ii) move the acoustic signal emitter <NUM> such that it is positioned under a second well in the first location <NUM>. The controller <NUM> provides instructions to repeat these two steps until a specified set of conditions are met. These conditions may be that a specified number of wells of the first location <NUM> have had a specified amount of the liquid sample transferred to the corresponding wells of the second location <NUM>. The controller <NUM> may be configured to provide instructions to the acoustic signal emitter <NUM> to emit the one or more acoustic signals <NUM> iteratively, varying the specified set of parameters until the specified amount of the liquid sample <NUM> is transferred. These parameters may include one or more of frequency, a power, an amplitude, a wavelength, a bandwidth, a period, or other parameters.

In some examples, the controller <NUM> may also be configured to determine when the specified amount of the liquid sample <NUM> has been transferred from the first location <NUM> to the second location <NUM>. In one example, the controller <NUM> may be configured to directly or indirectly measure an amount of the liquid sample <NUM> transferred from the first location <NUM> to the second location <NUM> using a fluid measurement technique. For example, volume loss in the first location <NUM> (such as volume loss in a well) can be measured to calculate the amount of liquid sample <NUM> transferred. For example, fluid displacement per ping can be measured, and multiplied by the number of pings. For example, droplet volume can be calculated based on one or more parameters as described herein. The amount of fluid transferred can be calculated from the number of droplets transferred. By way of example, from droplet diameter, may be determined from a diameter of a beam of acoustic signal <NUM>. By way of example, droplet diameter and/or volume may be determined optically. The controller may further determine if the amount of the liquid sample <NUM> transferred is the specified amount of the liquid sample <NUM> to be transferred. The controller may determine whether the specified amount of the liquid sample <NUM> has been transferred by (i) commanding the acoustic signal emitter <NUM> to apply one or more second acoustic signals to a first portion of the liquid sample <NUM> not transferred from the first location, (ii) determining an amount of the first portion of the liquid sample <NUM> not transferred based on the application of the second acoustic signals, and (iii) determining an amount of a second portion of the liquid sample <NUM> transferred based on the determination of the amount of the first portion of the liquid sample <NUM> not transferred. After determining the amount of the liquid sample <NUM> transferred, the controller <NUM> may compare the amount of the second portion and/or first portion of the sample to the specified amount of the liquid sample <NUM> to be transferred. If the specified amount of the liquid sample <NUM> has been transferred, the controller may command the acoustic signal emitter <NUM> to stop applying acoustic signals <NUM> to the current well and move to a different well.

In one example, the specified amount of the liquid sample <NUM> to be transferred may be all of the liquid sample <NUM>. In another example, the specified amount of the liquid sample <NUM> to be transferred may be a majority, a substantial portion (but not all), or some other portion of the liquid sample <NUM>. As used herein, a "substantial portion" of the liquid sample refers to a volume for which the number of iterations of acoustic signal required to move that volume is reproducible. If additional numerical detail is of interest, a substantial portion may refer to at least <NUM>%, <NUM>%, <NUM>%, or <NUM>% of the sample. As used herein, "substantially all" refers to a portion of the liquid sample for which the remaining amount of liquid sample is a volume insufficient to be moved by a reproducible number of iterations of acoustic signal. If additional numerical detail is of interest, substantially all of the liquid sample may refer to at least <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of the sample. In another example, the specified amount of the sample to be transferred is an amount sufficient to create a displacement along one or more axes on a meniscus of a portion of the liquid sample <NUM> remaining in the first location <NUM>. This displacement may be referred to as a mound, for example, the mound <NUM> depicted in <FIG>, which is formed when the acoustic energy focused on the liquid sample <NUM> in the first location <NUM> overcomes a threshold of ejection determined by the surface tension of the liquid sample <NUM>, causing ejection of a droplet, e.g., the droplet <NUM>, due to Rayleigh-Taylor instability, as discussed above in the background section.

The controller <NUM> may iteratively vary the parameters of the acoustic signals <NUM> until the specified amount of the liquid sample <NUM> has been transferred. The controller <NUM> may, for example, adjust the frequency of the acoustic signals <NUM>, iteratively increasing the frequency by no more than <NUM>, or by no more than <NUM> per iteration. In some examples, the applied acoustic signals <NUM> may have a frequency in the range of <NUM> to <NUM>, such as <NUM> to <NUM> or <NUM> to <NUM>. In other examples, depending on equipment used and intended use, the frequency range may be significantly wider than the range of <NUM> to <NUM>. The controller <NUM> may alternatively or additionally adjust other acoustic signal parameters, including a power, an amplitude, a wavelength, a bandwidth, a period, or combinations thereof. Power can be measured either directly in decibels of the output acoustic signals <NUM>, or indirectly, for example, by measuring a voltage applied to a transducer of the acoustic signal emitter <NUM>. In some examples, the power of the acoustic signals <NUM> may be in the range of <NUM> dB to <NUM> dB, such as <NUM> - <NUM> dB or <NUM> - <NUM> dB. In other examples, depending on equipment used and intended use, the power range may be significantly wider than the range of <NUM> dB to <NUM> dB.

When the specified amount of the liquid sample <NUM> has been transferred, e.g., as illustrated in <FIG>, which depicts all of the liquid sample <NUM> being transferred from the first location <NUM> to the second location <NUM>, the controller <NUM> is further configured to determine the viscosity of the liquid sample <NUM> based on a number (or quantity) of the acoustic signals <NUM> applied by the acoustic signal emitter <NUM> that are required to transfer the specified amount of the liquid sample <NUM> from the first location <NUM> to the second location <NUM>. For example, the controller <NUM> may determine that a first sample of the liquid sample <NUM> has a first viscosity when fifty acoustic signals <NUM> are required to transfer the specified amount of the liquid sample <NUM> from the first location <NUM> to the second location <NUM>, but that a second sample of the liquid sample <NUM> has a second viscosity, higher than the first viscosity, when one-hundred acoustic signals <NUM> are required to transfer the specified amount of the liquid sample <NUM> from the first location <NUM> to the second location <NUM>. The Applicant has discovered that there is a correlation between the viscosity of the liquid sample <NUM> and the number of the acoustic signals <NUM> required to transfer the specified amount of the liquid sample <NUM> from the first location <NUM> to the second location <NUM>. This correlation may be a <NUM>:<NUM> correlation, a <NUM>:<NUM> correlation, or some other correlation. In any event, the controller <NUM> may execute the logic <NUM> to cause the processor <NUM> to determine the viscosity of the sample <NUM> by comparing the number of the acoustic signals <NUM> applied to a predetermined relationship, stored in the memory <NUM>, between the number of the acoustic signals applied and the viscosity. The stored predetermined relationship may be for one or more parameters as described herein.

In some examples, controller <NUM> may determine the viscosity of the liquid sample <NUM> based on the number of the acoustic signals <NUM> required to transfer the specified amount and other factors or data. As an example, the viscosity determination may further be based on one or more parameters of the acoustic signals <NUM>, e.g., based on the frequency (or frequencies) of the applied acoustic signals <NUM>. Further yet, in some examples, when the controller <NUM> makes a viscosity determination, the controller <NUM> may update the predetermined relationship stored in the memory <NUM> to include that viscosity determination (by, for example, updating the predetermined relationship based on the number of the acoustic signals <NUM> required to transfer the specified amount and any other known factors or data). That is, the predetermined relationship may be further refined based on further empirical data.

In some examples, once the viscosity has been determined for a portion of the liquid sample <NUM> or the entire liquid sample <NUM>, the controller <NUM> may make a determination on whether the measured viscosity is acceptable (e.g., for facilitating analysis of the liquid sample <NUM>). The measured viscosity may be determined to be acceptable if it is within a range of predetermined values, equal to a predetermined value within a predetermined tolerance, less than a predetermined threshold, greater than a predetermined threshold, or in agreement with some other suitable standard. For example, the controller <NUM> may be calibrated based on a determined relationship between viscosity for a standard or known substance (e.g. cone-plate derived cP) and the number of first acoustic signals required to transfer the specified amount of the standard or known substance. For example, the controller <NUM> may be calibrated based on a determined relationship between viscosity for a standard or known substance and any of (i) number of first acoustic signals required to transfer the specified amount of the standard or known substance, (ii) SubEject Power(dB) required to transfer the specified amount of the standard or known substance, (iii) SubEjectAmp(Volt) required to transfer the specified amount of the standard or known substance, (iv) New EjectAmp(Volt) required to transfer the specified amount of the standard or known substance, (v) New EjectAmp+ThreshdB(Volt) required to transfer the specified amount of the standard or known substance, or (vi) Power Difference(Volt) required to transfer the specified amount of the standard or known substance. By way of example, the determined relationship may be a linear relationship, though some non-linear mathematical relationships may also be suitable. The calibrated controller <NUM> may determine the viscosity of one or more samples of unknown composition and/or viscosity. The calibrated controller may determine the viscosity of the one or more samples without further calibration. The measured viscosity may also be determined to be acceptable if it is measured to be a viscosity that will not prevent or hinder the successful operation of high-performance liquid chromatography (HPLC) or ultra-performance liquid chromatography (UPLC) as applied to the portion of the liquid sample. If the portion of the liquid sample <NUM> or the entire liquid sample <NUM> is determined to not be acceptable, the portion of the liquid sample <NUM> or the entire liquid sample <NUM> may be discarded, or the sample <NUM> may be diluted to bring the viscosity to an acceptable level for the HPLC or UPLC. The maximum viscosity tolerated by instruments such as HPLC and UPLC instruments can depend on several factors, including how much the sample is diluted during and after injection, injection needle and tubing diameter, as well as autosampler and system temperature. Accordingly, a predetermined threshold can be set at the maximum viscosity that will be tolerated by a particular instrument such as an HPLC or UPLC instrument. If a system or method as described herein ascertains that a sample <NUM> has a viscosity that exceeds the predetermined threshold (i.e., if the sample <NUM> is determined to be too viscous), the sample <NUM> can be not injected into the instrument, or the sample <NUM> can be diluted to bring the viscosity to a permissible level for that instrument. For example, a predetermined threshold may be that a liquid sample <NUM> has an acceptable viscosity to be used with HPLC or UPLC if the viscosity is determined to be less than <NUM> cP. In such an example, if the controller <NUM> determines that the liquid sample <NUM> has a viscosity of <NUM> cP, the liquid sample may be discarded or diluted to an acceptable viscosity.

Further, the Applicant has verified that the method and system described herein effectively determines the viscosity of a liquid sample while also overcoming the problems associated with the cone and plate method and other conventional techniques. <FIG> illustrate the correlation between the viscosities measured by the cone and plate method and the viscosities determined by the method and system described herein for the liquid samples <NUM> as a function of total iterations. A linear regression calculated from the correlation coefficient (R<NUM>) is shown. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having a first power setting and a stepwise increase in frequency across iterations according to the apparatus' default BP2 settings. It is noted that the default BP2 settings were configured with a greater step size per iteration than the adjusted settings in <FIG> and <FIG> (<NUM>) and <FIG> and <FIG> (<NUM>). It is further contemplated that a constant frequency across iterations, or a linear increase in frequency may also be suitable for some examples. It is also noted that instruments may have different power settings. For example, LabCyte's software for the Echo <NUM> Acoustic Liquid Handler has low, medium, and high power settings. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having a second power setting different from the first power setting and a stepwise increase in frequency between iterations according to the apparatus' default CP settings (the CP settings leverage dynamic fluid analysis). It is noted that the default CP settings were configured with a greater step size per iteration than the adjusted settings in <FIG> and <FIG> (<NUM>) and <FIG> and <FIG> (<NUM>). <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the first power setting and a step-wise increase in frequency of only <NUM> between iterations. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the second power setting and a step-wise frequency increase of only <NUM> between iterations. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the first power setting, and a step-wise frequency increase of only <NUM> between iterations. As described herein, it has been observed that a relatively small size of the frequency increase between iterations can yield superior (stronger) correlation coefficients compared to larger stepwise frequency increases. It is noted that stepwise increases in the range of <NUM> to <NUM> are relatively small increases. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the second power setting and a smaller step-wise frequency increase of <NUM> between iterations. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the first power setting and a step-wise frequency increase of <NUM> between iterations. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the first power setting and a relatively small step-wise increase of <NUM> between iterations. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the first power setting and a relatively smaller step-wise frequency increase of only <NUM> between iterations. <FIG> depicts the correlation when the two are tested with liquid samples <NUM> of concentrations ranging from <NUM> to <NUM>/mL and with acoustic signals <NUM> having the second power setting and a relatively smaller step-wise frequency increase of only <NUM> between iterations.

Upon further analysis, additional outputs required to move the liquid samples were shown to correlate with viscosity, including total iterations as outlined above (<FIG>; R<NUM>=<NUM>) SubEject Power(dB) required to transfer the specified amount of the sample (<FIG>, R<NUM>=<NUM>), (iii) SubEjectAmp(Volt) required to transfer the specified amount of the sample (<FIG>; R<NUM>=<NUM>), (iv) New EjectAmp(Volt) required to transfer the specified amount of the sample (<FIG>; R<NUM>=<NUM>), (v) New EjectAmp+ThreshdB(Volt) required to transfer the specified amount of the sample (<FIG>; R<NUM>=<NUM>), or (vi) Power Difference(Volt) required to transfer the specified amount of the sample (<FIG>; R<NUM>=<NUM>). Accordingly, it is contemplated that in methods and systems describe herein, in addition to total iterations required to transfer the specified amount of the sample from the first location to the second location, viscosity may be determined based on any of: SubEject Power(dB) required to transfer the specified amount of the sample (e.g., to the second location), SubEjectAmp(Volt) required to transfer the specified amount of the sample (e.g., to the second location), New EjectAmp(Volt) required to transfer the specified amount of the sample (e.g., to the second location), New EjectAmp+ThreshdB(Volt) required to transfer the specified amount of the sample (e. g, to the second location), and/or Power Difference(Volt) required to transfer the specified amount of the sample (e.g., to the second location). Accordingly, wherein viscosity determinations based on total iterations required to transfer the specified amount of the sample, it is contemplated that viscosity may also be determined based on any of : SubEject Power(dB) required to transfer the specified amount of the sample, SubEjectAmp(Volt) required to transfer the specified amount of the sample, New EjectAmp(Volt) required to transfer the specified amount of the sample, New EjectAmp+ ThreshdB(Volt) required to transfer the specified amount of the sample to the second location, and/or Power Difference(Volt) required to transfer the specified amount of the sample.

It will be appreciated from <FIG> that the strongest correlations (as indicated by R<NUM> value) were observed for the liquid samples <NUM> of higher concentrations. It will also be appreciated that correlations (as indicated by R<NUM>value) of about <NUM> or greater were observed for most of the liquid samples <NUM> at the first power setting and the second power setting, including R<NUM> values of about <NUM> or greater for the liquid samples <NUM> for the step-wise frequency increases shown in <FIG> and <FIG>. Further, the correlation (as indicated by R<NUM> value) between the cone and plate method and the method of the present disclosure is generally tighter when using higher concentrations of protein (compare <FIG> at <NUM> to <NUM>/mL to <FIG> at <NUM> to <NUM>/mL). It is further contemplated that adjusting the step size for varying the frequency between iterations can impact the acoustic measurement of viscosity (as indicated by correlation with cone-and-plate viscosity). In some embodiments, the step size for varying the frequency between iterations is decreased (i.e., the step size is made smaller) from a default or baseline value. However, smaller step sizes may present the tradeoff of requiring more acoustic signals <NUM> to be tested, thereby increasing the time required to transfer the specified amount of liquid sample <NUM> from the first location <NUM> to the second location <NUM>, and thus potentially reducing the throughput of the method of the present disclosure. It is noted, however, that even with a relatively lower throughput associated with a smaller step size (such as about <NUM> per step), methods and systems described herein are still considerably faster than a conventional cone and plate assay. In any event, the obtained correlation data, especially for small step sizes and higher concentrations of liquid sample <NUM>, demonstrate that the method and system described herein has competitive accuracy with the traditional cone and plate method.

For the data shown in <FIG>, <NUM> BTI mAbs were initially received at ~<NUM>/mL in A52SuT and concentrated to a target <NUM>/mL ±<NUM>% using <NUM> kDa MW cutoff filters. Concentrations were measured using a SoloVPE and respective extinction coefficient. Viscosity Measurements were done on an Anton Paar MCR Rheometer affixed with the following geometry: <NUM> <NUM>° cone plate, Peltier plate Steel - <NUM>. Viscosities were measured using the flow sweep setting from <NUM> to <NUM> shear rate. Viscosity values in this study are reported at <NUM>-<NUM>. <NUM>µL was loaded onto the plate for each measurement. For the Echo viscosity measurements, <NUM>µL of each sample was loaded into a <NUM> well plate compatible with the Echo <NUM>. The plate was then loaded into the Echo <NUM> "Source plate" location. The Echo <NUM> was set to transfer <NUM> nL of material from the source plate to a destination plate (optionally, the source plate can also be sealed, and the volume transferred to the seal; the sample does not have to go to a new plate). The number of iterations or "pings" needed to form a "Mound Image Print" (MIP) on the surface of the sample were recorded. The settings for the Echo <NUM> refer to the following fluid class nomenclature: B - buffer only; BP - buffer and proteins (moderate viscosity fluids and no surfactants) | min well fluid volume of <NUM>µL | max of <NUM>µL; GP -glycerol and proteins (high viscosity fluids with no surfactants) | min well fluid volume of <NUM>µL | max of <NUM>µL; CP - protein crystallography reagents (high viscosity fluids with low level surfactants) | min well fluid volume of <NUM>µL | max of <NUM>µL. Two protocols were evaluated, BP and CP power settings, to transfer the material, both involving a stepwise increase in frequency to transfer the material. It is noted that the CP mode uses Dynamic Fluid Analysis to dynamically adjust power based on measurements of the viscosity and surface tension of the fluid in the well, a mode that is contemplated to be applicable in transferring protein crystallography reagents and other aqueous fluids that may not be transferrable by other techniques.

<FIG> is a block diagram of one example of an iterative method <NUM> of determining the viscosity of a liquid sample (e.g., the liquid sample <NUM>) using an acoustic liquid handler (e.g., the acoustic liquid handler <NUM>) with ADE. In the depicted method <NUM>, the liquid sample is positioned into a first location of the acoustic liquid handler (block <NUM>). A set of parameters of an acoustic signal are initialized (block <NUM>) and a specified number of acoustic signals of the set of parameters is applied to a portion of the liquid sample in a well of the first location (block <NUM>). Next, the method <NUM> includes determining the amount of the portion of the liquid sample that has been transferred from the well of the first location to a well of the second location (block <NUM>). This amount is compared against a specified amount of the portion of the liquid sample to be transferred (block <NUM>). If an insufficient amount of the portion of the liquid sample has been transferred, then the set of the acoustic signal parameters may or may not be varied (blocks <NUM>, <NUM>), but a specified number of acoustic signals is applied again (block <NUM>) and the portion of the liquid sample that has been transferred is determined again (block <NUM>). Once the specified amount of the portion of the liquid sample has been transferred (block <NUM>), is the method <NUM> includes determining if a specified number of wells of the first location have had a specified amount of the portion of the liquid sample transferred (block <NUM>). If the specified number of wells of the first location have not had a specified amount of the portion of the liquid sample transferred, the acoustic liquid handler is adjusted so as to be is positioned to apply acoustic signals to a different well of the first location (block <NUM>) and a specified number of acoustic signals are applied again (block <NUM>) and the portion of the liquid sample that has been transferred is determined again (this portion of the liquid sample to be transferred may be a sample having a same or a different composition and/or viscosity than the portion that was previously transferred) (block <NUM>). Once the specified number of wells of the first location have had a specified amount of the portion of the liquid sample transferred, the method <NUM> includes determining the viscosity of the liquid sample based on the set of parameters and number of acoustic signals required to transfer the specified amount of the liquid sample (block <NUM>).

It will be appreciated that while the system and method described herein are used in the context of ADE, the system and method may also be used in connection with an analytical device for performing downstream analysis (e.g., mass spectrometry, high throughput dynamic light scattering viscosity, colloidal stability measurements, and/or biotherapeutic high molecular weight analysis by size exclusion chromatography). In a first example, liquid samples may be introduced to a mass spectrometer (e.g., a high-resolution accurate-mass (HRAM) mass spectrometer) using acoustic waves, applying a similar principle of Rayleigh-Taylor instability to electrospray ionization. The disclosed system and method may in turn measure viscosity and generate mass spectrometric data. Accordingly, the system may generate viscosity data and mass spectrometry data in the same run. The system and method need not strictly use electrospray operation, however. In such an example, the system and method may pass droplets through an electric field to generate the electrospray ionization phenomenon though atmospheric pressure ionization, rather than applying an electric field to a liquid sample confined in a narrow capillary. In other examples, atmospheric pressure chemical ionization may be used. In yet other examples, Atmospheric Matrix-Assisted Laser Desorption/Ionization (MALDI) ionization may be used. The system and method could manipulate droplets on to a MALDI target plate for subsequent atmospheric MALDI-mass spectrometry analysis. As such, the system or method may determine the viscosity of the sample and further transfer the sample or a portion thereof to a mass spectrometer and perform mass spectrometric analysis.

Claim 1:
A method for determining a viscosity of a liquid sample (<NUM>) of a protein, the method comprising:
positioning the liquid sample (<NUM>) of the protein in a first location (<NUM>) of an acoustic liquid handler (<NUM>);
applying, using the acoustic liquid handler (<NUM>), one or more first acoustic signals (<NUM>) until a specified amount of the liquid sample (<NUM>) has been transferred from the first location (<NUM>) to a second location (<NUM>) of the acoustic liquid handler (<NUM>); and
characterized by determining the viscosity of the liquid sample (<NUM>) based on (i) a number of the one or more first acoustic signals (<NUM>) required to transfer the specified amount of the liquid sample (<NUM>) from the first location (<NUM>) to the second location (<NUM>) and (ii) a set of parameters of the first acoustic signal (<NUM>).