Patent Description:
Capillary electrophoresis devices generally provide certain major components that include, for example, a capillary array, a separation medium source for providing medium to the capillaries (e.g., a polymer), a sample injection mechanism for loading samples into the capillaries, an optical detector component, an electrode, and anode buffer source on one end of the capillaries, and a cathode buffer source on the other end of the capillaries. Capillary electrophoresis devices generally also provide various heating components and zones to regulate the temperature of many of the aforementioned components. Regulating the temperature of many of these components can improve quality of results.

Stability and magnitude of capillary current are prerequisites for successful electrophoretic separation in capillary electrophoresis sequencing and fragment analysis. Irregularities in capillary current can be caused by various hardware faults, e.g. polymer filling issues like clogged capillaries or bubbles. Early detection of these issues is beneficial, especially detection before the sample injection phase to protect and preserve valuable sample. Corrective action can be taken by the system to fix the issue or if unsuccessful, the user can be notified.

Current multi-capillary electrophoresis products measure and monitor the sum of the capillary currents at the common anode or cathode. Due to the variability in magnitude of the capillary current it is very difficult to detect erroneous behavior of individual capillaries based on the sum of capillary currents and it's impossible to identify the faulty capillary.

During idle periods the capillary ends need to be protected from drying up. In capillary electrophoresis instruments this is accomplished by keeping the capillary ends immersed in buffer.

<CIT>, <CIT>, and <CIT> describe an electrophoresis apparatus, an electrophoresis method, and a multi-dimensional electrophoresis apparatus from the related art. In addition, a capillary electrophoresis analysis apparatus is known from <CIT>.

The present disclosure relates, in some embodiments, to a system or method for measuring capillary electrophoresis current. The system or method includes a plurality of capillaries, where each capillary has a cathode end and an anode end. The system further includes a plurality of cathode buffers. Each of the cathode buffers is configured to be electrically isolated from the other cathode buffers. Further, each cathode buffer is associated with one capillary of the plurality of capillaries. The cathode end of each capillary is immersed in its associated cathode buffer. The system includes a plurality of current sensors, each current sensor associated with one capillary of the plurality of capillaries for measuring current. In some embodiments, the plurality of capillaries is four capillaries.

In other embodiments, that are not claimed, a system or method for detecting a liquid level is provided. The system or method includes a plurality of cathodes, and an electrolytic buffer, where each of the plurality of cathodes is submerged in the electrolytic buffer. The system or method further includes a capacitance sensor connected to the plurality of electrodes configured to measure capacitance between the plurality of cathodes and the electrolytic buffer.

In other embodiments, not according to the claims, a system or method for performing capillary electrophoresis, comprises a capillary system, a high voltage system, and a low voltage system. The capillary system includes an array of capillaries and a tag configured to provide identifying information about the capillary system. The high voltage system is electrically coupled to the capillary system and includes a high voltage supply providing a voltage of at least <NUM> kilovolt and at least one circuit is electrically coupled to the high voltage supply. The low voltage system is coupled to the high voltage system. The tag provides at least one of (<NUM>) electrically isolation between the high voltage system and the low voltage system, (<NUM>) a data and/or control signal between the high voltage system and the low voltage system, or (<NUM>) power from the low voltage system to the high voltage system.

To provide a more thorough understanding of the present invention, the following description sets forth numerous specific details, such as specific configurations, parameters, examples, and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present invention, but is intended to provide a description of the exemplary embodiments.

It should also be recognized that the methods, apparatuses and systems described herein may be implemented in various types of systems, instruments, and machines such as biological analysis systems. For example, various embodiments may be implemented in a method, instrument, system or machine that performs capillary electrophoresis (CE) in a plurality of capillaries. While embodiments of the present invention are described herein for a capillary electrophoresis methods and systems, embodiments of the inventions may be extended to other methods, systems, instruments, and machines such as other types of biological analysis systems (e.g., polymerase chain reaction systems or methods, next generation sequencing systems or methods, and the like).

<FIG> provides a basic schematic representation of a portion of a capillary electrophoresis apparatus or system <NUM> according to embodiments of the present invention. In particular, <FIG> illustrates a capillary array assembly <NUM> comprising a plurality of capillaries <NUM>, electrode components (including anode <NUM> and a plurality of cathodes <NUM>), a polymer source <NUM>, a buffer source <NUM>, and polymer introduction mechanism <NUM> (illustrated as a syringe pump). A coupling <NUM> may be provided to connect the capillary array assembly <NUM> to a Polymer/Buffer structure <NUM>, which includes polymer source <NUM>, buffer source <NUM>, anode <NUM>, and syringe pump <NUM>. A temperature-controlled zone <NUM> controls the enclosed capillary array assembly <NUM> and cathodes <NUM>. In certain embodiments, additional temperature control may be included for the polymer source <NUM> and delivery path <NUM>. In certain embodiments, capillary electrophoresis apparatus <NUM> comprises a capillary cartridge, housing, or assembly <NUM> comprising capillary array assembly <NUM>. Capillary cartridge <NUM> may also include an enclosure <NUM> configured to support and/or house capillary array assembly <NUM>. In certain embodiments, capillary cartridge <NUM> may include or be integrated with one or more of the other components shown in <FIG> (e.g., may include any or all of anode <NUM>, cathodes <NUM>, polymer source <NUM>, buffer source <NUM>, polymer introduction mechanism, coupling <NUM>, and/or polymer introduction mechanism <NUM>). While capillary array assembly <NUM> comprises four capillaries <NUM> in the illustrated embodiment of <FIG>, capillary array assembly <NUM> may contain more or fewer capillaries <NUM> (e.g., <NUM> capillaries, <NUM> capillaries, <NUM> capillaries, <NUM> capillaries, <NUM> capillaries, <NUM> capillaries, or more than <NUM> capillaries). In certain embodiments, capillary array assembly <NUM> comprises a single capillary <NUM>.

Referring to <FIG>, in certain embodiments, apparatus <NUM> comprises a current measurement system <NUM> that is configured to provide individual capillary current sensing for individual capillaries of a plurality of capillaries <NUM>. Prior art multi-capillary electrophoresis systems measure and monitor the sum of the capillary currents at a common anode or cathode. If there is an error or variability in the current, it is difficult to detect which capillary may be faulty. As such, it has been found advantageous to monitor and measure each capillary current individually. In this way, the stability and magnitude of the individual capillary currents may be verified during the pre-run phase right after filling the capillaries with fresh polymer and before sample injection. Furthermore, embodiments of the present invention allow for monitoring individual capillary currents during the electro-kinetic injection and/or during electrophoretic separation phases for error detection and analysis.

System <NUM> comprises a multi-capillary electrophoresis system that implements the capability to measure and/or monitor the current of each of the capillaries through individual cathode connections. Capillaries <NUM> have a cathode portion or end and an anode portion or end. Each cathode is immersed in an individual cathode buffer container <NUM>. The anode ends of the capillaries may be immersed in anode buffer <NUM>. As illustrated in <FIG>, each individual cathode is immersed in an electrically isolated buffer or sample reagent. The cathode buffer containers <NUM> provide electrically isolated compartments for the run buffer. Samples are electrically isolated in wells of microtiter plates or tube strips. In the embodiment shown in <FIG>, the current is individually monitored from four capillaries <NUM>. The number of capillaries may be greater than or less than four. A current sensor <NUM>, connected to a high voltage supply <NUM>, is associated with each of the capillaries <NUM>.

Voltage supply <NUM> supplies a high voltage across capillaries <NUM>. For example, voltage supply may provide a negative voltage at the cathode side of capillaries <NUM> having a magnitude of, or about, <NUM> kilovolts (kV). Voltage supply <NUM> may supply other voltages levels depending on system parameters such as number of capillaries, capillary length, polymer or buffer solution characteristic, or the like. For example, voltage supply <NUM> may supply a negative voltage at the cathode end of the capillaries having a magnitude that is greater than or equal to <NUM> kV, greater than or equal to <NUM> kV, greater than or equal to <NUM> kV, greater than or equal to <NUM> kV, or greater than or equal to <NUM> kV. In certain situations, the voltage applied to the cathode side of the capillaries is less than or equal to <NUM>,<NUM> volts (e.g., approximately <NUM>,<NUM> volts for electrokinetic injection of a sample, or approximately <NUM> volts for checking the presences of bubbles in the capillaries). In certain embodiments, the voltage applied to the cathode side of the capillaries is a positive voltage in the ranges cited above. In other embodiments, the voltage applied to the cathode side of the capillaries is alternating field (e.g., a sinusoidal wave form).

When a capillary electrophoresis instrument is not in use, the capillary ends may be protected. Traditionally, this is done by immersing the capillary ends in buffer. However, if, for example, the buffer level is low due to continued use or evaporation, then the capillary ends may be immersed in buffer solution, which may cause damage to the capillaries. As such, according to various embodiments not claimed but described herein, a system is described that allows detection of the liquid level. This can ensure that there is an adequate buffer level and notify a user or system if the buffer level needs to be adjusted.

According to various embodiments, the liquid level is determined by sensing a capacitance (e.g., a double layer capacitance) formed between two or more cathodes in an electrolytic buffer. The double layer capacitance is proportional to the submerged electrode surface area and thus linear, or nearly linear, with the immersion depth of the cylindrical electrodes.

<FIG> illustrates a schematic representation of a system <NUM> for liquid level sensing according to various embodiments not in accordance with the claims but described herein (e.g., in capillary electrophoresis apparatus <NUM> and/or capillary cartridge <NUM>). At least two electrodes <NUM> in a common cathode buffer container or compartment <NUM> containing an electrolyte buffer <NUM> may be configured to sense the liquid level. The cathode buffer container <NUM> may provide one compartment for wash buffer (and one compartment for waste buffer) for all <NUM> capillaries. The double layer capacitance, for example, between the cathodes and the electrolytic buffer is measured with capacitance sensor <NUM> that is electrically coupled to a voltage supply <NUM> that may have the same or similar electrical properties as those of voltage supply <NUM> discussed above.

In the illustrated embodiment, there are two electrodes, each of which may be electrically coupled to a capillary. In such embodiments, the capacitance sensor may be configured to supply a slightly different voltage to the second electrode, for example, by using a voltage supply having a voltage of <NUM> to <NUM> volts. In certain embodiments, the capacitance sensor may comprise such a voltage supply having a voltage of <NUM> to <NUM> volts, for example, a voltage of <NUM> volts has been found to be advantageous in certain embodiments. In certain embodiments, the voltage supply is less than or equal to <NUM> volt. In such embodiments, a discharge curve extends to voltages near zero. Measurement of the capacitive and electrolyte characteristics above and below the dielectric breakdown voltage of a double layer may provide important data to improve liquid level measurement accuracy in the presence of buffer and environmental variability.

In certain embodiments, electrolyte solution <NUM> and/or capacitance sensor comprise more than two electrodes, for example, four electrodes in a common cathode buffer container, as shown in <FIG>. In such embodiments, one of the electrodes may be configured to have a nominal voltage, VI, while the other electrode has a different nominal voltage, V2. In such embodiments, capacitance sensor <NUM> may be configured to measure a capacitance between the electrode at voltage VI and one or more of the electrodes having the voltage V2.

In certain embodiments, each electrode <NUM> is electrically coupled to a different capillary. Alternatively, one of the electrodes <NUM> may be electrically coupled to a capillary and the other electrode may be electrically coupled to an electrical line or circuit that having similar electrical properties to that of the capillary (e.g., having the same or a similar resistance or impedance). For example, each of the capillaries <NUM> in current measurement system <NUM> may comprise its own liquid level sensing system <NUM>, wherein each cathode buffer container <NUM> contains two electrodes electrically couple to its own liquid level sensing system <NUM> (one electrode coupled to the capillary and the other electrode couple to a line or circuit as described above). Thus, system <NUM> may be configured to measure both liquid level in each cathode buffer container <NUM> and the current passing through each capillary <NUM>.

With the described concept, the liquid level of the wash buffer can continuously be monitored and a user or system can be notified and/or instructed when the liquid level falls below the level needed to ensure the capillaries do not dry out.

In certain embodiments, liquid level sensing system <NUM> may be configured for use during idle times to prevent capillary cathodes from drying out. This may be accomplished by immersing the capillary cathode electrodes in a buffer reservoir during storage or between instrument runs. Advantageously, rather than just detecting if the cathode tips are in contact with the buffer, system <NUM> is configured to provide a warning message that can be sent to a user or system when evaporation threatens to uncover the capillary electrodes. Thus, a user or system is advised of a potentially adverse condition before the capillary tips have been exposed to the air and can dry out.

In other embodiments, the capillary cathode tips may be covered with a capillary protector that immerses the capillary cathode tips in a gel to avoid drying out during storage and/or between uses. Before being loaded into an instrument, the capillary protector is removed. Advantageously, system <NUM> may be configured in certain embodiments to detect the absence or presence of the capillary protector before moving the sample plate. In such embodiments, system <NUM> may be configured to warn a user or system to remove the capillary protector if it is present, thus advantageously preventing damage to the instrument and/or capillary consumable (e.g., preventing a crash of the capillary consumable against the sample plate causing damage to the cartridge.

In certain embodiments, electrical impedance between two cathode electrodes immersed in a buffer reservoir (e.g., electrodes <NUM>) can be modeled as a series combination of (<NUM>) a known resistance (Rb) representing the resistance of a buffer solution and (<NUM>) a capacitance (C) comprised of, for example, a series combination of the double layer capacitances on the surface of the two electrodes. The double layer capacitance is proportional to the surface area of the electrodes immersed in the buffer. Therefore, by measuring or calculating this capacitance, the presence and/or level of liquid between the two sides or electrode of the capacitance can be determined.

According to various embodiments that are not claimed, measuring or calculating the capacitance can be accomplished by various systems and methods. For example, referring to <FIG>, one electrode of a circuit having a known impedance Rb may be driven with a voltage step of know characteristics. A transimpedance amplifier and A/D converter (or the like) may then be configured to measure an amplitude and decay time constant on the other electrode. From these measurements, the capacitance C may be determined and correlated to the presence and/or level of liquid between the two electrodes. In the current embodiment, a first electrode may be charged against a second electrode which is at the reference voltage level. The charge and/or discharge measurement may also be made on the first electrode against the second electrode. In this embodiment, the capacitor voltage is measured during the charge / discharge process.

Referring to <FIG>, in other embodiments, the capacitance may be charged through a known resistor and measuring the charging time constant, Tc, then discharging through a different known resistor and measuring the discharge time constant, Td. From these time constants, the capacitance C may be determined and correlated to the presence and/or level of liquid between the two electrodes. In contrast to the embodiment shown in <FIG>, here the charge and discharge currents may be measured and used to calculate the capacitance.

Referring to <FIG>, in other embodiments, one electrode of a circuit may be driven with a sine wave of known amplitude, frequency and phase angle. Using, for example, a transimpedance amplifier and phase detection circuit, the complex impedance may be measured or calculated. From the complex impedance, the capacitance C may be determined and correlated to the presence and/or level of liquid between the two electrodes.

<FIG> illustrates a block diagram of a system <NUM> according to embodiments described herein that is configured for power and data transmission across high a voltage isolation barrier <NUM>. The implementation of the methods and systems described above relate to individual current sensing and liquid level detection sensors connected to cathode electrodes <NUM>, which are connected to a high voltage supply <NUM>, with a high voltage potential referenced to a chassis ground (e.g., with a voltage the same or similar to that provided by voltage supply <NUM> discussed above). Thus, the sensor circuitry <NUM> is at the same, or approximately the same, high voltage potential. Advantageously, sensor circuitry <NUM> is electrically isolated from circuitry and conductive components near ground potential (e.g., to the right of high voltage isolation barrier <NUM>). In such embodiments, power and data transmissions are provided across a high voltage isolation barrier <NUM>. This can be accomplished through various means, to name a few: optical, mechanical, inductive, capacitive or radio waves. In certain embodiments, a microcontroller <NUM> is coupled to sensor circuitry <NUM> that is also at the same, or approximately the same, high voltage potential.

In certain embodiments, system <NUM> comprises a radio frequency identification (RFID) tag <NUM>, which is advantageously configured to (<NUM>) identify, tag, and/or provide data for a particular cartridge or system containing a particular capillary array assembly (e.g., comprising capillaries <NUM> or <NUM>), (<NUM>) electrically isolate low voltage control and data lines in communication with the high voltage components such as sensor circuitry <NUM>, and/or microcontroller <NUM>, and/or (<NUM>) provide power to the high voltage components such as sensor circuitry <NUM> and/or microcontroller <NUM>. The sensor circuit of the RFID may comprise a dynamic passive NFC (near- field communication)/RFID tag <NUM>. An RFID Reader/Writer <NUM> on the opposite side of the high voltage isolation barrier <NUM> powers and communicates with the sensor circuit wirelessly via RFID tag <NUM>.

In certain embodiments, RFID tag <NUM> is associated with a particular cartridge or capillary array assembly (e.g., one comprising capillaries <NUM> or <NUM>). In such embodiments, the RFID is used to both to (<NUM>) identify, tag, and/or provide data for the cartridge or assembly and (<NUM>) provide the isolation and/or data/power transmission discussed above. In other embodiments, the RFID is part of an instrument configured to receive the particular cartridge or capillary array assembly, in which case the RFID tag may be used only to provide the isolation and/or data/power transmission discussed above.

Additionally or alternatively, an optical isolator may be used to transmit power and/or data across high voltage isolation barrier <NUM> to high voltage components such as sensor circuitry <NUM> or microcontroller <NUM>. Light energy transmitted through the optically transmissive high voltage isolation barrier is converted to electrical energy by means of photovoltaic effect to power the high voltage components. Analog or digital optical data transmission is provided through the optically transmissive high voltage isolation barrier.

Additionally or alternatively, an inductive coupler may be used to transmit power and data across high voltage isolation barrier <NUM>. In such embodiments, inductors are located on both sides of high voltage isolation barrier <NUM> such that mutual inductance exists between the inductors. Electrical power is transmitted through the coupled inductors to the sensor circuitry through by means of AC currents. The AC currents are modulated to provide analog or digital data transmission using modulation methods known to the art including but not limited to amplitude and/or frequency modulation. The sensor circuitry may use backscatter modulation to send data across high voltage isolation barrier <NUM>.

In some embodiments, radio transmission is used to transmit power and data across high voltage isolation barrier <NUM>. On the sensor circuitry side, radio frequency energy harvesting is used to power the circuitry. Data is transmitted by means of modulation of the radio transmission and/or backscatter.

In the described embodiments, bidirectional data transmission and/or power transmission can be frequency multiplexed, time multiplexed and/or spatially separated into individual channels. Some embodiments may combine various methods described to transmit data and power, e.g. such that power may be transmitted inductively while data is transmitted optically.

In certain embodiments, commercially available wireless charging technology and standards may be used to transmit power and data. This approach is simple and cost effective due to the high integration and the prevalence of the commercially available technology.

According some embodiments, commercially available LF and HF RFID technology may be used to transmit power and data through inductive coupling. This approach is simple and cost effective due to the high integration and prevalence of the commercially available technology.

According to one embodiment, commercially available UHF RFID technology may be used to transmit power and data using radio waves. This approach is simple and cost effective due to the high integration and the prevalence of the commercially available technology.

The approaches according to the described embodiments may be simple and cost effective.

Claim 1:
A system (<NUM>) for measuring capillary electrophoresis current, the system comprising:
a plurality of capillaries (<NUM>), wherein each capillary has a cathode end and an anode end;
an anode buffer (<NUM>), wherein the anode ends of the capillaries are immersed in the anode buffer, a plurality of cathode buffers (<NUM>), wherein each of the cathode buffers is configured to be electrically isolated from the other cathode buffers, each cathode buffer is associated with one capillary of the plurality of capillaries, and the cathode end of each capillary is immersed in its associated cathode buffer;
a high voltage supply (<NUM>) connected to the anode buffer and
to a plurality of current sensors (<NUM>), each current sensor associated with one capillary of the plurality of capillaries for measuring current.