OpusXpress 6000A

Automated Parallel Voltage-Clamp Screening System For Oocytes

If you thought a single-channel automated voltage clamp was cheaper than an 8-channel parallel system, think again.

• Increase productivity and throughput with automated parallel experiments
  • Automated oocyte impalement
  • Computer-coordinated fluid delivery & data acquisition for 8 cells at once
  • Automated real-time analysis & cell viability monitoring
  • On-axis impalement to minimize membrane damage, for better quality data & longer-lasting experiments

• Sophisticated fluidics standard with each system for greater flexibility
  • Robotic fluid delivery from 96-well compound plates
  • Apply 24 compounds to each oocyte, 192 total compounds across 8 oocytes w/o intervention
  • Rapid onset of compound delivery with no dead volume or cross-contamination
  • Continuous flow or fixed-volume additions available with user-selectable flow rates
  • Use as little as 100 µl compound per test
  • No compounds wasted on non-viable oocytes
  • Sophisticated chamber design optimizes solution exchange

Table Assumptions

1 oocyte at a time
Assumes a single 20 minute set up time for either a 24 hour or 8 hour testing period. The figures shown DO NOT account for: 1) the time to replace bad electrodes in the middle of the testing period, or 2) the time taken to re-load the drug delivery plates or vessels. Both of these factors will reduce the number of compounds tested.

8 oocytes at a time
Assumes a 20 minute set up period for each 192 drugs screened. The figures shown DO account for: 1) the time to replace bad electrodes during the 20 min set up periods and 2) the time taken to replace drug delivery plates.

Neither accounts for time lost on bad oocytes.

6 min drug cycle: ctrl 1 min, drug 2 min, wash 3 min
3 min drug cycle: ctrl 1 min, drug 1 min, wash 1 min

• Highest performance voltage clamp and data acquisition for the best quality data
  • High compliance voltage clamp for large fast currents
  • Ultra-high DC gain to insure excellent voltage control
  • Electronics with wide recording bandwidth
  • Sample rates up to 30 kHz per channel for high-speed acquisition of rapid signals
  • Virtual ground to minimize bath error potentials
  • Wide angular displacement of electrodes reduces capacitive coupling, increasing bandwidth
  • Low-noise data acquisition using Digidata technology

• High-throughput data storage and retrieval for fast results
  • Real-time data analysis and analysis display
  • Clampfit 9 included for further off-line analysis

• Excellent system integration for high reliability and low maintenance
  • Software fully integrated with hardware components
  • System comes with all software & hardware needed for room temperature measurements, no external air or vacuum required
  • Intuitive software makes it easy to set up experiments & monitor experiment progress
  • Expert, helpful, personal technical support readily available
  • Field service support provided

Press the Play button to start the OpusXpress 6000A animation.
Turn on your speakers to hear the narration. A full-screen version is
also available on the Literature & Downloads link in the right menu.

Integrated System

OpusXpress 6000A is an integrated hardware and software package that builds on industry standard electrophysiology technologies developed at Axon Instruments. OpusXpress 6000A uses the two-electrode voltage clamp technique to record currents from eight Xenopus oocytes in parallel. Oocyte impalement, fluid delivery, data recording, and on-line analysis are all performed automatically under computer control and operate on all eight oocytes in parallel to increase throughput. Users can specify experimental design, experimental tolerances, and analysis parameters with software that is easy to use and highly flexible.

For Drug Screening and Basic Research

OpusXpress 6000A was designed to record from both ligand-gated and voltage-gated ion channels. The mechanical and electronic design of the system ensures good voltage control and recordings with high bandwidth. Oocyte impalement is on-axis to minimize tearing of the oocyte membrane and leak currents. Electrode pairs penetrate each oocyte with a wide angle of separation to minimize capacitive coupling between electrodes and to maximize bandwidth. The eight high compliance voltage clamps, designed for large fast currents, incorporate independent virtual grounds in each chamber to minimize bath error potentials. For these reasons, OpusXpress is suitable not only for drug discovery, but also for detailed studies of ion channel and transporter function in basic research settings.

Flexible System

OpusXpress 6000A supports continuous perfusion and a wide range of user-selectable flow rates, up to 50 ml/min. Our unique chamber design promotes rapid fluid exchange. Users can select solutions from two different buffer reservoirs for each oocyte and from 96 well compound plates. Up to 192 compounds can be tested across 8 oocytes before user intervention, with up to 24 compounds/concentrations tested per oocyte. The use of disposable pipette tips for drug delivery from 96-well compound plates prevents cross-contamination between drugs and eliminates dead volume. Decision-making features in the software can be used to optimize testing and to prevent drug delivery to oocytes that fail during testing. Output of analyzed data is compatible with major high throughput screening databases.

Ion Channel Assays with Xenopus Oocytes

The oocyte of the frog Xenopus laevis is widely used for expressing and analyzing ion channels and other transport proteins. The large size of Xenopus oocytes and the small number of endogenous ion channels in the cell membranes of oocytes make them an extremely useful model system for the study of exogenously expressed cloned ion channels using the two-electrode voltage clamp technique (TEVC). The use of TEVC gives the scientist a direct measurement of ion channel behavior and is, therefore, to be preferred over more indirect methods such as fluorescence indicators or simple binding assays.

OpusXpress automatically
impales oocytes.

Advantages of the Oocyte System

• Cells are easily available in large numbers.
• Cells are hardy and can survive in vitro for many days.
• Cells are big (>1 mm in diameter).
• Oocytes faithfully express injected foreign RNA and DNA.
• Oocytes contain few endogenous conductances.
• Direct electrophysiological measurements of ion channel function are possible.
• Channels are expressed rapidly, in 1 to 2 days.
• Good alternative when channels don't express well in mammalian expression systems.

Disadvantages of the Conventional Oocyte System

• Testing is a low throughput process, performed one oocyte at a time.
• Highly skilled technicians are required for testing.
• Equipment setup is painstaking.
• Organization of results is difficult.

Because of these difficulties, the use of conventional TEVC on Xenopus oocytes has been largely restricted to laboratories already skilled in the practice of electrophysiology. Although direct measurements of ion channel properties using TEVC should result in much more efficient screening of test compounds, the conventional method has not been exploited as a screening tool by the pharmaceutical industry because of the listed disadvantages.

Features

Computer-Controlled Operation

• Automated impalement, voltage clamp, and perfusion of up to eight oocytes in parallel.
• On-axis oocyte penetration for minimal membrane damage.
• Automated perfusion with solutions from 96 well compound plates.
• Automatic data acquisition and on-line analysis from eight oocytes in parallel.

Efficient Fluidics

• Solutions applied via disposable tips to eliminate any possibility of cross-contamination.
• Apply up to 24 compounds to each oocyte.
• A total of 192 unique compounds can be applied across the eight oocytes prior to user intervention.
• Zero dead volume for drug application.
• Rapid solution exchange rates: 1-3 seconds for 90% exchange at a typical 1 ml/min flow rate. Much faster changeovers possible by initiating changeover with higher flow rate and then tapering off to a low flow rate.
• Wide range of user selectable flow rates, from 0 flow to 50 ml/min.

Features to Optimize Drug Discovery

• Drug-saving strategies implemented.
• Electrode preservation mode allows electrode storage overnight.
• Bar code reader for 96-well compound plates.

High-Performance Data Acquisition, Display and Analysis

• Voltage- and ligand-gated channel assays supported.
• High-compliance TEVC for large, fast currents.
• Low noise recordings with high bandwidth and wide dynamic range.
• Ultra-high DC gain to minimize voltage errors with large currents from ligand-gated channels.
• Independent virtual grounds for bath series resistance compensation.
• Digitization using a proven industry standard acquisition system.
• Computer control of critical system parameters:
  • Electrode positioning and impaling.
  • Voltage clamp controls.
  • Robotic fluid handler and pumps.
  • Sequencing of drug delivery and data acquisition.
  • Data acquisition parameters and analysis.
• Real time data display.
• On-line analysis display.
• Decision-making features evaluating electrode properties and current magnitude with user-specified limits.
• Enhanced on-line statistics for first order data analysis.
• Clampfit 9 available for further off-line analysis.
• Data output compatible with major high throughput screening databases.

Major Components

Headstage and Chamber Assembly.
Two-Electrode Voltage Clamp amplifier with 8 modules.
Digitizer (built into Two-Electrode Voltage Clamp chassis).
Dual Motor Drive with 8 modules.
Fluid Handler.
Peristaltic pumps (3).
Syringe pump.
Cabinet: 60" x 32" x 70" (W x D x H).
Computer.
Computer cart: 30" x 30" x 53" (W x D x H).
OpusXpress 1.0 software.
Clampfit 9.0 software.

Electrical Requirements
Line voltage: 100 VAC to 120 VAC or 220 VAC to 240 VAC.
Total system power: 1.7 kVA (maximum), single phase.

Two-Electrode Voltage Clamp and Digitizer

Eight slide-in voltage-clamp amplifier modules (TEVC-1A) fit into a single chassis.
Front panel status lights indicate mode of operation.
Amplifier controls are in OpusXpress software.
Each TEVC-1A amplifier module has one dedicated voltage output and one Scaled Output.

DIGITIZER

A Digidata^® 1322A digitizer built into the voltage clamp chassis delivers voltage commands from the host computer to the TEVC-1A modules and digitizes analog data signals from the modules for the computer. Both Digidata Analog Outputs are connected to all modules. Analog Out 0 is the command signal for Setup mode and Analog Out 1 is the command signal for Voltage Clamp mode. Each of the two outputs from the eight TEVC-1A amplifier modules is connected to one of the 16 Digidata 1322A Analog Inputs.

Analog Input Channels:  16
Analog Output Channels:  2
Analog Input/Output resolution:  16 bits
Digitizer input range:  ±10 V
Maximum acquisition rate:  500 kHz or
    31.25 kHz per channel
Analog Input noise:  300 µVrms
Analog Output noise:  100 µVrms

HEADSTAGES

Unity-Gain Headstages.
Voltage (V) electrode headstage: current gain = x1, current-setting resistor = 10 MΩ.
Current (I) electrode headstage: current gain = x10, current-setting resistor = 1 MΩ.

AMPLIFIER MODULES (TEVC-1A)

Setup Mode
Total noise (10 kHz bandwidth):
Grounded inputs:
   3 µVrms for V headstage
   15 µVrms for I headstage
With 1 MΩ electrode resistance:
   15 µVrms for V headstage
   30 µVrms for I headstage
Working input voltage range:
   ±10V for both headstages for transients
   and steady state
Input resistance (both headstages):
   10¹¹ Ω
Input leakage current (both headstages):
   < 2 pA at 25 °C
Capacitance neutralization:
   V headstage only,  20 pF maximum
Current command input scaling (both headstages):
   10 nA/V (100nA maximum)
Pipette offset (both headstages):
   ±300 mV, voltages first averaged for
   20 ms.

Voltage Clamp Mode
Tested with the MCO-1U model cell (220 nF// 1 MΩ via 1 MΩ electrodes, Rs=1 kΩ)
Voltage rise time (10%-90%):
   60 µs for a 10 mV step (at optimum
   gain and stability)
Current settling time (to 10% of final level):  600 µs
   Voltage rise time and current settling
   time are similar on model cells that do
   not have a series resistance element.
Noise:
   Voltage (V):  20 µVrms (10 kHz)
   Current (I):
   5 nArms (10 kHz) for Gain = 2,000
   2 nArms (100 Hz) for Gain = 2,000
AC Voltage clamp gain:
   Range is 200 to 50,000
DC Voltage clamp gain:
   > 1,000,000, time constant = 15 ms Output compliance:
   ±180 V (Internal supply voltages ±200 V)
Stability:
   Phase lag range is 25 µs to 2200 µs
Holding potential:
   ±1000 mV
Voltage command input scaling:
   20 mV/V (±200 mV maximum)

Scaled Output
The Scaled Output multiplexer sets the output of the I electrode (voltage output in Setup mode and current output in Voltage Clamp mode). The selected signal is then filtered and amplified before being captured by the digitizer.

Scaled Output filter:
   Low-pass four pole Bessel filter
   Cut-off frequencies (-3 dB, Hz): 1, 2, 5,
   10, 20, 50, 100, 200, 500, 1k, 2k, 5k,
   13k, 20k, 30k (bypass)
Scaled Output gain (post-filter):
   1, 2, 5, 10, 20, 50, 100, 200
Output Offset DAC:
   ±1V compliance subtraction or
   ±10 µA in current mode
Noise:
   15 µVrms grounded input via 10 kHz filter
   referred to input.
   2 µVrms grounded input via 100 Hz filter
   referred to input.

Virtual Ground Bath Potential Compensation
The bath potential is actively clamped to zero mV at the voltage-sensing bath electrode (Ag/AgCl pellet) near the oocyte by passing current from the current-passing bath electrode (platinum wire).

Computer

Supplied with the OpusXpress 6000A workstation:
Windows^® XP Professional
Two 17" flat screen monitors
CD-RW drive

Dual Motor Drive

Eight slide-in modules (DMD-1A) fit into a single chassis.
Motor drive controls are in OpusXpress software.
Each module operates a pair of stepper motors for a single channel.
Front panel status lights indicate stepper motor position or action.

Micropositioners and Stepper Motors
Travel maximum: 50 mm
Step size: 3 µm
Maximum linear speed: 15 mm/sec

Fluidics System

Fluid Handler with high-force Z-arm
Probe positioning performance:
   Accuracy: ±0.5 mm in X/Y dimensions
      ±1 mm in Z dimension
   Repeatability:
      ±0.25 mm in X/Y/Z dimensions

Z-arm Nozzle Head
Attached to Fluid Handler Z-arm for picking up disposable tips for fluid delivery from 96-well plates to oocytes.
1 ml and 2 ml nozzle heads available
2 ml nozzle head uses four boxes of 2 ml disposable tips
1 ml nozzle head uses two boxes of 1 ml disposable tips

Eight-channel Peristaltic Pumps
Three eight-channel peristaltic pumps:
   Two pumps for perfusion of oocytes with
   fluids from two different buffer reservoirs.
   Each oocyte can be perfused by a
   different set of solutions.
   One pump for aspiration of fluids from
   oocyte chambers.
High speed: 0.01 rpm to 48 rpm.
Continuous speed adjustment from
0 rpm to 48 rpm:
   From 0 to 9.99 rpm, increments by
   0.01 rpm.
   Above 9.99 rpm increments by 0.1 rpm.
Inflow rate range: 0 ml/min to 4.8 ml/min
   Maximum set by tubing ID.
   Values given are for 1.15 mm ID tubing
   (red-red) that comes standard with unit.

Eight-channel Syringe Pump
For transferring fluids from 96-well plates to oocyte chambers.
Up to 24 drugs can be delivered to a single oocyte or 192 drugs across eight oocytes.
Syringe volume: 5 ml
Syringe type:
   borosilicate glass, PTFE plunger
Drive mechanism: stepper motor/lead screw
Step resolution: 1.25 µl
Minimum flow rate:
   25 µl/min (Fine mode)
Maximum flow rate:
   50 ml/min (Normal mode)
Flow rate resolution:
   5 µl/min (Fine mode)
   20 µl/min (Normal mode)
Volume accuracy: ±1%
Flow accuracy: ±1%

Camera System

CCD Color Camera
Format: ½" color chip, interline transfer.
Resolution: 768 (H) x 494 (V).
Output format: S-Video.
Light gathering capability:
   2 Lux @ F = 1.4 (AGC on).
Supplied with 6.5x parfocal manual
   zoom lens with 3 mm focus.
1x adapter and 0.5x lens attachment.
Total magnification range at the monitor:
   13x to 85x.
Maximum working distance: 175 mm.
PCI interface frame-grabber card for monitor display, S-video input.

Light source:
Lamp: 150 W, Tungsten, AC halogen adjustable lamp.
8 foot, ½" diameter light pipe with focusing spot lens.

Bar Code Reader

Capable of reading bar codes on 96-well compound plates.
Minimum bar width:
   Automated scanning: 0.25 mm (0.010")
   Handheld scanning: 0.19 mm (0.007")
   at 1" to 3"
Width of scan field: 28.6 mm (1.1") at face
Minimum bar height: 5 mm (0.2")

Consumables

96-Well Plates
The following 96-well plates have been tested for use with the OpusXpress workstation:
Becton Dickinson Product number 353966, polypropylene, conical bottom, 2.0 ml working volume.
Becton Dickinson Product number 353964, polypropylene, conical bottom, 1.0 ml working volume.
Wheaton Product number W845110, glass, conical vials, 1.0 ml working volume.

Disposable Pipette Tips
Rainin Product number RT48-L2000, 2 ml disposable tips, 48-well plate format box. Rainin Product number RT-L1000, 1 ml disposable tips, 96-well plate format box.

Glass Pipettes
Prefabricated glass pipettes designed specifically for use with the OpusXpress two-electrode voltage clamp system are available for purchase from Axon Instruments. Our gold-banded pipettes are held to strict tolerances and uniformity to optimize performance in the OpusXpress system.

Accessories

100 glass pipettes.
18 HL-OX electrode holders.
1 HLA-003 Ag/AgCl pellet assemblies,
   3/package.
1 package Microfil needles WPI 5/package
10 BD 96-well plates, 2 or 1 ml/well
   (depending on nozzle head selected).
16 boxes 2 ml tips or 8 boxes 1 ml tips
   (depending on nozzle head selected).
1 MC-OX model cell (Re 1MΩ, Cm 220 pF,
   Rm switched between 1MΩ or 10 kΩ).
Alignment tools for oocyte impaling and fluidics.
Extra bulb for light source.
Storage rack for electrode holders.
Theory and Operation manual.
Software User's manual

Options

1 ml or 2 ml nozzle head.

For more information and pricing, please contact the OpusXpress product manager at OpusXpress@moldev.com.

OpusXpress 6000A

• Integrated hardware and software package comes complete with all hardware, electronics, and software required for full operation, including a computer fully configured with OpusXpress software.
• When ordering, please specify which nozzle head you would like, 2 ml or 1 ml. If you do not specify an option, you will receive the 2 ml nozzle head.