Proposal Number: 1063347 Proposal Title: IDBR: High throughput instrumentation for lipid bilayers and single-channel patch-clamp
This award supports a project that will develop integrated micro-chip instrumentation used for recording the minute currents across biological cell membranes. The goal is an improvement of the sensitivity and the throughput of electrophysiology instruments for the study of membrane proteins, including functional analysis of ion channels and DNA identification using special channels with nano-scale pores. This project will also advance the sensitivity of patch-clamp recording systems and will allow inspection of the opening and closing of individual ion-channels whose conductance has previously been too low to examine. The proposed instrument will increase the number of recording channels by several hundred times. The research will advance the design of ultra-low noise instruments that maintain a small footprint and can be manufactured with standard and cheap microchip technologies. We will design, instrument and test integrated circuitry to increase the density of recording sites and miniaturize the recording equipment.
Current measurements are used throughout biomedical instruments and thus the work proposed here will have large applicability in medicine and engineering. The amplifier we will develop can be used in instruments for cellular biology and physiology, DNA sequencing with nanopores, low-power circuit for cellular interfaces, nano-sensors and biomedical nano- devices, low-noise acquisition of bio-signals. The societal impacts of the technology and ion-channel research are in the prevention of diseases, and in many other scientific fields that rely on cheap recording of genetic material, such as forensics, biology, anthropology. Low-cost high-throughput electrophysiology devices also improve drug development and delivery, both for disease prevention, gene therapy, as well as for personalized medicine. The principal investigators are involved in the Science Saturdays program for under-represented minority and women students. Within this acclaimed program, the PIs are working with children and teachers from K to 12, to promote practical science projects and to develop interest, abilities and communication skills. The investigators excite students interest with presentations in local schools, participation to the New Haven Science Fair, organizing laboratory tours and weekend science projects.
The Patch-clamp amplifier is the "gold standard" to measure currents ?owing through ion channels. Ion channels are structures embedded in the cell membrane that conduct electrical currents in the order of 1-10 pA. Ion channels are widely targeted by drugs used in therapy and therefore the high-throughput screening of drugs that seek to block or modulate the function of specific ion channels is of great interest. The patch-clamp technique o?ers the highest signal-to-noise ratio available to characterize ion channel activity, but is labor- intensive when performed manually. Therefore, an automated patch-clamp recording system that can produce higher-throughput assays is highly desirable. The limiting factor in designing a high-throughput patch-clamp system is the size and the cost of the amplifier. Amplifiers made from discrete electrical components occupy a large area and costs thousands of dollars. A patch-clamp amplifier system can be reduced to millimeter sized dimensions if it can be implemented on silicon as an integrated circuit. Once the photolithographic masks for implementing the design in silicon have been fabricated, the cost of manufacturing a chip-based amplifier is only a few dollars. We have designed, fabricated and tested an integrated patch-clamp amplifier system that has series resistance compensation and parasitic compensation capability. In addition, the system has the ability compensate for the distributed series resistance present in a population patch-clamp system. The circuit can also compensate for leak currents that result from inadequate sealing between the cell membrane and the electrode. We have integrated an anti-aliasing ?lter and an input reconstruction ?lter to the system to minimize the number of external components necessary for integration into larger systems. The circuit employs variable feedback to enable the recording of currents of varying magnitude. The entire system which consists of 4 fully functional patch-clamp channels, occupy an area of 4 × 8mm. We have demonstrated the circuit’s usefulness by recording ion channel currents from live cells. The system was fabricated using Silicon-on-Sapphire technology. The system can be used as is to substitute a commercial bench-top system or more importantly, it is ready to be integrated into a larger high-throughput system. The hope is that the integrated patch-clamp system would facilitate the fabrication of massively parallel high-throughput systems that would make the functional analysis of ion channels and genes and also the screening of drugs a much more efficient and fail-safe process.
