Project 02

Detection and Processing Of Full Channel Ionic Current Using Patch Clamp Technique

 

It is nearly 20 years since the introduction of the ion-channel patch-clamp recording technique, and over the last two decades its refinements and diverse applications such as Drug discovery have served to maintain it as the dominant technique in membrane physiology. Patch clamp technique was introduced by Neher and Sakmann (1976) for recording a current in the small patch of membrane under voltage clamp conditions, most notably the development of “gigaseal” by E.Neher (1981).

 

Patch clamp has been an essential tool in the study of ion channels. Drug discovery, however often requires high throughput methods given the large number of compounds in compound libraries that must be screened. Conventional patch clamp is a very high resolution technique, supplying both high quality data and high information content. Despite these advantages it remains a low efficiency technique such that even a skilled patch clamper can record data from only 20-30 cells during an 8-hour work day. In response to this major limitation, several companies have developed automated patch clamp systems that can record from hundreds to thousands of cells a day. Before automated path clamp systems, there were indirect high throughput assays such as binding assays, voltage-sensitive fluorescence resonance energy transfer, and flux assays. While these techniques are suited for high-throughput recordings, the information provided by them are extremely limited because they are not functional assays. Hits are often false-negatives or false-positives and each hit must be subjected to conventional patch clamp. False negatives can be particularly dangerous when screening for hERG blockade, especially when there are a large number of false negatives. This emphasizes the importance of confirmatory patch clamp measurements, and also emphasizes the importance of high content screening.

 

In this project, the design, implementation, simulation and recording of ultra low current by using transimpedence amplifier, are described, with the current sensitivity in the range of femto ampheres. Capacitive-feedback is used with active load to obtain a 20MΩ transimpedance gain. The challenging task in designing includes achieving adequate performance in gain, noise immunity and stability. The final results are recorded on a computer software which can be further analyzed for research purpose