Toward Electrochemical Detection of Saxitoxin: Signal Amplification by Redox Cycling at a Self-Contained Microelectrode Array in a Microchannel

by Fritsch, Ingrid; Gawley, Robert E.; Lewis, Penny M.

Detection methods for the marine toxin saxitoxin (STX) are bulky, expensive, or require loss of animal life. A sensitive, portable electrochem. assay for STX detection is being developed. The assay will employ a STX recognition element, saxiphilin c-lobe, immobilized in a microchannel to capture STX. An electroactive ferrocene-conjugated STX (FcSTX), which binds competitively to saxiphilin c-lobe, will be detected at a microelectrode array incorporated into the microchannel. The detection scheme involves signal amplification at the array by redox cycling between electrodes (generators) that oxidize FcSTX and nearby electrodes (collectors) that re-reduce it. The individually addressable array-which is entirely contained within the channel-consists of fourteen working electrodes (50-µm wide) sepd. by 25-µm gaps, as well as three counter electrodes (800-µm wide) and three pseudoreference electrodes (400-µm wide); therefore, external counter and ref. electrodes are not required. This presentation will focus on signal amplification studies in the confined, static soln. in the microchannel using a model redox species and various configurations of active generators and collectors. Amplification factors as high as 7.60 were obtained.