Fast scan cyclic voltammetry (FSCV) is a popular technique for the <i>in vivo</i> measurement of electroactive neuromodulators on a sub-second time scale with micrometer spatial resolution. A rapid (&gt;100 V/s) voltage sweep electrolyzes these molecules, with the shape of the resulting cyclic voltammogram providing a chemical identifier for the species of interest, and the resulting measured peak current being proportional to concentration. However, not all analytes of interest are electroactive and thus cannot be directly detected by FSCV. A popular method to detect molecules that are not electroactive is to use an enzyme modified microelectrode to generate an electroactive species through the consumption of the analyte of interest. However, the main challenge in fabricating enzyme-modified electrodes usually involves producing a stable coating which does not interfere with enzyme function. Chitosan is a natural polysaccharide that can be electrically deposited onto an electrode through the reduction of protons, inducing a local basic pH shift that causes chitosan to precipitate onto the electrode, trapping the enzyme with it. Unfortunately, this technique results in the formation of non-uniform films and the formation of bubbles on the film due to hydrogen gas produced during the reduction step. In this work, we show that the addition of redox mediators into the coating solution improves the ability of chitosan to create uniform and reproducible films onto carbon fiber microelectrodes suitable for FSCV detection. Glucose oxidase was embedded into these more uniform chitosan coatings to create enzyme-modified microelectrodes capable of detecting glucose. These sensors were characterized analytically, biochemically, and were shown to perform as well as those produced through the reduction of protons, though more robust and with higher throughput.

Improving the formation of electrically-deposited enzyme-embedded chitosan coatings onto carbon fiber microelectrodes

254th National Meeting (2017)

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