Distributed neurochemical sensing: in vitro experiments

Experimental results characterizing a VLSI multi-channel potentiostat sensor system designed for sensing distributed neurotransmitter activity are presented. Neurotransmitter concentration is electrochemically transduced using an external carbon fiber electrode. Resultant current is processed by an integrated potentiostat, consisting of a current amplification stage, current-mode delta-sigma A/D converter, and counting decimator. Electrical characterization has shown that the VLSI potentiostat is sensitive to picoampere levels of input current. Furthermore, both static and dynamic neurochemical measurements of dopamine are verified in vitro, proving the utility of the device for brain slice studies. Lastly, a biologically inspired experiment, whereby the catabolism of dopamine is emulated with the addition of the catechol-o-methyl transferase (COMT) enzyme to modulate dopamine levels in vitro.