Silicon Electrochemical Neurosensor Systems

Abstract

Arrays of silicon neurosensors that detect both electrical signals and neurotransmitter levels in human neuron cultures have been fabricated. Neurochemical sensing of dopamine and its metabolites is provided by voltammetry. Five versions of the passive device were fabricated with platinum working electrode areas as small as 4 mm2 and silver/silver chloride pseudo-reference electrodes. Living human neuron cultures survived and produced data on passive devices throughout a study period of seventy-five days. Calibration curves for dopamine taken in culture media with equipment optimized for the sensors suggests detection limits for dopamine below 100 nM. To minimize system noise, prototype devices incorporating active circuitry were developed. The active devices are formed by post-processing standard foundry-fabricated CMOS circuits from the MOSIS service to form the sensor-specific features. Data from these devices, and early results from in vivo electrochemical neurosensors, will be presented. Circuits developed for these active brain probes and for other implantable biosensors highlight several goals of circuits for biological applications: small system size; small electronics size, low voltage, and low power.