Microfabricated voltammetric neuro-arrays for use in vitro.

This work describes the manufacture and testing of microfabricated voltammetric electrode arrays for the neuroelectrical and neurochemical study of neurons in cell culture. Neurochemical sensing of dopamine and its metabolites is provided by voltammetry. Two versions of the device are presented: a passive device containing only the chemical sensing array, and a prototype active device with on-board signal amplification. The passive device contains a four by four array of sixteen neurochemical/neuroelectrical sensors. Five versions of the passive device are presented with platinum working electrode areas of 10000, 1024, 64, 16, and 4mum2. The reference electrodes on the device are silver/silver chloride pseudo-reference electrodes with areas of 12544, 1444, 196 and 64mum2 respectively. The active devices have working electrode areas of 64mum2 and reference electrode areas of 196mum2. Fabrication processes for passive and active arrays are described. The active devices are created by performing post-processing on standard CMOS foundry fabricated die obtained through the MOSIS service. Results from living human neuron cultures plated onto the passive devices are presented. The neurons survived and produced data throughout a study period of seventy-five days. Calibration curves for dopamine taken in buffer solution with commercial equipment show a detection limit of 662nM with a sensitivity of 224nA/M on the 64mum2 working electrode devices. Calibration data taken in culture media with equipment optimized for the sensors suggests detection limits for dopamine below 100nM. A technique for creating miniature silver/silver chloride reference electrodes in standard reactive-ion etch equipment is also presented. The process is characterized for the effect of the process parameters on the estimated lifetime of the devices soaking in phosphate buffer solution. A device using the optimized set of parameters should last approximately 35 days in phosphate buffer solution. The passive devices appear to be very effective neuroscience tools. The data collected from the human neuron culture suggests the ability to study not only the electrical communication among the cultured neurons, but also allow examination of corresponding neurotransmitter releases.Ph.D.Analytical chemistryApplied SciencesBiological SciencesBiomedical engineeringElectrical engineeringNeurosciencesPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124319/2/3137947.pd