Localized chemical release from an artificial synapse chip.

A device that releases chemical compounds in small volumes and at multiple, well defined locations would be a powerful tool for clinical therapeutics and biological research. Many biomedical devices such as neurotransmitter-based prostheses or drug delivery devices require precise release of chemical compounds. Additionally, the ability to control chemical gradients will have applications in basic research such as studies of cell microenvironments, stem cell niches, metaplasia, or chemotaxis. We present such a device with repeatable delivery of chemical compounds at multiple locations on a chip surface. Using electroosmosis to drive flow through microfluidic channels, we pulse minute quantities of a bradykinin solution through four 5-microm apertures onto PC12 cells and show stimulation of individual cells using a Ca(2+)-sensitive fluorescent dye. We also present basic computational results with experimental verification of both fluid ejection and fluid withdrawal by imaging pH changes by using a fluorescent dye. This "artificial synapse chip" is a prototype neural interface that introduces a new paradigm for neural stimulation, with eventual application in treating macular degeneration and other neurological disorders.