UC San Diego

The development of a viable sensing platform for the purpose of small molecule detection was explored on two different platforms: a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and an Interdigitated Electrode (IDE). A standard operating procedure (SOP) for the reliable fabrication of gold gated MOSFET platforms and IDE platforms was created via standard cleanroom techniques. The n-MOSFET platform (p-channel device) drain current (IDS) shifts due to the binding of a self assembled monolayer (SAM) onto the Au-gated FET. The IDS directly correlates to the (VG - VTH)². Binding of an electron donating pdiethyamino phenyl isocyanide SAM onto the gate results in an positive shifted IDS /decreased VTH, while an electron withdrawing species, 1,4-phenyl diisocyanide SAM exhibits a negative IDS/increased VTH. These changes in VTH shift corresponds to an electron donating species acting as a positive gate bias into the gold gate while electron acceptors acts as a negative gate bias. Binding studies show thiophene 3-boronic acid (TBA) readily binds glucose with a binding constant of Keq = 42M⁻¹, an order of magnitude larger than reported literature values for phenyl boronic acid. Chemical binding of 1,2-diol to poly-TBA was shown by fluorescent emission spectroscopy. Crystal structures of TBA bound to ethylene glycol and pinnacol confirm 1,2-diol binding. An IDE platform was functionized with thiophene 3-boronic acid (TBA) polymer via electrochemical deposition for direct detection of 1,2-diols. Conduction measurements were made upon exposure to 1,2-diol functional groups such as glucose. Buffered (pH 7.4) glucose solutions from 1 - 10 mM exhibited increases in the current across the poly- TBA, and attributed to glucose binding. We have demonstrated by chemical, optical, and electrochemical methods that 1,2-diols such as glucose directly binds to poly-TBA and is an alternative to traditional indirect glucose detection methods