Patterned Electrode-Based Amperometric Gas Sensor for Direct Nitric Oxide Detection within Microfluidic Devices

摘要

This article describes a thin amperometric nitric oxiden(NO) sensor that can be microchannel embedded tonenable direct real-time detection of NO produced by cellsncultured within the microdevice. A key for achieving thenthin (∼1 mm) planar sensor configuration required fornsensor-channel integration is the use of gold/indium tinnoxide patterned electrode directly on a porous polymernmembrane (pAu/ITO) as the base working electrode. Thenelectrochemically deposited Au hexacyanoferrate layernon pAu/ITO is used to catalyze NO oxidation to nitrite atnlower applied potentials (0.65 0.75 V vs Ag/AgCl) andnstabilize current output. Furthermore, use of a gas-npermeable membrane to separate internal sensor com-npartments from the sample phase imparts excellent NOnselectivity over common interfering agents (e.g., nitrite,nascorbate, ammonia, etc.) present in culture media andnbiological fluids. The optimized sensor design reversiblyndetects NO down to the ∼1 nM level in stirred buffer andn10 nM in flowing buffer when integrated within anpolymeric microfluidic device. We demonstrate utility ofnthe channel-embedded sensor by monitoring NO genera-ntion from macrophages cultured within non-gas-perme-nable microchannels, as they are stimulated with endotoxin.