Abstract
Described here is fabrication of a pH-sensitive, optically transparent transducer composed of a planar indium-tin oxide (ITO) electrode overcoated with a a poly(aniline) (PANI) thin film and a porous sol-gel layer. Adsorption of the PANI film renders the ITO electrode sensitive to pH, whereas the sol-gel spin-coated layer makes the upper surface compatible with fusion of phospholipid vesicles to form a planar supported lipid bilayer (PSLB). The response to changes in the pH of the buffer contacting the sol-gel/PANI/ITO electrode is pseudo-Nernstian with a slope of 52 mV/pH over a pH range of 4-9. Vesicle fusion forms a laterally continuous PSLB on the upper sol-gel surface that is fluid with a lateral lipid diffusion coefficient of 2.2 μm2/s measured by fluorescence recovery after photobleaching. Due to its lateral continuity and lack of defects, the PSLB blocks the pH response of the underlying electrode to changes in the pH of the overlying buffer. This architecture is simpler to fabricate than previously reported ITO electrodes derivatized for PSLB formation, and should be useful for optical monitoring of proton transport across supported membranes derivatized with ionophores and ion channels.
Highlights
An artificial lipid bilayer that modulates the transmembrane flux of ions to an underlying electrode is the basis for several types of bioelectronic devices, including biosensors and biomimetic fuel cells [1,2,3,4,5,6]
After curing for 18 hours at 50 °C, indium-tin oxide (ITO)/PANI/sol-gel electrodes were qualitatively tested to ensure that the solgel reaction was essentially complete by exposing slides to 30 mM universal buffer, pH 4
PANI adsorbed on an oxidized Si wafer produced a thickness of 2.9 nm (± 0.17, n=3), confirming that multilayer adsorption occurred on ITO
Summary
An artificial lipid bilayer that modulates the transmembrane flux of ions to an underlying electrode is the basis for several types of bioelectronic devices, including biosensors and biomimetic fuel cells [1,2,3,4,5,6]. [11,12,13,14,15,16,17]) To create these devices, lipid bilayer assemblies supported on a variety of electrode materials have been prepared and characterized Ion selectivity can be obtained by chemically modifying the electrode, and conductive polymers are promising candidates for this purpose. These polymers exhibit electrical properties characteristic of semiconductors [18], and like semiconductors, conductivity can
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