Optical enzymatic detection of glucose based on hydrogen peroxide-sensitive HiPco carbon nanotubes

We recently observed that surfactant sodium dodecyl sulfate (SDS)-encased HiPco single-walled carbon nanotubes (SWNTs) respond optically to hydrogen peroxide (H₂O₂) in the near-infrared region. In this report, we demonstrate that SDS-encased SWNTs immobilized with glucose oxidase (GO_x) can be used to optically detect an enzymatic reaction of glucose based on their H₂O₂sensitivity as well as pH sensitivity. Only the enzymatic product H₂O₂induces the SWNT near-infrared spectral changes in buffer solutions (pH = 6.0), but both H₂O₂and gluconic acid products do this in unbuffered solutions. The SWNT optical response to glucose possesses sensitivity and selectivity similar to an electrochemical method using carbon nanotube nanoelectrode arrays. Our results suggest possible carbon nanotube-based optical tools for molecular recognition applications.