The Rational Design of Nitric Oxide Selectivity in Single-Walled Carbon Nanotube near Infrared Fluorescence Sensors for Biological Detection

A major challenge in the synthesis of nanotube or nanowire sensors is imparting selective analyte binding through means other than covalent linkages which compromise electronic and optical properties. We synthesize a 3,4-diaminophenyl-functionalized dextran (DAP-dex) wrapping for single-walled carbon nanotubes (SWNT) that imparts rapid and selective fluorescence detection of NO, a messenger for biological signaling. The near infrared (nIR) fluorescence of SWNTDAP-dex is immediately and directly bleached by NO, but not by other reactive nitrogen and oxygen species. This bleaching is reversible and shown to be caused by electron transfer from the top of the valence band of SWNT to the lowest unoccupied molecular orbital (LUMO) of NO. The resulting optical sensor is capable of real-time and spatially resolved detection of NO produced by stimulating NO synthase (iNOS) in macrophage cells. We also demonstrate the first optical sensor capable of in-vivo NO detection in a mouse model.