Direct detection of low-concentration NO in physiological solutions by a new GaAs-based sensor

Nitric oxide (NO) acts as a signal molecule in the nervous system, as a def ense against infections, as a regulator of blood pressure, and as a gate ke eper of blood flow to different organs. In vivo, it is thought to have a li fetime of a few seconds. Therefore, its direct detection at low concentrati ons is difficult. Mie report on a new type of hybrid, organic-semiconductor , electronic sen-sor that makes detection of nitric oxide in physiological solution possible. The mode of action of the device is described to explain how its electrical resistivity changes as a result of NO binding to a laye r of native hemin molecules. These molecules are self-assembled on a GaAs s urface to which they are attached through a carboxylate binding group. The new sensor provides a fast and simple method for directly detecting NO at c oncentrations down to 1 muM in physiological aqueous (pH=7.4) solution at r oom temperature.