NITRIC-OXIDE RELEASE FROM A SINGLE CELL MEASURED INSITU BY A PORPHYRINIC-BASED MICROSENSOR

NITRIC oxide is an important bioregulatory molecule, being responsible, for example, for activity of endothelium-derived relaxing factor (EDRF)1-4. Acute hypertension5, diabetes6, ischaemia7 and atherosclerosis8 are associated with abnormalities of EDRF. Nitric oxide is thought to be a retrograde messenger in the central nervous system9. The technology is not yet available for rapid detection of NO released by a single cell in the presence of oxygen and/or nitrite, so the release, distribution and reactivity of endogenous NO in biological systems cannot be analysed. Here we describe a porphyrinic microsensor that we have developed and applied to monitoring NO release in a microsystem. We selectively measured in situ the NO released from a single cell with a response time of less than 10 ms. The microsensor consists of p-type semiconducting polymeric porphyrin and a cationic exchanger (Nafion) deposited on a thermally sharpened carbon fibre with a tip diameter of approximately 0.5-mu-m. The microsensor, which can be operated in either the amperometric or voltammetric mode, is characterized by a linear response up to 300-mu-M and a detection limit of 10 nM. Nitric oxide at the level of 10(-20) mols can be detected in a single cell.