An integrated nitric oxide sensor based on carbon fiber coated with selective membranes

Abstract

In vivo measurement of nitric oxide (NO) in a biological matrix is very difficult because of its assumed low stability and fugacity, in addition to the complexity of such matrix, limited space and volume of biological samples. Among different NO detection strategies, electrochemical NO sensors are still widely used by NO researchers. Though many kinds of NO sensors are commercial available from World Precision Instruments, Inc. and other companies, the small NO sensors still are needed for the NO detection, especially in single cell levels. In this article a NO-selective ultramicrosensor was developed as an easily applicable tool for real time nitric oxide (NO) detection. The sensor consists of a 7 μm carbon fiber working electrode coated with cation exchanger (Nafion), then covered with NO-selective gas permeable polymeric membranes, and Ag/AgCl micro-reference/counter electrode. Compared with other reported NO sensors, the sensor described herein offers several advantages: i) high selectivity against ascorbate (> 104:1), dopamine (> 103:1) and nitrite (104:1); ii) detection limit to low nanomolar concentration; iii) rapid, inexpensive and reproducible fabrication; iv) wide linear calibration range from 10nM to 5 μM with R2 = 0.995; v) integrated ultramicrosensor eliminating the need of an external reference electrode, accordingly, experiments in small volume are possible with an integrated ultramicrosensor, even at single cell levels.