Needle-type dual microsensor for the simultaneous monitoring of glucose and insulin

A miniature needle-type sensor suitable for the simultaneous amperometric monitoring of glucose and insulin is described. The integrated microsensor consists of dual (biologically and chemically) modified carbon-paste working electrodes inserted into a 14-guage needle. The glucose probe is based on the biocatalytic action of glucose oxidase, and the insulin one relies on the electrocatalytic activity of ruthenium oxide. The analytical performance of the dual sensor is assessed under flow injection conditions. The needle dual detector exhibits a very rapid response to dynamic changes in the concentrations of glucose and insulin. No apparent cross reactivity is observed in mixtures containing millimolar glucose levels and nanomolar insulin concentrations. The response is highly linear (to at least 1000 nM insulin and 14 mM glucose) and reproducible (RSD = 2.6-4.1%). The combination microsensor holds great promise for real-time measurements of the insulin/glucose ratio and for improved management of diabetes.