DEVELOPING A NOVEL, POINT-OF-CARE DIAGNOSTIC TEST FOR STROKE

Stroke is a leading cause of death and disability worldwide, but outcomes can be improved by reducing the time to reperfusion. A portable device that can assist clinicians with the differentiation of stroke from conditions with similar symptoms (‘stroke mimics’) and provide additional information about a given stroke prior to hospital admission could accelerate diagnosis and therefore treatment. Adenosine and its metabolites inosine, hypoxanthine, and xanthine (the ‘purines’) are promising candidate biomarkers, as stroke is associated with their elevated release into the extracellular space and peripheral blood. However, little is known about the specific pattern of purine release over the time course of a stroke. Therefore, we have used amperometric purine sensors to characterise this in rats subjected to experimental ischaemic stroke by stereotactic injection of endothelin-1. Purine levels were measured in peripheral blood before and after stroke induction using electrochemical biosensors functionalised with adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase, which catalyse the production of hydrogen peroxide from the purines. A ferric hexacyanoferrate (Prussian blue) mediator is also used to permit the reduction of hydrogen peroxide at a potential of around 0 V vs Ag/AgCl. Purine sensor recordings indicated an overall relative reduction signal compared to non-functionalised null sensors, which was most prominent between 30 and 45 minutes after stroke induction. Correlating stroke severity and timing with purine levels, measured with user-friendly tools like electrochemical biosensors, could speed up stroke diagnosis and improve outcomes for patients.