Development and electrochemical investigations of an EIS( electrolyte-insulator-semiconductor) based biosensor for cyanide detection

A cyanide biosensor based on a pH-sensitive p-doped electrolyte-insulator-semiconductor (EIS) structure with an immobilised enzyme (cyanidase) is realised at the laboratory scale. The immobilisation of the cyanidase is performed in two distinct steps: first, the covalent coupling of cyanidase to an N-hydroxysuccinimide-(NHS) activated Sepharose (TM) gel and then, the physical entrapment of NHS-activated Sepharose (TM) with the immobilised cyanidase in a dialysis membrane onto the EIS structure. The immobilisation of the cyanidase to the NHS-activated Sepharose (TM) is studied by means of gel electrophoresis measurements and investigations using an ammonia-(NH3) selective electrode. For the electrochemical characterisation of the cyanide biosensor, capacitance/voltage and constant capacitance measurements, respectively, have been carried out. A differential measurement procedure is presented to evaluate the cyanide concentration-dependent biosensor signals.