Evaluation of a new disposable screen-printed sensor strip for the measurement of NADH and its modification to produce a lactate biosensor employing microliter volumes

A combined sensor strip was fabricated by screen-printing a Meldola Blue modified carbon working electrode and a Ag/AgCl combined reference/counter electrode alongside each other on a PVC substrate. This was investigated as an amperometric sensor for NADH, at an applied potential of 0 V, both in bulk solutions under hydrodynamic conditions and using 20 mu L volumes without agitation. The former technique gave linear responses in the range 3-60 x 10(-6) mol dm(-3) and the latter in the range 10-5 x 10(-4) mol dm(-3) of NADH. Further modification of the electrodes with NAD(+) and lactate dehydrogenase converted the device to a biosensor for lactate both in spiked phosphate buffer and bovine serum. The sensors demonstrated good linear responses in the range 0-20 x 10(-3) mol dm(-3).