Chronocoulometric determination of urea in human serum using an inkjet printed biosensor

A biosensor for the determination of urea in human serum was fabricated using a combination of inkjet printed polyaniline nanoparticles and inkjet printed urease enzyme deposited sequentially onto screen-printed carbon paste electrodes. Chronocoulometry was used to measure the decomposition of urea via the doping of ammonium at the polyaniline-modified electrode surface at -0.3V vs. Ag/AgCl. Ammonium could be measured in the range from 0.1 to 100mM. Urea could be measured by the sensor in the range of 2-12mM (r2=0.98). The enzyme biosensor was correlated against a spectrophotometric assay for urea in 15 normal human serum samples which yielded a correlation coefficient of 0.85. Bland-Altman plots showed that in the range of 5.8-6.6mM urea, the developed sensor had an average positive experimental bias of 0.12mM