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 −0.3 V vs. Ag/AgCl. Ammonium could be measured in the range from 0.1 to 100 mM. Urea could be measured by the sensor in the range of 2–12 mM (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 5.8–6.6 mM urea, the developed sensor had an average positive experimental bias of 0.12 mM (<2% RSD) over the reference method.

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► A urease biosensor was fabricated using inkjet and screen printing.
► Polyaniline nanoparticles were inkjet printed onto screen-printed electrodes.
► Urease enzyme was also deposited using inkjet printing.
► Ammonium could be measured using chronocoulometry in the range 0.1–100 mM.
► Urea was measured in serum from 2 to 12 mM (r2 = 0.98) and correlated well with spectrophotometry (0.85).