Bi-enzyme l-arginine-selective amperometric biosensor based on ammonium-sensing polyaniline-modified electrode

A novel l-arginine-selective amperometric bi-enzyme biosensor based on recombinant human arginase I isolated from the gene-engineered strain of methylotrophic yeast Hansenula polymorpha and commercial urease is described. The biosensing layer was placed onto a polyaniline–Nafion composite platinum electrode and covered with a calcium alginate gel. The developed sensor revealed a good selectivity to l-arginine. The sensitivity of the biosensor was 110±1.3 nA/(mM mm2) with the apparent Michaelis–Menten constant (KMapp) derived from an l-arginine (l-Arg) calibration curve of 1.27±0.29 mM. A linear concentration range was observed from 0.07 to 0.6 mM, a limit of detection being 0.038 mM and a response time — 10 s. The developed biosensor demonstrated good storage stability. A laboratory prototype of the proposed amperometric biosensor was applied to the samples of three commercial pharmaceuticals (“Tivortin”, “Cytrarginine”, “Aminoplazmal 10% E”) for l-Arg testing. The obtained l-Arg-content values correlated well with those declared by producers.

Graphical AbstractCalibration curve for amperometric response on l-Arg of the developed bi-enzyme PANi-Nafion/Pt electrode. Inset: chronoamperometric current response upon subsequent additions of L-Arg. Conditions: −200 mV vs Ag/AgCl electrode in 30 mM Phosphate buffer, pH 7.5 at 22 °C.Figure optionsDownload full-size imageDownload as PowerPoint slide