Flow injection amperometric uric acid biosensor based on AuNPs-GO-CS porous composite cryogel coated on PB-PEDOT:PSS...

An enzymatic amperometric uric acid (UA) biosensor was successfully developed by modifying a screen-printed carbon electrode (SPCE) with Prussian blue-poly(3,4-ethylene dioxythiophene) polystyrene sulfonate composite (PB-PEDOT:PSS). The modified SPCE was coated with gold nanoparticles-graphene oxide-chitosan composite cryogel (AuNPs-GO-CS cry). Uricase (UOx) was directly immobilized via chemisorption on AuNPs. The nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, and Fourier transform infrared spectroscopy. The electrochemical characterization of the modified electrode was performed by cyclic voltammetry and electrochemical impedance spectroscopy. UA was determined using amperometric detection based on the reduction current of PB which was correlated with the amount of H₂O₂ produced during the enzymatic reaction. Under optimal conditions, the fabricated UA biosensor in a flow injection analysis (FIA) system produced a linear range from 5.0 to 300 μmol L^-1 with a detection limit of 1.88 μmol L^-1. The proposed sensor was stable for up to 221 cycles of detection and analysis was rapid (2 min), with good reproducibility (RSDs < 2.90 %, n = 6), negligible interferences, and recoveries from 94.0 ± 3.9 to 101.1 ± 2.6 %. The results of UA detection in blood plasma were in agreement with the enzymatic colorimetric method (P > 0.05).