An electrochemiluminescent biosensor based on polypyrrole immobilized uricase for ultrasensitive uric acid detection

An electrochemiluminescent (ECL) biosensor based on immobilized uricase has been developed for uric acid detection with luminol as signaler. The uricase has been embedded in polypyrrole (PPy) matrix on platinum electrode during the electropolymerization of pyrrole monomer at potential of 0.80 V versus Ag/AgCl. This ECL-based biosensor responds to uric acid due to yielded hydrogen peroxide during its catalytic oxidization by uricase with potassium ferricyanide acted as an electron receptor to promote the enzymatic reaction. The so-generated hydrogen peroxide enhanced the ECL intensity of luminol. The kinetic parameters of enzymatic reaction as maximum reaction rates (Vmax) and Michaelis–Menten constants (Km) are also evaluated for 1.42 × 10−3 A s−1 and 3.4 × 10−7 M in the presence of potassium ferricyanide, which were all greatly improved. The resulting biosensor showed excellent analytical performance for determination of uric acid as more than 50 times sensitivity than a bare electrode. It gives a 75 pM of detection limit and a relative standard deviation of 4.4% for 6.25 × 10−9 M uric acid (n = 6). This ECL-based biosensor has been successfully applied for determination of uric acid in porphyra and kelp samples.