Horseradish peroxidase-catalyzed polymerization of l-DOPA for mono-/bi-enzyme immobilization and amperometric biosensing of H2O2 and uric acid

Horseradish peroxidase (HRP)-catalyzed polymerization of l -DOPA (vs. dopamine) in the presence of H 2 O 2 (and uricase (UOx)) was exploited to immobilize mono-/bi-enzymes for hydroquinone-mediated amperometric biosensing of H 2 O 2 and uric acid (UA). The relevant polymeric biocomposites (PBCs) were prepared in phosphate buffer solution containing HRP and l -DOPA (or plus UOx) after adding H 2 O 2 . The mono-/bi-enzyme amperometric biosensors were prepared simply by casting some of the PBCs on Au-plated Au (Au plate /Au) electrodes, followed by coating with an outer-layer chitosan (CS) film for each. UV–vis spectrophotometry , scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy were used for film characterization and/or process monitoring. The HRP immobilized by enzyme catalysis well preserved its bioactivity, as confirmed by UV–vis spectrophotometry . Under optimized conditions, the monoenzyme CS/HRP-poly( l -DOPA) (PD)/Au plate /Au electrode potentiostated at −0.1   V responded linearly to H 2 O 2 concentration from 0.001 to 1.25   mM with a sensitivity of 700   μA   mM −1   cm −2 and a limit of detection (LOD) of 0.1   μM, and the bienzyme CS/UOx–HRP–PD/Au plate /Au electrode at −0.1   V responded linearly to UA concentration from 0.001 to 0.4   mM with a sensitivity of 349   μA   mM −1   cm −2 and a LOD of 0.1   μM. The mono-/bi-enzyme biosensors based on biosynthesized PD performed better than many reported analogues and those based on similarly biosynthesized polydopamine.