title: Electro-induced covalent cross-linking of chitosan and formation of chitosan hydrogel films: its application as an enzyme immobilization matrix for use in a phenol sensor.
abstract: We report a novel electrochemical method for making covalently cross-linked chitosan films on the surface of a screen printed carbon electrode. In the presence of a freely diffusing ruthenium complex, Ru(bpy)(2)Cl(2), soluble chitosan becomes irreversibly cross-linked in response to a reducing potential and subsequently deposits on the electrode surface to form a hydrogel film which shows robustness in harsh acidic conditions. The cross-linked chitosan film presents excellent ability to facilitate the diffusion and electron transfer process of the negatively charged redox couple [Fe(CN)(6)](3-)/[Fe(CN)(6)](4-) at the electrode surface, while its impact on the positively charged redox couple [Ru(NH(3))(6)](2+)/[Ru(NH(3))(6)](3+) is minimal. By covalently immobilizing the enzyme tyrosinase in a preformed cross-linked chitosan film via a similar mechanism, a sensitive phenol sensor is constructed with a broad dynamic range. The potential advantages of this method are also discussed.
authors.affiliation: Department of Chemistry, Morgan State University, Baltimore, Maryland 21251, USA. yongchao.zhang@morgan.edu
authors.forename: Yongchao
authors.initials: Y
authors.lastname: Zhang
authors.forename: Chang
authors.initials: C
authors.lastname: Ji
mesh_terms: D000363:Agaricales / Q000201:enzymology; D048271:Chitosan / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000378:metabolism; D019800:Phenol / Q000032:analysis*; D012680:Sensitivity and Specificity
chemical_list: D004800:Enzymes, Immobilized; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D019800:Phenol; D048271:Chitosan; D014442:Monophenol Monooxygenase