title: Integration of enzymes and electrodes: spectroscopic and electrochemical studies of chitosan-enzyme films.
abstract: A new film-forming solution was developed for the efficient immobilization of enzymes on solid substrates. The solution consisted of a biopolymer, chitosan (CHIT), that was chemically modified with a permeability-controlling agent, Acetyl Yellow 9 (AY9), using glutaric dialdehyde (GDI) as a molecular tether. A model enzyme, glucose oxidase (GOx), was mixed with the CHIT-GDI-AY9 solution and cast on the surface of platinum electrodes to form robust CHIT-GDI-AY9-GOx films for glucose biosensing. UV-visible and infrared spectroscopies were used to determine the composition of the films. The optimized films contained on average 1 molecule of AY9/3 glucosamine units of chitosan and 25 free GDI tethers/1 molecule of GOx. The electrochemical assays of the films indicated both a very high efficiency of enzyme immobilization (approximately 99%) and large enzyme activity (60 units cm(-2)). The latter translated into a high sensitivity (42 mA M(-1) cm(-2)) of the Pt/CHIT-GDI-AY9-GOx biosensor toward glucose. The biosensor operated at 0.450 V, had a fast response time (t90% < or = 3 s), and was free of typical interferences, and its dynamic range covered 3 orders of magnitude of glucose concentrations. The lowest actually detectable concentration was 10 microM glucose. In addition, the biosensor displayed a practical shelf life and excellent operational stability, e.g. its response was stable during 24-h testing under continuous polarization and continuous flow of 5.0 mM glucose solution. The proposed approach to enzyme immobilization is simple, efficient, and cost-effective and should be of importance in the development of biosensors based on other enzymes that are more expensive than glucose oxidase.
authors.affiliation: Department of Chemistry, University of Texas at San Antonio, 78249-0698 USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Wei
authors.forename: Juan
authors.initials: J
authors.lastname: Cruz
authors.forename: Waldemar
authors.initials: W
authors.lastname: Gorski
mesh_terms: D015374:Biosensing Techniques; D002240:Carbohydrate Sequence; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry*; D048271:Chitosan; D004563:Electrochemistry; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000737:chemistry*; D005947:Glucose / Q000032:analysis; D005949:Glucose Oxidase / Q000737:chemistry; D007202:Indicators and Reagents; D008567:Membranes, Artificial; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D004800:Enzymes, Immobilized; D007202:Indicators and Reagents; D008567:Membranes, Artificial; D002686:Chitin; D048271:Chitosan; D005949:Glucose Oxidase; D005947:Glucose