Coupling the lactate oxidase to electrodes by ionotropic gelation of biopolymer.
A direct ionotropic gelation of the polycationic biopolymer chitosan (CHIT) with the polyanionic enzyme lactate oxidase (LOx) was used to form thin biopolymer-enzyme films on the surface of platinum electrodes. The electrochemical assays of such films revealed a well-defined capacity of CHIT for the retention of LOx. The stoichiometry of the CHIT-LOx polyelectrolyte complexes was found to be approximately 1:40, i.e., on average, 1 CHIT chain retained 40 molecules of LOx in the CHIT-LOx films. The enzyme retention was ascribed to strong electrostatic interactions between the LOx and a fraction of the protonated amino groups on the CHIT chains. Although the LOx is inherently unstable outside its natural matrix, it displayed high surface activity of 0.26 units cm(-)(2) in the matrix of CHIT. This correlated with good stability of the biopolymer-enzyme films as demonstrated by a constant response of Pt/CHIT-LOx electrodes to lactate during continuous 24-h testing. When compared to other single-film lactate sensors, the Pt/CHIT-LOx electrodes displayed the best combination of analytical properties in terms of a low detection limit (50 nM), high sensitivity (0.23 A M(-)(1) cm(-)(2)), and fast response time (<1 s). Such a performance validated the CHIT-LOx system as an attractive sensing element for the development of new lactate biosensors.
Department of Chemistry, University of Texas at San Antonio, 78249-0698, USA.
Xin
X
Wei
Maogen
M
Zhang
Waldemar
W
Gorski
D001704:Biopolymers; D004563:Electrochemistry; D004566:Electrodes; D004800:Enzymes, Immobilized; D005782:Gels; D007202:Indicators and Reagents; D006899:Mixed Function Oxygenases / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry
D001704:Biopolymers; D004800:Enzymes, Immobilized; D005782:Gels; D007202:Indicators and Reagents; D006899:Mixed Function Oxygenases; C021497:lactate 2-monooxygenase; D010100:Oxygen