title: pH-Sensitive "on-off" switching behavior of layer-by-layer films assembled by concanavalin A and dextran toward electroactive probes and its application in bioelectrocatalysis.
abstract: Concanavalin A (Con A) and dextran (Dex) were assembled into {Con A/Dex}(n) layer-by-layer films on electrodes by the biospecific interaction between them. At {Con A/Dex}(n) film electrodes, the cyclic voltammetric (CV) response of different electroactive probes, such as Fe(CN)(6)(3-), Ru(NH(3))(6)(3+), ferrocenecarboxylic acid (Fc(COOH)), and ferrocenedicarboxylic acid (Fc(COOH)(2)), was very sensitive to the solution pH. For example, in pH 4.0 buffers, the films showed good permeability toward Fe(CN)(6)(3-), leading to a well-defined CV peak pair of Fe(CN)(6)(3-) with large peak currents at about 0.17 V vs SCE. In pH 9.0 buffers, however, the CV response of Fe(CN)(6)(3-) was significantly depressed or even could hardly be observed. This pH-sensitive "on-off" switching property of the films toward the probe should be attributed to the different electrostatic interaction between Fe(CN)(6)(3-) and the Con A constituent in the films at different pH and could be further used to control the electrocatalytic reduction of H(2)O(2) by horseradish peroxidase (HRP) with Fe(CN)(6)(3-) as the diffusional electron transfer mediator. Fc(COOH)(2) showed the similar pH-dependent "on-off" behavior at {Con A/Dex}(n) film electrodes, and the corresponding pH-sensitive electrocatalytic oxidation of glucose by glucose oxidase (GOD) with Fc(COOH)(2) as the mediator was also realized. This work provides a new interface system that has the pH-sensitive "on-off" CV property, and the better understanding of the interactions involved in this model system may guide us to develop the novel kind of controllable biosensors based on enzymatic electrocatalysis.
authors.affiliation: Department of Chemistry, Beijing Normal University, Beijing 100875, People's Republic of China.
authors.forename: Huiqin
authors.initials: H
authors.lastname: Yao
authors.forename: Naifei
authors.initials: N
authors.lastname: Hu
mesh_terms: D055162:Biocatalysis; D015374:Biosensing Techniques; D003208:Concanavalin A / Q000378:metabolism*; D003911:Dextrans / Q000378:metabolism*; D004563:Electrochemistry; D005292:Ferricyanides / Q000032:analysis / Q000737:chemistry; D005296:Ferrous Compounds / Q000032:analysis / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D000075163:Metallocenes; D017975:Ruthenium Compounds / Q000032:analysis / Q000737:chemistry; D055672:Static Electricity; D013379:Substrate Specificity; D013499:Surface Properties
chemical_list: D003911:Dextrans; D005292:Ferricyanides; D005296:Ferrous Compounds; D000075163:Metallocenes; D017975:Ruthenium Compounds; D003208:Concanavalin A; C032949:ferrocenecarboxylic acid; C007931:hexacyanoferrate III; C031584:hexammineruthenium