ИСТИНА

The efficient coupling of biomolecules, in particular enzymes to surface of electrodes within man-made devices is a crucial aspect when engineering (bio)analytical sensors. Generally, efficiency of enzyme immobilization determines the quality of an analytical device, its sensitivity, and eventually its market competitiveness. Among the wide variety of known methods of enzyme immobilization, the modification of the sensor surface by “smart” polymer microgels, which are able to significant quickly and reversibly change their properties when environmental conditions vary, is very promising. In particular, pH- and thermosensitive copolymer microgels poly(N-isopropylacrylamide-co-N-[3-(dimethylamino) propyl]methacrylamide), P(NIPAM-co-DMAPMA), are of particular interest, being composed of thermosensitive PNIPAM (major component) and incorporating pH-sensitive (chargeable) tertiary amino groups of DMAPMA as a comonomer. In a deprotonated (uncharged) and collapsed state such microgels possess high adhesion to hydrophobic surfaces, while in a swollen and protonated (charged) state, even being adsorbed they are able to bind considerable amounts of oppositely charged enzymes, and at the same time, provide a favorable water-rich microenvironment for the bound biomolecules. This work examines the adsorption of P(NIPAM-co-DMAPMA) onto solid hydrophobic surfaces, the subsequent capacious loading of the adsorbed microgel with glucose oxidase (GO), and the stability of the surface-bound microgel-enzyme complex under various pH- and salt conditions, which could trigger a release of GO from the adsorbed P(NIPAM-co-DMAPMA) microgel. The stimuli-responsive properties of the P(NIPAM-co-DMAPMA) microgel in aqueous solutions were characterized by potentiometric titration, dynamic light scattering, and laser microelectrophoresis. The peculiarities of the adsorptive behavior of the microgel and its electrostatic interaction with the GO were revealed by quartz crystal microbalance with dissipation monitoring upon the subsequent deposition of the components onto surface of gold-coated quartz crystals. The revealed optimal conditions were further applied for the two-stage fabrication of P(NIPAM-co-DMAPMA)/GO films on the surface of planar graphite electrodes (preliminarily modified with manganese dioxide nanoparticles to impart them sensitivity to hydrogen peroxide). The analytical performance of the fabricated constructs as amperometric biosensors for quantification of glucose was examined and the analytical characteristics (sensitivity, linear range, limit of detection) for glucose assay as well as the operational stability of the developed electrochemical biosensors were determined. (pp. 759-760)