title: Dual-stimuli-sensitive microgels as a tool for stimulated spongelike adsorption of biomaterials for biosensor applications.
abstract: This work examines the fabrication regime and the properties of microgel and microgel/enzyme thin films adsorbed onto conductive substrates (graphite or gold). The films were formed via two sequential steps: the adsorption of a temperature- and pH-sensitive microgel synthesized by precipitation copolymerization of N-isopropylacrylamide (NIPAM) and 3-(N,N-dimethylamino)propylmethacrylamide (DMAPMA) (poly(NIPAM-co-DMAPMA) at the pH-condition corresponding to its noncharged state (first step of adsorption), followed by the enzyme, tyrosinase, adsorption at the pH-condition when the microgel and the enzyme are oppositely charged (second step of adsorption). The stimuli-sensitive properties of poly(NIPAM-co-DMAPMA) microgel were characterized by potentiometric titration and dynamic light scattering (DLS) in solution as well as by atomic force microscopy (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D) at solid interface. Enhanced deposition of poly(NIPAM-co-DMAPMA) microgel particles was shown at elevated temperatures exceeding the volume phase transition temperature (VPTT). The subsequent electrostatic interaction of the poly(NIPAM-co-DMAPMA) microgel matrix with tyrosinase was examined at different adsorption regimes. A considerable increase in the amount of the adsorbed enzyme was detected when the microgel film is first brought into a collapsed state but then was allowed to interact with the enzyme at T < VPTT. Spongelike approach to enzyme adsorption was applied for modification of screen-printed graphite electrodes by poly(NIPAM-co-DMAPMA)/tyrosinase films and the resultant biosensors for phenol were tested amperometrically. By temperature-induced stimulating both (i) poly(NIPAM-co-DMAPMA) microgel adsorption at T > VPTT and (ii) following spongelike tyrosinase loading at T < VPTT, we can achieve more than 3.5-fold increase in biosensor sensitivity for phenol assay. Thus, a very simple, novel, and fast strategy for physical entrapment of biomolecules by the polymeric matrix was proposed and tested. Being based on this unique stimuli-sensitive behavior of the microgel, this stimulated spongelike adsorption provides polymer films comprising concentrated biomaterial.
authors.affiliation: Department of Chemistry, M. V. Lomonosov Moscow State University , 119991 Moscow, Russia.
authors.forename: Larisa V
authors.initials: LV
authors.lastname: Sigolaeva
authors.forename: Snezhana Yu
authors.initials: SY
authors.lastname: Gladyr
authors.forename: Arjan P H
authors.initials: AP
authors.lastname: Gelissen
authors.forename: Olga
authors.initials: O
authors.lastname: Mergel
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Pergushov
authors.forename: Ilya N
authors.initials: IN
authors.lastname: Kurochkin
authors.forename: Felix A
authors.initials: FA
authors.lastname: Plamper
authors.forename: Walter
authors.initials: W
authors.lastname: Richtering
mesh_terms: D000178:Acrylamides / Q000737:chemistry; D000327:Adsorption; D001672:Biocompatible Materials / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods; D005782:Gels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force / Q000379:methods; D044367:Phase Transition; D058105:Polymerization; D011108:Polymers / Q000737:chemistry; D013499:Surface Properties; D044366:Transition Temperature
chemical_list: D000178:Acrylamides; D001672:Biocompatible Materials; D005782:Gels; D011108:Polymers; C583028:N-(3-(dimethylamino)propyl)methacrylamide; C067295:N-isopropylacrylamide