The study on intelligent bioelectrocatalysis predicated on stimuli-responsive components or interfaces is of great significance for biosensors and other bioelectronic devices. of the films was explored by comparative experiments and attributed to the different electrostatic interaction between the films and the probes at different pH. This stimuli-responsive films could be used to realize active/inactive electrocatalytic oxidation of glucose by GOD in the films and mediated by Fc(COOH)2 in answer which may establish a foundation for fabricating novel stimuli-responsive electrochemical biosensors based on bioelectrocatalysis with immobilized enzymes. enzyme-catalyzed reactions. Compare to pH-sensitive chitosan-GOD films  which exhibited an “on” state at pH 5.0 and “off” state at pH 9.0 Con A/GODn films have the same pH sensitive range and ΔpH = 4.0. While works on either biospecific interactions between Con A and GOD [18 21 or pH-switchable bioelectrocatalysis of glucose with immobilization of GOD enzymes such as chitosan-GOD film  have been reported previously to the best of our knowledge studies on combining them together have not been reported up to now. This work provides a novel example of the construction of a pH stimuli-responsive enzyme-immobilized biointerface and intelligent bioelectrocatalysis of glucose based on the lectin-glycoenzyme Calcipotriol monohydrate biospecific LbL assembly which may find its potential application in designing new kinds of stimuli-responsive biosensors and bioelectronic devices and also in mechanistic studies of metabolic pathways. 2 Experimental Section 2.1 Reagents Poly(diallyldimethylammonium) (PDDA 20 concanavalin A extracted from Jack beans (Con A type V MW ≈ 104 0 glucose oxidase (GOD E.C. 220.127.116.11 type VII MW ≈ 160 0 192 0 models·g?1) esterase from porcine liver (Est 17 0 models·g?1) urease from Jack beans (Ur E.C. 18.104.22.168 type III 39 290 units·g?1) 1 1 acid (Fc(COOH)2) ferrocenecarboxylic acid (Fc(COOH)) ferrocenemethanol (FcMeOH) tris(hydroxymethyl) aminomethane (Tris) 3 (MPS 90 and hexaammineruthenium(III) chloride (Ru(NH3)6Cl3) were purchased from Sigma-Aldrich (Beijing China). Ethyl butyrate urea potassium ferricyanide (K3Fe(CN)6) potassium ferrocyanide (K4Fe(CN)6) were obtained from Beijing Chemical Engineering Herb (Beijing China). All the chemicals were reagent-grade and Calcipotriol monohydrate used as received. Buffers were usually 0.05 mol·dm?3 sodium acetate (pH 4-6) or 0.05 mol·dm?3 potassium dihydrogen phosphate (pH 6.5-8) all containing 0.1 mol·dm?3 NaCl. The pH value of buffers was adjusted to the desired value with dilute HCl or NaOH solutions. The d-glucose stock solutions were allowed Calcipotriol monohydrate to mutarotate at room heat for 24 h before being used. 0.1 M Tris-HCl buffers at pH 7.0 containing 0.1 M NaCl 1 mM MnCl2 and 1 Calcipotriol monohydrate mM Calcipotriol monohydrate CaCl2 were used to prepare Con A and GOD solutions . Deionized water (103S Still High-Q Inc. Wilmette IL USA) with a resistivity of >10.0 MΩ was used in all experiments. 2.2 Film Rabbit Polyclonal to FZD4. Assembly For electrochemical study basal plane pyrolytic graphite (PG) disk electrodes (geometric area 0.16 cm2 Advanced Ceramics Strongsville Oh USA) were used as the substrate for film assembly. Prior to assembly the PG electrodes were abraded on 600-grit metallographic sandpaper while flushing with water. After being sonicated in water for 30 Calcipotriol monohydrate s and dried in air flow the electrodes were first immersed in 1 mg·mL?1 PDDA aqueous solutions for 20 min forming a PDDA precursor layer on PG surface. The PG/PDDA electrodes were then alternately immersed into Con A (1 mg·mL?1 pH 7.0) and GOD (1 mg·mL?1 pH 7.0) solutions for 20 min each with intermediate water washing for about 10 s and air flow stream drying until the desired variety of bilayers (SCE. QCM was completed using a CHI 420 electrochemical analyzer (CH Equipment). The quartz crystal resonator (AT-cut) includes a fundamental resonance regularity of 8 MHz and it is covered by slim gold movies on both edges (geometric region 0.196 cm2 per one side). After every adsorption stage the QCM silver electrodes were cleaned thoroughly in drinking water dried out under a nitrogen stream as well as the regularity change was after that measured in surroundings by QCM. The pH measurements had been performed with PHSJ-3F pH-meter (Shanghai Accuracy & Scientific Equipment Shanghai China). The top SEM of the films.