Alternate adsorption of positively charged colloid-Au nanoparticles(nano-Au^(⊕))and negatively charged hemoglobin(Hb)on L-cysteine(L-cys)modified gold electrode resulted in the assembly of{Hb/nano-Au^(⊕)}n layer-by-layer films/L-cys modified gold electrode.The nano-Au^(⊕)was characterized by transmission electron micrograph(TEM)and microelectrophoresis.The modified electrode interface morphology was characterized by electrochemical impedance spectroscopy(EIS),atomic force mi-croscopy(AFM),cyclic voltammograms(CV)and chronoamperometry.Direct electron transfer between hemoglobin and gold electrodes was studied,and the apparent Michaelis-Menten constant(k_(m)^(app))of the modified electrode was evaluated to be 0.10 mmol·L^(-1).Moreover,the higher activity of proteins in the nano-Au^(⊕)films could be retained compared with the electropolymerization membrane,since the pro-teins in nano-Au^(⊕)films retained their near-native structure.Direct electron transfer between hemoglo-bin and electrode and electrochemically catalyzed reduction of hydrogen peroxide on a modified elec-trode was studied,and the linear range was from 2.1×10^(-8)to 1.2×10^(-3)mol·L^(-1)(r=0.994)with a detection limit of 1.1×10^(-8)mol·L^(-1)H_(2)O_(2).
YUAN RuoCAO ShuRuiCHAI YaQinGAO FengXianZHAO QingTANG MingYuTONG ZhongQiangXIE Yi
Electrochemical sensing of carcinoembryonic antigen(CEA)on a gold electrode modified by the se- quential incorporation of the mediator,thionine(Thi),and gold nanoparticles(nano-Au),through co- valent linkage and electrostatic interactions onto a self-assembled monolayer configuration is de- scribed in this paper.The enzyme,horseradish peroxidase(HRP),was employed to block the possible remaining active sites of the nano-Au monolayer,avoid the non-specific adsorption,instead of bovine serum albumin(BSA),and amplify the response of the antigen-antibody reaction.Electrochemical ex- periments indicated highly efficient electron transfer by the imbedded Thi mediator and adsorbed nano-Au.The HRP kept its activity after immobilization,and the studied electrode showed sensitive response to CEA and high stability during a long period of storage.The working range for the system was 2.5 to 80.0 ng/mL with a detection limit of 0.90 ng/mL.The model membrane system in this work is a potential biosensor for mimicking the other immunosensor and enzyme sensor.
A novel capacitive sensor for pazufloxacin mesilate (pazufloxacin) determination was developed by electropolymerizing p-aminobenzene sulfonic (p-ABSA) and molecularly imprinted polymers (MPs), which was synthesized through thermal radical copolymerization of metharylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of pazufloxacin template molecules, on the gold electrode surface. Furthermore, 1-dedecanethiol was used to insulate the modified electrode. Alternating current (ac) impedance experiments were carried out with a Model IM6e to obtain the capacitance responses. Under the optimum conditions, the sensor showed linear capacitance response to pazufloxacin in the range of 5 ng·mL?1 to 5 μg·mL?1 with a relative standard deviation (RSD) 5.3% (n=7) and a detection limit of 1.8 ng·mL?1. The recoveries for different concentration levels of pazufloxacin samples varied from 94.0% to 102.0%. Electrochemical experiments indicated the capacitive sensor exhibited good sensitivity and selectivity and showed excellent parameters of regeneration and stability.
