Direct electrochemistry and enzymatic activity of hemoglobin in positively charged colloid Au nanoparticles and hemoglobin layer-by-layer self-assembly films

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).