A novel biosensor was fabricated by the electrochemical polymerization of poly-L-proline（P-LP） and ferricyanide（FC） to form a compound film on a glassy carbon electrode（GCE）. The compound film modified electrode（P-LP/FC/GCE） shows electrocatalytic activity toward dopamine（DA） in a phosphate buffer solution（PBS, pH = 4.0） with a diminution of the overpotential and an increase in peak current. P-LP/FC/GCE was used to study the electrocatalytic oxidation of DA and ascorbic acid（AA） by means of cyclic voltammetry（CV）, differential pulse voltammetry（DPV） and amperometric i-t curve techniques. The overlapping anodic peaks of DA and AA were resolved into two well-defined voltammetric peaks in CV and DPV with the potential differences of about 200 and 225 mV, respectively. The peak current of DA is linearly change with the concentration of DA in a range of 1 × 10^-7 to 1.14 × 10^-4 mol/L with the correlation coefficient of 0.9997. The detection limit is 4.4~10-8 mol/L（S/N=3）. P-LP/FC/GCE exhibited an excellent selectivity, sensibility and stability for the determination of DA, and can be applied to the determination of dopamine injections with satisfied results.
CAO Yan-xiu LIU Xing-mei HUANG Hui ZHANG Xue-yu ZHANG Zhi-quan
The direct electron transfer of hemoglobin at the PAMAM-MWNTs-AuNPs composite film modified glassy carbon electrode was studied. In a phosphate buffer solution（PBS, pH=7.0）, the formal potential（E^0） of Hb was -0.105 V versus SCE, the electron transfer rate constant was 4.66 s-1. E^0＇ of Hb at the modified electrode was linearly varied in a pH range of 5.0-8.0 with a slope of-49.2 mV/pH. The Hb/PAMAM-MWNTs-AuNPs/GCE gave an excellent electrocatalytic response to the reduction of hydrogen peroxide. The catalytic current increased linearly with H2O2 concentration in a range of 1.0× 10^-6 to 2.2× 10^-3 mol/L. The detection limit was 2.0× 10^-7 mol/L at a signal to noise ratio of 3. The Michaelis-Menten constant（Km^app） was 2.95 mmol/L.
LIU Xing-meiZHANG Xue-yuZHAO Yi-liLIU Wei-luWANG Bao-junZHANG Yi-huaZHANG Zhi-quan
