Biosensors & Bioelectronics

Recently, great attention has been devoted to the graphene because of its unique properties, such as high charge carrier mobility even at a high charge carrier concentration at room temperature, the existence of massless Dirac fermions, Quantum Hall effect at room temperature, gas sensing at the single molecule level and gate controlled transport (electron or hole) properties. Gas concentration effect on electrical conductivity of graphene by Green function method has been modeled however sensor analytical modeling needs to be done. In this paper injected carriers by Prostate Specific Antigen (PSA) concentration are simulated and carrier controlling parameters (F, pH) are suggested. Injected carriers from PSA to the graphene surface are monitored and their effect on the capacitance is modeled. Finally comparison with experimental data which illustrates good agreement between them is considered.

This study examines the use of square wave voltammetry (SWV) to quantify reduced glutathione (GSH) dissolved in phosphate buffer (pH 7.5) using a static mercury drop electrode (working), Ag/AgCl electrode (standard) and a platinum wire (auxiliary). The applied voltage ranged from -0.7 to -0.2 V. Increasing concentrations of GSH (13-188 μmol/L) correlated with the voltammogram peak area (R²=0.99) and with the current at peak potential (Ip) (R=0.99). The reaction of GSH with diamide was monitored for validation of the method. Addition of increasing concentrations of diamide (13.3-50.8 μmol/L) to a fixed concentration of GSH (120 μmol/L) decreased the Ip, and the results obtained presented a relative deviation (RD) ≤ 14.5% (compared with expected concentrations by stoichiometry) for GSH concentrations above 33.8 μmol/L, whereas the spectrophotometric method (Elman’s reagent) presented RD ≤ 25.6%. These data indicate that SWV method is more accurate and presented equal precision (SD<8%) as compared to the commonly used spectrophotometric method. This method seems suitable for measuring GSH concentrations at room temperature and pH 7.5 (near biological conditions). Other advantages of this method that make it highly desirable for rapid diagnostic purposes include low cost, simplicity, sensitivity, rapid response and no prior sample preparation.