The effect of cathodic polarization on the electrochemical behavior of the thin titanium dioxide film formed by anodic pretreatment over pure commercial titanium metal for biomaterial application was investigated in situ using scanning electrochemical microscopy (SECM). Quantitative information on the electron transfer rates (keff) at the titanium surface was obtained using the feedback operation of SECM using ferrocene-methanol (FcMeOH) as electrochemical mediator. An increase of keff values with the increase of the negative polarization was detected, a feature that correlates well with the decrease of titanium oxide resistance with increasing cathodic polarization observed using electrochemical impedance spectroscopy (EIS). In addition, SECM operation in the redox competition mode proved that hydrogen was absorbed in the surface oxide film leading to changes in conductivity and electrochemical reactivity.

In this paper, for the first time, electroactivated disposable pencil graphite electrode (ePGE) was used for the detection of bioflavonoid hesperidin with cyclic and differential pulse voltammetry. The electroactivation efficiency of the pencil graphite electrode (PGE) was examined employing electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) and the enhancement of electron transfer kinetics of the PGE after the electroactivation was found. Hesperidin is irreversibly oxidized on the ePGE and its oxidation was the most pronounced at pH=5.0. Two electrode processes were detected, on one hand, a mixed diffusion and adsorption control was observed for the first electrode process. On the other hand, only diffusion control was observed in the second electrode process. Linear dependence between the peak current and the hesperidin concentration was obtained in the concentration range from 5×10−7 mol dm−3 to 1×10−5 mol dm−3 and the determined lower limit of detection (LOD) was 2×10−7 mol dm−3. Moreover, hesperidin in pharmaceutical formulation (containing active substance, hesperidin, and excipients) was quantified using ePGE. A good correlation was obtained between experimentally obtained hesperidin concentration by voltammetric analysis and concentration determined by standard HPLC technique (R2=0.9462).

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Scanning electrochemical microscopy (SECM) in combined amperometric/potentiometric operation was employed to characterize the electrochemical activity of nitinol biomaterial, prior and after anodic treatment, in 0.1 M NaCl solution. SECM operation in the feedback mode proved that the nitinol surface was homogeneously passive following surface finishing and storage in ambient condition, whereas heterogeneous surface characteristics occurred after the application of anodic polarization even for a limited time. That is, the development of anodic and cathodic sites owing to the onset of localized corrosion processes was detected on the metal surface. Hydrogen gas evolution from localized sites was monitored using SECM in the substrate generation/tip collection mode (SG/TC), whereas SECM operated in potentiometric mode was used to map the pH distribution in the electrolyte volume adjacent to the nitinol surface. Local acidification around anodic spots related to Ni 2+ discharge, as well as alkalization above the cathodic areas were observed.

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