The preparation and electrochemical performance of the carbon nanotube paste electrode modified with ferrocene (FCMCNPE) was investigated for electrocatalytic behaviour toward oxidation of 𝑁-acetyl-𝐿-cysteine (NAC) in the presence of tryptophan (Trp) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed an efficient electrocatalytic activity of FCMCNPE toward oxidation of NAC and Trp, as the electrooxidation of NAC and Trp together gave two well-defined anodic peaks, revealing the applicability of this modified electrode for simultaneous voltammetric detection of mentioned compounds in the same solution. The values of catalytic rate constant (𝑘) and the apparent diffusion coefficient (D_app) were also calculated using chronoamperometry. The DPV method was applied as a sensitive method for the quantitative detection of trace amounts of NAC and Trp. A linear dynamic range from 1.0 to 18.0 𝜇M for NAC and 2.0 to 150.0 𝜇M for Trp was obtained using DPV method in pH 7.00 buffered solution and the detection limit (3𝜎) was determined as 0.49 𝜇M and 0.54 𝜇M for NAC and Trp, respectively. The proposed method was also applied for analysis of NAC tablet, investigating the applicability of the proposed voltammetric method for determination of NAC in real sample.

A simple and highly sensitive electrochemical DNA sensor for the rapid detection of a specific DNA sequence related to the p53 gene is described. The structure and morphology of the synthesized graphene nanosheets and Au nanoparticles were characterized through transmission electron microscopy, UV–Vis spectroscopyand energy dispersion X-ray spectroscopy techniques. The new electrochemical biosensor was prepared by modifying a graphite screen printed electrode (SPE) with gold nanoparticles decorated on graphene (AuNPs/G) nanocomposite. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniqueswere employed to clarify the changes in charge transfer during the fabrication and utilization of the DNA biosensor. The DNA hybridization event was monitored by differential pulse voltammetry (DPV). Under optimal conditions, the decrease of the peak current had a linear relation with the logarithm of the concentration of target complementary DNA in the range 0.5 fM to 0.05 nM, with a detection limit of 0.36 ± 0.04 fM.