In this proof-of-concept study, gold nanoparticles (AuNPs) were immobilized on glassy carbon electrode (GCE) surfaces using a surface-anchored diazonium salt of 4-aminothiophenol (GCE-Ph-S-AuNPs). X-ray photoelectron spectroscopy (XPS) studies confirmed the attachment of the AuNPs via 4-thiophenol onto the surface of the modified electrode. Differential pulse voltammetry (DPV) was performed for the simultaneous determination of guanine (G) and 8-hydroxyguanine (8-OH-G). The calibration curves were linear up to 140 µM and 60 µM with a limit of detection of 0.02 µM and 0.021 µM for G and 8-OH-G, respectively. Moreover, chronoamperometric studies were carried out for the determination of diffusion coefficients of 8-OH-G and G. The GCE-Ph-S-AuNPs were also applied in genomic DNA-spiked samples for the determination of G and 8-OH-G with recovery rates between 98.5% and 103.3%. The novel electrochemical surface provided a potential platform for the sensitive detection of 8-OH-G related to oxidative stress-induced DNA damage in clinical studies.

In this proof‐of‐concept study, a graphite paste electrode was modified with a novel hybrid nanocomposite of multi‐walled carbon nanotubes and iron‐oxide nanoparticles for the simultaneous voltammetric detection of guanine and inosine. The nanocomposite was characterized using transmission electron microscopy. The incorporation of iron oxide nanoparticles with multiwalled carbon nanotubes to the modified graphite paste electrode provided an enhanced electrocatalytic activity as studied by cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry. The linearity ranges were 0.1–9.0 μM and 0.5–55 μM with a detection limit of 0.05 μM and 0.12 μM for guanine and inosine, respectively. Moreover, chronoamperometric studies were carried out for the determination of diffusion coefficients, and heterogenous rate constants of guanine and inosine. The sensor was also used for the simultaneous detection of guanine and inosine in commercially available bovine serum samples with recovery values ranging from 96 % to 104 %. We envisage the nanocomposite‐modified sensor provides a promising platform for the detection of guanine and inosine in pharmaceutical formulations and biological samples as biomarkers of oxidative damage related to cancer research.