Development of a nanocomposite-based electrochemical sensor for 8-hydroxy-2'-deoxyguanosine detection

8-Hydroxy-2'-deoxyguanosine (8-OHdG) is one of the most employed studied targets for oxidized metabolites and is used as a specific marker for oxidative stress. The amount of 8-OHdG can be used to appraise the degree of endogenous oxidative DNA damage in the human body. Normally, 8-OHdG can be found in several biological samples, e.g., urine, saliva, blood or serum, and tissue [1], and its corresponding concentration is further correlated with various diseases, such as cancers, aging, diabetes, and neurological disorders [2]. For routine clinical analysis, the development of an effective approach for the detection of 8-OHdG is of great importance for disease risk assessment and early diagnosis. Currently, electroanalytical methods have emerged as attractive alternative methods for biomarker detection due to their simplicity, high sensitivity and accuracy, fast analysis time, low cost, portability, and compact setup. In addition, electrochemical devices have a small portable size in comparison with a conventional instrument. Moreover, these devices require only a small sample volume for analysis. Nowadays, screen-printed electrodes (SPEs) are a kind of disposable electrochemical sensor based on screen-printing technology. It has been substantially considered for the fabrication of portable, disposable, and cost-effective devices. In comparison with conventional electrodes, SPEs have many advantages, such as simple fabrication, small size, and the requirement for a small sample volume [3]. To successfully accomplish the assay with high sensitivity and selectivity, surface modification of electrodes can be performed by using a type of nanomaterial and a variety of modifiers. Hence, in this work, we report for the first time on the development of a novel electrochemical sensor based on poly(amino acid) and gold nanoparticle-modified screen-printed graphene electrodes for 8-OHdG detection. For the fabrication process of the electrochemical sensor, graphene and silver/silver chloride (Ag/AgCl) ink were screened onto the transparent sheet to obtain screen-printed graphene electrodes (SPGEs). Afterward, the sequential “layer-by-layer” film was fabricated on SPGE via cyclic voltammetry (CV), which involves two steps: (1) electrodeposition of gold nanoparticles (AuNPs) on SPGE and (2) electropolymerization of L-methionine on AuNPs/SPGE. The preparation process of the fabricated electrochemical sensor for 8-OHdG detection is summarized in Fig. 1. Then, the electrochemical oxidation of 8-OHdG in phosphate buffer solution using square wave voltammetry (SWV) was investigated. To enhance the performance, various experimental parameters, such as the influence of the formation of film on the electrode surface, the effect of pH values and scan rates, potential increment, amplitude, and frequency, were studied. Under optimal conditions, the linearity between the anodic peak current and the 8-OHdG concentration was obtained within the range of 0.08–10 µM, and the limit of detection (3SD/Slope) and limit of quantification (10SD/Slope) were found to be 24 and 81 nM, respectively. This developed sensor provided highly sensitive and potential detection and could be used as an alternative device for the determination of 8-OHdG in biological fluid samples.