Nor Syafirah Zambry, Khi Khim Beh, Mohd Syafiq Awang, Asrulnizam Abd Manaf, Hairul Hisham Hamzah, Yazmin Bustami, Godwin A. Obande, Muhammad Fazli Khalid, Aziah Ismail


Electrochemical biosensors have been proven as a significant diagnostic device to handle various clinical problems in diagnosing infectious diseases caused by pathogenic bacteria and viruses. This is due to the high sensitivity, rapid response, operational simplicity, affordability, readiness and easy-to-use bio-detection principles of the biosensor. The integration of the developed method into a portable electrochemical system readout can potentially be made into a miniaturised electrochemical biosensor and subsequently, offers high portability, low reagent uses and sample volumes, both in its development and application. These favourable characteristics allow the electrochemical device to be an ideal tool for rapid point of-care (POC) detection of severe acute respiratory syndrome coronavirus 2 (SARS CoV2) infection. COVID-19 disease has triggered serious public health issue due to its rapid transmission and has led to a global pandemic. Presently, various electrochemical immunosensor assays for the detection of SARS-CoV2 have been developed due to good selectivity and low detection limit. Nevertheless, these methods are generally less sensitive than nucleic acid-based tests as in the early stage of infection, the human immune system may not be active and thus, could cause a false-negative diagnosis. Therefore, the present study aimed to develop a label-free miniaturised electrochemical sensor based on deoxyribonucleic acid (DNA) for SARS-CoV2 detection. In this study, a miniaturised 3 gold (Au) electrode electrochemical sensor was fabricated using conventional printed circuit board (PCB) technology. A thiolated ssDNA probe-based label-free system was immobilized onto a working electrode surface using self-assembly monolayer (SAM) formation. To prevent the unspecific binding, the working electrode was treated with 50 mM 6-mercapto-1-hexanol (MCH) before the detection to passivate any residual active sites from the electrode surface. The analytical performance of the designed sensor was characterized using electrochemical measurements namely cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Then, the target DNA was exposed onto the functionalised working electrode and allowed to hybridize with the immobilised DNA probe. The optimum DNA hybridisation time was investigated through electrochemical measurements. The results from CV and EIS measurement demonstrated that the hybridization occurred between the DNA probe and target DNA. The designed miniaturized DNA sensor can detect the target DNA within 5 min of response time. In summary, this miniaturised DNA sensor could potentially be used as a precise platform for rapid, simple, selective, and portable sensor for the detection of COVID-19.

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