Recently, a plethora of ecofriendly methods have been developed for the synthesis of AuNPs using a multitude of biogenic agents. Polyphenols from plants are particularly attractive for producing AuNPs because in addition to helping with the synthesis of AuNPs, the polyphenol capping of the NPs can be used as a platform for versatile applications. Polyphenol-capped AuNPs could also make the detection of AuNPs possible, should they be released into the environment. Because polyphenols are redox-active, they can be used as a probe to detect AuNPs using electrochemical techniques. In this work, we have developed an MWCNT-rGO nanocomposite electrode for the sensitive detection of AuNPs capped with gallic acid (GA, a green-tea-derived polyphenol) using differential pulse voltammetry (DPV). The reduction of gallic acid-capped AuNPs was used as the quantification signal, and the calibration curve displayed a detection limit of 2.57 pM. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), we have shown that the modification of the electrode surface with an MWCNT-rGO hybrid nanocomposite resulted in a 10-fold increase in current response leading to the sensitive detection of GA-AuNPs compared to unmodified electrodes. We have also demonstrated the applicability of the electrochemical sensor in detecting GA-AuNPs in various analytical matrixes such as human serum and natural creek water (Highland Creek, ON) with good recovery.

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This laboratory experiment introduces the fundamentals of electrochemical techniques to the undergraduate students by developing a simple and cost-effective miniaturized electrochemical setup for detecting UV-induced DNA damage. This is an imperative experiment, as it provides students first-hand experience with electrochemical techniques while reinforcing lecture material on the biosensing applications. In this experiment, a simple and daily use material such as an ordinary pencil lead acts as a platform for an electrochemical DNA sensor. A threeelectrode cell setup is utilized to monitor UV-induced DNA damage. Students will test the hypothesis about UV-induced DNA damage by measuring the redox signal of guanine under various experimental conditions. The simple, fast, and inexpensive setup allows students to examine the factors that would influence the electrochemical signals. This experimental work provides an opportunity for students to learn how to design a simple electrochemical experiment for research purposes as well as handling the biological samples. Proposing a hypothesis and testing it by designing an experiment are the experiences that will be gained by the students while learning about the optimization and validation of an analytical technique.