Optimized Photoelectrochemical Detection of Essential Drugs Bearing Phenolic Groups

Abstract

The World Health Organization (WHO) model “List of Essential Medicines” includes among indispensable medicines antibacterials and pain and migraine relievers. Monitoring their concentration in the environment, while challenging, is important in the context of antibiotic resistance as well as their production of highly toxic compounds via hydrolysis. Traditional detection methods such as high-performance liquid chromatography (HPLC) or LC combined with tandem mass spectrometry or UV–vis spectroscopy are time-consuming, have a high cost, require skilled operators and are difficult to adapt for field operations. In contrast, (electrochemical) sensors have elicited interest because of their rapid response, high selectivity, and sensitivity as well as potential for on-site detection. Previously, we reported a novel sensor system based on a type II photosensitizer, which combines the advantages of enzymatic sensors (high sensitivity) and photoelectrochemical sensors (easy baseline subtraction). Under red-light illumination, the photosensitizer produces singlet oxygen which oxidizes phenolic compounds present in the sample. The subsequent reduction of the oxidized phenolic compounds at the electrode surface gives rise to a quantifiable photocurrent and leads to the generation of a redox cycle. Herein we report the optimization in terms of pH and applied potential of the photoelectrochemical detection of the hydrolysis product of paracetamol, i.e., 4-aminophenol (4-AP), and two antibacterials, namely, cefadroxil (CFD, β-lactam antibiotic) and doxycycline (DXC, tetracycline antibiotic). The optimized conditions resulted in a detection limit of 0.2 μmol L–1 for DXC, but in a 10 times higher sensitivity, 20 nmol L–1, for CFD. An even higher sensitivity, 7 nmol L–1, was noted for 4-AP.

Electroanalysis of Cefadroxil Antibiotic at Carbon Nanotube/Gold Nanoparticle Modified Glassy Carbon Electrodes

“…The sensitivity at AuNP/MWCNT/GCE was 7 times higher than that obtained at the bare GCE under the same experimental conditions. The LOD at the AuNP/CNT‐modified electrode is as low as that obtained by the more sensitive DPV at the unmodified GCE and can be used up to higher concentrations; the only lower LOD in Table uses the more complicated photoelectrochemical procedure . Many sequential measurements can be made at the same AuNP/CNT modified electrode without any significant interference from adsorbed oxidation products.…”

Nanobody-Based Immunosensor Detection Enhanced by Photocatalytic-Electrochemical Redox Cycling

“…The applied potential is an important parameter of the suggested amperometric detection scheme and affects both the sensitivity to phenols and background currents in blank buffers. 35 has a limited average diffusion length due to its short lifetime. Less than 0.1% of produced 1 O 2 will diffuse 250 nm in water even in the absence of any quenchers).…”

The Role of Singlet Oxygen, Superoxide, Hydroxide, and Hydrogen Peroxide in the Photoelectrochemical Response of Phenols at a Supported Highly Fluorinated Zinc Phthalocyanine

“…Briefly, the aerobically produced 1 O 2 by a photosensitizer (type II PS) placed on a PEC sensor, oxidizes phenolic compounds, followed by their reduction at the electrode surface to generate a signal and a redox cycle. A highly sensitive sensor was thus developed, with detection limits (LOD) for antibiotics and phenols in the nmol L −1 range [2a,b] . However, how experimental conditions, such as pH and applied potential, influence the generation of ROS and their contribution to the observed photocurrents is not understood.…”

“…Specifically, why the oxidative contribution to the reductive photocurrent increases with the alkalinity of the buffer solution was unclear. This pH effect was observed during the optimization of the PEC detection for antibiotics [2a] . Thus, a detailed analysis of the ROS contributions to the photocurrent responses is necessary for the understanding of the PEC sensor behavior, as well as to implement and optimize the 1 O 2 ‐driven oxidation of the phenols.…”