Sanjeev Kumar Kannan

Spermine (SPM) is considered a biomarker for prostate cancer and detecting it becomes highly challenging due to its electro- and optical-inactive nature. SPM has a tendency to interact with groups such as phosphates and sulfides to form macrocyclic arrangements known as nuclear aggregates of polyamines. Using this tendency, an electrochemical sensor has been developed using a polysulfide (PS) modified Au electrode (PS@Au electrode). PS has been synthesized from elemental sulfur by hydrothermal method and characterized using UV–Vis, fluorescence, FTIR, SEM, and XPS analyses. The PS@Au electrode was employed for electrochemical sensing of SPM. In the presence of SPM, a decrease in gold oxide reduction current was noted which is proportional to the concentration of SPM. The decrease in gold oxide reduction (0.5 V) current was attributed to the complexing nature of SPM-PS at the electrode interface. The reason for the decrease in current has been substantiated using XRF, XPS, and spectroelectrochemical studies. Under the optimized conditions, the PS@Au electrode exhibited a linear range of 1.55–250 µM with LOD of 0.511 ± 0.02 µM (3σ). The electrochemical strategy for SPM sensing exhibited better selectivity even in the presence of possible interferents. The selectivity stems from the selective interaction of SPM with PS on the Au electrode surface; the tested amino acids, and other molecules do not complex with PS and hence they could not interfere. The PS@Au electrode has been subjected to the determination of SPM in artificial urine samples and exhibited outstanding performance in the synthetic sample. Graphical Abstract

A disposable micropipette tip based liquid–organogel interface, in the presence/absence of calixarene has been developed as a platform for sensing acetylcholine and is highly suitable for electrified soft interface sensing applications.

Cadaverine and putrescine are well known biogenic amines for food spoilage, their presence along with histamine increases the food toxicity to manifold and rapid detection of these analytes remains challenging. To address these problems, poly(neutral red) (PNR) based electrochemical sensor for sensing of cadaverine and putrescine has been developed. Neutral red (NR) polymerised over glassy carbon electrode (GCE) has been utilized for sensing of biogenic amines. Positively charged groups on PNR/GCE surface forms ion-pair complex with putrescine or cadaverine via diphosphate ion bridging which facilitates the sensing ability and the formation of ion-pair, as evidenced by DFT calculations. PNR/GCE exhibited detection ability in the range of 0.025 to 414 μ M with a limit of detection of 0.22 μ M and 0.25 μ M for cadaverine and putrescine, respectively. The developed non-enzymatic electrochemical sensor for cadaverine and putrescine exhibited good anti-interference ability towards common ions and amino acids were studied. Demonstrated non-enzymatic electrochemical sensor method is simple and convenient for tracing biogenic amines in real samples like spoilage in fish specimen.

Biogenic amines (BA) are biomolecules of low molecular weight with organic basic functionalities (amine group) that are formed by the microbial decarboxylation of amino acids of fermented food/beverages. Hence BAs are an important indicator in estimating the freshness and quality of meat, seafood, and industrial food products with high protein content. The reaction of BAs with nitrites available in certain meat products forms nitrosoamine, a carcinogenic compound. Hence BAs are in general considered to be a food hazard and monitoring the level of BAs in food samples becomes crucial as their high concentrations may lead to health problems. This review offers an overview of the available chemical and electrochemical methods that are typically used for the sensing of BAs in food samples. Certain compounds are known to selectively interact with BAs via chemical or non-covalent interactions and these interactions are often accompanied by fluorescence or visible color changes (sometimes visual detection) that could be monitored/assessed using a fluorescence spectrophotometer or UV-vis spectrophotometer (colorimetric methods). The colorimetric methods are limited by sensitivity and selectivity as they are based on straight-forward chemical reactions. In the case of electrochemical sensing of BAs, mediators are often used which undergo oxidation/reduction to produce intermediates that could interact with BAs accompanied by changes in their electrochemical potential. Overall, this review summarizes the available chemical and electrochemical strategies towards the sensing of BAs with a discussion on further prospects.