The modern epoch of semiconductor nanotechnology focuses on its application in biology, especially in medical sciences, to fetch direct benefits to human life. Fabrication of devices for biosensing and bioimaging is a vibrant research topic nowadays. Luminescent quantum dots are the best option to move with, but most of them are toxic to living organisms and hence cannot be utilized for biological applications. Recent publications demonstrate that surface treatment on the nanoparticles leads to enhanced luminescence properties with a drastic reduction in toxicity. The current work introduces surface-modified CdS, prepared via a simple green chemical route with different medicinal leaf extracts as the reaction media. Lower toxicity and multiple emissions in the visible region, observed for the CdS-O.tenuiflorum hybrid structures, make them a better option for future biological applications. Furthermore, the hybrid structure showed enhanced electrical properties, which promises its use in modifying the current optoelectronic devices.

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The homeostatic control of Sodium (Na+) ion in the human body assumes paramount relevance owing to its physiological importance. Any deviation from the normal level causes serious health problems like hypernatremia, hyponatremia, stroke, kidney problems etc. Therefore, quantification of Na+ levels in body fluids has significant diagnostic and prognostic importance. However, interfering ions like Potassium ion (K+) is the major hurdle in sodium detection. In this work, we synthesized the clusters of 3–9 nm-sized highly stable and pure Copper nanoparticles surface functionalised with curcumin, through chemical reduction method. Each cluster of particles is encapsulated in a curcumin layer which is clearly visible in TEM images. The results show that these curcumin functionalized Cu NPs (CuC) are highly selective to the colorimetric detection of Na+. The ions like K+, Mg2+ and Zn2+ did not interfere with the Na+ in this sensing technique. Low-cost paper-based sensor strips are fabricated and calibrated for the sensing of sodium in the physiological range and shade cards were developed as a calorimetric guide for estimation of Na+ which makes them ideal point of care diagnostic platform. We demonstrate that the proposed CuC paper strip can be used for detecting Na+ concentration within the whole physiological range in both blood serum and urine.

Metal nanoparticles-based sensors invoked much research attention in the biomedical field, especially in applications involving live cell imaging and monitoring. Here, a simple cost-effective method is adopted to synthesize glutathione coated copper nanoclusters (Cu-GSH NCs) with strong bright red fluorescence (625 nm). The clusters were found to be containing five Cu(0) atoms complexed with one molecule of glutathione (GSH) as evidenced by MALDI-TOF MS analysis. The synthesized Cu-GSH NCs system responds linearly to the pH in the acidic and alkaline ranges with a high degree of in vitro pH reversibility, projecting its potential as a real time pH sensor. Higher intensity emission observed in acidic conditions can be exploited for its employability as cellular organelle markers. The imaging and sensing potential of Cu-GSH NCs in the live human adenocarcinoma cell line, the HeLa cells, was tested. The treatment of HeLa cells for 48 h imparted deep red fluorescence, owing to the lower level of intracellular pH in cancer cells. In contrast, the imaging using normal cell lines (L-132, lung epithelial cell line) showed significantly lower fluorescence intensity as compared to that of HeLa cells. The subcellular pH-dependent fluorescence emission of Cu-GSH NCs was further assessed by treating HeLa cells with proton pump (V-ATPase) inhibitor Bafilomycin A1, which increases the vesicular pH. Interestingly, the fluorescent intensity of HeLa cells decreases with increasing concentration of Bafilomycin A1 in the presence of Cu-GSH NCs, as evidenced by the fluorescence microscopic images and quantitative fluorescent output. Accordingly, the developed Cu-GSH NCs system can be employed as an efficient pH-based bioimaging probe for the detection of cancer cells with an implied potential for the label free subcellular organelle tracking and marking. Importantly, the Cu-GSH NCs can be used for live cell pH imaging owing to their high degree of reversibility in sensing of pH variation.