Handheld, Low-Cost, Aptamer-Based Sensing Device for Rapid SARS-CoV-2 RNA Detection Using Novelly Synthesized Gold Nanoparticles.

The development of a cost-efficient device to rapidly detect pandemic viruses is paramount. Hence, an innovative and scalable synthesis of metal nanoparticles followed by its usage for rapid detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been reported in this work. The simple synthesis of metal nanoparticles utilizing tin as a solid-state reusable reducing agent is used for the SARS-CoV-2 ribonucleic acid (RNA) detection. Moreover, the solid-state reduction process occurs faster and leads to the enhanced formation of silver and gold nanoparticles (AuNPs) with voltage. By adding tin as a solid-state reducing agent with the precursor, the nanoparticles are formed within 30 s. This synthesis method can be easily scaled up for a commercially viable process to obtain different-sized metal nanoparticles. This is the first disclosure of the usage of tin as a reusable solid-state reducing agent for metal nanoparticle synthesis. An electronic device, consisting of AuNPs functionalized with a deoxyribonucleic acid (DNA)-based aptamer, can detect SARS-CoV-2 RNA in less than 5 min. With an increase in SARS-CoV-2 variants, such as Delta and Omicron, the detection device could be used for identifying the nucleic acids of the COVID-19 variants by modifying the aptamer sequence. The reported work overcomes the drawbacks of complex instrumentation, trained labor, and increased turnaround time.

Studies on l-histidine capped Ag and Au nanoparticles for dopamine detection.

This work demonstrates the effective surface functionalization of Ag, Au and bimetallic Ag-Au nanoparticles using l-histidine for colorimetric detection of dopamine (DA) which plays majorly in recognizing the neurological disorder. l-Histidine (l-His) capped Ag, Au, and bimetallic Ag-Au nanoparticles are characterized using physico-chemical techniques. The optical behaviour of nanoparticles has been analysed at various time intervals using UV-Vis absorption spectroscopy. FT-IR results provide the evidence of chemical bonding between l-histidine and metal nanoparticles. Its structure with the capping of l-His was clearly shown in HR-TEM images. The average size of nanoparticles has calculated from TEM image fringes are 11nm, 5nm and 6.5nm respectively, matches with crystals size calculated from X-ray diffraction pattern. Enhanced optical nature of nanoparticles provides the best platform to develop a colorimetric-based biosensor for DA detection. After addition of DA, a rapid colour change has been noted in colloids of nanoparticles. The substantial changes in absorbance and λmax in metal nanoparticles respect to DA concentration have been observed and formulated. This is one of the successive methods for trace level determination of DA and will be going to a significant material for designing biosensor to determine DA in real extracellular body fluids.

Rapid sensing of melamine in milk by interference green synthesis of silver nanoparticles.

A highly sensitive, selective, and rapid interference green synthesis based determination of potential milk adulterant melamine has been reported here. Melamine is a nitrogenous compound added to milk for mimicking proteins, consumption of which leads to kidney stones and renal failures. Melamine interacts with ascorbic acid (AA) through strong hydrogen-bonding interactions, thus resulting in an interference/interruption in the formation of silver (Ag) nanoparticles which was confirmed by UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). The corresponding benchmark validations for melamine spiked milk samples were performed using High Performance Liquid Chromatography (HPLC). This interference in the formation of Ag nanoparticles resulted in color change that varies with concentration of melamine, thereby enabling in-situ rapid sensing of melamine from milk to a lower limit of 0.1ppm with a linear correlation coefficient of 0.9908.