Severe acute respiratory syndrome SARS-CoV-2 virus led to notable challenges amongst researchers in view of development of new and fast detecting techniques. In this regard, surface-enhanced Raman spectroscopy (SERS) technique, providing a fingerprint characteristic for each material, would be an interesting approach. The current study encompasses the fabrication of a SERS sensor to study the SARS-CoV-2 S1 (RBD) spike protein of the SARS-CoV-2 virus family. The SERS sensor consists of a silicon nanowires (SiNWs) substrate decorated with plasmonic silver nanoparticles (AgNPs). Both SiNWs fabrication and AgNPs decoration were achieved by a relatively simple wet chemical processing method. The study deliberately projects the factors that influence the growth of silicon nanowires, uniform decoration of AgNPs onto the SiNWs matrix along with detection of Rhodamine-6G (R6G) to optimize the best conditions for enhanced sensing of the spike protein. Increasing the time period of etching process resulted in enhanced SiNWs’ length from 0.55 to 7.34 µm. Furthermore, the variation of the immersion time in the decoration process of AgNPs onto SiNWs ensued the optimum time period for the enhancement in the sensitivity of detection. Tremendous increase in sensitivity of R6G detection was perceived on SiNWs etched for 2 min (length=0.90 µm), followed by 30s of immersion time for their optimal decoration by AgNPs. These SiNWs/AgNPs SERS-based sensors were able to detect the spike protein at a concentration down to 9.3 × 10 −12 M. Strong and dominant peaks at 1280, 1404, 1495, 1541 and 1609 cm −1 were spotted at a fraction of a minute. Moreover, direct, ultra-fast, facile, and affordable optoelectronic SiNWs/AgNPs sensors tuned to function as a biosensor for detecting the spike protein even at a trace level (pico molar concentration). The current findings hold great promise for the utilization of SERS as an innovative approach in the diagnosis domain of infections at very early stages.

Biosynthesis of novel therapeutic nano-scale materials for biomedical and pharmaceutical applications has been enormously developed, since last decade. Herein, the authors report an ecological way of synthesising the platinum nanoparticles (PtNPs) using sp. for the first time The produced PtNPs exhibited the face centred cubic system. The fourier transform infrared spectrum revealed the existence of amino acids in proteins which serves as an essential reductant for the formation of PtNPs. The spherical morphology of the PtNPs with an average size of 20-50 nm was observed from topographical images of atomic force microscopy and field emission scanning electron microscopy. The X-ray fluorescence spectrum confirms the presence of PtNPs with higher purity. The PtNPs size was further confirmed with transmission electron microscopy analysis and the particles were found to exist in the same size regime. Additionally, PtNPs showed the characteristic surface plasmon resonance peak at 262 nm. Dynamic light scattering studies report that 97.2% of particles were <100 nm, with an average particle diameter of about 45 nm. Furthermore, 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-tetrazolium assay based cytotoxicity analysis was conducted for the PtNPs, which showed the inhibitory concentration (IC) at 31.2 µg/ml against Michigan Cancer Foundation-7 breast cancer cells.

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In this work, development of fast, selective and highly sensitive sensor for detecting severe acute respiratory syndrome coronavirus 2 (known as SARS CoV-2 or COVID19) spike protein has been reported. Surface enhanced Raman spectroscopy (SERS) based direct detection of spike protein was investigated by fabricating silver nanoparticles decorated Si (AgNPs/Si) using a facile wet chemical process. Fabrication parameters such as immersion time and precursor concentration were varied; their corresponding morphological characteristics were well elucidated while assuring homogeneous decoration of AgNPs on Si substrate. Classical dye molecule such as rhodamine 6G (R6G) was utilised for the optimisation of fabricated sensor. Based on acquired intensity of R6G, the best sensor was selected, which was further employed for label free direction of spike protein. The developed sensor exhibited high sensitivity in pico-molar range with excellent reproducibility. Selectivity studies were demonstrated using DNA and H1N1 protein as well. The current findings will launch new state of art in the field of medical diagnostics.

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