In this review, we discuss the recent advances in green synthesis of silver nanoparticles, their application as antimicrobial agents and mechanism of antimicrobial mode of action.

Herein, we report the synthesis of silver nanoparticles (AgNPs) by a green route using the aqueous leaf extract of Morus indica L. V1. The synthesized AgNPs exhibited maximum UV-Vis absorbance at 460 nm due to surface plasmon resonance. The average diameter (~54 nm) of AgNPs was measured from HR-TEM analysis. EDX spectra also supported the formation of AgNPs, and negative zeta potential value (−14 mV) suggested its stability. Moreover, a shift in the carbonyl stretching (from 1639 cm−1 to 1630 cm−1) was noted in the FT-IR spectra of leaf extract after AgNPs synthesis which confirm the role of natural products present in leaves for the conversion of silver ions to AgNPs. The four bright circular rings (111), (200), (220) and (311) observed in the selected area electron diffraction pattern are the characteristic reflections of face centered cubic crystalline silver. LC-MS/MS study revealed the presence of phytochemicals in the leaf extract which is responsible for the reduction of silver ions. MTT assay was performed to investigate the cytotoxicity of AgNPs against two human cell lines, namely HepG2 and WRL-68. The antibacterial study revealed that MIC value of the synthesized AgNPs was 80 µg/ml against Escherichia coli K12 and Staphylococcus aureus (MTCC 96). Finally, the synthesized AgNPs at 10 µg/ml dosages showed beneficial effects on the survivability, body weights of the Bombyx mori L. larvae, pupae, cocoons and shells weights via enhancing the feed efficacy.

In this present study, we have described the diversity of nine Ocimum genotypes naturally grown in the Dakshin Dinajpur district of West Bengal, India. Their diversity was determined on the basis of morphological, chemical and randomly amplified polymorphic DNA (RAPD) to determine the level of variation present in the genus Ocimum. Among nine Ocimum genotypes six (O. americanum, O. × africanum, O. basilicum, O. gratissimum, O. kilimandscharicum and O. tenuiflorum) are found to be different Ocimum species and the rest are as varieties. A total of 18 qualitative and 17 quantitative morphological traits and chemical compositions were evaluated. Significant variations were observed in the morphological traits except O. × africanum and O. basilicum species. Cluster generated from the morphological data showed two different groups viz. basilicum group and sanctum group. Chemical analysis did not show much variation between morphologically similar species viz. O. × africanum and O. basilicum. However, RAPD analyses clearly showed that O. × africanum and O. basilicum are different species. Thus the combined analyses of morphological traits, chemical and molecular markers represent the best possible approach to confirm taxonomic delineation. Moreover, we are reporting O. × africanum for the first time from this region as well as from West Bengal, India.

Type I and Type II pneumocytes are two forms of epithelial cells found lining the alveoli in the lungs. Type II pneumocytes exclusively secrete ‘pulmonary surfactants’, a lipo-protein complex made up of 90% lipids (mainly phospholipids) and 10% surfactant proteins (SP-A, SP-B, SP-C, and SP-D). Respiratory diseases like influenza, SARS-CoV and SARS-CoV-2 are reported to preferentially attack type II pneumocytes of the lungs. After viral invasion, consequent viral propagation and destruction of type II pneumocytes causes altered surfactant production, resulting in dyspnea and Acute respiratory distress syndrome (ARDS) in COVID-19 patients. Exogenous animal-derived or synthetic pulmonary surfactant therapy has already shown immense success in the treatment of neonatal respiratory distress syndrome (RDS) and has the potential to contribute efficiently to repairing damaged alveoli and preventing SARS-CoV-2-associated respiratory failure. Furthermore, the early detection of surfactant collectins (SP-A and SP-D) in the circulatory system can be a significant clinical marker for disease prognosis in the near future.

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