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Significance and Impact of the Study: Although the synthesis, structural characteristics and biofunction of silver nanoparticles are well understood, their application in antimicrobial therapy is still at its infancy as only a small number of microorganisms are tested to be sensitive to nanoparticles. A thorough knowledge of the mode of interaction of nanoparticles with bacteria at subcellular level is mandatory for any clinical application. The present study deals with the interactions of Ag-SiO 2 NC with the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, which would contribute substantially in strengthening the therapeutic applications of silver nanoparticles. AbstractThe study was carried out to understand the effect of silver-silica nanocomposite (Ag-SiO 2 NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drug-resistant bacterium. Bacterial sensitivity towards antibiotics and Ag-SiO 2 NC was studied using standard disc diffusion and death rate assay, respectively. The effect of AgSiO 2 NC on cell wall integrity was monitored using SDS assay and fatty acid profile analysis, while the effect on metabolism and genetic stability was assayed microscopically, using CTC viability staining and comet assay, respectively. Pseudomonas aeruginosa was found to be resistant to b-lactamase, glycopeptidase, sulfonamide, quinolones, nitrofurantoin and macrolides classes of antibiotics. Complete mortality of the bacterium was achieved with 80 lg ml À1 concentration of Ag-SiO 2 NC. The cell wall integrity reduced with increasing time and reached a plateau of 70% in 110 min. Changes were also noticed in the proportion of fatty acids after the treatment. Inside the cytoplasm, a complete inhibition of electron transport system was achieved with 100 lg ml À1 Ag-SiO 2 NC, followed by DNA breakage. The study thus demonstrates that Ag-SiO 2 NC invades the cytoplasm of the multiple drugresistant P. aeruginosa by impinging upon the cell wall integrity and kills the cells by interfering with electron transport chain and the genetic stability.

Natural fiber-reinforced hybrid composites are prime focus materials for numerous engineering applications. In this research work, chopped neem (Azadirachta indica) fibers and bidirectional banyan (Ficus benghalensis) woven fabric-reinforced epoxy hybrid composites were fabricated using the conventional hand lay-up technique. Two fibers, namely chopped neem fiber and woven banyan fiber, were stacked in three different sequences. The weight fraction of these two fibers was varied to quantify the strength of the hybrid composite. The mechanical properties, such as tensile, compression, and impact tests, were carried out to quantify the effect of the fiber weight fraction and the stacking sequence of fiber on the strength of the hybrid composite. The increase in 9 % woven banyan fiber weight fraction has a positive influence on the tensile and compressive strengths of the natural fiber-reinforced hybrid composites. Further, the stacking sequence of these two fibers has significant influence on the compressive strength of the hybrid composites. The impact energy absorption capacity of the hybrid composite is more significantly increased with an increase in the 9 % chopped neem fiber weight fraction than with an increase in the banyan fiber weight fraction. The scanning electron microscopy surface morphological analysis revealed the dominant mode of failure in the hybrid composites.

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