Microbial biofilms are factions of surface-colonized cells encompassed in a matrix of extracellular polymeric substances. Profound application of antibiotics in order to treat infections due to microbial biofilm has led to the emergence of several drug-resistant microbial strains. In this context, a novel type of 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine (pytz)-capped silver nanoparticles (TzAgNPs) was synthesized, and efforts were given to test its antimicrobial and antibiofilm activities against Pseudomonas aeruginosa, a widely used biofilm-forming pathogenic organism. The synthesized TzAgNPs showed considerable antimicrobial activity wherein the MIC value of TzAgNPs was found at 40 μg/mL against Pseudomonas aeruginosa. Antibiofilm activity of TzAgNPs was also tested against Pseudomonas aeruginosa by carrying out an array of experiments like microscopic observation, crystal violet assay, and protein count using the sub-MIC doses of TzAgNPs. Since TzAgNPs showed efficient antibiofilm activity, thus, in the present study, efforts were put together to investigate the underlying cause of biofilm attenuation of Pseudomonas aeruginosa by using TzAgNPs. To this end, we discerned that the sub-MIC doses of TzAgNPs increased ROS level considerably in the bacterial cell. The result showed that the ROS level and microbial biofilm formation are inversely proportional. Thus, the attenuation in microbial biofilm could be attributed to the accumulation of ROS level. Furthermore, it was also duly noted that microorganisms upon treatment with TzAgNPs exhibited considerable diminution in virulence factors (protease and pyocyanin) in contrast to the control where the organisms were not treated with TzAgNPs. Thus, the results indicated that TzAgNPs exhibit considerable reduction in the development of biofilms and spreading of virulence factors. Taken together, all the results indicated that TzAgNPs could be deemed to be a promising agent for the prevention of microbial biofilm development that might assist to fight against infections linked to biofilm.

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Mesoporous silica nanoparticles (MSN) with enlarged pores were prepared and characterized, and reversibly dissociated subunits of concanavalin A were entrapped in the mesopores, as shown by multiple biochemical and material characterizations. When loaded in the MSN, we demonstrated protein stability from proteases and, upon release, the subunits reassociated into active proteins shown through mannose binding and o-phthalaldehyde fluorescence. We have demonstrated a versatile and facile method to load homomeric proteins into MSN with potential applications in enhancing the delivery of large therapeutic proteins.

Four water soluble copper(II) complexes, [Cu(HL) 2 (H 2 O) 2 ]Cl 2 (1), [Cu(HL) 2 (ClO 4) 2 ](2), [Cu(HL) 2 (SCN) 2 ](3) and [CuL 2 ]•8H 2 O(4), where HL is pyridine 2-carboxamide, have been synthesized and characterized by various spectroscopic techniques. Structures have been determined by single crystal X-ray crystallography. The pH induced inter-conversion of Cu(HL) 2 (H 2 O) 2 ]Cl 2 (1) and [CuL 2 ]•8H 2 O(4) through coordination mode switching was investigated thoroughly with the help of absorption spectroscopy. Complexes 1-3 were found to be active catalysts for the oxidation of toluene, ethyl benzene and cyclohexane in the presence of hydrogen peroxide as the oxidant under mild conditions. Toluene was oxidized to benzyl alcohol and benzaldehyde, ethyl benzene was oxidized to 1-phenylethanol and acetophenone and cyclohexane was oxidized to yield cyclohexanol and cyclohexanone Antimicrobial activities have been investigated with these copper(II) complexes against gram +ve bacteria, gram −ve bacterial and fungal species.

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