FTIR spectra (a) Aqueous plant extracts (b) AgNPs spectra.

<p>FTIR spectra (a) Aqueous plant extracts (b) AgNPs spectra.</p

TEM images of bacterial cells treated with AgNPs and their EDX spectra.

<p>TEM images of bacterial cells treated with AgNPs and their EDX spectra.</p

Reactive oxygen species experiments.

<p>(a) ROS production in presence of AgNPs in (a) <i>E</i>. <i>coli</i> (b) <i>S</i>. <i>mutans</i>. Error bars represent standard deviations of triplicate incubations. (b) Visualization of ROS generation by DCFH-DA green fluor probe in nanoparticle treated bacterial biofilms. AgNPs show the significant increment of green color fluorescence (ROS specific DCFH-DA probed) during 60 min incubation as compared to control bacterial biofilms. (i)a <i>S</i>. <i>mutans</i> control biofilm (i)b <i>S</i>. <i>mutans</i> treated biofilm. (ii)a <i>E</i>. <i>coli</i> control biofilm (ii)b <i>E</i>. <i>coli</i> treated biofilm. (c) Plasmid (DNA) cleavage assay in presence AgNPs (1.5 μg ml^-1) and various free radical scavengers (DMSO, NaN3, TBA, and SOD). Lane 1, 3, 4 and 5 show the intact plasmid DNA; Lane 2 shows the cleaved plasmid DNA.</p

Graphical presentation of the anti-biofilm potency of the nanoparticles on catheter surface using scanning electron microscopy.

<p>(a) Untreated catheter incubated bacterial biofilm (b) nanoparticles treated catheter showing inhibition of biofilm on nano-modified surface.</p

Leakage of reducing sugars (a) and proteins (b) from <i>E</i>. <i>coli</i> and <i>S</i>. <i>mutans</i> cells treated with AgNPs (Concentration of AgNPs is in μg ml^-1).

<p>Error bars represent standard deviations of triplicate incubations.</p

MICs and MBCs values of chemically synthesized and biogenic AgNPs.

<p>MICs and MBCs values of chemically synthesized and biogenic AgNPs.</p

Cell line (HeLa) toxicity assessment of the AgNPs.

<p>Error bars represent standard deviations of triplicate incubations.</p

Interaction of meropenem with ‘N’ and ‘B’ isoforms of human serum albumin: a spectroscopic and molecular docking study

<p>Carbapenems are used to control the outbreak of β-lactamases expressing bacteria. The effectiveness of drugs is influenced by its interaction with human serum albumin (HSA). Strong binding of carbapenems to HSA may lead to decreased bioavailability of the drug. The non-optimal drug dosage will provide a positive selection pressure on bacteria to develop resistance. Here, we investigated the interaction between meropenem and HSA at physiological pH 7.5 (N-isoform HSA) and non-physiological pH 9.2 (B-isoform HSA). Results showed that meropenem quenches the fluorescence of both ‘N’ and ‘B’ isoforms of HSA (Δ<i>G</i> < 0 and binding constant ~10⁴ M⁻¹). Electrostatic interactions and van der Waal interactions along with H-bonds stabilized the complex of meropenem with ‘N’ and ‘B’ isoforms of HSA, respectively. Molecular docking results revealed that meropenem binds to HSA near Sudlow’s site II (subdomain IIIA) close to Trp-214 with a contribution of a few residues of subdomain IIA. CD spectroscopy showed a change in the conformation of both the isoforms of HSA upon meropenem binding. The catalytic efficiency of HSA (only N-isoform) on p-nitrophenyl acetate was increased primarily due to a decrease in <i>K</i>_m and an increase in <i>k</i>_cat values. This study provides an insight into the molecular basis of interaction between meropenem and HSA.</p

Antibiofilm action of a toluidine blue O-silver nanoparticle conjugate on <i>Streptococcus mutans</i>: a mechanism of type I photodynamic therapy

<p>The objective of this study was to evaluate the anti-biofilm efficacy of photodynamic therapy by conjugating a photosensitizer (TBO) with silver nanoparticles (AgNP). <i>Streptococcus mutans</i> was exposed to laser light (630 nm) for 70 s (9.1 J cm⁻²) in the presence of a toluidine blue O–silver nanoparticle conjugate (TBO–AgNP). The results showed a reduction in the viability of bacterial cells by 4 log₁₀. The crystal violet assay, confocal laser scanning microscopy and scanning electron microscopy revealed that the TBO–AgNP conjugates inhibited biofilm formation, increased the uptake of propidium iodide and leakage of the cellular constituents, respectively. Fluorescence spectroscopic studies confirmed the generation of OH^<i>•</i> as a major reactive oxygen species, indicating type I phototoxicity. Both the conjugates down-regulated the expression of biofilm related genes compared to TBO alone. Hence TBO–AgNP conjugates were found to be more phototoxic against <i>S. mutans</i> biofilm than TBO alone.</p

Growth curves of bacteria under the influence of AgNPs.

<p>(a) <i>E</i>. <i>coli</i> (b) <i>S</i>. <i>mutans</i>.</p