A novel bacterial isolate Stenotrophomonas maltophilia as living factory for synthesis of gold nanoparticles

<p>Abstract</p> <p>Background</p> <p>The synthesis of gold nanoparticles (GNPs) has received considerable attention with their potential applications in various life sciences related applications. Recently, there has been tremendous excitement in the study of nanoparticles synthesis by using some natural biological system, which has led to the development of various biomimetic approaches for the growth of advanced nanomaterials. In the present study, we have demonstrated the synthesis of gold nanoparticles by a novel bacterial strain isolated from a site near the famous gold mines in India. A promising mechanism for the biosynthesis of GNPs by this strain and their stabilization via charge capping was investigated.</p> <p>Results</p> <p>A bacterial isolate capable of gold nanoparticle synthesis was isolated and identified as a novel strain of <it>Stenotrophomonas malophilia </it>(AuRed02) based on its morphology and an analysis of its 16S rDNA gene sequence. After 8 hrs of incubation, monodisperse preparation of gold nanoparticles was obtained. Gold nanoparticles were characterized and found to be of ~40 nm size. Electrophoresis, Zeta potential and FTIR measurements confirmed that the particles are capped with negatively charged phosphate groups from NADP rendering them stable in aqueous medium.</p> <p>Conclusion</p> <p>The process of synthesis of well-dispersed nanoparticles using a novel microorganism isolated from the gold enriched soil sample has been reported in this study, leading to the development of an easy bioprocess for synthesis of GNPs. This is the first study in which an extensive characterization of the indigenous bacterium isolated from the actual gold enriched soil was conducted. Promising mechanism for the biosynthesis of GNPs by the strain and their stabilization via charge capping is suggested, which involves an NADPH-dependent reductase enzyme that reduces Au³⁺to Au⁰through electron shuttle enzymatic metal reduction process.</p

A Novel Approach for Combating Klebsiella pneumoniae Biofilm Using Histidine Functionalized Silver Nanoparticles

Treating pathogens is becoming challenging because of multidrug resistance and availability of limited alternative therapies which has further confounded this problem. The situation becomes more alarming when multidrug resistant pathogens form a 3D structure known as biofilm. Biofilms are formed in most of the infections especially in chronic infections where it is difficult to eradicate them by conventional antibiotic therapy. Chemically synthesized nanoparticles are known to have antibiofilm activity but in the present study, an attempt was made to use amino acid functionalized silver nanoparticles alone and in combination with gentamicin to eradicate Klebsiella pneumoniae biofilm. Amino acid functionalized silver nanoparticles were not only able to disrupt biofilm in vitro but also led to the lowering of gentamicin dose when used in combination. To the best of our knowledge, this is the first study demonstrating the application of amino acid functionalized silver nanoparticles in the eradication of young and old K. pneumoniae biofilm

Membrane Penetrating-Cationic Peptide BP100 Functionalized Silver Nanoparticles as Efficient Antibacterial Agents

In the present scenario, resistance to antibiotics has become a threatening situation for public health. To find a solution for this, conjugation of a cationic peptide with silver nanoparticles is emerging as a promising route to attain enhanced antibacterial activity. In this direction, this work reports the synthesis of lysine-based cationic peptide (BP100: NH2–KKLFKKILKYL–amide) functionalized silver nanoparticles (BP100@AgNPs). The cationic peptide interacts electrostatically with the silver nanoparticles in an aqueous medium. The developed nanosystem followed green chemistry principles, owing to the use of water and a one-step strategy for the synthesis of peptide functionalized nanoparticles. Moreover, the developed BP100@AgNPs were characterized by UV–vis spectroscopy, zeta potential analysis, FTIR, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). In addition to this, in order to have a deeper insight into the interaction between BP100 and silver nanoparticles, NMR analysis of the peptide (BP100) and the developed nanosystem (BP100@AgNPs) was carried out. This was further authenticated by 1D (1H,13C) NMR and 2D NMR (1H-COSY (correlation spectroscopy)), 13C-HSQC (heteronuclear single quantum coherence)). Moreover, the developed BP100@AgNPs were tested for antibacterial activity against Gram-negative (E. coli) and Gram-positive (S. aureus) bacterial strains. The nanosystem displayed good inhibition with MIC values of 3.60 and 13.20 μg/mL for E. coli and S. aureus, respectively. The destruction in the cellular membrane of the bacterial cells upon treatment with the nanosystem was observed via field emission scanning electron microscopy (FESEM) which confirmed the efficient antibacterial activity of the developed nanosystem. Hence, the synthesized nanosystem displayed considerable potential to be used as an excellent candidate for antibacterial applications

Facile synthesis, structural evaluation, antimicrobial activity and synergistic effects of novel imidazo[1,2-a]pyridine based organoselenium compounds

A simple and efficient method has been described to synthesize the hitherto unknown imidazo[1,2-a] pyridine selenides (5a-1) by reaction of 2-chloroimidazo [1,2-a]pyridines with aryl/heteroaryl selenols, generated in situ by reduction of various diselenides with hypophosphorous acid. The crystal structures of 3-nitro-2-(phenylselanyl)-imidazo[1,2-a]pyridine (5a), 2-(mesitylselanyl)-3-nitro-imidazo[1,2-a]pyridine (5d) and 3-nitro-2-(pyridin-2-ylselanyl)-imidazo[1,2-a]pyridine (5e) were confirmed by X-ray crystallography and the DFT calculations were performed to determine various structural parameters which were correlated with the X-ray crystal structures. The synthesized compounds were subjected to antimicrobial evaluation and it was found that compounds 5a and 5j were active against gram negative bacterium Escherichia coli whereas compound 5e was active against different fungal strains. Time kill assay was performed to understand the microbial activity of synthesized organoselenium compounds and the toxicity of these compounds was evaluated against human cell lines. Synergistic effects of active compounds 5a and 5e were tested with existing antibiotic drugs which exhibited that the antibiotic combination with synthesized organoselenium compounds efficiently enhanced the antimicrobial activity. (C) 2016 Elsevier Masson SAS. All rights reserved

A Facile Approach for Synthesis and Intracellular Delivery of Size Tunable Cationic Peptide Functionalized Gold Nanohybrids in Cancer Cells

Peptide-based drug delivery systems have become a mainstay in the contemporary medicinal field, resulting in the design and development of better pharmaceutical formulations. However, most of the available reports employ tedious multiple reaction steps for the conjugation of bioactive cationic peptides with drug delivery vehicles. To overcome these limitations, the present work describes a one-step approach for facile and time efficient synthesis of highly cationic cell penetrating peptide functionalized gold nanoparticles and their intracellular delivery. The nanoconstruct was synthesized by the reduction of gold metal ions utilizing cell penetrating peptide (CPP), which facilitated the simultaneous synthesis of metal nanoparticles and the capping of the peptide over the nanoparticle surface. The developed nanoconstruct was thoroughly characterized and tested for intracellular delivery into HeLa cells. Intriguingly, a high payload of cationic peptide over gold particles was achieved, in comparison to conventional conjugation methods. Moreover, this method also provides the ability to control the size and peptide payload of nanoparticles. The nanoconstructs produced showed enhanced cancer cell penetration (μM) and significant cytotoxic effect compared to unlabeled gold nanoparticles. Therefore, this novel approach may also have significant future potential to kill intracellular hidden dreaded pathogens like the human immunodeficiency virus, Mycobacterium tuberculosis, and so forth