Terrestrial snail-mucus mediated green synthesis of silver nanoparticles and in vitro investigations on their antimicrobial and anticancer activities.

Over the past few years, biogenic methods for designing silver nanocomposites are in limelight due to their ability to generate semi-healthcare and para-pharmaceutical consumer goods. The present study reports the eco-friendly synthesis of silver nanoparticles from the hitherto unexplored mucus of territorial snail Achatina fulica by the facile, clean and easily scalable method. The detailed characterization of the resultant samples by UV-Visible Spectroscopy, FESEM-EDS, XRD and FTIR Spectroscopy techniques corroborated the formation of silver nanoparticles in snail mucus matrix. The resultant samples were tested against a broad range of Gram positive and Gram negative bacteria like Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and a fungal strain Aspergillus fumigatus by well diffusion method. The results indicate that silver nanoparticles in mucus matrix exhibit strong antibacterial as well as antifungal activity. The pertinent experiments were also performed to determine the inhibitory concentration against both bacterial and fungal strains. Anticancer activity was executed by in vitro method using cervical cancer cell lines. Curiously, our biogenically synthesized Ag nanoparticles in biocompatible mucus revealed anticancer activity and demonstrated more than 15% inhibition of Hela cells. We suggest an interesting possibility of formulating antimicrobial and possibly anticancer creams/gels for topical applications in skin ailments.

Hydrothermal Generation of 3-Dimensional WO3 Nanocubes, Nanobars and Nanobricks, Their Antimicrobial and Anticancer Properties.

In our current endeavor, 3-dimensional (3D) tungsten oxide (WO3) nanostructures (nanocubes, nanobars and nanobricks) have been swiftly generated via hydrothermal route at 160 °C for 24 h. Physico-chemical characterization of the resultant powder revealed formation of WO3 nanostructures with predominantly faceted cube, brick and rectangular bar-like morphology. The present study was also aimed at exploring the antimicrobial and anticancer potential of WO3 nanostructures. Antimicrobial activity was tested against different micro-organisms viz., Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli and Aspergillus fumigatus. The antibacterial and antifungal activity was ascertained against these micro-organisms by measuring the diameter of inhibition zone in agar well diffusion test which revealed that the resultant WO3 nanostructures acted as excellent antibacterial agents against both bacteria and fungi but were more effective against the fungus, A. fumigatus. To examine the growth curves of bacterial cells, time kill assay was monitored for E. coli, against which significant antibacterial action of WO3 nanostructures was noted. The anti-cancer activity of WO3 nanostructures was found to be concentration-dependent against KB cell line by viable cell count method. In our pilot study, WO3 nanostructures suspension with concentration in the range of 10-1 to 10-5 mg/ml was found to kill KB cells effectively.

Description and genomic insights into a multidrug resistant novel bacterium Savagea serpentis sp. nov., isolated from the scats of a vine snake (Ahaetulla nasuta).

Two Gram-stain positive, endospore forming, non-motile, rod shaped bacterial strains SN6T and SN6b were isolated from scats of a mildly venomous vine snake (Ahaetulla nasuta). Strains were phenotypically resistant to multiple antibiotics of four different classes i.e. aminoglycosides, ß-lactams, fluoroquinolones and sulphonamides. Cells of both the strains were catalase positive and oxidase negative. Phylogenetic analysis based on 16S rRNA gene sequence analysis of these two strains showed closest similarity (99.2% and 99.3%) with Savagea faecisuis Con12T, the only species of the genus Savagea and ≤ 94.9% with the species of other closest genera of the family Planococcaceae. The 16S rRNA gene sequence similarity (99%), DNA-DNA relatedness (95%) and similar phenotypic characteristics between the strains SN6T and SN6b revealed their phylogenetic affiliation to the same species. Hence, strain SN6b is an additional strain of the type strain SN6T. DNA-DNA relatedness of strain SN6T with S. faecisuis Con12T was 32.8%. Predominant fatty acids were iso-C15:0 (32.0%), iso-C16:1 ω11c (19.2%) and iso-C17:1 ω10c (12.1%). MK-6 (100%) was the only respiratory quinone of strain SN6T. Diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine were the major polar lipids. Cell wall peptidoglycan was A4α; L-Lys-Gly-D-Glu type. The DNA G + C content (mol%) of SN6T was 40.8. Whole genome sequence of SN6T consisted of 26,37,389 base pairs in length with 2667 annotated genes, out of which 1021 corresponds to hypothetical proteins and 1646 with functional assignments including antibiotic resistance, multidrug resistance efflux pumps, invasion and virulence factors. Comparative polyphasic study of the strains SN6T, SN6b and S. faecisuis Con12T elucidated the differentiating characteristics which led to describing strain SN6T and SN6b as a novel species of the genus Savagea for which the name Savagea serpentis sp. nov is proposed. The type strain of Savagea serpentis is SN6T (= KCTC 33546T = CCUG 6786T).

Selective antifungal and antibacterial activities of Ag-Cu and Cu-Ag core-shell nanostructures synthesized in-situ PVA.

A simple chemical reduction method was employed to synthesize Cu-Ag and Ag-Cu core-shell nanostructures inside polyvinyl alcohol (PVA) matrix at room temperature. The core-shell nanostructures have been synthesized by varying the two different concentrations (i.e. 0.1 and 0.01 M) of the respective metal ions in equimolar ratios using successive reduction with hydrazine hydrate (HH) as a reducing agent. The core-shell nanostructures have been further characterized by different characterization techniques. The UV-visible spectroscopy exhibit the respective shift in the band positions suggesting the formation of core-shell nanostructures, which was further confirmed by field emission transmission electron microscopy-high-angle-annular dark field elemental mapping. The effect of metal ion concentration of the core-shell nanostructure on various Gram positive and Gram negative bacteria like Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and one fungal species Aspergillus fumigatus was observed by performing MIC and MBC/MFC study. Cu-Ag core-shell nanostructures were found to be effective antibacterial agent against all tested Gram-positive and Gram-negative bacteria, whereas Ag-Cu core-shell nanostructures were more efficient against a particular fungal species known as A. fumigatus. The highest value of MIC (75 µg ml-1) for Ag-Cu 0.1M core shell nanostructures (D1) was noted against S. aureus and E. coli whereas the lowest value (20 µg ml-1) was observed with P. aeruginosa. While in case of Cu-Ag 0.1M core shell nanostructures (E1) the highest value of MIC (100 µg ml-1) was noted against S. aureus and P. aeruginosa whereas the lowest value (15 µg ml-1) was observed with A. fumigatus. Also, field effect scanning electron microscope (FESEM) images of untreated and core-shell nanoparticles treated micro-organisms showed that 0.1 M Ag-Cu and 0.1 M Cu-Ag core-shell nanostructure can successfully break the cell wall of the fungi A. fumigatus and bacteria P. aeruginosa, respectively. Thus the present study concludes that, Cu-Ag & Ag-Cu core-shell nanostructures damage the cell structure of micro-organisms and inhibits their growth. Hence, the present Cu-Ag & Ag-Cu core-shell nanostructure acts as good antimicrobial agent against the bacteria and fungi, respectively.

Highly sensitive label-free bio-interfacial colorimetric sensor based on silk fibroin-gold nanocomposite for facile detection of chlorpyrifos pesticide.

Herein, the preparation of gold nanoparticles-silk fibroin (SF-AuNPs) dispersion and its label-free colorimetric detection of the organophosphate pesticide, namely chlorpyrifos, at ppb level are reported. The silk fibroin solution was extracted from B. mori silk after performing degumming, dissolving and dialysis steps. This fibroin solution was used for synthesis of gold nanoparticles in-situ without using any external reducing and capping agent. X-ray Diffractometry (XRD), Field Emission Transmission Electron Microscopy (FETEM) along with Surface Plasmon Resonance based optical evaluation confirmed generation of gold nanoparticles within SF matrix. The resultant SF-AuNPs dispersion exhibited rapid and excellent colorimetric pesticide sensing response even at 10 ppb concentration. Effect of additional parameters viz. pH, ionic concentration and interference from other pesticide samples was also studied. Notably, SF-AuNPs dispersion exhibited selective colorimetric pesticide sensing response which can be calibrated. Furthermore, this method was extended to various simulated real life samples such as tap water, soil and agricultural products including plant residues to successfully detect the presence of chlorpyrifos pesticide. The proposed colorimetric sensor system is facile yet effective and can be employed by novice rural population and expert researchers alike. It can be exploited as preliminary tool for label-free colorimetric chlorpyrifos pesticide sensing in water and agricultural products.

Silver Nanoparticles-Silk Fibroin Nanocomposite Based Colorimetric Bio-Interfacial Sensor for On-Site Ultra-Trace Impurity Detection of Mercury Ions.

Innovative colorimetric biosensing platform has been realized by in-situ synthesis of silver nanoparticles in silk-fibroin matrix derived from domesticated silkworm species Bombyx mori. As-synthesized nano-biocomposite dispersion was characterized by UV-Vis spectroscopy and transmission electron microscopy. In a pilot attempt to develop hassle free on-site screening protocol, such green hybrid systems were explored for colorimetric detection of broad range of metal ion targets, viz. toxic heavy metals such as mercury and chromium (which adversely affect hydrosphere, lithosphere, anthroposphere and biosphere) as well as relatively less-toxic metals like copper and iron in a solution. Quite interestingly, our simple biointerfacial-sensing approach reveals highly selective colorimetric sensor response down to ppb level for mercury ions analyte.

Designing Ecofriendly Bionanocomposite Assembly with Improved Antimicrobial and Potent on-site Zika Virus Vector Larvicidal Activities with its Mode of Action.

Dialyzed natural polymer, fibroin, from Bombyx mori was used to synthesize biocompatible silver and gold nanoparticles in-situ in dispersion form. The films of pure fibroin (PF), fibroin-silver nanocomposite (FSNC) and fibroin-gold nanocomposite (FGNC) were fabricated by drop casting method. The characterization of the resultant dispersion and films was performed by visual color change, UV-Vis spectroscopy and atomic force microscopy. The dispersions of PF, FSNC and FGNC were tested for antibacterial activity against E. coli NCIM 2065, S. aureus NCIM 5021, K. pneumoniae NCIM 2957, P. aeruginosa ATCC 9027 and antifungal activity against A. fumigatus NCIM 902. FSNC dispersion exhibited an effective antimicrobial action against all the tested microbes as compared to FGNC dispersion. The mechanism of action for FSNC and FGNC against these microorganisms is proposed. Additionally, the larvicidal activity of the films was investigated against the larvae of Aedes aegypti. The films of FSNC exhibited 100% mortality while the films of FGNC revealed 86-98% mortality against all the larval instars and pupae of A. aegypti. The phytotoxicity study of the nanocomposite films was also carried out to confirm the reusability of water. This is first noble metal nanocomposite based report on larvicidal activity of zika virus vector.

Nanoscale Mo- MoO3 Entrapped in Engineering Thermoplastic: Inorganic Pathway to Bactericidal and Fungicidal Action.

In our contemporary endeavor, metallic molybdenum (Mo) and semiconducting molybdenum trioxide (MoO3) nanostructures have been simultaneously generated via solid state reaction between molybdenum (III) chloride (MoCl3) and polyphenylene sulfide (PPS) at 285 (°)C in unimolar ratio for different time durations, namely, 6 h, 24 h, and 48 h. The resultant nanocomposites (NCs) revealed formation of predominantly metallic Mo for all the samples. However, MoO3 gradually gained prominent position as secondary phase with rise in reaction time. The present study was intended to investigate the antibacterial potential of metal-metal oxide-polymer NCs, i.e., Mo- MoO3-PPS against microorganisms, viz., Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae, and Aspergillus fumigatus. The antibacterial activity of the NCs was evaluated by agar well diffusion investigation. Maximum sensitivity concentrations of NCs were determined by finding out minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC). Moreover, the NCs prepared at reaction time of 48 h exhibited best MBC values and were tested with time kill assay which revealed that the growth of S. aureus was substantially inhibited by Mo- MoO3-PPS NCs. This synchronized formation of Mo- MoO3 nanostructures in an engineering thermoplastic may have potential antimicrobial applications in biomedical devices and components. Prima facie results on antifungal activity are indicative of the fact that these materials can show anti-cancer behavior.