Development of chitosan decorated Fe3O4 nanospheres for potential enhancement of photocatalytic degradation of Congo red dye molecules.

Fe3O4 nanospheres (Nsps) and chitosan (Cts)/Fe3O4 Nsps were prepared using a one-pot hydrothermal method and subsequently used as photocatalysts against the degradation of Congo red (CR) dye molecules. The sphere-shaped Fe3O4 nanoparticles were heterogeneously decorated by the Cts matrix, which was confirmed by powder X-ray diffraction, scanning and transmission electron microscopies. The Cts/Fe3O4 Nsps demonstrated 98% efficient photocatalytic activity against CR dye molecules upon 60 min exposure to visible light compared to Fe3O4 Nsps (77% for 60 min). When compared to Fe3O4 Nsps, the visible light photocatalytic efficiency of Cts/Fe3O4 Nsps against CR dye molecules was significantly improved.

Highly efficient antibacterial activity of graphene/chitosan/magnetite nanocomposites against ESBL-producing Pseudomonas aeruginosa and Klebsiella pneumoniae.

In the present study, chitosan-containing nanocomposites were investigated as new antibacterial agents. Magnetite (Fe3O4) nanoparticles (NPs) as well as chitosan (CS)/Fe3O4 nanocomposites (NCs) and graphene(Gr)/CS/Fe3O4 NCs were synthesized by simple hydrothermal method. Their composition, structure and morphology were studied, followed by the evaluation of their antibacterial activity against ESBL-producing and gram-negative P. aeruginosa and K. pneumoniae bacterial strains. The Gr/CS/Fe3O4 NCs showed significantly higher antibacterial activity compared to Fe3O4 NPs and CS/Fe3O4 NCs (105 and 69 % higher against P. aeruginosa as well as 91 and 77 % higher against K. pneumoniae, respectively). The minimum inhibitory concentration (MIC) of Gr/CS/Fe3O4 NCs against P. aeruginosa and K. pneumoniae were 60 and 70 µg/mL, respectively. The synergistic antibacterial activity and facile synthesis of Gr/CS/Fe3O4 NCs suggests their applicability as novel highly efficient antibacterial agents with potential for a wide range of biomedical applications, where antibacterial properties are needed.

Rapid assessment of heavy metal toxicity using bioluminescent bacteria Photobacterium leiognathi strain GoMGm1.

Several commercial test kits such as Microtox, LUMIStox, ToxAlert, Aboatox, and ToxScreen have been widely used for toxicity screening. Though this time saving assays offer excellent sensitivity, cost-effectiveness, and accuracy, these commercial assays are limited in terms of real-time monitoring in Indian coastal environment due to warmer temperatures. This necessitates the need to develop a rapid and accurate assay that can be effectively employed for real time monitoring with respect to heavy metals in the Indian coastal waters. With this objective, the present study was conducted by isolating an indigenous luminescent bacterium from the light organs of chordates Gazza minuta which showed higher luminescence in a wide range of temperatures. The isolate could grow well in the temperature of 30 ± 2 °C and withstand temperature up to 35 ± 2 °C. The isolated bacterium was identified as Photobacterium leiognathi GoMGm1 based on 16S rDNA and luxA gene sequences. The suitable growing medium was optimized using central composite rotational design (CCRD) method to obtain optimal growth and luminescence. The optimized medium exemplified the maximal growth and luminescence of P. leiognathi at OD600 nm of 5.78 ± 0.12 and RLU of 12.49 ± 0.43. The isolate was used to assess the toxicity of several heavy metals. The IC50 values of 0.0051, 1.13, 1.37, 3.1, and 6.68 mg L-1 were observed for the Hg, Cr, Cu, Ni, and Zn, respectively, after 15 min of exposure. Results obtained from principal component analysis (PCA) displayed the present assay's compatibility with other luminescent bacterial assay and commercial Microtox™ assay. Thus, it would the right candidate as an early detection system for heavy metals in aquatic bodies in tropical countries. Schematic representation of the present study.

Highly efficient multifunctional graphene/chitosan/magnetite nanocomposites for photocatalytic degradation of important dye molecules.

Multifunctional chitosan/magnetite (CS/Fe3O4) and graphene/chitosan/magnetite (Gr/CS/Fe3O4) nanocomposites (NCs) were synthesized using a simple hydrothermal method. The NCs were subsequently evaluated as magnetic photocatalysts towards the photodegradation of dye molecules that are detrimental to the environment. In the present study, sphere shaped Fe3O4 nanoparticles (NPs) were found to uniformly decorate CS and Gr surfaces. The synthesized Fe3O4 NPs, CS/Fe3O4 and Gr/CS/Fe3O4 NCs were characterized by powder X-ray diffraction, Fourier-transform infrared and Raman spectroscopy, thermogravimetric analysis, UV-visible diffuse reflectance and photoluminescence spectroscopy, and field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The Gr/CS/Fe3O4 NCs showed 100% photocatalytic efficiency against rhodamine B (40 min), bromothymol blue (60 min), methylene blue (80 min) and methyl orange (100 min) compared to Fe3O4 NPs (100 min for Rh-B, 120 min for BTB, 160 min for MB and 180 min for MO) and CS/Fe3O4 NCs (90 min for Rh-B, 100 min for BTB, 140 min for MB and 150 min for MO). The photocatalytic irradiation efficiency of Fe3O4 NPs, CS/Fe3O4 and Gr/CS/Fe3O4 NCs, evaluated against visible light, was found to be significantly higher for Rh-B (100% within 40 min) compared to the other tested dyes.

Biosynthesized silver nanoparticles for inhibition of antibacterial resistance and biofilm formation of methicillin-resistant coagulase negative Staphylococci.

The ability of a natural stabilizing and reducing agent on the synthesis of silver nanoparticles (Ag NPs) was explored using a rapid and single-pot biological reduction method using Nocardiopsis sp. GRG1 (KT235640) biomass. The UV-visible spectral analysis of Ag NPs was found to show a maximum absorption peak located at a wavelength position of ∼422 nm for initial conformation. The major peaks in the XRD pattern were found to be in excellent agreement with the standard values of metallic Ag NPs. No other peaks of impurity phases were observed. The morphology of Ag NPs was confirmed through TEM observation, demonstrating that the particle size distribution of Ag NPs entrenched in spherical particles is in a range between 20 and 50 nm. AFM analysis further supported the nanosized morphology of the synthesized Ag NPs and allowed quantifying the Ag NPs surface roughness. The synthesized Ag NPs showed significant antibacterial and antibiofilm activity against biofilm positive methicillin-resistant coagulase negative Staphylococci (MR-CoNS), which were isolated from urinary tract infection as determined by spectroscopic methods in the concentration range of 5-60 µg/ml. The inhibition of biofilm formation with coloring stain was morphologically imaged by confocal laser scanning microscopy (CLSM). Morphological alteration of treated bacteria was observed by SEM analysis. The results clearly indicate that these biologically synthesized Ag NPs could provide a safer alternative to conventional antibiofilm agents against uropathogen of MR-CoNS.

Chitosan/silver nanocomposites for colorimetric detection of glucose molecules.

This study was about the simple method for the rapid colorimetric and visual detection of glucose molecules in water medium. Silver nanoparticles were spread on the chitosan surface (CS/Ag NCs) and it was characterized by UV-visible spectroscopy, fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The CS/Ag NCs displayed a strong surface plasmon resonance band at 429 nm which disappears in the addition of accelerative concentrations of glucose molecules and it was attended by color alteration from yellow to colorless. The interaction of glucose molecules on the CS/Ag NCs was displayed through TEM technique. Glucose molecules was detected not only by naked eyes (from yellow to purple grey) but also by UV-vis spectrophotometer in the concentration range between 0 and 100 µM, with limit detection of 5 µM and a good linear relationship of R2 value = 0.99. The proposed paper was used for the application of the detection of glucose molecules in water sample with adequate outcome. This CS/Ag NCs was very simple and low cost system without using any other enzymatic catalyst and organic chromogenic agents for glucose molecules detection.

Biologically synthesized copper oxide nanoparticles enhanced intracellular damage in ciprofloxacin resistant ESBL producing bacteria.

Copper oxide nanoparticles (CuO NPs) were synthesized biologically using leaf extract of Camilla japonica. The typical UV-visible spectral peak of CuO NPs was observed at a wavelength of ∼290 nm, which confirmed their successful synthesis. From scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses, the synthesized CuO NPs were found to possess spherical shape. Energy dispersive X-ray analyzer (EDX) results revealed that the CuO NPs are almost pure with atomic percentages of 50.92 for Cu and 49.08 for O. Fourier transform infrared (FTIR) confirmed the presence of an absorption peak located at a wavenumber position of ∼480 cm-1 typical for highly pure CuO NPs. TEM images displayed that the particles are relatively uniform in size ∼15-25 nm. The P. aeruginosa and K. pneumonia showed complete resistance against Hexa 077 antibiotic discs. The result of ≤22 ceftazidime and ≤27 cefotaxime confirmed that both the uropathogens were ESBL producers. The ≥8 mm of the MIC stripe further confirmed that both the uropathogens were ESBL producers. Furthermore, the antibacterial activity of CuO NPs against selected ESBL producing P. aeruginosa and K. pneumoniae at minimum inhibition concentration (MIC) of 100 µg/mL. The decreased cell viability and damaged membrane construction of both the uropathogens were observed by confocal laser scanning microscope (CLSM) using AO/EB stains at desired MIC dose. The morphological damage of the bacterial cells was demonstrated by SEM analysis. Hence, based on the above in vitro findings, the results suggested that the CuO NPs are efficient antibacterial compounds against ESBL producing bacteria, and that the plant leaf mediated CuO NPs can be considered as novel and promising material to act against various infectious bacteria.

Antibacterial and anticancer potential of marine endophytic actinomycetes Streptomyces coeruleorubidus GRG 4 (KY457708) compound against colistin resistant uropathogens and A549 lung cancer cells.

The aim of the current study is to identify bioactive compound from marine endophytic actinomycetes (MEA) isolated from Gulf of Mannar region, Southeast coast of India. Among the isolated actinomycetes, strain GRG 4 exhibited excellent ability to inhibit isolated colistin resistant (CR) Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae), which is a emerging threat to the world. The strain was identified as Streptomyces coeruleorubidus GRG 4 (KY457708), based on morphological, biochemical, phenotypic and genotypic characters. The bioactive metabolites present in the methanolic extract were partially purified by TLC and preparative HPLC. The active HPLC fraction 2 showed 15, 20 mm zone of inhibition against both CR P. aeruginosa and K. pneumoniae respectively. Analytical HPLC and FT-IR results of fraction 2 showed with carbonyl group. Both GC-MS and LC-MS results confirmed that the fraction 2 contained chemical constituents of Bis (2-Ethylhexyl) Phthalate (BEP). The compromised structure with loosely integrated and ruptured cell wall of BEP treated CR bacteria were observed by confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM) at 75 µg/mL of minimum inhibitory concentration (MIC) dose. Further, cytotoxic effect of BEP against A549 human lung cancer cells revealed complete inhibition by cell proliferation and apoptosis was observed at 100 µg/mL in 24 h treatment. In addition, irreversible ROS dependent oxidative damage was clearly observed at the IC50 concentration of BEP. The toxicity of BEP was also studied against Vibrio fischeri (V. fischeri) and found to be highly toxic after 15 and 30 min of treatment. Based on the results it could be concluded that the identified compound BEP is a potent inhibitor for CR bacteria and A549 lung cancer cells.

Biologically synthesized zinc oxide nanoparticles as nanoantibiotics against ESBLs producing gram negative bacteria.

The accelerative outgrowth of extended spectrum ß-lactamases (ESBLs) producing Escherichia coli (E. coli) and Proteus mirabilis (P. mirabilis) was mainly due to incessant relentless influence of antibiotics thereby increasing incidence and death rate which was obvious from the survey of ESBLs producing bacteria related health problem. In the present paper, we synthesized and characterized zinc oxide nanoparticles (ZnO NPs) employing using Camellia japonica leaf extract, bactericidal action of these NPs against extended spectrum ß lactamases (ESBLs) positive E. coli and P. mirabilis clinical strains owing the minimal inhibitory concentration (MIC) percentage 83, 81% at 100 µg/mL concentration and minimum bactericidal concentration (MBC) final inhibiting concentration at 150 µg/mL. Moreover, confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM) results evident for loss of viability, cell shrinkage, disarrangement of cell membrane, and cell wall lysis activity of ZnO NPs against ESBLs positive E. coli BDUMS3 (KY617770) and P. mirabilis BDUMS1 (KY617768) strains. From the results, it was observed that the biologically synthesized ZnO NPs has stronger antibacterial effect against ESBLs producing bacterial strains. Nevertheless, current date there is no reports of antibacterial activity of metal oxide (ZnO) NPs against ESBL producing gram negative bacteria. Consequently, this finding is the first report in this respect and it shows band gap energy and ROS accumulation to damage the cell wall and inhibit the growth of ESBL producing gram negative strains.