Fabrication of graphene oxide-p-phenylenediamine nanocomposites as fluorescent chemosensors for detection of metal ions.

In this work, graphene oxide-p-Phenylenediamine nanocomposites of two different ratios of Graphene oxide: p-Phenylenediamine (1:1 and 1:5) were prepared and characterized by using analytical, spectroscopic and microscopic studies (GO-pPD 11 and GO-pPD 15). These nanocomposites were employed as fluorescent chemosensors for sensing potential cations. Remarkably, graphene oxide-p-Phenylenediamine nanocomposites of ratio 1:1 (GO-pPD 15) was selective and sensitive to Ag+ ions, whereas the graphene oxide-p-Phenylenediamine nanocomposites of ratio 1:5 (GO-pPD 15) was selective to Ce3+ions. A possible mechanism as switch "off-on" is proposed built on the inhibition of the photo induced electron transfer process in both the fluorescent probes in detecting the metal ions. In addition, interference studies were performed with the help of competitive complexation analysis and no significant interference were found by other potentially competing cations. The pH studies revealed that both the chemosensors can be used at the physiological pH for the ion detection and also the detection time was within 2-3 min. Both the chemosensors show good reversibility and hence the sensors can be used for multiple times. The newer nanocomposites were then utilized in the real water sample analysis as to check its real level application purpose.

Partially purified actinomycetes compounds enhance the intracellular damages in multi-drug resistant P. aeruginosa and K. pneumoniae.

Based on the excellent nutrient level, the current study was focused on isolation and anti-bacterial activity of the actinomycetes from marine mangrove soil samples. As result, 10 different strains of actinomycetes strains were identified on actinomycetes isolation agar plates. The identified strains were shown with white, clear, uncontaminated well matured spore producing ability. Based on the initial observation, the isolated colonies were actinomycetes. The partially extracted crude compound shown excellent anti-bacterial activity against P. aeruginosa and K. pneumoniae with 15 mm and 13 mm zone of inhibitions were observed at 500 µL concentrations. The minimum inhibition concentration result was also confirmed the 500 µL concentration against both the tested concentration with high inhibition rate. Then, the intracellular damages, decreased cell growth of the crude actinomycetes extract treated bacterial strains were clearly observed by confocal laser scanning electron microscope. The extracellular damages of bacterial cell wall and shape of the both the pathogens were clearly shown by scanning electron microscope. Therefore, all the results were clearly supported to the partially extracted crude compound and it has excellent anti-bacterial activity against tested multi drug resistant bacteria.

Adsorption of nickel ions from electroplating effluent by graphene oxide and reduced graphene oxide.

Heavy metal pollution in the water bodies causes a serious threat to all living beings. Extended exposure of heavy metals such as nickel (Ni) ions causes cancer. Henceforth, the current study investigated the removal of Ni ions from the electroplating effluent using nanocomposites namely, Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) in the presence of various factors such as contact time, pH, agitation speed and sorbent dosage. Further, it was determined the rate kinetic model and adsorption equilibrium isotherms. The study also focused on comparing the removal efficiency of two nanocomposites. The maximum sorption efficiency were found to be 90.8% and 84.4% at optimized pH (8), contact time (180-1440 m), RPM (250-300) and adsorbent dosage (0.2 mg/L) for GO and rGO respectively. Furthermore, toxicity of treated and untreated effluent were tested against Phosphobacter and Azospirillium using GO and rGO and found that the treated effluent was non-toxic. The contribution of this study to agriculture in using recycled effluent for crop cultivation was being verified by seed germination of Lablab purpureus seeds watered with treated and untreated effluent. Finally we concluded that the results of treated water can be used for cultivation as there was healthy growth of plants.

Identification of carbapenems resistant genes on biofilm forming K. pneumoniae from urinary tract infection.

The multi-drug resistant effect of the Gram negative bacteria K. pneumoniae was identified by disc diffusion method using specific UTI panel discs of Kleb 1 HX077 and Kleb 2 HX090 HEXA. Among the multi-drug resistant bacteria, the carbapenem resistant (CR) effect of the K. pneumoniae was screened by specific carbapenem detection antibiotics of HEXA HX066 and HX0103 HEXA by disc diffusion method. In addition, the effective antibiotics were further performed against K. pneumoniae by minimum inhibition concentration method. Further, the carbapenemase genes of VIM 1 and IMP 1 were detected from the isolated strains by multiplex PCR method. Furthermore, the biofilm forming ability of selected carbapenem resistant K. pneumoniae was initially identified by tissue culture plate method and confirmed by exopolysaccharide arrest ability of congo red agar assay. Finally, our result was proved that the identified K. pneumoniae is carbapenemase producing strain, and its virulence was extended with strong biofilm formation.

Anti-biofilm activity of LC-MS based Solanum nigrum essential oils against multi drug resistant biofilm forming P. mirabilis.

Urinary tract infections are second most important diseases worldwide due to the increased amount of antibiotic resistant microbes. Among the Gram negative bacteria, P. mirabilis is the dominant biofilm producer in urinary tract infections next to E. coli. Biofilm is a process that produced self-matrix of more virulence pathogens on colloidal surfaces. Based on the above fact, this study was concentrated to inhibit the P. mirabilis biofilm formation by various in-vitro experiments. In the current study, the anti-biofilm effect of essential oils was recovered from the medicinal plant of Solanum nigrum, and confirmed the available essential oils by liquid chromatography-mass spectroscopy analysis. The excellent anti-microbial activity and minimum biofilm inhibition concentration of the essential oils against P. mirabilis was indicated at 200 µg/mL. The absence of viability and altered exopolysaccharide structure of treated cells were showed by biofilm metabolic assay and phenol-sulphuric acid method. The fluorescence differentiation of P. mirabilis treated cells was showed with more damages by confocal laser scanning electron microscope. Further, more morphological changes of essential oils treated cells were differentiated from normal cells by scanning electron microscope. Altogether, the results were reported that the S. nigrum essential oils have anti-biofilm ability.

Monitoring the decolourisation efficacy of advanced membrane fabricated phytosilica nanoparticles in textile effluent water treatment.

Silica nanoparticles are generally mesoporous that are predominant in the sand and rocks. Silica nanoparticles have a wide range of applications in various fields such as medicine, waste management, effluent treatment and electronics. The present work has explored the synthesis of silica nanoparticles through acid and alkaline leaching method from Pedalium murex which is a common weed that is found in southern parts of Tamil Nadu. Silica nanoparticles (SiNps) and its functional groups were confirmed by EDX and FTIR analysis with their respective energy dispersion levels and wavenumbers. Size, shape and morphological features of SiNps were analysed by PSA, TEM and SAED analysis. Synthesised and characterized nanosilica was crosslinked over nylon-66 and cellulose nitrate membranes and were confirmed by FTIR analysis for their crosslinking with SiNps. Water retention activity of the crosslinked and non crosslinked membranes was analysed by contact angle measurement to ensure the receptability of the membranes to remove contaminants by the adsorption. The decolourisation efficiency of the crosslinked nylon 66 membrane was found as a potential source for the treatment with 65.5% colour reduction when compared with other membranes. A slight reduction of solid profiles and COD ranges were achieved for crosslinked membranes than non crosslinked membranes.

Photocatalytic reduction and anti-bacterial activity of biosynthesized silver nanoparticles against multi drug resistant Staphylococcus saprophyticus BDUMS 5 (MN310601).

In this study, silver nanoparticles (Ag NPs) was eco-friendly synthesized using purified flavonoid rich content of Morinda citrifolia (M. citrifolia) extract. The synthesized Ag NPs was exhibited at 420 nm in UV-spectrometer, and surface morphology with available chemical composition, shape and size of the Ag NPs were confirmed by X-ray diffraction (XRD) variation, scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) and transmission electron microscope (TEM). In addition, the excellent phytochemicals and anti-oxidant activity of the Ag NPs were confirmed by total anti-oxidant and DPPH free radical scavenging assays. Further, the concentration dependent inhibition of synthesized Ag NPs against biofilm forming Staphylococcus aureus (S. aureus) was confirmed by minimum inhibition concentration (MIC). The growth cells were arrested in the log phase of the culture and detected by flow cytometry analysis. In addition, the bacterial viability, exopolysaccharide degradation, intracellular membrane damage, matured biofilm inhibition, architectural damage and morphological alteration were confirmed by confocal laser scanning electron microscope (CLSM) and SEM. Furthermore, the synthesized Ag NPs reacted with methylene blue (MB) dye molecules has 100% degradation at an irradiation time of 140 min. Conclusively, the eco-friendly synthesized Ag NPs has excellent anti-oxidant, anti-bacterial through intracellular membrane damage, cell cycle arrest and methylene blue dye removal.

Anti-biofilm investigation of graphene/chitosan nanocomposites against biofilm producing P. aeruginosa and K. pneumoniae.

In this study graphene/chitosan nanoparticles (GR/CS NCs) were developed. The homogenous combination of GR and CS was confirmed by FTIR spectroscopy. The combination of CS with GR sheets reduced the XRD intensity of the GR peak in GR/CS NCs, while TEM images revealed the immobile CS coating of GR sheets. Further, the anti-biofilm activity of GR/CS NCs was tested. The tests showed that the formation of biofilm by Pseudomonas aeruginosa and Klebsiella pneumoniae was inhibited at 40□g/mL GR/CS NCs up to 94 and 92 %, respectively. The intracellular and cell surface damage of the bacteria was observed by CLSM and SEM. Also, GR/CS NCs produced a toxic effect of 90 % on Artemia franciscana at 70□g/mL upon 24 h incubation. The recorded properties of the synthesized GR/CS NCs qualify them as potential agents against multi-drug resistant bacteria.