Henna Sood

Synthesis, spectroscopy, structures and antimicrobial activity of mixed-ligand zinc(II) complexes of 5-nitro-salicylaldehyde thiosemicarbazones

A series of new complexes of zinc(II) with 5-nitro-salicylaldehyde-N1-substituted thiosemicarbazones {5-NO2-C6H4(2-OH)-C2(H)N3–N2H–C1(S)–N1HR; H2L1–NHR, R = H, Me, Et, Ph: respective thio-ligands} using bipyridines/phenanthrolines (L′) as co-ligands have been synthesized and characterized using elemental analysis, infrared, NMR, electronic absorption and fluorescence spectroscopy and single crystal X-ray crystallography. Thio-ligands coordinate to the metal center as di-anions (O,N,S-L-NHR)2− in their complexes, [Zn(κ3-O,N,S-L-NHR)(κ2-N,N-L′)] {R, (N,N-L′): H, bipy 1, phen, 2; Me, bipy 3, phen 4; Et, bipy 5, phen, 6; Ph, bipy, 7, phen 8}. The geometries of complexes fall into three categories: distorted trigonal bipyramidal (1-molecule II, 5, 7); distorted square pyramidal (4, 6 and 8-molecule II) and geometry in between square pyramidal and trigonal bipyramidal (1-molecule I, 8-molecule II). These zinc(II) complexes have shown significant antimicrobial activity against Staphylococcus aureus (MTCC740), methicillin resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae (MTCC109), Shigella flexneri (MTCC1457), Salmonella typhimurium (MTCC741) and Candida albicans (MTCC227). The activity against MRSA and S. aureus is a significant development in antimicrobial investigations vis-a-vis lack of activity of gentamicin against MRSA or low antimicrobial activity against S. aureus as per literature reports. All complexes are active against K. pneumoniae and S. typhimurium, while complexes reported in the literature were found to be inactive. Complexes tested were found to be cytotoxic to microorganisms (bactericidal/fungicidal).

Synthesis, structures, and ESI-mass studies of silver(I) derivatives of imidazolidine-2-thiones: Antimicrobial potential and biosafety evaluation

The basic objective of this investigation is to explore potential metallo-organic antimicrobial agents based on silver-heterocyclic-2-thiones. In this respect, a series of silver(I) halide complexes with imidazolidine-2-thiones (L-NR, R=H, Me, Et, Prn, Bun, Ph), namely, mononuclear [AgX(L-NR)(PPh3)2] (X, R: Cl, Bu, 1; Br, Ph, 7); [AgX(L-NR)3] (Br, Bu, 5; Br, Prn, 8) and halogen bridged dinuclear [Ag2(μ-X)2(L-NR)2(PPh3)2] (Cl, Bun, 2; Cl, Ph, 3; Cl, Prn, 4; Br, Ph, 6) have been synthesized and characterized using modern techniques. The thio-ligands are terminally S-bonded in all the complexes. The in vitro antimicrobial potential and biosafety evaluation of the above complexes as well as that of previously reported analogous silver complexes has been studied against Gram positive bacteria, namely, Staphylococcus aureus (MTCC 740) and Methicillin resistant Staphylococcus aureus (MRSA), Gram negative bacteria Klebsiella pneumoniae (MTCC 109), Salmonella typhimurium (MTCC 98) and a yeast Candida albicans (MTCC 227). Most of the complexes tested have shown significant antimicrobial activity with low values of minimum inhibitory concentration (MIC). Significantly, the activity against MRSA is an important outcome of this investigation. Among complexes tested for their cytotoxicity using MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assay, some complexes showed low cellular toxicity with high percent cell viability. A dinuclear complex [Ag2(μ-Cl)2(L-NPh)2(PPh3)2] 3 with 93.3% cell viability emerges the most important candidate for further investigations.

Synthesis, structures and antimicrobial activity of copper derivatives of N-substituted imidazolidine-2-thiones: unusual bio-activity against Staphylococcus epidermidis and Enterococcus faecalis

The main objective of this study was to explore the antimicrobial activity of several copper(I) complexes with N,S-donor thio-ligands against Gram positive bacteria, namely Staphylococcus aureus (MTCC 740), Staphylococcus epidermidis (MTCC 435), and Enterococcus faecalis (MTCC 439), Gram negative bacteria, Shigella flexneri (MTCC 1457) and Escherichia coli (MTCC 119), and yeast, Candida tropicalis (MTCC 230). New copper complexes were prepared from copper(I) halides and imidazolidine-2-thiones (L-NR, R = Et; Prn; Bun; Ph) with triphenylphosphine as a co-ligand. The complexes are mononuclear, [CuX(L-NR)(PPh3)2] (X, R: Cl, Prn, 1; Br, Prn, 2; Cl, Bun, 3; I, Bun, 4; I, Ph, 6) and [CuBr(L-NPh)2(PPh3)] 5, and halogen-bridged dinuclear, [Cu2(μ-X)2(L-NR)2(PPh3)2] (Br, Et, 7; Cl, Prn, 8; Br, Prn, 9; I, Prn, 10; Br, Ph, 11; I, Ph, 12). These complexes were characterized using analytical data, IR, 1H/13C-NMR spectroscopy, single crystal X-ray crystallography, electron spray ionization mass spectrometry (ESI-MS) and techniques for antimicrobial study (agar diffusion, agar dilution, MTT assay). All of the complexes are found to be bactericidal against Staphylococcus aureus. The most significant outcome of this investigation is that several complexes have shown significant activity against Staphylococcus epidermidis and Enterococcus faecalis, which is higher than that of the standard drug Gentamicin. Finally, these complexes were nearly inactive against Shigella flexneri, Escherichia coli and yeast Candida tropicalis.

Preliminary investigation of the effect of doping of copper oxide in CaO-SiO2-P2O5-MgO bioactive composition for bone repair applications

A diopside based bioactive system with a nominal composition of xCuO-(45.55-x)CaO-29.44 SiO2-10.28P2O5-14.73 MgO (x=0,1,3 and 5mol%) has been prepared by sol gel technique in the laboratory. X-ray Diffraction, Fourier Transform Infra-Red and Raman Spectroscopy, Field Emission Scanning Electron Microscopy along with Energy Dispersive X-ray Analysis and pH studies have been undertaken on the prepared samples before and after dipping the samples in simulated body fluid. It has been observed that hydroxyapatite layer starts to form with in 24h during immersion in simulated body fluid. Degradation studies have also been employed to check the degradation behavior in Tris-HCl. Dynamic light scattering studies show that particles are mostly agglomerated and have an average size of 356nm. Zeta potential studies have been undertaken to check the surface charge and it has been estimated that samples carry negative charge when dipped in simulated body fluid. Negative surface charge may contribute to attachment and proliferation of osteoblasts. Samples have also shown the antimicrobial properties against the Vibro cholerae and Escherichia coli pathogens. To check the non-toxic nature of the samples, cell cytotoxic and cell culture studies have been undertaken using the MG-63 cell lines. Samples have shown good response with good percentage viability of the cells in the culture media and hence, provides friendly environment to the growth of cells. The particle size, bioactivity, negative values of zeta potential, antimicrobial properties and good cell viability indicate the potential of the synthesized compositions as possible candidates for bone repair applications.

Investigation of bioactive CaO-P2O5-MgO-SiO2 ceramic composition for orthopedic applications

Bioactive sample of the composition 41CaO-8P2O5-17MgO-34SiO2 has been prepared in the laboratory by quick alkali mediated sol-gel method. 1M ammonia solution has been used to form the gel. Bioactivity of the sample has been analyzed by soaking the samples in simulated body fluid. Degradation study has also undertaken to check the degradation behavior of the sample. MTT cytotoxic test has also been done to know the toxicity of the sample and results show that samples has good percentage of cell viability in the cell culture media. Formation of the hydroxyapatite has been confirmed by the XRD, Raman spectroscopy and FESEM-EDX study.