P.T. Kalaichelvan

Biogenic synthesis of silver nanoparticles and their synergistic effect with antibiotics: a study against gram-positive and gram-negative bacteria

UNLABELLED The development of a reliable green chemistry process for the biogenic synthesis of nanomaterials is an important aspect of current nanotechnology research. Silver nanoparticles (AgNPs) have been known for their inhibitory and bactericidal effect. Resistance to antimicrobial agents by pathogenic bacteria has emerged in recent years and is a major challenge for the health care industry. In the present investigation the use of the fungus Trichoderma viride for the extracellular biosynthesis of AgNPs from silver nitrate solution is reported. It was observed that the aqueous silver (Ag(+)) ions, when exposed to a filtrate of T. viride, were reduced in solution, thereby leading to formation of extremely stable AgNPs. These AgNPs were characterized by means of several techniques. The nanoparticles show maximum absorbance at 420 nm on ultraviolet-visible spectra. The presence of proteins was identified by Fourier transform-infrared spectroscopy. The reduction of Ag(+) ions to elemental silver was characterized by x-ray photoelectron spectrophotometry. Electrokinetic measurements (zeta potential) of AgNPs as a function of pH in 1 x 10(-3) mol dm(-3) aqueous solution were evaluated. The transmission electron micrograph revealed the formation of polydispersed nanoparticles of 5-40 nm, and the presence of elemental silver was confirmed by energy-dispersed spectroscopy analysis. The nanoparticles were also evaluated for their increased antimicrobial activities with various antibiotics against gram-positive and gram-negative bacteria. The antibacterial activities of ampicillin, kanamycin, erythromycin, and chloramphenicol were increased in the presence of AgNPs against test strains. The highest enhancing effect was observed for ampicillin against test strains. The result showed that the combination of antibiotics with AgNPs have better antimicrobial effects. A mechanism was also proposed to explain this phenomenon. FROM THE CLINICAL EDITOR Silver nanoparticles (Ag NP-s) represent an important nanomedicine-based advance in the fight against polyresistent bacteria. In this study, the fungus Trichoderma viride was utilized for extracellular biosynthesis of extremely stable Ag Nps. The antibacterial activities of kanamycin, erythromycin, chloramphenicol and especially of ampicillin were increased in the presence of Ag NPs against test strains.

Synthesis of silver nanoparticles using Acalypha indica leaf extracts and its antibacterial activity against water borne pathogens

In the present study, biosynthesis of silver nanoparticles and its activity on water borne bacterial pathogens were investigated. Silver nanoparticles were rapidly synthesized using leaf extract of Acalypha indica and the formation of nanoparticles was observed within 30min. The results recorded from UV-vis spectrum, scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) support the biosynthesis and characterization of silver nanoparticles. From high-resolution transmission electron microscopy (HRTEM) analysis, the size of the silver nanoparticles was measured 20-30nm. Further, the antibacterial activity of synthesized silver nanoparticles showed effective inhibitory activity against water borne pathogens Viz., Escherichia coli and Vibrio cholerae. Silver nanoparticles 10microg/ml were recorded as the minimal inhibitory concentration (MIC) against E. coli and V. cholerae. Alteration in membrane permeability and respiration of the silver nanoparticle treated bacterial cells were evident from the activity of silver nanoparticles.

Mycobased synthesis of silver nanoparticles and their incorporation into sodium alginate films for vegetable and fruit preservation.

Biosynthesis of silver nanoparticles using Trichoderma viride and their incorporation into sodium alginate for vegetable and fruit preservation has been demonstrated in this study. Aqueous silver (Ag(+)) ions when exposed to the filtrate of T. viride are reduced in solution. These extremely stable silver nanoparticles were characterized by means of UV-vis spectrophotometer, FTIR, TEM, and EDS. The nanoparticles exhibit maximum absorbance at 421 nm in the UV spectrum. The presence of proteins was identified by FTIR. TEM micrograph revealed the formation of polydispersed nanoparticles, and the presence of elemental silver was confirmed by EDS analysis. The silver nanoparticle incorporated sodium alginate thin film shows good antibacterial activity against test strains. This film increases the shelf life of carrot and pear when compared to control with respect to weight loss and soluble protein content. These results show silver nanoparticle incorporated sodium alginate coated vegetables and fruits are suitable for preservation.

Fungal based synthesis of silver nanoparticles—An effect of temperature on the size of particles

A simple and effective approach to aqueous based biosynthesis of silver nanoparticles was demonstrated and the effect of temperature on controlling size of silver nanoparticles was studied. The morphology and uniformity of silver nanoparticles were investigated by UV-Vis spectroscopy, X-ray diffraction and HrTEM. The functional group of protein molecule was identified using FTIR. Increase in reaction temperature leads to decrease in size of silver nanoparticles and increase in monodispersity.

Blue orange light emission from biogenic synthesized silver nanoparticles using Trichoderma viride

Recent advances in nanomaterial have produced a new class of fluorescence labels by conjugating noble metal with biomolecules. The nanometer size metal conjugates are water soluble, biocompatible and provide important advantage over the fluorescence dyes. In this regard we synthesized silver nanoparticles at the size of 2-4 nm using biological route and studied fluorescence property of these nanoparticles. We observe that these silver (Ag(+)) ions when exposed to filtrate of Trichoderma viride are reduced in solution, thereby leading to the formation of an extremely stable silver hydrosol. These silver nanoparticles were characterized by means of UV-vis spectrophotometer, FTIR, HrTEM, EDX, XRD and fluorescence spectroscopy. The nanoparticles exhibit maximum absorbance at 405 nm in UV-vis spectrum. The presence of proteins was identified by FTIR. The HrTEM micrograph revealed the formation of monodispersed spherical nanoparticles and the presence of elemental silver was confirmed by EDX analysis and XRD. These monodispersed silver nanoparticles showed emission in the range of 320-520 nm wavelength.

Acalypha indica Linn: Biogenic synthesis of silver and gold nanoparticles and their cytotoxic effects against MDA-MB-231, human breast cancer cells

This study reports the in vitro cytotoxic effect of biologically synthesized silver and gold nanoparticles against MDA-MB-231, human breast cancer cells. Formation of silver and gold nanoparticles was observed within 30 min and the various characterization techniques such as UV–vis spectrophotometer, FE-SEM, TEM and XRD studies were confirmed the synthesis of nanoparticles. Further, MTT, acridine orange and ethidium bromide (AO/EB) dual staining, caspase-3 and DNA fragmentation assays were carried out using various concentrations of silver and gold nanoparticles ranging from 1 to 100 μg/ml. At 100 μg/ml concentration, the plant extract derived nanoparticles exhibited significant cytotoxic effects and the apoptotic features were confirmed through caspase-3 activation and DNA fragmentation assays. Thus, the results of the present study indicate that biologically synthesized silver and gold nanoparticles might be used to treat breast cancer; however, it necessitates clinical studies to ascertain their potential as anticancer agents.

Biosynthesis of anisotropic gold nanoparticles using Maduca longifolia extract and their potential in infrared absorption.

Metal nanoparticles, in general, and gold nanoparticles, in particular, are very attractive because of their size- and shape-dependent properties. Biosynthesis of anisotropic gold nanoparticles using aqueous extract of Madhuca longifolia and their potential as IR blockers has been demonstrated. The tyrosine residue was identified as the active functional group for gold ion reduction. These gold nanoparticles were characterized by of UV-Vis spectrophotometer, FTIR, TEM and HrTEM. The presence of proteins was identified by FTIR, SDS-PAGE, UV-Vis and fluorescence spectroscopy. The micrograph revealed the formation of anisotropic gold nanoaprticles. The biologically synthesized gold nanotriangles can be easily coated in the glass windows which are highly efficient in absorbing IR radiations.

Purification, characterization and crystallization of an extracellular alkaline protease from Aspergillus nidulans HA-10

Aspergillus nidulans is a highly potent fungus used in the production of alkaline protease. Extracellular alkaline protease was purified from A. nidulans in a two‐step procedure involving ammonium sulphate precipitation and Sephadex G‐100 column chromatography. The molecular mass of the enzyme was determined to be 42 kDa by SDS‐PAGE. The enzyme activity was also analyzed by zymogram with gelatin. The enzyme was more stable over a wide range of pH (6–10) and the temperatures up to 50 °C. It showed optimum enzyme activity at pH 8.0 and a temperature of 35 °C. The protease enzyme was completely inhibited by the serine protease inhibitor of phenylmethylsulfonyl fluoride (PMSF). The crystallization of the purified enzyme was performed by hanging drop vapour diffusion method using PEG 6000 as the precipitant. The micro crystals occurred in 40% of PEG 6000. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Inactivation of microbial infectiousness by silver nanoparticles-coated condom: a new approach to inhibit HIV- and HSV-transmitted infection.

Recent research suggests that today’s condoms are only 85% effective in preventing human immunodeficiency virus (HIV) and other sexually transmitted diseases. In response, there has been a push to develop more effective ways of decreasing the spread of the disease. The new nanotechnology-based condom holds the promise of being more potent than the first-generation products. The preliminary goal of this study was to develop a silver nanoparticles (Ag-NPs)-coated polyurethane condom (PUC) and to investigate its antimicrobial potential including the inactivation of HIV and herpes simplex virus (HSV) infectiousness. The Ag-NPs-coated PUC was characterized by using ultraviolet-visible spectrophotometry, Fourier transform-infrared spectroscopy, high-resolution scanning electron microscopy, and energy-dispersive analysis of X-ray spectroscopy. Nanoparticles were stable on the PUC and not washed away by water. Morphology of the PUC was retained after coating. The NP binding is due to its interaction with the nitrogen atom of the PUC. No significant toxic effects was observed when human HeLa cells, 293T and C8166 T cells were contacted to Ag-NPs-coated PUC for three hours. Interestingly, our results demonstrated that the contact of the Ag-NPs-coated PUC with HIV-1 and HSV-1/2 was able to efficiently inactivate their infectiousness. In an attempt to elucidate the antiviral action of the Ag-NPs, we have demonstrated that the anti-HIV activity was primarily mediated by the Ag-NPs, which are associated with the PUC. In addition, the data showed that both macrophage (M)-tropic and T lymphocyte (T)-tropic strains of HIV-1 were highly sensitive to the Ag-NPs-coated PUC. Furthermore, we also showed that the Ag-NPs-coated PUC was able to inhibit the growth of bacteria and fungi. These results demonstrated that the Ag-NPs-coated PUC is able to directly inactivate the microbe’s infectious ability and provides another defense line against these sexually transmitted microbial infections.

Mycosynthesis of silver and gold nanoparticles: Optimization, characterization and antimicrobial activity against human pathogens

This study was aimed to isolate soil fungi from Kolli and Yercaud Hills, South India with the ultimate objective of producing antimicrobial nanoparticles. Among 65 fungi tested, the isolate, Bios PTK 6 extracellularly synthesized both silver and gold nanoparticles with good monodispersity. Under optimized reaction conditions, the strain Bios PTK 6 identified as Aspergillus terreus has produced extremely stable nanoparticles within 12h. These nanoparticles were characterized by UV-vis. spectrophotometer, HR-TEM, FTIR, XRD, EDX, SAED, ICP-AES and Zetasizer analyses. A. terreus synthesized 8-20 nm sized, spherical shaped silver nanoparticles whereas gold nanoparticles showed many interesting morphologies with a size of 10-50 nm. The presence and binding of proteins with nanoparticles was confirmed by FTIR study. Interestingly, the myco derived silver nanoparticles exhibited superior antimicrobial activity than the standard antibiotic, streptomycin except against Staphylococcus aureus and Bacillus subtilis. The leakage of intracellular components such as protein and nucleic acid demonstrated that silver nanoparticles damage the bacterial cells by formation of pores, which affects membrane permeability and finally leads to cell death. Further, presence of nanoparticles in the bacterial membrane and the breakage of cell wall were also observed using SEM. Thus, the obtained results clearly reveal that these antimicrobial nanoparticles could be explored as promising candidates for a variety of biomedical and pharmaceutical applications.