Kalimuthu Kalishwaralal

BIOSYNTHESIS, PURIFICATION AND CHARACTERIZATION OF SILVER NANOPARTICLES USING ESCHERICHIA COLI

The application of nanoscale materials and structures, usually ranging from 1 to 100 nanometers (nm), is an emerging area of nanoscience and nanotechnology. Nanomaterials may provide solutions to technological and environmental challenges in the areas of solar energy conversion, catalysis, medicine, and water-treatment. The development of techniques for the controlled synthesis of nanoparticles of well-defined size, shape and composition, to be used in the biomedical field and areas such as optics and electronics, has become a big challenge. Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. One of the options to achieve this objective is to use natural factories such as biological systems. This study reports the optimal conditions for maximum synthesis of silver nanoparticles (AgNPs) through reduction of Ag(+) ions by the culture supernatant of Escherichia coli. The synthesized silver nanoparticles were purified by using sucrose density gradient centrifugation. The purified sample was further characterized by UV-vis spectra, fluorescence spectroscopy and TEM. The purified solution yielded the maximum absorbance peak at 420 nm and the TEM characterization showed a uniform distribution of nanoparticles, with an average size of 50 nm. X-ray diffraction (XRD) spectrum of the silver nanoparticles exhibited 2theta values corresponding to the silver nanocrystal. The size-distribution of nanoparticles was determined using a particle-size analyzer and the average particle size was found to be 50 nm. This study also demonstrates that particle size could be controlled by varying the parameters such as temperature, pH and concentration of AgNO(3).

Silver nanoparticles impede the biofilm formation by Pseudomonas aeruginosa and Staphylococcus epidermidis.

Biofilms are ensued due to bacteria that attach to surfaces and aggregate in a hydrated polymeric matrix. Formation of these sessile communities and their inherent resistance to anti-microbial agents are the source of many relentless and chronic bacterial infections. Such biofilms are responsible play a major role in development of ocular related infectious diseases in human namely microbial keratitis. Different approaches have been used for preventing biofilm related infections in health care settings. Many of these methods have their own demerits that include chemical based complications; emergent antibiotic resistant strains, etc. silver nanoparticles are renowned for their influential anti-microbial activity. Hence the present study over the biologically synthesized silver nanoparticles, exhibited a potential anti-biofilm activity that was tested in vitro on biofilms formed by Pseudomonas aeruginosa and Staphylococcus epidermidis during 24-h treatment. Treating these organisms with silver nanoparticles resulted in more than 95% inhibition in biofilm formation. The inhibition was known to be invariable of the species tested. As a result this study demonstrates the futuristic application of silver nanoparticles in treating microbial keratitis based on its potential anti-biofilm activity.

Antitumor activity of silver nanoparticles in Dalton's lymphoma ascites tumor model.

Nanomedicine concerns the use of precision-engineered nanomaterials to develop novel therapeutic and diagnostic modalities for human use. The present study demonstrates the efficacy of biologically synthesized silver nanoparticles (AgNPs) as an antitumor agent using Dalton’s lymphoma ascites (DLA) cell lines in vitro and in vivo. The AgNPs showed dose- dependent cytotoxicity against DLA cells through activation of the caspase 3 enzyme, leading to induction of apoptosis which was further confirmed through resulting nuclear fragmentation. Acute toxicity, ie, convulsions, hyperactivity and chronic toxicity such as increased body weight and abnormal hematologic parameters did not occur. AgNPs significantly increased the survival time in the tumor mouse model by about 50% in comparison with tumor controls. AgNPs also decreased the volume of ascitic fluid in tumor-bearing mice by 65%, thereby returning body weight to normal. Elevated white blood cell and platelet counts in ascitic fluid from the tumor-bearing mice were brought to near-normal range. Histopathologic analysis of ascitic fluid showed a reduction in DLA cell count in tumor-bearing mice treated with AgNPs. These findings confirm the antitumor properties of AgNPs, and suggest that they may be a cost-effective alternative in the treatment of cancer and angiogenesis-related disorders.

Antiangiogenic properties of silver nanoparticles

Angiogenesis is an important phenomenon involved in normal growth and wound healing processes. An imbalance of the growth factors involved in this process, however, causes the acceleration of several diseases including malignant, ocular, and inflammatory diseases. Inhibiting angiogenesis through interfering in its pathway is a promising methodology to hinder the progression of these diseases. The function and mechanism of silver nanoparticles (Ag-NPs) in angiogenesis have not been elucidated to date. PEDF is suggested to be a potent anti-angiogenic agent. In this study, we postulated that Ag-NPs might have the ability to inhibit angiogenesis, the pivotal step in tumor growth, invasiveness, and metastasis. We have demonstrated that Ag-NPs could also inhibit vascular endothelial growth factor (VEGF) induced cell proliferation, migration, and capillary-like tube formation of bovine retinal endothelial cells like PEDF. In addition, Ag-NPs effectively inhibited the formation of new blood microvessels induced by VEGF in the mouse Matrigel plug assay. To understand the underlying mechanism of Ag-NPs on the inhibitory effect of angiogenesis, we showed that Ag-NPs could inhibit the activation of PI3K/Akt. Together, our results indicate that Ag-NPs can act as an anti-angiogenic molecule by targeting the activation of PI3K/Akt signaling pathways.

Biosynthesis of silver and gold nanoparticles using Brevibacterium casei

The present study demonstrates an unprecedented green process for the production of spherical-shaped Au and Ag nanoparticles synthesized and stabilized using a bacterium, Brevibacterium casei. Aqueous solutions of chloroaurate ions for Au and Ag(+) ions for silver were treated with B. casei biomass for the formation of Au nanoparticles (AuNP) and Ag nanoparticles (AgNP). The nanometallic dispersions were characterized by surface plasmon absorbance measuring at 420 and 540 nm for Ag and Au nanoparticles, respectively. Transmission electron microscopy showed the formation of nanoparticles in the range of 10-50 nm (silver), and 10-50 nm (gold). XRD analysis of the silver and gold nanoparticles confirmed the formation of metallic silver and gold. Further analysis carried out by Fourier Transform Infrared Spectroscopy (FTIR), provides evidence for the presence of proteins as possible biomolecules responsible for the reduction and capping agent which helps in increasing the stability of the synthesized silver and gold nanoparticles. The biological activities of the synthesized particles were confirmed based on their stable anti-coagulant effects. The use of bacterium for nanoparticles synthesis offers the benefits of ecofriendliness and amenability for large-scale production.

Nanosilver--the burgeoning therapeutic molecule and its green synthesis.

Nanotechnology is a field that is burgeoning day by day, making an impact in all spheres of human life. Biological methods of synthesis have paved way for the greener synthesis of nanoparticles and these have proven to be better methods due to slower kinetics, they offer better manipulation and control over crystal growth and their stabilization. This has motivated an upsurge in research on the synthesis routes that allow better control of shape and size for various nanotechnological applications. Nanosilver has developed as a potent antibacterial, antifungal, anti-viral and anti-inflammatory agent. The recent advancement in the field includes the enzymatic method of synthesis suggesting enzymes to be responsible for the nanoparticle formation. The biomedical applications of silver nanoparticle can be effective by the use of biologically synthesized nanoparticles which minimize the factors such as toxicity and cost and are found to be exceptionally stable. The targeting of cancer cells using silver nanoparticles has proven to be effective, but neither the exact mechanism of action nor the modes of activation of the downstream signaling molecules have been revealed yet. The review illustrates a probable signaling pathway and mechanism by which silver nanoparticles target the cancer cells. The current review also examines the historical background of nanoparticles, role of silver nanoparticles in various biomedical applications and also focusing on better methods of the synthesis of nanoparticles.

Anti-oxidant effect of gold nanoparticles restrains hyperglycemic conditions in diabetic mice

BackgroundOxidative stress is imperative for its morbidity towards diabetic complications, where abnormal metabolic milieu as a result of hyperglycemia, leads to the onset of several complications. A biological antioxidant capable of inhibiting oxidative stress mediated diabetic progressions; during hyperglycemia is still the need of the era. The current study was performed to study the effect of biologically synthesized gold nanoparticles (AuNPs) to control the hyperglycemic conditions in streptozotocin induced diabetic mice.ResultsThe profound control of AuNPs over the anti oxidant enzymes such as GSH, SOD, Catalase and GPx in diabetic mice to normal, by inhibition of lipid peroxidation and ROS generation during hyperglycemia evidence their anti-oxidant effect during hyperglycemia. The AuNPs exhibited an insistent control over the blood glucose level, lipids and serum biochemical profiles in diabetic mice near to the control mice provokes their effective role in controlling and increasing the organ functions for better utilization of blood glucose. Histopathological and hematological studies revealed the non-toxic and protective effect of the gold nanoparticles over the vital organs when administered at dosage of 2.5 mg/kilogram.body.weight/day. ICP-MS analysis revealed the biodistribution of gold nanoparticles in the vital organs showing accumulation of AuNPs in the spleen comparatively greater than other organs.ConclusionThe results obtained disclose the effectual role of AuNPs as an anti-oxidative agent, by inhibiting the formation of ROS, scavenging free radicals; thus increasing the anti-oxidant defense enzymes and creating a sustained control over hyperglycemic conditions which consequently evoke the potential of AuNPs as an economic therapeutic remedy in diabetic treatments and its complications.

Optimization of media composition for Nattokinase production by Bacillus subtilis using response surface methodology

Response surface methodology and central composite rotary design (CCRD) was employed to optimize a fermentation medium for the production of Nattokinase by Bacillus subtilis at pH 7.5. The four variables involved in this study were Glucose, Peptone, CaCl2, and MgSO4. The statistical analysis of the results showed that, in the range studied; only peptone had a significant effect on Nattokinase production. The optimized medium containing (%) Glucose: 1, Peptone: 5.5, MgSO4: 0.2 and CaCl2: 0.5 resulted in 2-fold increased level of Nattokinase (3194.25U/ml) production compared to initial level (1599.09U/ml) after 10h of fermentation. Nattokinase production was checked with fibrinolytic activity.

Silver nanoparticles inhibit VEGF induced cell proliferation and migration in bovine retinal endothelial cells.

Angiogenesis, the growth of new blood vessels from pre-existing vasculature is of physiological and pathological importance. We have investigated the anti-angiogenic potential of silver nanoparticles, produced by Bacillus licheniformis. Bovine retinal endothelial cells (BRECs) were treated with the different concentrations of silver nanoparticles for 24 h in the presence and absence of vascular endothelial growth factor (VEGF), where 500 nM (IC50) of silver nanoparticle concentration, was able to block the proliferation and migration of BRECs. The cells showed a clear enhancement in caspase-3 activity and formation of DNA ladders, evidence of induction of apoptosis. Here we report for the first time that silver nanoparticles inhibit cell survival via PI3K/Akt dependent pathway in Bovine retinal endothelial cells.

Biological synthesis of gold nanocubes from Bacillus licheniformis

Microorganisms play an important role in the eco-friendly synthesis of metal nanoparticles. This study illustrates the synthesis of gold nanocubes using the bacterium Bacillus licheniformis after 48 h of incubation at room temperature. The morphology of the samples was analyzed using scanning electron microscopy (SEM) and the particles formed were characterized to be nanocubes. The size of gold nanocubes in aqueous solution has been calculated using UV-Vis spectroscopy, XRD and SEM measurements. The nanoparticles are found to be polydisperse nanocubes in the size range 10-100 nm.