Sougata Ghosh

Synthesis of silver nanoparticles using Dioscorea bulbifera tuber extract and evaluation of its synergistic potential in combination with antimicrobial agents.

Background Development of an environmentally benign process for the synthesis of silver nanomaterials is an important aspect of current nanotechnology research. Among the 600 species of the genus Dioscorea, Dioscorea bulbifera has profound therapeutic applications due to its unique phytochemistry. In this paper, we report on the rapid synthesis of silver nanoparticles by reduction of aqueous Ag+ ions using D. bulbifera tuber extract. Methods and results Phytochemical analysis revealed that D. bulbifera tuber extract is rich in flavonoid, phenolics, reducing sugars, starch, diosgenin, ascorbic acid, and citric acid. The biosynthesis process was quite fast, and silver nanoparticles were formed within 5 hours. Ultraviolet-visible absorption spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction confirmed reduction of the Ag+ ions. Varied morphology of the bioreduced silver nanoparticles included spheres, triangles, and hexagons. Optimization studies revealed that the maximum rate of synthesis could be achieved with 0.7 mM AgNO3 solution at 50°C in 5 hours. The resulting silver nanoparticles were found to possess potent antibacterial activity against both Gram-negative and Gram-positive bacteria. Beta-lactam (piperacillin) and macrolide (eryth-romycin) antibiotics showed a 3.6-fold and 3-fold increase, respectively, in combination with silver nanoparticles selectively against multidrug-resistant Acinetobacter baumannii. Notable synergy was seen between silver nanoparticles and chloramphenicol or vancomycin against Pseudomonas aeruginosa, and was supported by a 4.9-fold and 4.2-fold increase in zone diameter, respectively. Similarly, we found a maximum 11.8-fold increase in zone diameter of streptomycin when combined with silver nanoparticles against E. coli, providing strong evidence for the synergistic action of a combination of antibiotics and silver nanoparticles. Conclusion This is the first report on the synthesis of silver nanoparticles using D. bulbifera tuber extract followed by an estimation of its synergistic potential for enhancement of the antibacterial activity of broad spectrum antimicrobial agents.

Gnidia glauca flower extract mediated synthesis of gold nanoparticles and evaluation of its chemocatalytic potential.

BackgroundNovel approaches for synthesis of gold nanoparticles (AuNPs) are of utmost importance owing to its immense applications in diverse fields including catalysis, optics, medical diagnostics and therapeutics. We report on synthesis of AuNPs using Gnidia glauca flower extract (GGFE), its detailed characterization and evaluation of its chemocatalytic potential.ResultsSynthesis of AuNPs using GGFE was monitored by UV-Vis spectroscopy and was found to be rapid that completed within 20 min. The concentration of chloroauric acid and temperature was optimized to be 0.7 mM and 50°C respectively. Bioreduced nanoparticles varied in morphology from nanotriangles to nanohexagons majority being spherical. AuNPs were characterized employing transmission electron microscopy, high resolution transmission electron microscopy. Confirmation of elemental gold was carried out by elemental mapping in scanning transmission electron microscopic mode, energy dispersive spectroscopy and X-ray diffraction studies. Spherical particles of size ~10 nm were found in majority. However, particles of larger dimensions were in range between 50-150 nm. The bioreduced AuNPs exhibited remarkable catalytic properties in a reduction reaction of 4-nitrophenol to 4-aminophenol by NaBH4 in aqueous phase.ConclusionThe elaborate experimental evidences support that GGFE can provide an environmentally benign rapid route for synthesis of AuNPs that can be applied for various purposes. Biogenic AuNPs synthesized using GGFE exhibited excellent chemocatalytic potential.

Rapid efficient synthesis and characterization of silver, gold, and bimetallic nanoparticles from the medicinal plant Plumbago zeylanica and their application in biofilm control

Background Nanoparticles (NPs) have gained significance in medical fields due to their high surface-area-to-volume ratio. In this study, we synthesized NPs from a medicinally important plant – Plumbago zeylanica. Materials and methods Aqueous root extract of P. zeylanica (PZRE) was analyzed for the presence of flavonoids, sugars, and organic acids using high-performance thin-layer chromatography (HPTLC), gas chromatography-time of flight-mass spectrometry (GC-TOF-MS), and biochemical methods. The silver NPs (AgNPs), gold NPs (AuNPs), and bimetallic NPs (AgAuNPs) were synthesized from root extract and characterized using ultraviolet-visible spectra, X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The effects of these NPs on Acinetobacter baumannii, Staphylococcus aureus, and Escherichia coli biofilms were studied using quantitative biofilm inhibition and disruption assays, as well as using fluorescence, scanning electron microscopy, and atomic force microscopy. Results PZRE showed the presence of phenolics, such as plumbagin, and flavonoids, in addition to citric acid, sucrose, glucose, fructose, and starch, using HPTLC, GC-TOF-MS, and quantitative analysis. Bioreduction of silver nitrate (AgNO3) and chloroauric acid (HAuCl4) were confirmed at absorbances of 440 nm (AgNPs), 570 nm (AuNPs), and 540 nm (AgAuNPs), respectively. The maximum rate of synthesis at 50°C was achieved with 5 mM AgNO3 within 4.5 hours for AgNPs; and with 0.7 mM HAuCl4 within 5 hours for AuNPs. The synthesis of AgAuNPs, which completed within 90 minutes with 0.7 mM AgNO3 and HAuCl4, was found to be the fastest. Fourier-transform infrared spectroscopy confirmed bioreduction, while EDS and XRD patterns confirmed purity and the crystalline nature of the NPs, respectively. TEM micrographs and DLS showed about 60 nm monodispersed Ag nanospheres, 20–30 nm Au nanospheres adhering to form Au nanotriangles, and about 90 nm hexagonal blunt-ended AgAuNPs. These NPs also showed antimicrobial and antibiofilm activity against E. coli, A. baumannii, S. aureus, and a mixed culture of A. baumannii and S. aureus. AgNPs inhibited biofilm in the range of 96%–99% and AgAuNPs from 93% to 98% in single-culture biofilms. AuNPs also showed biofilm inhibition, with the highest of 98% in S. aureus. AgNPs also showed good biofilm disruption, with the highest of 88% in A. baumannii. Conclusion This is the first report on rapid and efficient synthesis of AgNPs, AuNPs and AgAuNPs from P. zeylanica and their effect on quantitative inhibition and disruption of bacterial biofilms.

Antidiabetic Activity of Gnidia glauca and Dioscorea bulbifera: Potent Amylase and Glucosidase Inhibitors

Diabetes is a metabolic disorder affecting about 220 million people worldwide. One of the most critical complications of diabetes is post-prandial hyper-glycemia (PPHG). Glucosidase inhibitor and α-amylase inhibitors are class of compounds that help in managing PPHG. Low-cost herbal treatment is recommended due to their lesser side effect for treatment of diabetes. Two plants with significant traditional therapeutic potential, namely, Gnidia glauca and Dioscorea bulbifera, were tested for their efficiency to inhibit α-amylase and α-glucosidase. Stem, leaf, and flower of G. glauca and bulb of D. bulbifera were sequentially extracted with petroleum ether, ethyl acetate, and methanol as well as separately with 70% ethanol. Petroleum ether extract of flower of G. glauca was found to inhibit α-amylase significantly (78.56%). Extracts were further tested against crude murine pancreatic, small intestinal, and liver glucosidase enzyme which revealed excellent inhibitory properties. α-glucosidase inhibition provided a strong in vitro evidence for confirmation of both G. glauca and D. bulbifera as excellent antidiabetic remedy. This is the first report of its kind that provides a strong biochemical basis for management of type II diabetes using G. glauca and D. bulbifera. These results provide intense rationale for further in vivo and clinical study.

Dual Drug Conjugated Nanoparticle for Simultaneous Targeting of Mitochondria and Nucleus in Cancer Cells

Effective targeting of mitochondria has emerged as an alternative strategy in cancer chemotherapy. However, considering mitochondrias crucial role in cellular energetics, metabolism and signaling, targeting mitochondria with small molecules would lead to severe side effects in cancer patients. Moreover, mitochondrial functions are highly dependent on other cellular organelles like nucleus. Hence, simultaneous targeting of mitochondria and nucleus could lead to more effective anticancer strategy. To achieve this goal, we have developed sub 200 nm particles from dual drug conjugates derived from direct tethering of mitochondria damaging drug (α- tocopheryl succinate) and nucleus damaging drugs (cisplatin, doxorubicin and paclitaxel). These dual drug conjugated nanoparticles were internalized into the acidic lysosomal compartments of the HeLa cervical cancer cells through endocytosis and induced apoptosis through cell cycle arrest. These nanoparticles damaged mitochondrial morphology and triggered the release of cytochrome c. Furthermore, these nanoparticles target nucleus to induce DNA damage, fragment the nuclear morphology and damage the cytoskeletal protein tubulin. Therefore, these dual drug conjugated nanoparticles can be successfully used as a platform technology for simultaneous targeting of multiple subcellular organelles in cancer cells to improve the therapeutic efficacy of the free drugs.

Synthesis of gold nanoanisotrops using dioscorea bulbifera tuber extract

Biosynthesis of metal nanoparticles employing plant extracts and thereby development of an environmentally benign process is an important branch of nanotechnology. Here, the synthesis of gold nanoparticles using Dioscorea bulbifera tuber extract (DBTE) as the reducing agent is reported. Field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), and UV-visible absorption spectroscopy confirmed the reduction of gold ions to AuNPs. The anisotropic nanoparticles consist of a mixture of gold nanotriangles, nanoprisms, nanotrapezoid, and spheres. The kinetics of particle formation was time dependent and was enhanced by the increase of temperature from 6° to 50°, the optimum being 50°. The optimum concentration of chloroauric acid was found to be 1mM. Complete reduction of the metal ions within 5 hours by DBTE highlights the development of a novel ecofriendly route of biological synthesis of gold nanoparticles. This is the first paper on synthesis of gold nanoparticles using DBTE.

Diosgenin from Dioscorea bulbifera: Novel Hit for Treatment of Type II Diabetes Mellitus with Inhibitory Activity against α-Amylase and α-Glucosidase

Diabetes mellitus is a multifactorial metabolic disease characterized by post-prandial hyperglycemia (PPHG). α-amylase and α-glucosidase inhibitors aim to explore novel therapeutic agents. Herein we report the promises of Dioscorea bulbifera and its bioactive principle, diosgenin as novel α-amylase and α-glucosidase inhibitor. Among petroleum ether, ethyl acetate, methanol and 70% ethanol (v/v) extracts of bulbs of D. bulbifera, ethyl acetate extract showed highest inhibition upto 72.06 ± 0.51% and 82.64 ± 2.32% against α-amylase and α-glucosidase respectively. GC-TOF-MS analysis of ethyl acetate extract indicated presence of high diosgenin content. Diosgenin was isolated and identified by FTIR, 1H NMR and 13C NMR and confirmed by HPLC which showed an α-amylase and α-glucosidase inhibition upto 70.94 ± 1.24% and 81.71 ± 3.39%, respectively. Kinetic studies confirmed the uncompetitive mode of binding of diosgenin to α-amylase indicated by lowering of both Km and Vm. Interaction studies revealed the quenching of intrinsic fluorescence of α-amylase in presence of diosgenin. Similarly, circular dichroism spectrometry showed diminished negative humped peaks at 208 nm and 222 nm. Molecular docking indicated hydrogen bonding between carboxyl group of Asp300, while hydrophobic interactions between Tyr62, Trp58, Trp59, Val163, His305 and Gln63 residues of α-amylase. Diosgenin interacted with two catalytic residues (Asp352 and Glu411) from α-glucosidase. This is the first report of its kind that provides an intense scientific rationale for use of diosgenin as novel drug candidate for type II diabetes mellitus.

Transport of oxygen atoms mediated by electronic excitation

Abstract Diffusion of oxygen from substrate to the film was observed under the influence of large electronic excitation. CuO thin film ∼210 nm on float glass was irradiated with 210 MeV I ions. We noticed the transport of oxygen from the substrate to the CuO film through the interface. The amount of oxygen transport from glass to the film was found to be fluence dependent. The loss of oxygen from the films was also observed. The erosion of Cu atoms was also observed beyond a fluence of 9.6×10 13 ions/cm2. The measurements were performed by on-line elastic recoil detection using a large area position sensitive detector. Since the electronic energy loss dominates in the present case of 210 MeV I ions, the observed changes at the interface and surface are attributed to inelastic collisions of the incident ions with the atomic electrons in the sample.

Phytochemical Analysis and Free Radical Scavenging Activity of Medicinal Plants Gnidia glauca and Dioscorea bulbifera

Gnidia glauca and Dioscorea bulbifera are traditional medicinal plants that can be considered as sources of natural antioxidants. Herein we report the phytochemical analysis and free radical scavenging activity of their sequential extracts. Phenolic and flavonoid content were determined. Scavenging activity was checked against pulse radiolysis generated ABTS•+ and OH radical, in addition to DPPH, superoxide and hydroxyl radicals by biochemical methods followed by principal component analysis. G. glauca leaf extracts were rich in phenolic and flavonoid content. Ethyl acetate extract of D. bulbifera bulbs and methanol extract of G. glauca stem exhibited excellent scavenging of pulse radiolysis generated ABTS•+ radical with a second order rate constant of 2.33×106 and 1.72×106, respectively. Similarly, methanol extract of G. glauca flower and ethyl acetate extract of D. bulbifera bulb with second order rate constants of 4.48×106 and 4.46×106 were found to be potent scavengers of pulse radiolysis generated OH radical. G. glauca leaf and stem showed excellent reducing activity and free radical scavenging activity. HPTLC fingerprinting, carried out in mobile phase, chloroform: toluene: ethanol (4: 4: 1, v/v) showed presence of florescent compound at 366 nm as well as UV active compound at 254 nm. GC-TOF-MS analysis revealed the predominance of diphenyl sulfone as major compound in G. glauca. Significant levels of n-hexadecanoic acid and octadecanoic acid were also present. Diosgenin (C27H42O3) and diosgenin (3á,25R) acetate were present as major phytoconstituents in the extracts of D. bulbifera. G. glauca and D. bulbifera contain significant amounts of phytochemicals with antioxidative properties that can be exploited as a potential source for herbal remedy for oxidative stress induced diseases. These results rationalize further investigation in the potential discovery of new natural bioactive principles from these two important medicinal plants.

Adiantum philippense L. Frond Assisted Rapid Green Synthesis of Gold and Silver Nanoparticles

Development of an ecofriendly, reliable, and rapid process for synthesis of nanoparticles using biological system is an important bulge in nanotechnology. Antioxidant potential and medicinal value of Adiantum philippense L. fascinated us to utilize it for biosynthesis of gold and silver nanoparticles (AuNPs and AgNPs). The current paper reports utility of aqueous extract of A. philippense L. fronds for the green synthesis of AuNPs and AgNPs. Effect of various parameters on synthesis of nanoparticles was monitored by UV-Vis spectrometry. Optimum conditions for AuNPs synthesis were 1 : 1 proportion of original extract at pH 11 and 5 mM tetrachloroauric acid, whereas optimum conditions for AgNPs synthesis were 1 : 1 proportion of original extract at pH 12 and 9 mM silver nitrate. Characterization of nanoparticles was done by TEM, SAED, XRD, EDS, FTIR, and DLS analyses. The results revealed that AuNPs and AgNPs were anisotropic. Monocrystalline AuNPs and polycrystalline AgNPs measured 10 to 18 nm in size. EDS and XRD analyses confirmed the presence of elemental gold and silver. FTIR analysis revealed a possible binding of extract to AuNPs through –NH2 group and to AgNPs through C=C group. These nanoparticles stabilized by a biological capping agent could further be utilized for biomedical applications.