Hina Singh

Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles

In the present study, the strain Brevibacterium frigoritolerans DC2 was explored for the efficient and extracellular synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were characterized by ultraviolet-visible spectrophotometry, which detected the formation of silver nanoparticles in the reaction mixture and showed a maximum absorbance at 420 nm. In addition, field emission transmission electron microscopy revealed the spherical shape of the nanoparticles. The dynamic light scattering results indicated the average particle size of the product was 97 nm with a 0.191 polydispersity index. Furthermore, the product was analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental mapping, which displayed the presence of elemental silver in the product. Moreover, on a medical platform, the product was checked against pathogenic microorganisms including Vibrio parahaemolyticus, Salmonella enterica, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans. The nanoparticles demonstrated antimicrobial activity against all of these pathogenic microorganisms. Additionally, the silver nanoparticles were evaluated for their combined effects with the commercial antibiotics lincomycin, oleandomycin, vancomycin, novobiocin, penicillin G, and rifampicin against these pathogenic microorganisms. These results indicated that the combination of antibiotics with biosynthesized silver nanoparticles enhanced the antimicrobial effects of antibiotics. Therefore, the current study is a demonstration of an efficient biological synthesis of silver nanoparticles by B. frigoritolerans DC2 and its effect on the enhancement of the antmicrobial efficacy of well-known commercial antibiotics.

Extracellular synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 and their biological applications

The present study highlights the microbial synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 strain, in an efficient way. The synthesized nanoparticles were characterized by ultraviolet-visible spectrophotometry, which displayed maximum absorbance at 424nm and 531nm for silver and gold nanoparticles, respectively. The spherical shape of nanoparticles was characterized by field emission transmission electron microscopy. The energy dispersive X-ray spectroscopy and elemental mapping were displayed the purity and maximum elemental distribution of silver and gold elements in the respective nanoproducts. The X-ray diffraction spectroscopy results demonstrate the crystalline nature of synthesized nanoparticles. The particle size analysis demonstrate the nanoparticles distribution with respect to intensity, volume and number of nanoparticles. For biological applications, the silver nanoparticles have been explored in terms of MIC and MBC against pathogenic microorganisms such as Vibrio parahaemolyticus, Escherichia coli, Salmonella enterica, Bacillus anthracis, Bacillus cereus and Staphylococcus aureus. Moreover, the silver nanoparticles in combination with commercial antibiotics, such as vancomycin, rifampicin, oleandomycin, penicillin G, novobiocin, and lincomycin have been explored for the enhancement of antibacterial activity and the obtained results showed that 3μg concentration of silver nanoparticles sufficiently enhance the antimicrobial efficacy of commercial antibiotics against pathogenic microorganism. Furthermore, the silver nanoparticles potential has been reconnoitered for the biofilm inhibition by S. aureus, Pseudomonas aeruginosa and E. coli and the results revealed sufficient activity at 6μg concentration. In addition, gold nanoparticles have been applied for catalytic activity, for the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride and positive results were attained.

Biosynthesis of anisotropic silver nanoparticles by bhargavaea indica and their synergistic effect with antibiotics against pathogenic microorganisms

The strain Bhargavaea indica DC1 isolated from four-year-old P. ginseng rhizospheric soil was used to perform rapid and extracellular biosynthesis of anisotropic silver nanoparticles. The ultraviolet-visible (UV-vis) spectra of the reaction mixture containing silver nanoparticles showed a peak at 460 nm, corresponding to the surface plasmon absorbance of silver nanoparticles. Field-emission transmission electron microscopy (FE-TEM) structural characterization revealed the nanobar, pentagon, spherical, icosahedron, hexagonal, truncated triangle, and triangular nanoparticles, with the size range from 30 to 100 nm. The energy-dispersive X-ray (EDX) analysis and elemental mapping results also confirmed that the silver was the predominant component of isolated nanoparticles. The X-ray diffraction (XRD) results correspond to the purity of silver nanoparticles and dynamic light scattering (DLS) result indicated that the average diameter of particles was 111.6 nm. In addition, enhancement in antimicrobial activity of commercial antibiotics was observed against various pathogenic microorganisms such as Vibrio parahaemolyticus, Salmonella enterica, Staphylococcus aureus, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans.

Green and rapid synthesis of silver nanoparticles using Borago officinalis leaf extract: anticancer and antibacterial activities

Abstract This study highlights the facile, reliable, cost effective, and ecofriendly synthesis of silver nanoparticles (AgNPs) using Borago officinalis leaves extract efficiently. The biosynthesis of AgNPs was verified by UV–Vis spectrum which showed the surface plasmon resonance (SPR) band at 422 nm. Transmission electron microscope (TEM) analysis revealed that the particles were spherical, hexagonal, and irregular in shape and had size ranging from 30 to 80 nm. The energy dispersive X-ray spectroscopy (EDX) and elemental mapping have displayed the purity and maximum distribution of silver in the AgNPs. The crystalline nature of AgNPs had been identified using X-ray diffraction (XRD) and selected area diffraction pattern (SAED). The particle size analysis revealed that the Z-average diameter of the AgNPs was 50.86 nm with polydispersity index (PDI) 0.136. Zeta potential analysis displayed the colloidal stability of AgNPs. This work also showed the efficacy of AgNPs against lung cancer cell lines (A549) and cervical cancer cell line (HeLa), in vitro. The AgNPs showed cytotoxicity to the A549 and HeLa cancer cell line at the concentrations 5 and 2 μg/ml. The AgNPs were also explored for the antibacterial activity including biofilm inhibition against pathogenic bacteria. The B. officinalis leaves extract can be used efficiently for green synthesis AgNPs. The biosynthesized AgNPs demonstrated potentials as anticancer and antibacterial agents. This work provides helpful insight into the development of new anticancer and antimicrobial agents.

Pedobacter daejeonensis sp. nov. and Pedobacter trunci sp. nov., isolated from an ancient tree trunk, and emended description of the genus Pedobacter.

Two Gram-stain-negative, yellow, aerobic and rod-shaped bacterial isolates, designated THG-DN3.18(T) and THG-DN3.19(T), were isolated from an ancient tree trunk from Daejeon, South Korea. 16S rRNA gene sequence similarity showed that both strains belong to the genus Pedobacter within the family Sphingobacteriaceae . Strain THG-DN3.18(T) exhibited maximum sequence similarity with Pedobacter boryungensis KCTC 23344(T) (98.5%) while strain THG-DN3.19(T) exhibited maximum sequence similarity with Pedobacter nyackensis LMG 24260(T) (97.3%). In DNA-DNA hybridization tests, the two strains showed less than 35% relatedness with respect to closely related species of the genus Pedobacter . Both strains contained iso-C(15 : 0) and C(16 : 1)ω6c and/or C(16 : 1)ω7c (summed feature 3) as the predominant fatty acids and MK-7 as the major isoprenoid quinone. The DNA G+C contents of strains THG-DN3.18(T) and THG-DN3.19(T) were 35.5 and 40.1 mol%, respectively. The genotypic analysis, biochemical properties, and phenotypic and chemotaxonomic characteristics indicate that strains THG-DN3.18(T) and THG-DN3.19(T) represent novel species of the genus Pedobacter , for which the names Pedobacter daejeonensis sp. nov. and Pedobacter trunci sp. nov. are proposed. The type strains are THG-DN3.18(T) ( = KCTC 42230(T) = JCM 30352(T)) and THG-DN3.19(T) ( = KCTC 42233(T) = JCM 30353(T)), respectively.

Ecofriendly synthesis of silver and gold nanoparticles by Euphrasia officinalis leaf extract and its biomedical applications

Abstract Biogenic synthesis of silver (AgNPs) and gold nanoparticles (AuNPs) using aqueous extract of Euphrasia officinalis has been reported. Stable AgNPs and AuNPs were formed on adding aqueous solutions of silver nitrate and chloroauric acid with E. officinalis leaf extract, in 19 min and 2 min, respectively. The synthesis method used in present study was simple, reliable, rapid, cost effective and ecofriendly. The synthesized nanoparticles were characterized with field emission transmission electron microscopy (FE-TEM), elemental mapping, selected area diffraction pattern (SAED), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), particle size distribution, zeta potential and Fourier-transform infrared spectroscopy (FTIR). The UV–Vis spectrum confirmed the synthesis of nanoparticles as the absorption band was observed at 450 nm for AgNPs and at 558 nm for AuNPs. The TEM images revealed quasi-spherical shape of AgNPs and AuNPs. The size of nanoparticles was determined to be 40.37 ± 1.8 nm for AgNPs and 49.72 ± 1.2 nm for AuNPs. The zeta potential value demonstrated the negative surface charge and stable nature of nanoparticles. Crystalline nature of the nanoparticles in the face-centred cubic (fcc) structure was confirmed by the peaks in the XRD pattern and SAED pattern. FTIR results showed the functional groups involved in reduction of silver and gold ions to metal nanoparticles. For biomedical application, the nanoparticles have been explored for anticancer, antibacterial and biofilm inhibition activities. It was observed that AgNPs exert anticancer activity against human lung cancer (A549) and human cervical cancer (HeLa) cell lines. On the other hand, AuNPs were able to inhibit only human cervical cancer cells. Furthermore, the AgNPs were active against clinically isolated human pathogens like Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Vibrio parahaemolyticus. Additionally, AgNPs also showed biofilm inhibition activity against S. aureus and P. aeruginosa.

Biosynthesis of silver nanoparticles by Novosphingobium sp. THG-C3 and their antimicrobial potential

Abstract The present study described biosynthesis of silver nanoparticles (AgNPs) using a bacterial strain Novosphingobium sp. THG-C3, isolated from soil, and their application in antibacterial activity. The maximum absorbance values of the synthesized AgNPs was measured at 406 nm in ultraviolet-visible spectrophotometry and were mostly spherical in shape with particle size in range of 8–25 nm by field emission transmission electron microscopy analysis. X-ray diffraction pattern corresponding to planes (111), (200), (220), and (311) demonstrated the crystalline nature of the AgNPs. The synthesized AgNPs exhibited antimicrobial activity against various pathogens inculding Staphylococcus aureus, Candida tropicalis, Pseudomonas aeruginosa, Escherichia coli, Vibrio parahaemolyticus, Candida albicans, Salmonella enterica, Bacillus subtilis, and Bacillus cereus. In addition, the AgNPs in combination with commercial antibiotics enhanced antimicrobial activity against P. aeruginosa, S. enterica, E. coli, and V. parahaemolyticus. The AgNPs synthesized by strain Novosphingobium sp. THG-C3 are comparatively simple, green, cost-effective, and may serve as a potential antimicrobial agent.

Biosynthesis of silver nanoparticles using Aeromonas sp. THG-FG1.2 and its antibacterial activity against pathogenic microbes.

Abstract Silver nanoparticles were prepared through green route with the aid of Aeromonas sp. THG-FG1.2 as reductant. Visual observation, ultraviolet–visible spectroscopy, transmission electron microscopy, elemental mapping, energy dispersive X-ray spectroscopy, selected area diffraction pattern (SAED), and X-ray diffraction (XRD) were used to characterize the synthesized silver nanoparticles. UV visible studies indicated the surface plasmon resonance at 400 nm which depicts the formation of silver nanoparticles. The TEM images show spherical silver nanoparticles of 8–16 nm. XRD and SAED fringes revealed the structure of silver nanoparticles as face centered cubic (fcc). These silver nanoparticles also tested for their antimicrobial potential and showed effective antimicrobial activity against tested pathogens and thus applicable as potent antimicrobial agent. Furthermore, the nanoparticles potential has been reconnoitered for their enhanced synergistic effect with antibiotics against multidrug resistant bacteria. Thus, the silver nanoparticles synthesized by Aeromonas sp. THG-FG1.2, were effective in inhibition of pathogenic microbes and also show enhanced antibacterial activity with antibiotics.

Nocardioides albidus sp. nov., an actinobacterium isolated from garden soil.

A novel bacterial strain, designated THG-S11.7T, was isolated from garden soil in Incheon, South Korea. Cells of the strain were Gram-stain-positive, aerobic, non-motile cocci, and were catalase- and oxidase-positive. Colonies of the strain were white. Strain THG-S11.7T grew optimally at 28 °C, at pH 7.0 and in the presence of 2.0 % NaCl. 16S rRNA gene sequence analysis indicated that the strain was a member of the genus Nocardioides. Strain THG-S11.7T showed a 16S rRNA gene sequence similarity of 98.2 % to Nocardioides kongjuensis KCTC 19054T, 98.0 % to Nocardioides caeni KCTC 19600T, 97.9 % to Nocardioides daeguensis KCTC 19799T, 97.8 % to Nocardioides nitrophenolicus KCTC 047BPT, 97.6 % to Nocardioides aromaticivorans KACC 20613T, 97.5 % to Nocardioides simplex KACC 20620T and 97.0 % to Nocardioides ginsengisoli KCTC 19135T. DNA-DNA relatedness values between strain THG-S11.7T and the closest phylogenetic neighbours were below 45.0 % and the DNA G+C content of strain THG-S11.7T was 72.2 mol%. Strain THG-S11.7T was characterized chemotaxonomically as having ll-diaminopimelic acid in the cell-wall peptidoglycan and menaquinone MK-8(H4) as the predominant isoprenoid quinone. The major phospholipid was determined to be diphosphatidylglycerol. The major cellular fatty acids of strain THG-S11.7T were iso-C15 : 0, C16 : 0 and iso-C16 : 0. Based on the phenotypic, genotypic and phylogenetic analyses, it is proposed that the isolate represents a novel species of the genus Nocardioides, for which the name Nocardioides albidus sp. nov. is proposed. The type strain is THG-S11.7T ( = KCTC 39607T = CCTCC AB 2015297T).

In vitro anti-inflammatory activity of spherical silver nanoparticles and monodisperse hexagonal gold nanoparticles by fruit extract of Prunus serrulata: a green synthetic approach

Abstract Recently, green metal nanoparticles have received global attention owing to their economical synthesis, biocompatible nature, widespread biomedical and environmental applications. Current study demonstrates a sustainable approach for the green synthesis of silver nanoparticles (P-AgNPs) and gold nanoparticles (P-AuNPs) from P. serrulata fresh fruit extract. The silver and gold nanoparticles were synthesized in a very rapid, efficient and facile manner, within 50 min and 30 s at 80 °C, respectively. The nanoparticles were characterized by using visual observation, UV–Vis, FE-TEM, EDX, elemental mapping, FT-IR, XRD and DLS, which confirmed the formation of monodispersed, crystalline and stable nanoparticles. Further, we explored these nanoparticles for anti-inflammatory activity through inhibition of downstream NF-κB activation in macrophages (RAW264.7). We demonstrated that the nanoparticles reduced expression of inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PEG2), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) was attenuated in lipopolysaccharide (LPS)-induced RAW264.7 cells. Furthermore, nanoparticles significantly suppressed LPS-induced activation of NF-κB signalling pathway via p38 MAPK in RAW 264.7 cells. To the best of our knowledge, this is the first report on the efficient green synthesis of P-AgNPs and P-AuNPs using P. serrulata fresh fruit extract and its in vitro anti-inflammatory effects. Collectively, our results suggest that P. serrulata fresh fruit extract is a green resource for the eco-friendly synthesis of P-AgNPs and P-AuNPs, which further can be utilized as a novel therapeutic agent for prevention and cure of inflammation due to their biocompatible nature.