Biogenic Gold Nanoparticle Supplementation to Plant Beneficial Pseudomonas monteilii was Found to Enhance its Plant Probiotic Effect.

Rhizosphere provides unique space for intensive chemical conversation between plant and microorganisms. The common rhizobacterial mechanisms which have been demonstrated to promote plant growth include production of phytohormones, nitrogen fixation, synthesis of 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) and phosphate solubilization. The microbially produced phytohormone indole-3-acetic acid (IAA) is considered to have significant role in interaction between plant and bacteria. Hence any substance with modulatory effect on rhizobacterial IAA production can expect to have its impact on plant-microbe interaction. With the advent of nanotechnology, nanoparticles are being used for diverse applications. However, applications of nanotechnology in agriculture have not been studied in detail. In the study, rhizospheric Pseudomonas monteilii was selected to investigate the concentration-dependent effect of biogenic gold nanoparticles (AuNPs) on its IAA production. For this, AuNPs synthesized by Bacillus subtilis SJ15 were characterized by UV-Vis spectroscopy, FT-IR, TEM and EDS. The results showed AuNPs to have spherical, hexagonal and triangular shapes with a size range of 12-32 nm and absorption peak at 545 nm. Further, various concentrations of AuNPs were used to identify its impact on IAA production by P. monteilii. From this, enhanced production of IAA by P. monteilii was found to take place in the presence of 50 µg/mL AuNPs. When Vigna unguiculata seedlings were grown in presence of 50 µg/mL of AuNPs, increased growth was observed. The results of the study thus showed the ability of AuNPs to augment the IAA-producing potential of P. monteilii.

Biofabricated silver nanoparticles incorporated polymethyl methacrylate as a dental adhesive material with antibacterial and antibiofilm activity against Streptococcus mutans.

In this study, polymethyl methacrylate (PMMA) thin films incorporated with biofabricated silver nanoparticles were used to evaluate the in vitro antimicrobial and antibiofilm activity against the cariogenic bacterium Streptococcus mutans. For this, silver nanoparticles (AgNPs) were generated using Bacillus amyloliquefaciens SJ14 culture (MAgNPs) and extract from Curcuma aromatica rhizome (CAgNPs). The AgNPs were further characterized by UV-Vis spectroscopy and high-resolution transmission electron microscopy. The minimum inhibitory concentration, minimum bactericidal concentration and antibiofilm activity of AgNPs against S. mutans were also assessed. Here, MAgNPs were found to have superior antimicrobial activity when compared to CAgNPs. The MAgNPs and CAgNPs also demonstrated 99% and 94% inhibition of biofilm formation of S. mutans at concentrations of 3 µg/mL and 50 µg/mL, respectively. The AgNPs were further incorporated into PMMA thin films using solvent casting method. The thin films were also characterized by scanning electron microscopy and UV-Vis spectroscopy. Subsequently, both PMMA/MAgNPs and PMMA/CAgNPs nanocomposite thin films were subjected to antimicrobial and antibiofilm analysis. The microbicidal activity was found to be higher for the PMMA/MAgNPs thin film, which highlights the potency of microbially synthesized AgNPs as excellent agents to inhibit cariogenic bacteria from colonising dental restorative material.

Microbially and phytofabricated AgNPs with different mode of bactericidal action were identified to have comparable potential for surface fabrication of central venous catheters to combat Staphylococcus aureus biofilm.

In spite of newer innovations and process improvements, catheter related infections still pose serious threat to hospitalized patients. Silver nanoparticles (AgNPs) are well demonstrated to have antibacterial properties and also have been implemented for surface fabrication of many indwelling medical devices. So, herein we sought to compare the performance of AgNPs generated through biogenic routes using bacteria and plant extract for their antibacterial and antibiofilm potential against biofilm forming Staphylococcus aureus. The biosynthesized AgNPs were characterized by UV- Visible spectroscopy, HR-TEM and EDS analysis. The antibacterial efficiency of the nanoparticles was detected by Disc diffusion assay, MIC and MBC analysis. The antibiofilm properties of the nanoparticles were also investigated. The antibacterial mode of interaction of both nanoparticles on the bacterium was analyzed by HR-TEM. Insight into mode of interaction and mechanism of antibacterial activity of both AgNPs showed them to have promises for surface fabrication of central venous catheters. No study has been conducted so far to compare the efficiency of two different biogenic AgNPs and this highlights the novelty of the current work. Though both AgNPs were observed to exhibit comparable activity in terms of bactericidal and antibiofilm, the mode of bacterial interaction and degree of damage caused was entirely different.

Plant growth and diosgenin enhancement effect of silver nanoparticles in Fenugreek (Trigonella foenum-graecum L.).

Various methods have been used to enhance production of chemically diverse phytochemicals especially medicinal natural products. With the advancement in nanotechnology, nanoparticles have been reported to have varying impact in plant growth and inducibility of phytochemical composition. Major objective of the study was to study the secondary metabolite modulatory effect of silver nanoparticles. In the current study, treatment of fenugreek seedlings with biosynthesized silver nanoparticles (Ag-NPs) was found to have significant impact on its growth parameters such as leaf number, root length, shoot length and wet weight. On HPLC based analysis, Ag-NPs treated seedlings showed an enhancement in the production of major phytochemical diosgenin to a level of 214.06 ± 17.07 µg/mL. An untreated control gave an yield of only 164.44 ± 7.67 µg/mL of diosgenin, and the observed phytochemical enhancement effect induced by Ag-NP was very significant. Most remarkably, the Ag-NP used in the study was found to play dual role of enhancement of both plant growth and diosgenin synthesis. Hence the study is of immense application as it opens up development of new methods based on nanoelicitors to enhance the biosynthesis of medicinal natural products in plants.

Exploration of photocatalytic properties of microbially designed silver nanoparticles on Victoria blue B.

Victoria blue B (VBB) belongs to triphenylmethane group of dyes, which is widely used in textile industries. Hence development of novel treatment methods are of considerable applications in its removal. In the current study, silver nanoparticles (AgNPs) formed by Bacillus amyloliquefaciens was investigated for the degradation of VBB. Interestingly, the UV-Vis spectroscopy analysis of VBB-AgNPs treated samples showed a decrease in absorption at 615 nm, which is characteristic of pure VBB. This time-dependent degradation process was further investigated by changing the initial dye concentration, AgNPs concentration and pH. Approximately 78 % of reduction was observed within 8 h of the study and hence the result of the study is with promising applications for the development of novel dye degradation technologies. Phytotoxicity analysis of degradation product using Vigna unguiculata revealed the non-toxic effect of degradation product when compared to VBB and this confirms the promising potential and applications of the study.

Electrospun Polycaprolactone Membrane Incorporated with Biosynthesized Silver Nanoparticles as Effective Wound Dressing Material.

Biosynthesized silver nanoparticles (AgNPs) incorporated polycaprolactone (PCL) nanomembrane was prepared by electrospinning as a cost-effective nanocomposite for application as an antimicrobial agent against wound infection. The nanocomposite membrane was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis and Scanning Electron microscopy (SEM). The hydrophilicity analysis of electrospun membranes as evaluated by water contact angle measurement showed the change of hydrophobicity of PCL to hydrophilic upon incorporation of silver nanoparticles. Better mechanical properties were also observed for PCL membrane due to the incorporation of silver nanoparticles and are highly supportive to explore its biomedical applications. Further antibacterial analysis of silver nanoparticle-incorporated PCL membrane against common wound pathogens coagulase-negative Staphylococcus epidermidis and Staphylococcus haemolyticus showed remarkable activity. As biosynthesized AgNPs are least explored for clinical applications, the current study is a promising cost-effective method to explore the development of silver nanoparticle-based electrospun nanocomposite to resist wound-associated infection.

Inhibitory effect of silver nanoparticle fabricated urinary catheter on colonization efficiency of Coagulase Negative Staphylococci.

Multiple antibiotic resistance and diverse mechanisms for biofilm formation make Coagulase Negative Staphylococci (CoNS) to cause infections associated with insertion of medical devices. As the infectious life style of CoNS pose difficult to treat conditions, materials with multitargeted antimicrobial effect can offer promising ways to modify the surface of devices to limit microbial growth. The broad spectrum of antimicrobial properties shown by silver nanoparticles (AgNPs) make it as an excellent candidate to act on device surface as persistent antimicrobial structures. In the current study, AgNPs assembled by soil bacteria under visible light at room temperature were analysed for its physical properties by UV-Vis spectroscopy, FTIR, SEM, HR-TEM and EDS and they also showed significant antimicrobial and antibiofilm properties against selected members of CoNS like Staphylococcus epidermidis and Staphylococcus haemolyticus. Very interestingly, further analysis on antibacterial mechanism of AgNPs showed their remarkable ability to cause disorganization of bacterial cell membrane. Further, surface engineering application of AgNPs on urinary catheter showed its excellent potential to prevent the attachment and colonization of CoNS which make result of study with significantly novel medical applications.

Antibacterial properties of silver nanoparticles synthesized by marine Ochrobactrum sp.

Metal nanoparticle synthesis is an interesting area in nanotechnology due to their remarkable optical, magnetic, electrical, catalytic and biomedical properties, but there needs to develop clean, non-toxic and environmental friendly methods for the synthesis and assembly of nanoparticles. Biological agents in the form of microbes have emerged up as efficient candidates for nanoparticle synthesis due to their extreme versatility to synthesize diverse nanoparticles with varying size and shape. In the present study, an eco favorable method for the biosynthesis of silver nanoparticles using marine bacterial isolate has been attempted. Very interestingly, molecular identification proved it as a strain of Ochrobactrum anhtropi. In addition, the isolate was found to have the potential to form silver nanoparticles intracellularly at room temperature within 24 h. The biosynthesized silver nanoparticles were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). The UV-visible spectrum of the aqueous medium containing silver nanoparticles showed a peak at 450 nm corresponding to the plasmon absorbance of silver nanoparticles. The SEM and TEM micrographs revealed that the synthesized silver nanoparticles were spherical in shape with a size range from 38 nm - 85 nm. The silver nanoparticles synthesized by the isolate were also used to explore its antibacterial potential against pathogens like Salmonella Typhi, Salmonella Paratyphi, Vibrio cholerae and Staphylococcus aureus.

Antibacterial activity and synergistic effect of biosynthesized AgNPs with antibiotics against multidrug-resistant biofilm-forming coagulase-negative staphylococci isolated from clinical samples.

Silver nanoparticles form promising template for designing antimicrobial agents against drug resistant pathogenic microorganisms. Thus, the development of a reliable green approach for the synthesis of nanoparticles is an important aspect of current nanotechnology research. In the present investigation, silver nanoparticles synthesized by a soil Bacillus sp. were characterized using UV-vis spectroscopy, FTIR, SEM, and EDS. The antibacterial potential of biosynthesized silver nanoparticles, standard antibiotics, and their conjugates were evaluated against multidrug-resistant biofilm-forming coagulase-negative S. epidermidis strains, S. aureus, Salmonella Typhi, Salmonella Paratyphi, and V. cholerae. Interestingly, silver nanoparticles (AgNPs) showed remarkable antibacterial activity against all the test strains with the highest activity against S. epidermidis strains 145 and 152. In addition, the highest synergistic effect of AgNPs was observed with chloramphenicol against Salmonella typhi. The results of the study clearly indicate the promising biomedical applications of biosynthesized AgNPs.

Antibacterial properties of silver nanoparticles synthesized by marine Ochrobactrum sp.

Metal nanoparticle synthesis is an interesting area in nanotechnology due to their remarkable optical, magnetic, electrical, catalytic and biomedical properties, but there needs to develop clean, non-toxic and environmental friendly methods for the synthesis and assembly of nanoparticles. Biological agents in the form of microbes have emerged up as efficient candidates for nanoparticle synthesis due to their extreme versatility to synthesize diverse nanoparticles with varying size and shape. In the present study, an eco favorable method for the biosynthesis of silver nanoparticles using marine bacterial isolate has been attempted. Very interestingly, molecular identification proved it as a strain of Ochrobactrum anhtropi. In addition, the isolate was found to have the potential to form silver nanoparticles intracellularly at room temperature within 24 h. The biosynthesized silver nanoparticles were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). The UV-visible spectrum of the aqueous medium containing silver nanoparticles showed a peak at 450 nm corresponding to the plasmon absorbance of silver nanoparticles. The SEM and TEM micrographs revealed that the synthesized silver nanoparticles were spherical in shape with a size range from 38 nm - 85 nm. The silver nanoparticles synthesized by the isolate were also used to explore its antibacterial potential against pathogens like Salmonella Typhi, Salmonella Paratyphi, Vibrio cholerae and Staphylococcus aureus.

Extracellular synthesis of silver nanoparticles by the Bacillus strain CS 11 isolated from industrialized area.

Biological synthesis of silver nanoparticles using microorganisms has received profound interest because of their potential to synthesize nanoparticles of various size, shape and morphology. In the current study, synthesis of silver nanoparticles by a bacterial strain (CS 11) isolated from heavy metal contaminated soil is reported. Molecular identification of the isolate showed it as a strain of Bacillus sp. On treating the bacteria with 1 mM AgNO3, it was found to have the ability to form silver nanoparticles extracellularly at room temperature within 24 h. This was confirmed by the visual observation and UV-Vis absorption at 450 nm. Further characterization of nanoparticles by transmission electron microscopy confirmed the size of silver nanoparticles in 42-92 nm range. Therefore, the current study is a demonstration of an efficient synthesis of stable silver nanoparticle by a Bacillus strain.