Antimicrobial Efficacy Of Silver Nanoparticles Research Articles

Enhanced Cellular Internalization: A Bactericidal Mechanism More Relative to Biogenic Nanoparticles than Chemical Counterparts.

Biogenic synthesis of silver nanoparticles for enhanced antimicrobial activity has gained a lot of momentum making it an urgent need to search for a suitable biocandidate which could be utilized for efficient capping and shaping of silver nanoparticles with enhanced bactericidal activity utilizing its secondary metabolites. Current work illustrates the enhancement of antimicrobial efficacy of silver nanoparticles by reducing and modifying their surface with antimicrobial metabolites of cell free filtrate of Trichoderma viride (MTCC 5661) in comparison to citrate stabilized silver nanoparticles. Nanoparticles were characterized by visual observations, UV-visible spectroscopy, zetasizer, and transmission electron microscopy (TEM). Synthesized particles were monodispersed, spherical in shape and 10-20 nm in size. Presence of metabolites on surface of biosynthesized silver nanoparticles was observed by gas chromatography-mass spectroscopy (GC-MS), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The antimicrobial activity of both silver nanoparticles was tested against Shigella sonnei, Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) by growth inhibition curve analysis and colony formation unit assay. Further, it was noted that internalization of biosynthesized nanoparticles inside the bacterial cell was much higher as compared to citrate stabilized particles which in turn lead to higher production of reactive oxygen species. Increase in oxidative stress caused severe damage to bacterial membrane enhancing further uptake of particles and revoking other pathways for bacterial disintegration resulting in complete and rapid death of pathogens as evidenced by fluorescein diacetate/propidium iodide dual staining and TEM. Thus, study reveals that biologically synthesized silver nanoarchitecture coated with antimicrobial metabolites of T. viride was more potent than their chemical counterpart in killing of pathogenic bacteria.

Antimicrobial efficacy of silver nanoparticles with and without different antimicrobial agents against Enterococcus faecalis and Candida albicans

Introduction: The aim of this ex vivo study was to check the antimicrobial efficacy of silver nanoparticles with and without different antimicrobials against Enterococcus faecalis and Candida albicans. Materials and Methods: Two-hundred and fifty two freshly extracted single-rooted human teeth were contaminated with E. faecalis and C. albicans. The teeth were randomly divided into five experimental (n = 21) and one control group (n = 21). Each subgroup was then exposed to different antimicrobials, namely calcium hydroxide (Ca(OH)2) (Group 1), 2% chlorhexidine (CHX) (Group 2), silver nanoparticles (SNP) (Group 3), SNP with Ca(OH)2 (Group 4), SNP with 2% CHX (Group 5), and saline as control group (Group 6). Cultures were made from each group after 24 h, 7 days, and 14 days, and colony forming units were counted. The Kruskal–Wallis test was used to compare the study parameters among the groups at 24 h, 7 days, and 14 days. Results: Significant difference was found in the antimicrobial efficacy of different intracanal medicaments against E. faecalis and C. albicans after 24 h, 7 days, and 14 days. 2% CHX was found to be the most effective medicament at 24 h, 7 days, and 14 days against E. faecalis and C. albicans. Combination of SNP with 2% CHX and Ca(OH)2 and SNP alone ranked second in their antimicrobial efficacy against E. faecalis and C. albicans at 24 h, 7 days, and 14 days, respectively. Conclusion: 2% CHX was more effective as intracanal medicament against E. faecalis and C. albicans biofilm in both short as well as long-term duration, i.e., at 24 h, 7 days, and 14 days.

Antimicrobial Property of Hydrocolloid Impression Material Incorporated with Silver Nanoparticles AgainstStaphylococcusAureus

Dental impressions can easily become contaminated with patient’s blood and saliva which are capable of transmitting infectious diseases to dental personnel. The addition of antimicrobial agents into impression materials could be effective in reducing the chances of cross-infection. Silver nanoparticles have been applied in dentistry as a potent antimicrobial agent. This study aims to evaluate the in vitro antimicrobial efficacy of silver nanoparticles incorporated to irreversible hydrocolloid impression material against Staphylococcus aureus . Silver nanoparticles (AgZrPO 4 , National Direct Network Company, Thailand) at concentrations of 0.25%, 0.50%, 1.00% and 1.50% w/w were added to powder of impression materials (Kromopan, Lascod, Ilaty). Impression material samples were prepared on sterile plate in accordance with manufacturer’s instruction. After setting, a 100 microliter of S. aureus ATCC6538 suspension (10 6 cells/mL) were inoculated on the surface of the impression sample and left for 10 minutes. The amount of S. aureus on the surface was quantified using imprint technique on Mannitol Salt agar. Impression materials incorporated with AgZrPO 4 showed antimicrobial property against S. aureus (up to 95% reduction) compared with control (impression material without AgZrPO 4 ). Even though the mechanism of antimicrobial action was not clearly understood, AgZrPO 4 incorporated to impression material was demonstrated to possess an inhibitory effect against pathogenic bacteria. Further studies are needed to investigate physical properties of the material and the clinical usage.

Schottky barrier dependent antimicrobial efficacy of silver nanoparticles

The antimicrobial efficacy of silver nanoparticles (Ag NPs) modified material was generally governed by the dose of the particles or their capability to release silver ions. Here, it was found that Ag NPs acted against microbes by cooperating with tantalum oxide (TAO) in a Schottky barrier dependent manner. Size tunable Ag NPs were in situ fabricated and immobilized on TAO coating by a silver plasma immersion ion implantation process (Ag PIII). The antibacterial efficacy of these Ag NPs was reversely dependent on their size, that is large particles (~20nm) were more efficiency than small ones (~10nm) in defeating the invasion by bacteria. The result is consistent with the prediction of Schottky-Mott theory, which rectified the electron transfer nature across the interfaces between Ag NPs and the TAO substrate.

Thidiazuron-enhanced biosynthesis and antimicrobial efficacy of silver nanoparticles via improving phytochemical reducing potential in callus culture of Linum usitatissimum L.

Green synthesis of silver nanoparticles (AgNPs) by using plants is an emerging class of nanobiotechnology. It revolutionizes all domains of medical sciences by synthesizing chemical-free AgNPs for various biomedical applications. In this report, AgNPs were successfully synthesized by using whole plant extract (WPE) and thidiazuron-induced callus extract (CE) of Linum usitatissimum. The phytochemical analysis revealed that the total phenolic and flavonoid contents were higher in CE than that in WPE. Ultraviolet-visible spectroscopy of synthesized AgNPs showed a characteristic surface plasmon band in the range of 410–426 nm. Bioreduction of CE-mediated AgNPs was completed in a shorter time than that of WPE-mediated AgNPs. Scanning electron microscopy showed that both types of synthesized AgNPs were spherical in shape, but CE-mediated AgNPs were smaller in size (19–24 nm) and more scattered in distribution than that of WPE-mediated AgNPs (49–54 nm). X-ray diffraction analysis confirmed crystalline nature (face-centered cubic) of both types of AgNPs. Fourier-transform infrared spectroscopy revealed that the polyphenols and flavonoids were mainly responsible for reduction and capping of synthesized AgNPs. Energy dispersive X-ray analysis further confirmed the successful synthesis of AgNPs. Moreover, the synthesized AgNPs were found to be stable over months with no change in the surface plasmon bands. More importantly, CE-mediated AgNPs displayed significantly higher bactericidal activity against multiple drug-resistant human pathogens than WPE-mediated AgNPs. The present work highlighted the potent role of thidiazuron in in vitro-derived cultures for enhanced biosynthesis of chemical-free AgNPs, which can be used as nanomedicines in many biomedical applications.

Extracellular Biofabrication, Characterization, and Antimicrobial Efficacy of Silver Nanoparticles Loaded on Cotton Fabrics Using Newly IsolatedStreptomycessp. SSHH-1E

Biological method for silver nanoparticles synthesis has been developed to obtain cost effective, clean, nontoxic, and ecofriendly size-controlled nanoparticles. The objective of this study is extracellular biosynthesis of antimicrobial AgNPs using cell-free supernatant of a localStreptomycessp. strain SSHH-1E. Different medium composition and fermentation conditions were screened for maximal AgNPs biosynthesis using Plackett-Burman experimental design and the variables with statistically significant effects were selected to study their combined effects and to find out the optimum values using a Box-Behnken design. The synthesized AgNPs were characterized using UV-visible spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Rapid biosynthesis of AgNPs was achieved by addition of 1 mM AgNO3solution to the cell-free supernatant. The produced particles showed a single surface plasmon resonance peak at 400 nm by UV-Vis spectroscopy which confirmed the presence of AgNPs.Streptomycessp. SSHH-1E was identified asStreptomyces narbonensisSSHH-1E. Transmission electron microscopy study indicated that the shape of AgNPs is spherical and the size is ranging from 20 to 40 nm. Fourier transform infrared spectroscopy analysis provides evidence for proteins as possible reducing and capping agents. Furthermore, the biosynthesized AgNPs significantly inhibited the growth of medically important pathogenic Gram-positive and Gram-negative bacteria and yeast. The maximum biosynthesis of AgNPs was achieved at initial pH of 8, peptone of 0.5 g, and inoculum age of 48 h. The statistical optimization resulted in a 4.5-fold increase in the production of AgNPs byStreptomyces narbonensisSSHH-1E.

Antimicrobial efficacy of silver nanoparticles in transparent wood coatings

Results on the antimicrobial efficacy of silver nanoparticles in transparent wood coatings for outdoor application are presented. The performance of different hydrophobic, transparent coating systems with and without silver was studied during 2 years of natural weathering. In addition, laboratory efficacy tests were carried out on non-weathered and weathered specimens to assess the resistance of the coatings against mold, blue stain and algae. The protective effect of the tested silver containing coatings against common microorganisms was insufficient, even under initial, non-weathered conditions. Reasons for the failure are the inadequate initial silver concentrations below 50 ppm in the coatings and the associated insufficient availability of free silver ions on the coating surface.

Evaluation of Antimicrobial Activity of Synthesized Silver Nanoparticles using Phyllanthus amarus and Tinospora cordifolia Medicinal Plants

The main aim of this study is to evaluate the comparison of antimicrobial efficacy of silver nanoparticles synthesized from aqueous plant extracts of Phyllanthus amarus and Tinospora cordifolia. The synthesized silver nanoparticles were characterzed by UV-VIS spectroscopy, Fourier Transform Infra-Red spectroscopy, Transmission Electron Microscopy, Dynamic Light Scattering and zeta potential. The antimicrobial activity of synthesized silver nanoparticles was compared with their respective plant extracts by agar well diffussion method and minimum inhibitory concentration was also calculated. The zone of inhibition varied in range of 12 ± 1 to17 ± 0.58 mm with 100 μg/ml silver nanoparticles concentration, while acetonic, methanolic and aqueous extracts of respective plants does not showed any activity even at 1 mg/ml i.e. 10 times more than that of silver nanoparticles. MIC of silver nanoparticles was found to be in a range of 6.25-25 μg/ml against all tested microbes. The antimicrobial activity of synthesized silver nanoparticles was higher than that of the standard drug i.e. streptomycin (for bacteria) and ketoconazole (for fungus). The synthesized nanoparticles of P. amarus and T. cordifolia have shown good antimicrobial efficacy as compared to plant extracts and may prove to be better antimicrobial agent against wide range of microbes.

Enhancing silver nanoparticle and antimicrobial efficacy by the exfoliated clay nanoplatelets

The antimicrobial efficacy of silver nanoparticles (AgNP) is enhanced by using the exfoliated clay nanoscale silicate platelets (NSP) as the supports. The NSP were in the dimension of 80 nm × 80 nm × 1 nm and were derived from the exfoliation of natural clays such as sodium montmorillonite. Increasing the amount of NSP addition at the relative Ag/silicate composition ratios from 0.5/99.5 to 50/50 w/w significantly altered the particle size AgNP from 3.6 nm to 35 nm in diameter. Evaluation of antibacterial activities for these nanohybrids demonstrated the effect of the amount of NSP support and Ag size on inhibiting the growth of dermal pathogens including Gram-positive and Gram-negative bacteria. Scanning electron microscope observations further revealed the interaction of the AgNP/NSP nanohybrids in contact with individual bacteria surface. The tailoring of the AgNP/NSP nanostructures has largely affected the bacterial surface interaction by NSP adherence and hence the antimicrobial efficacy.

Antimicrobial Activity of Silver Nanoparticles Prepared Under an Ultrasonic Field

Nanotechnology has great promise for improving the therapeutic potential of medicinal molecules and related agents. In this study, silver nanoparticles of different sizes were synthesized in an ultrasonic field using the chemical reduction method with sodium borohydride as a reducing agent. The size effect of silver nanoparticles on antimicrobial activity were tested against the microorganisms Staphylococcus aureus (MTCC No. 96), Bacillus subtilis (MTCC No. 441), Streptococcus mutans (MTCC No. 497), Escherichia coli (MTCC No. 739) and Pseudomonas aeruginosa (MTCC No. 1934). The results shows that B. subtilis, and E. coli were more sensitive to silver nanoparticles and its size, indicating the superior antimicrobial efficacy of silver nanoparticles.