Epigallocatechin-3-gallate-capped Ag nanoparticles: preparation and characterization

Synergistic Antibacterial Effects of Gallate Containing Compounds with Silver Nanoparticles in Gallate Crossed Linked PVA Hydrogel Films

Currently available silver-based antiseptic wound dressings have limited patient effectiveness. There exists a need for wound dressings that behave as comfortable degradable hydrogels with a strong antibiotic potential. The objectives of this project were to investigate the combined use of gallates (either epi gallo catechin gallate (EGCG), Tannic acid, or Quercetin) as both PVA crosslinking agents and as potential synergistic antibiotics in combination with silver nanoparticles. Crosslinking was assessed gravimetrically, silver and gallate release was measured using inductively coupled plasma and HPLC methods, respectively. Synergy was measured using 96-well plate FICI methods and in-gel antibacterial effects were measured using planktonic CFU assays. All gallates crosslinked PVA with optimal extended swelling obtained using EGCG or Quercetin at 14% loadings (100 mg in 500 mg PVA with glycerol). All three gallates were synergistic in combination with silver nanoparticles against both gram-positive and -negative bacteria. In PVA hydrogel films, silver nanoparticles with EGCG or Quercetin more effectively inhibited bacterial growth in CFU counts over 24 h as compared to films containing single agents. These biocompatible natural-product antibiotics, EGCG or Quercetin, may play a dual role of providing stable PVA hydrogel films and a powerful synergistic antibiotic effect in combination with silver nanoparticles.

Diospyros montana mediated reduction, stabilization, and characterization of silver nanoparticles and evaluation of their mosquitocidal potentiality against dengue vector Aedes albopictus

Recent research has focused on nanoparticles. Aedes albopictus is a potential vector that transmits fatal diseases. Recently, Phyto-reduced silver nanoparticles (AgNPs) were shown to be mosquito larvicides. This study aimed to synthesize silver nanoparticles using Diospyros montana leaf extract, characterize them, and test their efficacy as larvicide and pupicide against Ae. albopictus mosquitoes, determine their duration of effectiveness as a larvicide, identify plant compounds that help to synthesize nanoparticles, and assess their effects on non-target organisms. Quercetin, luteolin, kaempferol, gallocatechin gallate, epigallocatechin gallate, and capsaicin are among the novel reducing and capping agents found in D. montana leaf through LCMS analysis. The color shift and distinctive peak in UV-Vis spectroscopy made it simple to see how biogenic AgNPs were produced by converting Ag+ ions into Ag0. Substantial negative value (- 19.10 mv) of zeta potential demonstrated the long-term stability of AgNPs. A moderate range (8.72 - 50.75 nm) of particle size distribution pattern was obtained using the DLS technique. SEM and TEM images depicted the quasi-spherical (or polyhedral) and spherical shape of the nanoparticles, having approximately 16.75 nm average size. Synthesized AgNPs had a low LC90 value (< 10 ppm) for all larval instars and pupae of Ae. albopictus and had negligible mal effect on non-target organisms. Regression equations showed dose-dependent mortality by the positive correlation between mortality rate and AgNPs concentration, and each time the regression coefficient (R2) value was larger than zero. This study shows that D. montana leaf extract is an environment-friendly and sustainable source of an effective reducing and capping agent to synthesize highly stable, ecologically acceptable silver nanoparticles and their application as mosquitocide.

Green Synthesis of Silver-Decorated Magnetic Particles for Efficient and Reusable Antimicrobial Activity

Metal and metal hybrid nanostructures have shown tremendous application in the biomedical and catalytic fields because of their plasmonic and catalytic properties. Here, a green and clean method was employed for the synthesis of silver nanoparticle (Ag NP)-SiO₂-Fe₂O₃ hybrid microstructures, and biomolecules from green tea extracts were used for constructing the hybrid structures. The SiO₂-Fe₂O₃ structures were synthesized using an ethanolic green tea leaf extract to form Bio-SiO₂-Fe₂O₃ (BSiO₂-Fe₂O₃) structures. Biochemical studies demonstrated the presence of green tea biomolecules in the BSiO₂ layer. Reduction of the silver ions was performed by a BSiO₂ layer to form Ag NPs of 5–10 nm in diameter in and on the BSiO₂-Fe₂O₃ microstructure. The reduction process was observed within 600 s, which is faster than that reported elsewhere. The antimicrobial activity of the Ag-BSiO₂-Fe₂O₃ hybrid structure was demonstrated against Staphylococcus aureus and Escherichia coli, and the nanostructures were further visualized using confocal laser scanning microscopy (CLSM). The magnetic properties of the Ag-BSiO₂-Fe₂O₃ hybrid structure were used for studying reusable antimicrobial activity. Thus, in this study, we provide a novel green route for the construction of a biomolecule-entrapped SiO₂-Fe₂O₃ structure and their use for the ultra-fast formation of Ag NPs to form antimicrobial active multifunctional hybrid structures.

Scalable Electrochemical Synthesis of Novel Biogenic Silver Nanoparticles and Its Application to High-Sensitive Detection of 4-Nitrophenol in Aqueous System

This study reports a scalable green electrochemical synthesis of novel biogenic silver nanoparticles colloid (biogenic AgNPs) in large scale up to 5 liters using the bulk silver bar and the green tea leaves (Camellia sinensis) extract (GTE) as reducing agent during the electrochemical process. Under a direct-current voltage source, the biomolecules in GTE can release electrons to promote the reducing process of Ag+ to Ag0. More interestingly, the formation of the intermediate complex helps to cap on the nanoparticles, which leads to stabilizing AgNPs. The as-synthesized biogenic AgNPs with the size of 34 nm exhibit the outstanding electrochemical properties due to the presence of biomolecules on the biogenic AgNPs surface, which facilitates the effective attaching of AgNPs on the carbon surface of the screen-printed carbon electrode (SPE) through the formation of the strong C-O coordinate bonds between O atom of oxygen functional groups and C atom of SPE. The electrochemical properties of the biogenic AgNPs-modified SPE are enhanced significantly in comparison with bare SPE and pure AgNPs-SPE. The biogenic AgNPs-SPE is applied successfully to the detection of 4-nitrophenol (4-NP). The electrochemical sensor using biogenic AgNPs can reliably detect 4-NP in the linear range from 0.1 to 25 μM with the sensitivity about 6.69 μA μM-1 cm-2. The present work reveals, as the greener synthesis method with ultra-large scalable ability, high purity, and excellent electrochemical properties of biogenic AgNPs is very promising for technological applications in high-sensitive electrochemical chemosensors, nanopharmaceuticals, and other fields.

Sennoside A drug capped biogenic fabrication of silver nanoparticles and their antibacterial and antifungal activities

Sennoside A (dianthrone glycoside) shows laxative properties and used as a folk traditional medicine. Sennoside A capped silver nanoparticles (Ag/sennoside A) were synthesized at room temperature for the first time by using sennoside A as reducing and capping agent. UV-visible spectroscopic data reveals that the absorption peaks of pure sennoside A was appeared at 266, and 340 nm, which red shifted to 304, and 354 nm at higher sennoside A concentration. Upon addition of the Ag+ ions, an additional peak also observed at 398 nm, indicating the formation of spherical sennoside A capped silver nanoparticles (Ag/sennoside A). Cetyltrimethylammonium bromide (CTAB) was used a stabilizing agent to determine the role of cationic micelles on the nucleation and growth processes of Ag/sennoside A NPs formation. The 2,2-diphenyl-1-picrylhydrazyl nitrogen radical (DPPH · ), two bacteria strains (Staphylococcus aureus and Escherichia coli) and two yeast strains (Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019) were used to determine the antioxidant and antimicrobial properties of Ag/sennoside A NPs. In addition, Rhein-9-anthrone (4,5-dihydroxy-10-oxo-9H-anthracene-2-carboxylate) was isolated from the acidic hydrolysis of glycoside linkage of sennoside A and characterized. The antioxidant and antimicrobial activities of rhein-9-anthrone were also determined against DPPH radical, antibacterial and antifungal strains. The minimum inhibitory concentration was determined and discussed.

Developing biocompatible silver nanoparticles using epigallocatechin gallate for dental use

OBJECTIVE

To develop silver nanoparticles (AgNPs) using epigallocatechin gallate (EGCG) and evaluate its biocompatibility and inhibition effect on Streptococcus mutans biofilm growth.

DESIGN

AgNPs were synthesized using EGCG as a reducing agent. Cytotoxicity was assessed using half-maximal inhibitory concentration (IC₅₀) against human gingival fibroblast (HGF-1) and stem cells from human exfoliated deciduous teeth (SHED). Antibacterial properties were evaluated with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against S. mutans. Dentine blocks were treated with AgNPs, silver nitrate (AgNO₃), or water before being incubated with S. mutans. The kinetics, morphology and viability of the biofilm at different time points were assessed by colony-forming units (CFUs), scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM), respectively. Lactic acid and polysaccharide production of the biofilm were also investigated.

RESULTS

Spherical AgNPs with diameter 17 ± 7 nm were developed. The IC₅₀ of AgNPs and AgNO₃ against HGF-1 were 44.88 ± 11.39 μg/mL and 11.53 ± 6.96 μg/mL, respectively (p < 0.001), whereas those against SHED were 68.02 ± 24.48 μg/mL and 9.54 ± 6.63 μg/mL, respectively (p = 0.02). The MIC of AgNPs and AgNO₃ were 32.22 ± 7.34 μg/mL and 48.89 ± 15.11 μg/mL, respectively (p = 0.01), whereas their MBC was 63.33 ± 11.73 μg/mL and 85.00 ± 20.77 μg/mL, respectively (p = 0.02). Log CFUs of the AgNPs group were the lowest among the groups (p < 0.001). SEM and CLSM found a confluent biofilm in AgNO₃ and water groups but not in AgNPs group. Biofilms in AgNPs group was revealed with lowest level of acidic acid and polysaccharides production (p < 0.001).

CONCLUSION

This study developed biocompatible AgNPs which inhibited the growth of a cariogenic biofilm.

Green tea extract-assembled nanoclusters for combinational photothermal and chemotherapy

Gold nanoclusters were developed by a “green chemistry” method, wherein green tea acts as a reducing agent, co-polymerization site and stabilizer.

Rapid colorimetric sensing of gadolinium by EGCG-derived AgNPs: the development of a nanohybrid bioimaging probe

Polyphenol functionalized AgNPs are demonstrated as colorimetric sensors for the selective detection of gadolinium and the generated nanohybrids exhibit bioimaging potential.

Practical mediated-assembly synthesis of silver nanowires using commercial Camellia sinensis extracts and their antibacterial properties

Camellia sinensis is a well-known plant used for health purposes due to its high phenolic compound content and antioxidant properties.

Nanoscale water soluble self-assembled zero-valent iron: role of stabilizers in their morphology

Self-assembled water soluble sheet-like zero-valent iron nano-composites were prepared using a simple one-pot chemical reduction method in an aqueous solution of FeCl₃and NaBH₄both with and without CTAB and SDS.

Biosynthesis of silver nanoparticles and its antibacterial and antifungal activities towards Gram-positive, Gram-negative bacterial strains and different species of Candida fungus

Biomimetic and economic method for the synthesis of silver nanoparticles (AgNPs) with controlled size has been reported in presence of shape-directing cetlytrimethylammonium bromide (CTAB). Biochemical reduction of Ag(+) ions in micellar solution with an aqueous lemon extract produced spherical and polyhedral AgNPs with size ranging from 15 to 30 nm. The influence of [CTAB] and [lemon extract] on the size of particles, fraction of metallic silver and their antimicrobial properties is discussed. The AgNPs were evaluated for their antimicrobial activities (antibacterial and antifungal) against different pathogenic organisms. For this purpose, AgNPs were tested against two model bacteria (Staphylococcus aureus (MTCC3160) and Escherichia coli (MTCC405)) and three species of Candida fungus (Candida albicans (ATCC90028), Candida glabrata (ATCC90030) and Candida tropicalis (ATCC750). AgNPs were found to be highly toxic towards both bacteria. The inhibition action was due to the structural changes in the protein cell wall.

Synthesis, characterization and kinetics of formation of silver nanoparticles by reduction with adrenaline in the micellar media

The present paper describes about the easy, simple and convenient procedure for the synthesis of silver nanoparticles (Ag-NPs) in aqueous solutions by the reduction of silver nitrate with adrenaline. The surfactant molecules of cetyltrimethylammonium bromide (CTABr) and sodium dodecyl ate (SDS) behaved differently during the reduction of Ag(+) ions by adrenaline. The obtained data suggest that the variation of [CTABr] gave a maxima-like curve for rate constant versus [CTABr], while, the values of rate constant decreased with the increase in [SDS]. The addition of surfactant molecules stabilized the Ag-NPs. The UV-Visible spectra were analyzed to deduce the particle size. The calculated sizes of the nanoparticles were further compared by the TEM images. The XRD spectrum confirmed the crystalline nature of silver nanoparticles having the face-centered cubic crystal structure. The edge length of unit cell was found 4.076 Å. The kinetics of formation of Ag-NPs was performed at different concentrations of adrenaline, AgNO3, NaOH and [surfactant]. The values of rate constant were independent on [adrenaline] and [AgNO3]. The increase in [NaOH] increased the rate of agglomeration of silver particles to form Ag-NPs. A linear relationship was obtained for the plot of rate constant versus [NaOH].