Preparation of silver nanoparticles in the presence of chitosan by electrochemical method

Facile synthesis of mPEG-luteolin-capped silver nanoparticles with antimicrobial activity and cytotoxicity to neuroblastoma SK-N-SH cells

We firstly report a facile route for the green synthesis of mPEG-luteolin-capped silver nanoparticles (mPEG-luteolin-AgNPs) using mPEG-luteolin as both the reducer and stabilizer. The reaction was carried out in a stirred aqueous solution at 50°C without additional poisonous reagents. The prepared mPEG-luteolin-AgNPs was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), zeta potential and UV-vis (UV-vis) spectrum, respectively. The proportions of mPEG-luteolin capped silver nanoparticles is about 89.9%, and the content of silver is 6.65%. The mPEG-luteolin-AgNPs was evaluated the antimicrobial effects on Staphlococcus aureus, Extended spectrum β-Lactamases Staphlococcus aureus, Escherichia Coli and Extended spectrum β-Lactamases Escherichia Coli using drilling hole method. The results showed that both gram-positive and gram-negative bacteria were killed by the mPEG-luteolin-AgNPs at low concentration. Meanwhile, the cell viability assay demonstrated that mPEG-luteolin-AgNPs had toxic effects on human neuroblastoma SK-N-SH cells.

Durable antibacterial and UV-protective Ag/TiO2@ fabrics for sustainable biomedical application

A facile method was developed to endow cotton fabric with remarkable antibacterial and ultraviolet (UV)-protective properties. The flower-like TiO₂ micro-nanoparticles were first deposited onto cotton fabric surface via hydrothermal deposition method. Then, the Ag NPs with a high deposition density were evenly formed onto TiO₂@cotton surface by sodium hydroxide solution pretreatment and followed by in situ reduction of ANO₃. This work focused on the influence of different hydrothermal reaction durations and the concentration of AgNO₃ on antibacterial activity against relevant microorganisms in medicine as well as on the UV-blocking property. Ag NPs-loaded TiO₂@cotton exhibited high antibacterial activity with an inhibition rate higher than 99% against Staphylococcus aureus and Escherichia coli bacteria. Moreover, the as-prepared cotton fabric coated with Ag NPs and TiO₂ NPs demonstrated outstanding UV protective ability with a high ultraviolet protection factor value of 56.39. Morphological image of the cells revealed a likely loss of viability as a result of the synergistically biocidal effects of TiO₂ and Ag on attached bacteria. These results demonstrate a facile and robust synthesis technology for fabricating multifunctional textiles with a promising biocidal activity against common Gram-negative and Gram-positive bacteria.

Chitosan-zinc oxide nanocomposite coatings for the prevention of marine biofouling

Marine biofouling is a worldwide problem affecting maritime industries. Global concerns about the high toxicity of antifouling paints have highlighted the need to develop less toxic antifouling coatings. Chitosan is a natural polymer with antimicrobial, antifungal and antialgal properties that is obtained from partial deacetylation of crustacean waste. In the present study, nanocomposite chitosan-zinc oxide (chitosan-ZnO) nanoparticle hybrid coatings were developed and their antifouling activity was tested. Chitosan-ZnO nanoparticle coatings showed anti-diatom activity against Navicula sp. and antibacterial activity against the marine bacterium Pseudoalteromonas nigrifaciens. Additional antifouling properties of the coatings were investigated in a mesocosm study using tanks containing natural sea water under controlled laboratory conditions. Each week for four weeks, biofilm was removed and analysed by flow cytometry to estimate total bacterial densities on the coated substrates. Chitosan-ZnO hybrid coatings led to better inhibition of bacterial growth in comparison to chitosan coatings alone, as determined by flow cytometry. This study demonstrates the antifouling potential of chitosan-ZnO nanocomposite hybrid coatings, which can be used for the prevention of biofouling.

Antimicrobial Properties of Biofunctionalized Silver Nanoparticles on Clinical Isolates of Streptococcus mutans and Its Serotypes

(1) Background: Streptococcus mutans (S. mutans) is the principal pathogen involved in the formation of dental caries. Other systemic diseases have also been associated with specific S. mutans serotypes (c, e, f, and k). Silver nanoparticles (SNP) have been demonstrated to have good antibacterial effects against S. mutans; therefore, limited studies have evaluated the antimicrobial activity of biofunctionalized SNP on S. mutans serotypes. The purpose of this work was to prepare and characterize coated SNP using two different organic components and to evaluate the antimicrobial activity of SNP in clinical isolates of S. mutans strains and serotypes; (2) Methods: SNP with bovine serum albumin (BSA) or chitosan (CS) coatings were prepared and the physical, chemical and microbiological properties of SNP were evaluated; (3) Results: Both types of coated SNP showed antimicrobial activity against S. mutans bacteria and serotypes. Better inhibition was associated with smaller particles and BSA coatings; however, no significant differences were found between the different serotypes, indicating a similar sensitivity to the coated SNP; (4) Conclusion: This study concludes that BSA and CS coated SNP had good antimicrobial activity against S. mutans strains and the four serotypes, and this study suggest the widespread use of SNP as an antimicrobial agent for the inhibition of S. mutans bacteria.

Quaternized Carboxymethyl Chitosan-Based Silver Nanoparticles Hybrid: Microwave-Assisted Synthesis, Characterization and Antibacterial Activity

A facile, efficient, and eco-friendly approach for the preparation of uniform silver nanoparticles (Ag NPs) was developed. The synthesis was conducted in an aqueous medium exposed to microwave irradiation for 8 min, using laboratory-prepared, water-soluble quaternized carboxymethyl chitosan (QCMC) as a chemical reducer and stabilizer and silver nitrate as the silver source. The structure of the prepared QCMC was characterized using Fourier transform infrared (FT-IR) and ¹H nuclear magnetic resonance (NMR). The formation, size distribution, and dispersion of the Ag NPs in the QCMC matrix were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis), transmission electron microscopy (TEM), and field emission scanning electron microscope (FESEM) analysis, and the thermal stability and antibacterial properties of the synthesized QCMC-based Ag NPs composite (QCMC-Ag) were also explored. The results revealed that (1) QCMC was successfully prepared by grafting quaternary ammonium groups onto carboxymethyl chitosan (CMC) chains under microwave irradiation in water for 90 min and this substitution appeared to have occurred at -NH₂ sites on C2 position of the pyranoid ring; (2) uniform and stable spherical Ag NPs could be synthesized when QCMC was used as the reducing and stabilizing agent; (3) Ag NPs were well dispersed in the QCMC matrix with a narrow size distribiution in the range of 17–31 nm without aggregation; and (4) due to the presence of Ag NPs, the thermal stability and antibacterial activity of QCMC-Ag were dramatically improved relative to QCMC.

Photo-induced green synthesis and antimicrobial efficacy of poly (ɛ-caprolactone)/curcumin/grape leaf extract-silver hybrid nanoparticles

This study reports the photo-induced green synthesis and antimicrobial assessment of poly(ɛ-caprolactone)/curcumin/grape leaf extract-Ag hybrid nanoparticles (PCL/Cur/GLE-Ag NPs). PCL/Cur/GLE NPs were synthesized via emulsion-solvent evaporation in the presence of PVA as a capping agent, then used as active nano-supports for the green synthesis and stabilization of AgNPs on their surfaces. Both Cur and GLE were selected and incorporated into the PCL nano-supports due to their reported promising antimicrobial activity that would further enhance that of the synthesized AgNPs. The developed PCL/Cur/GLE NPs and PCL/Cur/GLE-Ag hybrid NPs were characterized using UV-visible spectrophotometry, high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). HRTEM images showed that the PCL/Cur/GLE NPs are monodispersed and spherical with size of about 270nm, and the AgNPs were formed mainly on their surfaces with average size in the range 10-30nm. The synthesized AgNPs were found to be crystalline as shown by XRD patterns with fcc phase oriented along the (111), (200), (220) and (311) planes. The antimicrobial characteristics of the newly developed NPs were investigated against gram-positive and gram-negative bacteria in addition to two fungal strains. The results demonstrated that the PCL/Cur/GLE-Ag hybrid NPs have a potential antimicrobial activity against pathogenic bacterial species and could be considered as an alternative antibacterial agent.

Comparative study of preparation, characterization and anticandidal activities of a chitosan silver nanocomposite (CAgNC) compared with low molecular weight chitosan (LMW-chitosan)

A chitosan-silver nanocomposite (CAgNC) was synthesized in a green manner using low molecular weight chitosan (LMW-chitosan) and silver nitrate without applying external chemical reducing agents.

Enzymatic functionalization of cork surface with antimicrobial hybrid biopolymer/silver nanoparticles

Laccase-assisted assembling of hybrid biopolymer-silver nanoparticles and cork matrices into an antimicrobial material with potential for water remediation is herein described. Amino-functional biopolymers were first used as doping agents to stabilize concentrated colloidal dispersions of silver nanoparticles (AgNP), additionally providing the particles with functionalities for covalent immobilization onto cork to impart a durable antibacterial effect. The solvent-free AgNP synthesis by chemical reduction was carried out in the presence of chitosan (CS) or 6-deoxy-6-(ω-aminoethyl) aminocellulose (AC), leading to simultaneous AgNP biofunctionalization. This approach resulted in concentrated hybrid NP dispersion stable to aggregation and with hydrodynamic radius of particles of about 250 nm. Moreover, laccase enabled coupling between the phenolic groups in cork and amino moieties in the biopolymer-doped AgNP for permanent modification of the material. The antibacterial efficiency of the functionalized cork matrices, aimed as adsorbents for wastewater treatment, was evaluated against Escherichia coli and Staphylococcus aureus during 5 days in conditions mimicking those in constructed wetlands. Both intrinsically antimicrobial CS and AC contributed to the bactericidal effect of the enzymatically grafted on cork AgNP. In contrast, unmodified AgNP were easily washed off from the material, confirming that the biopolymers potentiated a durable antibacterial functionalization of the cork matrices.

Alginate fibers embedded with silver nanoparticles as efficient catalysts for reduction of 4-nitrophenol

Silver nanoparticles (AgNPs) have attracted much attention as promising catalysts in various electron transfer reactions due to their high catalytic efficiency.

Electrospun chitosan nanofibers with controlled levels of silver nanoparticles. Preparation, characterization and antibacterial activity

The ideal wound dressing would have properties that allow for absorption of exudates, and inhibition of microorganism for wound protection. In this study, we utilized an electrospinning (ELSP) technique to design a novel wound dressing. Chitosan (CTS) nanofibers containing various ratios of silver nanoparticles (AgNPs) were obtained. AgNPs were generated directly in the CTS solution by using a chemical reduction method. The formation and presence of AgNPs in the CTS/AgNPs composite was confirmed by x-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV) and thermogravimetric analysis (TGA). The electrospun CTS/AgNPs nanofibers were characterized morphologically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These nanofibers were subsequently tested to evaluate their antibacterial activity against gram-negative Pseudomonas aeruginosa (P. aeruginosa) and gram-positive Methicillin-resistant Staphylococcus aureus (MRSA). Results of this antibacterial testing suggest that CTS/AgNPs nanofibers may be effective in topical antibacterial treatment in wound care.

Green synthesis of chondroitin sulfate-capped silver nanoparticles: characterization and surface modification

A one-step route for the green synthesis of highly stable and nanosized silver metal particles with narrow distribution is reported. In this environmentally friendly synthetic method, silver nitrate was used as silver precursor and biocompatible chondroitin sulfate (ChS) was used as both reducing agent and stabilizing agent. The reaction was carried out in a stirring aqueous medium at the room temperature without any assisted by microwave, autoclave, laser irradiation, γ-ray irradiation or UV irradiation. The transparent colorless solution was converted to the characteristics light red then deep red-brown color as the reaction proceeds, indicating the formation of silver nanoparticles (Ag NPs). The Ag NPs were characterized by UV-visible spectroscopy (UV-vis), photon correlation spectroscopy, laser Doppler anemometry, transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The results demonstrated that the obtained metallic nanoparticles were Ag NPs capped with ChS. In this report, dynamic light scattering (DLS) was used as a routinely analytical tool for measuring size and distribution in a liquid environment. The effects of the reaction time, reaction temperature, concentration and the weight ratio of ChS/Ag+ on the particle size and zeta potential were investigated. The TEM image clearly shows the morphology of the well-dispersed ChS-capped Ag NPs are spherical in shape, and the average size (<20 nm) is much smaller than the Z-average value (76.7 nm) measured by DLS. Meanwhile, the ChS-capped Ag NPs coated with N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) were prepared by an ionic gelation method and the surface charge of Ag NPs was switched from negative to positive.

Facile and green synthesis of silver nanoparticles in quaternized carboxymethyl chitosan solution

A facile and green method to synthesize stable Ag nanoparticles (Ag NPs) with a narrow size distribution in water is reported. Water-soluble quaternized carboxymethyl chitosan (QCMC) with a surfactant-like structure was used as both a reducing and stabilizing agent under microwave irradiation via the modified Tollens reaction. In order to study the preparation mechanism, carboxymethyl chitosan (CMC) and quaternized chitosan (QCS) were compared as both reducing and stabilizing agents. Full characterization was performed using UV-vis, XRD, TEM, AAS, FT-IR, NMR and TGA. The results revealed that the prepared Ag NPs were mostly spherical with a small proportion being cylinders or cuboids; they were stable due to the package of the macromolecules; the diameters were 10.24 ± 3.13 nm. The Tollens reaction followed first order kinetics, and the Ea was 102.4 kJ mol(-1) for QCMC/Ag NP composite. During the growth of the Ag NPs, some quaternary ammonium groups and carboxymethyl groups were respectively oxidized to -CH2COCH3 and -CH3 groups, and the quaternary ammonium groups were more helpful for the growth of Ag NPs than the carboxymethyl groups. In addition, QCMC/Ag NP composite had much higher thermal stability than QCMC.

Antibacterial property and characterization of cotton fabric treated with chitosan/AgCl-TiO₂ colloid

The antibacterial activity of cotton fabric was studied by using chitosan/AgCl-TiO2 colloid. Different blend ratios of chitosan to AgCl-TiO2 colloid were used to investigate the efficacy of antibacterial activity against Staphylococcus aureus (gram positive) and Escherichia coli (gram negative) and its effect on physical properties of cotton fabric. Our study shows that the combination of chitosan with AgCl-TiO2 colloid produced better antibacterial activity than the fabric treated without chitosan; 100% bacterial reduction against S. aureus and E. coli obtained with chitosan/AgCl-TiO2 colloid at concentrations of 4 g/L and 10 g/L respectively. Moreover, the treated cotton indicates improved tensile strength and wrinkle recovery angle (WRA). Increasing chitosan concentration slightly affected the fabric stiffness and whiteness. The treated cotton fabrics were further characterized by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), energy dispersive X-ray (EDX) and wide angle X-ray (WAXD). We can expect a direct industrial application of our proposed work because it is simple one go pad-dry-cure method and the low cost commercial grades of chitosan and AgCl-TiO2 are conveniently available in the market.

Antibacterial activity of silver bionanocomposites synthesized by chemical reduction route

Background

The aim of this study is to investigate the functions of polymers and size of nanoparticles on the antibacterial activity of silver bionanocomposites (Ag BNCs). In this research, silver nanoparticles (Ag NPs) were incorporated into biodegradable polymers that are chitosan, gelatin and both polymers via chemical reduction method in solvent in order to produce Ag BNCs. Silver nitrate and sodium borohydride were employed as a metal precursor and reducing agent respectively. On the other hand, chitosan and gelatin were added as a polymeric matrix and stabilizer. The antibacterial activity of different sizes of silver nanoparticles was investigated against Gram-positive and Gram-negative bacteria by the disk diffusion method using Mueller-Hinton Agar.

Results

The properties of Ag BNCs were studied as a function of the polymer weight ratio in relation to the use of chitosan and gelatin. The morphology of the Ag BNCs films and the distribution of the Ag NPs were also characterized. The diameters of the Ag NPs were measured and their size is less than 20 nm. The antibacterial trait of silver/chitosan/gelatin bionanocomposites was investigated. The silver ions released from the Ag BNCs and their antibacterial activities were scrutinized. The antibacterial activities of the Ag BNC films were examined against Gram-negative bacteria (E. coli and P. aeruginosa) and Gram-positive (S. aureus and M. luteus) by diffusion method using Muller-Hinton agar.

Conclusions

The antibacterial activity of Ag NPs with size less than 20 nm was demonstrated and showed positive results against Gram-negative and Gram-positive bacteria. The Ag NPs stabilized well in the polymers matrix.