Chitosan-silver Nanocomposites Research Articles

Synthesis and spectral characterization of silver embedded chitosan matrix nanocomposite for the selective colorimetric sensing of toxic mercury

Polymer matrix type chitosan-silver nanocomposite containing different weight percentage of silver was synthesized by the chemical method. HRTEM images confirm the embedment of silver in the chitosan matrix. The binding of silver to the NH2 and OH groups of chitosan is evident from XPS and FTIR studies. An increase in the absorbance observed from UV–Vis analysis on raising the weight percentage of silver showed the increase in the amount of silver in the nanocomposite. The face centered cubic structure of silver and the semi-crystalline nature of chitosan are evident from the XRD studies. On interaction with mercury the UV–Vis spectra of the composite showed a decrease in intensity and a blue shift confirming the use of the composite as a colorimetric sensor for the detection of mercury. The limit of detection was found to be about 7.2×10−8M. High specificity and the sensitivity of the environmental friendly and non-toxic nanocomposite to detect very low concentrations of mercury make the system a perspective one.

GREEN SYNTHESIS OF SILVER NANOPARTICLES USING CHITOSAN HYDROLYSATE AS STABILIZING AGENT AND THEIR ANTIBACTERIAL ACTIVITY

Silver nanoparticles were successfully synthesized with chitosan hydrolysate as stabilizing agent at room temperature. Silver nitrate, glucose and sodium hydroxide were used as silver precursor, reducing agent and accelerator respectively. Chitosan hydrolysate was produced by enzymatic process with papain enzyme. Molecular weight of chitosan hydrolysate determined by viscosimetry methode based on Mark-Howink equation. The effect of molecular weight of chitosan hydrolysate as stabilizing agent and AgNO 3 concentration toward surface plasmon resonance (SPR) of silver nanoparticle was investigated. It is also reported the antibacterial activity of silver-chitosan nanocomposites against Staphylococcus aureus and Escherichia coli . The products of silver nanoparticles were characterized by UV- Vis spectroscopy and transmission electron microscopy (TEM). The result showed that the formation of silver nanoparticles was shown by the appearance of surface plasmon resonance (SPR) at 403–421nm from the corresponding UV- Vis spectra. The molecular weight of chitosan hydrolysate affects the absorbance intensity and the wavelength of SPR. Silver nanoparticles were spherical in shape as identified by TEM images with size in range of 4–26nm. The silver nanoparticles have showed high antibacterial activity against Escherichia coli and Staphylococcus aureus. Key word: green synthesis, silver nanoparticles, chitosan hydrolysate, stabilizing agent, antibacterial activity

Chitosan Silver Nano Composites (CAgNCs) as Antibacterial Agent Against Fish Pathogenic Edwardsiella tarda

Recently nano particles have proven for wide array of bioactive properties. In the present study, antibacterial properties of chitosan silver nano composites (CAgNCs) were investigated against fish pathogenic Edwardsiella tarda. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CAgNCs against E. tarda were 25 μg/mL and 125 μg/mL, respectively. The field emission scanning electron microscope (FE-SEM) image of CAgNCs treated E. tarda showed the strongly damaged bacteria cells than non-treated bacteria. Furthermore, treatment of CAgNCs induced the level of intracellular reactive oxygen species (ROS) in E. tarda cells in concentration and time dependent manner suggesting that it may generate oxidative stress leading to bacterial cell death. In addition, MTT assay results showed that the lowest cell viability at 100 μg/mL of CAgNCs treated E. tarda. Overall results of this study suggest that CAgNCs is a potential antibacterial agent to control pathogenic bacteria.

Physicochemical Studies on Nano Silver Particles Prepared by Green and Chemical Methods

AgNPs were synthesized by two different methods chemically using sodium citrate as reducing agent, plant mediated by achyranthes aspera as reducing agent. Chitosan (CS) biopolymer is used as a capping agent in order to enhance the stability and dispersibility as well as to remove aggregation. The appearance of surface Plasmon band in the ultraviolet-visible spectra (410-445 nm) is due to the formation of AgNPs in different sizes. Also the data was clarified that the CS molecules coordinate to the surface of nanoAg particles through their head-groups. FTIR spectra were recorded in a Perkin Elmer version 10.03.06, Spectro Photometer. The FTIR analysis suggests that the prepared chitosan silver nanocomposite film consists of an intermediate/or complex of tri-ammonium citrate, chitosan and metal ions. Finally Antibacterial activity of Ag-CS composites indicating that highest antibacterial activity was detected with green film than chemical film.

Chitosan Silver Nano Composites (Cagncs) as Potential Antibacterial Agent to Control Vibrio tapetis

Nanocomposites exhibit high performance on antimicrobial activities and have the potential to be developed alternative antibiotics. In this study, antibacterial effects of chitosan silver nano composites (CAgNCs) were investigated using pathogenic Vibrio tapetis as a bacterial model. Agar disc diffusion and turbidimetric assay results showed that CAgNCs could inhibit the growth of V. tapetis in concentration depended manner. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CAgNCs against V. tapetis were 50 μg/mL and 100 μg/mL, respectively. The field emission scanning electron microscopy (FE-SEM) images analysis of V. tapetis showed severe structural damage to cells after treating CAgNCs at 75 μg/mL compared to un-treated bacteria. Moreover, CAgNCs induce the intracellular ROS level, leakage of nucleic materials (RNA and DNA), decrease the cell viability and protein level in V. tapetis cells. Herein, we demonstrate that CAgNCs as effective antibacterial agent with capability to disrupt cell membrane, de-stabilize the membrane permeability, induce the oxidative stress and inhibit the expression of protein or synthesis of macromolecules. Overall results from this study suggest that mode of action of CAgNCs may be associated with excessive generation of ROS, loss in membrane integrity and inhibiting protein synthesis that cause the bacterial cell death.

Synthesis and characterization of chitosan–silver nanocomposite

Chitosan–silver (CS–Ag) nanocomposite materials were synthesized by a simple chemical method. The synthesized CS–Ag nanocomposite contains 20 wt% silver. Silver nanoparticles were synthesized by chemical reduction method as well. The CS–Ag nanocomposite was characterized using Field emission scanning electronic microscope (FESEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The XRD pattern indicated the presence of both silver and chitosan in the nanocomposite. It is observed from the XRD pattern of silver that it is of cubic structure. The spherical morphology of silver nanoparticles was confirmed from the FESEM image. FTIR spectroscopy was used for the structural elucidation. CS–Ag nanocomposite exhibits good antimicrobial and antitumor properties.

Preparation, Characterization and Antibacterial Properties of Silver-Chitosan Nanocomposites Using Different Molecular Weight Grades of Chitosan

Purpose : To study the effect of chitosan molecular weight on the physicochemical and antibacterial properties of silver-chitosan nanoparticles. Methods : A series of silver-chitosan nanoparticles of different sizes were produced using various molecular weight (MW) grades of chitosan by an aqueous chemical reduction method. The nanoparticles were characterized by ultraviolet-visible absorption spectroscopy (UV-Vis), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic light scattering (DLS) and laser Doppler electrophoresis (LDE). The antibacterial properties of the nanoparticles were also evaluated by agar diffusion method. Results : The size of the silver-chitosan nanoparticles, ranging from 21.9 to 175.3 nm, was influenced by chitosan MW as well as by other process conditions. Although, the nanoparticles were not stable in liquid form, they however showed good stability in the solid state due to their low zeta potential. SEM images indicate that the nanoparticles were spherical. The antibacterial activity of the nanoparticles against Staphylococcus aureus increased with decrease in particle size owing to increase in surface area. The smallest particle size (21.9 nm) was obtained by using high chitosan MW at 4 °C and a stirring speed of 800 rpm. Conclusion : Chitosan is an effective agent for the preparation of silver nanoparticles. The size of the nanoparticles can be modulated by varying both chitosan MW and process conditions such as temperature and stirring speed.

Synergistic antibacterial activity of chitosan–silver nanocomposites on Staphylococcusaureus

The approach of combining different mechanisms of antibacterial action by designinghybrid nanomaterials provides a new paradigm in the fight against resistant bacteria. Here,we present a new method for the synthesis of silver nanoparticles enveloped in thebiopolymer chitosan. The method aims at the production of bionanocomposites withenhanced antibacterial properties. We find that chitosan and silver nanoparticlesact synergistically against two strains of Gram-positive Staphylococcus aureus(S. aureus). As a result the bionanocomposites exhibit higher antibacterial activitythan any component acting alone. The minimum inhibitory (MIC) and minimumbactericidal (MBC) concentrations of the chitosan–silver nanoparticles synthesized at0 °C were found to be lower than those reported for other types of silver nanoparticles. Atomicforce microscopy (AFM) revealed dramatic changes in morphology of S. aureus cells due todisruption of bacterial cell wall integrity after incubation with chitosan–silvernanoparticles. Finally, we demonstrate that silver nanoparticles can be used not only asantibacterial agents but also as excellent plasmonic substrates to identify bacteria andmonitor the induced biochemical changes in the bacterial cell wall via surface enhancedRaman scattering (SERS) spectroscopy.

Fabrication of porous chitosan films impregnated with silver nanoparticles: A facile approach for superior antibacterial application

The present investigation involves the synthesis of porous chitosan–silver nanocomposite films in view of their increasing areas of application in wound dressing, antibacterial application, and water purification. The entire process consists of three-steps including silver ion-poly(ethylene glycol) matrix preparation, addition of chitosan matrix, and removal of poly(ethylene glycol) from the film matrix. Uniform porous and brown colour chitosan films impregnated with silver nanoparticles (AgNPs) were successfully fabricated by this facile approach. Both, poly(ethylene glycol) (PEG) and chitosan (CS) played vital roles in the reduction of metal ions into nanoparticles (NPs) as well as provided good stability to the formed nanoparticles. The developed porous chitosan–silver nanocomposite (PCSSNC) films were characterized by UV–vis and FTIR spectroscopy, and thermogravimetric analysis for the confirmation of nanoparticles formation. The morphology of silver nanoparticles in nanocomposite films was tested by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The embedded AgNPs were clearly observed throughout the film in SEM and the extracted AgNPs from the porous chitosan–silver nanocomposite showed ∼12 nm in TEM. Improved mechanical properties were observed for porous chitosan–silver nanocomposite than for chitosan blend (CSB) and chitosan–silver nanocomposite (CSSNC) films. Further, the examined antibacterial activity results of these films revealed that porous chitosan–silver nanocomposite films exhibited superior inhibition.