Preparation And Application Of Nanocellulose Based Antibacterial Materials

Silver antimicrobial materials are inorganic antibacterial agents.They have many advantages,such as low toxicity,heat resistance,long duration and wide antibacterial property.However,silver nanoparticles are easy to agglomerate,which may affect their antibacterial properties.To circumvent this challenge,passivating agents such as polyvinyl pyrrolidone?PVP?,polyvinyl alcohol?PVA?,hyperbranched polyurethane?HP?,and poly acrylonitrile?PAN?with reducing agents such as sodium borohydride,hydrazine,hydroxylamine to mention a few,have been used successfully in the synthesis and stabilization of silver nanoparticles.Nanocellulose,extracted from lignocellulosic materials,is paid more and more attention due to its unique properties such as large specific surface area,high mechanical properties,good biocompatibility and chemical accessibility.In this study,we propose an ideal protective agent for the preparation of Ag-NPs.DANC was used as both reducing and stabilizing agent to prepare Ag-NPs.DANC can also be used as reducing agent and base materials to crosslink with polyvinylamine and chitosan to obtain antibacterial hydrogels.First of all,nanocrystalline cellulose,prepared from fully bleached hardwood kraft pulp by sulfuric acid hydrolysis,was oxidized by sodium periodate to yield dialdehyde nanocellulose?DANC?.AgNO₃ was reduced by DANC as both reducing and stabilizing agent to obtain silver nanoparticles.The synthesized NC-Ag-NPs were characterized by using Fourier transform infrared spectroscopy?FT-IR?,UV-Vis spectroscopy,transmission electron microscopy?TEM?,X-ray diffraction?XRD?,atomic absorption spectroscopy?AAS?and thermo gravimetric analysis?TGA?.Furthermore,the antimicrobial activity was investigated.The results showed that DANC could react with silver nitrate to form silver nanoparticles.With the increase of pH and the proceeding of time,the silver percentage in the composite increased.XRD data showed diffraction peaks at 2?38.33o,44.55o,64.27o,77.66o,which can be indexed to?111?,?200?,?220?,?311?,and?222?planes of pure silver,indicating the biosynthesis of silver nanoparticles.TEM images show that the silver nanoparticles are attached to the nanocellulose,covering almost the entire surface of the cellulose.The antibacterial property of the composite was determined by the method of bacteriostatic circle.The prepared samples showed antibacterial activity to Gramnegative Escherichia coil and Grampositive Staphylococcus aureus.The obtained NC-Ag-NPs were added into the old corrugated container pulp as an additive,and the antibacterial property and the physical properties were tested.The paper exhibited antibacterial properties and the the tensile index,tear indexwere improved.Silver nitrate solution was added into the dialdehyde nanocellulose to generate the silver nanoparticles,and then crosslinked with polyvinylamine?PVAm?to obtain NC-PVAm-Ag hydrogel.The hydrogels were characterized by using FT-IR,XRD,TGA and SEM-EDAX.The silver content,surface morphology,particle size and crystal structure were investigated.The antibacterial properties of NC-PVAm-Ag were investigared.The effect of pH on the Zeta potential and swelling ratio of the hydrogel was discussed.It was found that the NC-PVAm-Ag nanocomposite was amphoteric,and its electropiont was about 6.0.At pH 6,the swelling ratio was only 600%.It was 1100%at pH 11.The hydrogel exhibited strong antibacterial activity against Escherichia coli and Staphylococcus aureus.Finally,Silver nitrate solution was added into the dialdehyde nanocellulose to generate the silver nanoparticles,and then crosslinked with chitosan?CS?to obtain NC-CS-Ag hydrogel.The hydrogels were characterized by using FT-IR,XRD,TGA and SEM-EDAX.Then,the antibacterial properties were investigated against Escherichia coli and Staphylococcus aureus.The results show that the silver nanoparticles were successfully generated and uniformly distributed in the hydrogel.The hydrogel showed strong antibacterial activity against Escherichia coli and Staphylococcus aureus.