Preparation And Evaluation Of Antibacterial Bacterial Cellulose Membranes Impregnated Silver Nanoparticles

Promotion of wound healing is one of the important fields in clinical medical research. Functional medical dressing which has high moisturizing effect and antibacterial activity plays a vital role during the course of treatment as a temporary skin substitute. Bacterial cellulose (BC) is a kind of high purity cellulose made by microorganisms. It's the most elaborate nanometer material in nature. It is generally recognized that the structure and properties of bacterial cellulose dressing accord with the modern medical theory about wound healing since BC has several advantages of great moisture absorption ability, promoting healing, reducing pain and reducing the times of dressing replacement. According to the different culture conditions, we can get different membrane material with different characters in order to cope with the different exudate quantity and infection extent, so it is a kind of potential "ideal" wound dressing materials.Based on the purpose of medical application development of bacterial cellulose, the research was focused on the effects of the microstructure of the BC template, produced by different fermentation media. BC from different fermentation media had the surface area ranged from 60-90 m2/g, pore volume ranged from 0.17-0.25 cm3/g, average pore size ranged from 10-11 nm, and water holding capacity maintained more than 99.7%. The water swelling ratio of BC membrane ranged from 54.4-76.8 folds, water retention ratio ranged from 4.7-8.0 folds, water vapor transmission rate ranged from 45-75 g/(m2-h), diffusivity ranged from 13.6-40.0 mm/mm. Besides, BC from different fermentation media had excellent mechanical properties.However, bacterial cellulose itself does not have antibacterial properties, therefore it is difficult to deal with the bacterial infection of the wound. As we known, the antibacterial ability of silver nanoparticles (AgNPs) is 200 times better than silver particles with micrometer grade, therefore, silver nanoparticle impregnated bacterial cellulose membrane is an "ideal" potential functional medical dressing owning efficient moisturizing and antibacterial ability. BC/AgNPs composites were prepared by using the BC membranes from different fermentation media, and the size, morphology of the AgNPs as well as the silver contents and antibacterial effects of the BC/AgNPs composites were analysed. The BC/AgNPs composites had the silver content ranging of 0.64-1.19%; AgNPs was able to attach well in the 3-D network structure of bacterial cellulose and size distribution of AgNPs ranged from 5-14 nm. The antimicrobial activities of the BC/AgNPs composites prepared from different carbon sources were tested against E. coli and S. aureus by the zone of inhibition and log reduction methods, respectively. The results showed that the antibacterial properties against E. coli. were better than S. aureus.The situ preparation conditions of BC/AgNPs composites were optimized, such as concentration of AgNO3 solution and impregnating time as well as the drying methods, which would influence the size, morphology of the AgNPs as well as the silver contents and antibacterial effects of the BC/AgNPs composites. As the concentration and the impregnating time of AgNO3 solution was improved, the size of the AgNPs and the silver contents increased and the MIC value against E. coli. became bigger, while the antibacterial effects decreased. After impregnation, half dry BC/AgNPs composites had higher MIC value against E. coli. than absolutely dry BC.The comprehensive evalution of optimized BC/AgNPs composites was made in our research. The result showed there were a little higher water holding capacity, water swelling ratio, water vapor transmission rate and mechanical properties than pure BC, as well as there were much higher surface area, pore volume and average pore size. Optimized BC/AgNPs composites had the release time more than 72 h, at the same time owned the great antibacterial effect in 96 h against E. coli. and S. aureus. Besides that, we have done the preliminary research on the biocompatibility of BC/AgNPs composites. The results demonstrated that it had good effects and it supplied the basic data to do further research on the possibility of BC as the wound dressing.