Preparation And Evaluation Of Bacterial Cellulose Composite Hydrogel

Bacterial cellulose (BC) is a kind of natural macromolecule hydrogel synthesized by microorganism. BC is extensively applied in food, paper, cosmetics, acoustic diaphragms, mining and refinery, waste treatment, biomedical materials due to its high purity and crystallinity:high water retention rate and permeability; appropriate tensile strength and elastic modulus:good biosecurity, etc. As one kind of newly developed biomedical nanomaterial with green and inexhaustible attractes, BC has recently become one focus of the international researches.In the biomedical area, BC has gained wide ranges of researches from artificial vessel: wound dressing; nerve conduit; meniscus implant to cartilage tissue support and so on. Among these, wound dressing has been put into commercial use. Although the good performance of BC has laid a solid foundation to its development, limitations still exist. For instance, high water-containing BC has a relative low wet strength, which restrains its further application in certain materials with higher mechanical requirement. Furthermore water inside the BC network was easily squeezed out, which leads to its decrease of water-holding ability. In addition. BC itself does not have any antibacterial property that is crucial to prevent wound infection. Therefore, many researches recently were focused on the modification of BC to further improve its properties and deepen its application into a broader space. In this aspect, one effective way was to form double network hydrogel with high mechanical strength due to the interpenetrating, semi-interpenetrating or hybrid between the two polymers combined by ionic bond and covalent bond. Meanwhile, the nano-reticular hydrogel was supposed as an excellent matrix for the stabilization and dispersedness of metal nanoparticles, as well as control their size.In this work, we aimed to improve the properties of BC so to further its medical application by synthesis of polyacrylamide (PAM) networks inside its matrices via free radical polymerization. SEM and FTIR results both showed the successful formation of BC/PAM, and the thermal stability was obviously improved. Beside, increased N, N-methylene methylene double acrylamide (MBA) concentration could greatly improve the water retention rate of BC/PAM. Both AM and MBA could largely increase the Yong’s modules of the composite, leading to a stronger and more durable material. Preliminary evaluation of the biocompatibility of the material was conducted, pig iliac endothelial cells (PIECs) and mouse fibroblast cells (L929) were utilized as cell sources in vitro. MTT assay turned out that both BC and BC/PAM could support the proliferation of PIEC to some extent, but BC did much better than BC/PAM. However, both BC and BC/PAM were not sustainable for the proliferation of L929. Cell images obtained by SEM showed both cells exhibited extremely stretched phenotypes on BC and BC/PAM.Though BC/PAM has greatly improved the mechanical strength over BC, the swelling ratio was still insufficient. In order to further the biomedical application of BC, the wide used alginate (mainly calcium alginate. CA) as wound dressing, was choosen as the second network for the systhsis of BC/CA double network. SEM images showed the denser fiber networks were formed in BC/CA after the crosslinking with CaCl2With the increase of alginate concentration, both swelling and water retention ratio could be largely improved, especially for the water retention ratio. The monomer influencing mechanical property of BC/CA just showed as BC/PAM. a great improvement of Yong’s module was found. MTT assay showed both BC and BC/CA could support PIEC cell proliferation and growth well but not the L929cell. The SEM photos revealed a better cellular morphology of PIEC than1.929on all materias.Silver nanoparticle (AgNPs) as one kind of spectrum antibacterial agents has been widely studied. In situ synthesis of AgNPs inside the matrices of DN hydrogel has been turned out as one promising synthetic strategy, as well as largely broadened the function of composite material. Our work was carried out with the idea of in situ synthesis of AgNPs base on the properties improved composites, so as to further improve its applications as biomedical materials, especially wound dressings. According to our work, the silver content varied from1.46%(BC/PAM-AgNPs) to 2.28%(BC/AgNPs). BC/PAM-AgNPs gained the highest average diameter of silver nanoparticls,68nm, but the other materials mainly gave around25nm. All of them shared a relative narrow size distribution scope and high antibacterial properties against Staphylococcus aureus. However, these silver nanoparticles composites obviously inhibited the proliferation of PIEC and L929with silver concentration dependence.