Study On Photocatalysis And Antibacterial Properties Of Bacterial Cellulose Composites

Bacterial cellulose (BC), which is a kind of natural polymer synthesized by microorganisms, possesses unique ultra-fine nano-network, high water holding capacity, mechanical properties and good biocompatibility. As a result, BC has been widespread concerned for its composites recently. In this study, bacterial cellulose was chosen as a support for preparing titanium dioxide/bacterial cellulose (TiO2/BC), silver/bacterial cellulose(Ag/BC) and quaternary phosphonium salt /bacterial cellulose(QPS/BC) composites. And their application in photocatalytic degradation for organic waste water and antimicrobial material were studied. The preparation for those composites is simple and owns excellent performance, which causes a broad application prospect.Firstly, TiO2 nanoparticle was prepared by the sol-gel method in the surface and gap of bacterial cellulose fiber, thus TiO2/BC composite was obtained. And then the study of its photocatalytic degradation, antibacterial properties and biocompatibility was carried out. In order to improve the efficiency quantum of TiO2, rare earth elements was doped. La(Ce)-TiO2/BC composites were prepared by immersing TiO2/BC into the rare earth nitrate (La(NO3)3, Ce(NO3)3) of a certain concentration, and we investigated systematically into the photocatalytic degradation for organic dyes. Characterization of the composites demonstrated that anatase TiO2 distributed in the microfibrils and gaps of BC evenly, which certified that the rare earth elements had been introduced into the TiO2/BC composite successfully. The resultes of photocatalysis on methyl orange of different concentrations under UV irradiation showed that comparing with TiO2/BC, there is substantial increase in the degradation rate of La(Ce)-TiO2/BC and the degradation rate of cerium doped composite is higher than that of the composite doped with lanthanum element. La(Ce)-TiO2/BC can be recycled for many times due to its good repeat degradation performance. Moreover, antibacterial properties and cell compatibility of TiO2/BC nano-composite materials were studied. The results showed that TiO2/BC has a strong inhibitory effect on E.coli and S.aureus, diameters of the inhibition circles are 15mm and 10mm respectively. After cultured in the composite surface for 7 days, the 3T3 cells were tightly attached to the surface of TiO2/BC, normal growing, migrating and spreading, which was seen in SEM pictures and indicated that the TiO2/BC composite materials is of good biocompatibility and non-toxic.In addition, organic and inorganic antimicrobial agent were also loaded with BC in this article. It is well known that nano-silver has the advantage of broad-spectrum and long-acting antimicrobial property. Ag/BC composite material was prepared using NaBHH4 as a reducing agent. And the antibacterial properties and cell compatibility of Ag/BC were also studied. The results showed that Ag/BC has a strong inhibitory effect on E.coli and S.aureus, and the antibacterial property was improved with the increase of silver concentration, the maximum inhibitory rate was reached 99.4% and 98.4% respectively. SEM pictures showed the 3T3 cells was proliferated well on the surface of the Ag/BC composite, which proved that the Ag/BC composite materials is of good biocompatibility and non-toxic.Finally, Quaternary phosphonium salt (QPS) with different length of carbon chain was successfully loaded on BC. And the antibacterial properties and cell compatibility of QPS/BC was studied. The results showed that the antibacterial activity of QPS/BC was enhanced with the increase of the alkyl chain length. Compared with that of pure QPS, QPS in QPS/BC is released slowly. The concentration of QPS is increased gradually in 72 h, and QPS/BC has a good antibacterial properties in 72 h. Moreover, it is found that after the antibacterial action of 24 h, QPS/BC got a better antibacterial ratio, that is, the antimicrobial action time for the BC composite was extended, which demonstrated that the nano-network structure of BC had sustained release on QPS. And QPS/BC composite materials is of good biocompatibility, which is expected to be a new type of long-term antimicrobial dressing.