Plackett-Burman experimental design for bacterial cellulose-silica composites synthesis.

Bacterial cellulose-silica hybrid composites were prepared starting from wet bacterial cellulose (BC) membranes using Stöber reaction. The structure and surface morphology of hybrid composites were examined by FTIR and SEM. The SEM pictures revealed that the silica particles are attached to BC fibrils and are well dispersed in the BC matrix. The influence of silica particles upon BC crystallinity was studied using XRD analysis. Thermogravimetric (TG) analysis showed that the composites are stable up to 300°C. A Plackett-Burman design was applied in order to investigate the influence of process parameters upon silica particle sizes and silica content of BC-silica composites. The statistical model predicted that it is possible for silica particles size to vary the synthesis parameters in order to obtain silica particles deposed on BC membranes in the range from 34.5 to 500 nm, the significant parameters being ammonia concentration, reaction time and temperature. The silica content also varies depending on process parameters, the statistical model predicting that the most influential parameters are water-tetraethoxysilane (TEOS) ratio and reaction temperature. The antimicrobial behavior on Staphylococcus aureus of BC-silica composites functionalized with usnic acid (UA) was also studied, in order to create improved surfaces with antiadherence and anti-biofilm properties.