Non leaching biomimetic antimicrobial surfaces via surface functionalisation of cellulose nanofibers with aminosilane

Uncontrolled growth of bacteria is always a major concern for various industries such as food, cosmetic and pharmaceutical industries. Taking this issue into account, a non-leaching antimicrobial surface was developed using cellulose nanofibers with a post grafting green method to mimic the antibacterial activity of chitosan. A series of experiments was designed for silylation of nanofibers with 3-aminopropyl trimethoxysilane, varying the initial concentration of silane and the solvent employed during the grafting. The results, validated by Fourier transform infrared spectroscopy, thermogravimetric analysis and elemental analysis, provided evidence of successful functionalization. Moreover, SEM–EDX indicated that a heterogeneous grafting occurred at the surface and cross section of the film. Strong antimicrobial activity against gram positive (Bacillus subtilis and Staphylococcus aureus) and gram negative (Escherichia coli) was recorded. In aqueous solution, the optimum results were obtained using grafting silane concentration of 50 g/L. The grafted CNF showed no change in the morphology or thermal stability, meanwhile a significant reduction in bacterial concentration of 1.3 logs for B. subtilis, 1.8 log for S. aureus and 3.8 logs for E. coli was observed. Regarding the solvent used during the grafting, acetone showed the reversibility of bonds between silanol groups and cellulose nanofibers or high self-condensation reaction which was depicted by the Si NMR and formation of zones of inhibition. Furthermore, water employed as grafting solvent depicted better grafting efficiency than acetone, 10.2 versus 6.4 % respectively, at the similar concentration with apparent lower grafting time.