Vanillin Esterified TEMPO-Oxidised Nanocellulose Derived from Sugarcane Bagasse for Antibacterial Applications

Nanocellulose extracted from sugarcane bagasse underwent chemical modification. Then 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) -mediated oxidation followed by esterification with vanillin, resulting in the development of a novel antibacterial material. The sequential processes of alkali treatment, bleaching, and acid hydrolysis effectively eliminated non-cellulosic components, producing purified cellulose nanofibers with enhanced crystallinity (88%) and well-defined morphology, as confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) analyses. TEMPO oxidation selectively converted primary C6 hydroxyl groups to carboxylic acids, as evidenced by FTIR and solid-state 13C nuclear magnetic resonance (¹³C SS-NMR) spectroscopy. The esterification of the oxidised nanocellulose with vanillin was accomplished using FTIR spectra, ¹³C SS-NMR. The vanillin-functionalized nanocellulose exhibited reduced thermal stability checked by thermogravimetric analysis (TGA). Notably, the modified nanocellulose demonstrated significant antibacterial activity against both Gram-positive and Gram-negative bacteria, with inhibition zones 20.33 to 21.66 mm comparable to those of pure vanillin, indicating the retention of vanillin bioactivity upon esterification. These findings underscore the potential of vanillin-esterified TEMPO-oxidised nanocellulose as a sustainable, bioactive material for antibacterial applications.