Enhanced antimicrobial activity of cellulose nanocrystals with added triazole and imidazolium groups

The development of sustainable materials with active functionalities is crucial for advancing a circular economy. Cellulose nanocrystals (CNCs), derived from the most abundant biopolymer, offer a renewable and biocompatible platform for such materials. In this work, CNCs were chemically modified with imidazolium and triazole-imidazolium cations to create sustainable antimicrobial agents. The strategies involved chlorination of CNCs, followed by two approaches, i) substitution with N -methyl imidazolium (MI) groups to obtain CNC-MI, or ii) a click chemistry reaction for triazole-imidazolium (TrMI) modification to obtain CNC-TrMI. The analysis of the modified CNCs using Fourier transform infrared spectroscopy (FTIR), elemental analysis, and solid-state nuclear magnetic resonance (ssNMR) confirmed the successful modifications, resulting in CNC-MI showing a 30% degree of substitution, and CNC-TrMI demonstrating a 50% degree of substitution. However, such modifications affected both the structure and thermal stability of the CNCs as determined by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Nevertheless, the resulting cationic CNC derivatives, confirmed by Zeta potential analysis, exhibited remarkable antimicrobial activity against both Gram-positive Staphylococcus epidermidis and Gram-negative Pseudomonas aeruginosa . In particular CNC-TrMI exhibited excellent activity giving a reduction of more than 99.99% against both bacteria.