Intelligent Cellulose Nanofibers with Excellent Biocompatibility Enable Sustained Antibacterial and Drug Release via a pH-responsive Mechanism.

A novel nano-sized biomass-based pH-responsive cellulose nanofibers (CNF-PEI) with excellent biocompatibility was tailored by grafting polyethyleneimine (PEI) onto carboxylated cellulose nanofibers (CNF-COOH), the active site (-COOH, 0.96 mmol/g) was anchored on cellulose nanofibers (CNF) to introduce the PEI with a high density (10.57 mmol/g) of amino groups. The as-prepared CNF-PEI not only maintained the good properties of CNF but also possessed excellent biocompatibility and pH-responsive properties, offering interesting perspectives for pH-inducing drug sustained release and medical dressing. The CNF-PEI showed a rapid wettability conversion from hydrophilic, underwater superoleophobic (WCA=20.7°, OCA=159.3°) to hydrophobic, superoleophilic (WCA=129.6°, OCA=29.7°) in response to pH change from acidic conditions to alkaline conditions. The antibacterial properties of CNF-PEI for Escherichia coli and Listeria monocytogenes were 100% and 94.6% under acidic conditions, respectively. Furthermore, the pH-responsive mechanism of CNF-PEI was proposed by XPS, 13C NMR, 1H NMR and AFM analyses.