Bifunctional performance of cellulose nanofibers grafted with polyhexamethylene guanidine in Pickering emulsion: Antibacterial activity and interfacial stability

This study developed the multifunctional cellulose nanofibers (CNFs) as emulsifier for preparation of antibacterial, ultrastable and non-toxic emulsion. To achieve these properties, CNFs were oxidated using sodium periodate to introduce aldehyde groups, which served as Schiff-base reaction sites for amino groups of polyhexamethylene guanidine (PHMG), yielding PHMG-grafted CNFs (PCNFs). The modified CNFs retained good emulsification ability while acquiring antibacterial properties. PCNFs were irreversibly absorbed onto the droplet surface, forming dense covering layers that prevented coalescence. Their strong entanglement and bridging flocculation capacities bonded adjacent droplets, creating stable droplet-fiber network structures. This enabled a creaming index of 90 % with only 4.0 % PCNFs. Emulsion stabilized by PCNFs achieved over 99 % antibacterial rate and 99 % cell viability, confirming their effective inactivation of bacteria and good biocompatibility. These findings showed the potential of PCNFs for developing antibacterial, ultrastable, and non-toxic emulsions for daily and biomedical applications.