Nisin-loaded gelatin microparticles for the enhanced bioactivity of bacterial nanocellulose

Bacterial nanocellulose (BnC) is of immense importance in medicine, although its lack of bioactivity present intriguing issue. We propose a method to modify BnC with gelatin and nisin biomolecules, and explore their synergistic effect on the antimicrobial activity. Gelatin microparticles (without/with nisin loading) with a size ~0.5 μm and ~ 1.3 μm were prepared by spray drying and stabilised by dehydrothermal treatment. Modified BnC-based membranes supported the formation of biologically relevant minerals and were non-cytotoxic to human gingival fibroblast cells (HGF). The presence of gelatin microparticles improved the viability of HGF by approximately 20 %, due to the effect of gelatin alone, independent of the addition of nisin. BnC coated with a nisin/gelatin solution reduces the viability of HGF by about 20 %, but this negative effect is not observed by nisin coated gelatin microparticles. The cell viability of BnC membranes was above 90 % in both porcine and human urothelial cells. The antimicrobial activity study confirmed an inhibitory effect of membranes modified with nisin-coated microparticles or a gelatin/nisin solution against Staphylococcus aureus at a non-cytotoxic nisin dose (150 μg/mL). The study demonstrates the structural effects of gelatin and gelatin/nisin mixtures on the bioactivity of BnC and provides a rationale for the modification procedure.