Preparation of crosslinked chitosan film (CC), crosslinked chitosan-LNP film (CC-LNP) and crosslinked chitosan-Ag@LNP film (CC-Ag@LNP)

All films were prepared by a casting method. Petri dish (diameter: 3.5 cm) was used as a mould. Chitosan (1 g) was added to 100 mL deionized water which contains 0.572 mL acetic acid. For CC film, 2.95 g of prepared chitosan solution (1 wt%) and 180 μL of prepared glutaraldehyde solution (0.25 wt%) were mixed and poured into a petri dish. After evaporation under ambient temperature, the CC film was carefully removed from the mould. For CC-LNP film, the mixed solution contained 1.75 g chitosan solution, 180 μL glutaraldehyde solution and 3 mL LNP dispersion, with the other procedures were the same as above. For CC-Ag@LNP, Ag@LNP dispersion was used instead of LNP dispersion, and the other procedures were similar.