A versatile food packaging film fabricated by gallic acid/octanoic acid grafted chitosan: Preparation, characterization, high-efficient cells capture and photodynamic eradication of bacteria and biofilms

This study aims to construct a versatile film fabricated by gallic acid/octanoic acid-grafted-chitosan (GA/OA-g-CS) for high photodynamic antibacterial and antibiofilm efficacy with blue light (BL, 420 nm) irradiation. First, the GA/OA-g-CS conjugates were synthesized by a green radical-induced grafting reaction in the redox system composed of ascorbic acid/hydroxyl peroxide (AA/H2O2). Then, the molecular structural and physicochemical characteristics of the conjugates, as well as the mechanisms of the free radical grafting reaction were further studied. Results showed that ascorbate radical (Asc•−) and hydroxyl radical (•OH) were produced in the AA/H2O2 system, and •OH reacted with CS to produce CS macro-radicals (•CS). UV–vis, Fourier transform infrared, nuclear magnetic resonance spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis confirmed that GA/OA was attached onto CS through •OH. Notably, the films constructed by GA/OA-g-CS exhibited robust multi-modal functionalities, including intriguing bacteria-capturing and contact-killing, as well as BL-driven photodynamic sterilization, ascribed to the inherent merits based on the massive photoactive GA, hydrophobic and high membrane affinity of OA within the CS chains. As a result, the GA/OA-g-CS (2:1) film plus BL irradiation can efficiently eradicate Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and their biofilms. After BL irradiation for 30 min, the GA/OA-g-CS (2:1) film showed a reduction of 5.2 Log CFU/mL against E. coli. More importantly, the film with BL irradiation can efficiently not only inhibit the formation of biofilms but also jeopardize the matured biofilms. This research provides a potential platform and promises for applications in active and intelligent food packaging.