Piperine-mediated regulation of intermolecular interactions and network architecture in citric acid-crosslinked chitosan biofilms

Bioactive polysaccharide biofilms with tunable interfacial interactions and multifunctional properties are promising for the development of biodegradable biointerfaces. However, chitosan biofilms often show poor mechanical and barrier properties and limited antioxidant and antibacterial activities. We hypothesized that piperine (PIP) could serve as both a bioactive component and network regulator in citric acid (CA)-crosslinked chitosan biofilms by promoting hydrogen bonding and hydrophobic interactions. Herein, PIP-reinforced chitosan biofilms were fabricated through a CA-assisted casting strategy, in which PIP served as both a bioactive component and a network-regulating agent. Molecular interactions between PIP and chitosan promoted hydrogen bonding and hydrophobic associations, while CA crosslinking further densified the polymer network. The optimized biofilm containing 20% acetic acid, 0.5 mg/mL PIP, and 15% CA exhibited a tensile strength of 2.23 MPa, representing a 374% increase compared with the control, together with a ~23% reduction in water vapor permeability and enhanced surface hydrophobicity. PIP incorporation also markedly improved antioxidant and antibacterial activities, with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity reaching 77.08% and minimum inhibitory concentrations of 10 and 30 μg/mL against Staphylococcus aureus and Escherichia coli , respectively. The optimized biofilm maintained high cytocompatibility, with cell viability above 90%, and underwent substantial disintegration in soil within 10 d. Application to pork, beef, chicken, and fish further demonstrated delayed pH elevation, discoloration, exudation, and overall quality deterioration during storage. These findings demonstrate that PIP can regulate the molecular interactions and network architecture of chitosan biofilms while simultaneously imparting antioxidant and antibacterial functions, providing a versatile strategy for constructing biodegradable bioactive interfaces.