Collagen and multifunctional epoxides, which are respectively the common constituents of natural and polymer interfaces, were combined to fabricate integrative biointerfaces with device/tissue heterogeneous affinity. Further, the traditional 2D and advanced 2.5D conformational designs were achieved on collagen-based biointerfaces. The 2D conformational biointerfaces were formed by the self-entanglement of collagen molecules based on extensive hydrogen bonds among molecules, and the lamellar structures of 2D conformational biointerfaces could act as barriers to protect both biointerfaces and substrates from enzymes and corrosion. The unique stacking structures of 2.5D conformational biointerfaces were formed by cross-linking microaggregates that were established and connected by epoxy cross-linking bonds and provided the extra 0.5D degree of freedom on structure design and functional specialization through artificially manipulating the constituents and density of microaggregates. Besides, the intersecting channels among microaggregates gave 2.5D biointerfaces diffusion behaviors, which further brought good wettability and biodegradability. The integrative biointerfaces behaved well on cell viability and enhanced the cell adhesion strength in vitro, which could be attributed to the collaborations of collagen and epoxy groups. The subcutaneous implant model in rats was utilized to investigate soft tissue response, and the results demonstrated that the tissues around implantation areas healed well and without calcification or infection. The coating of integrative biointerfaces alleviated the fibrosis around implantation areas, and the inflammatory responses and foreign body reactions were improved.

This study developed an active and intelligent collagen-based packaging film with high strength for visually monitoring the freshness of fish. The results of scanning electron microscopy and atomic force microscopy showed that the film based on cross-linked collagen/delphinidin catalyzed by laccase exhibited a denser layer structure and a rougher surface. The dry and wet tensile strengths of the laccase-catalyzed collagen/delphinidin film (Col/Dp-LA film) increased by 41.74 MPa and 13.13 MPa in comparison with that of the pure collagen film, respectively. Moreover, the Col/Dp-LA film presented good antioxidant and barrier properties demonstrated by the results of free radical scavenging rate, light transmission rate, and water vapor permeability. The intelligent collagen-based film was obtained by incorporating Vaccinium oxycoccus pigment into the Col/Dp-LA film, which could change color under different pH values. When applied to the preservation of fish fillets, the film could release Dp to minimize oxidative rancidity and prolong the shelf life of the fish for 2 days. Meanwhile, the film showed visual color changes from purplish-red to greyish-blue after the fish spoilage. These results indicated that the collagen film treated with delphinidin, laccase, and Vaccinium oxycoccus pigment has potential application value in the field of active and intelligent food packaging. Graphical Abstract