High-flexible chitosan-based composite membrane with multi-layer biopolymer coatings for anti-bacterial drug delivery and wound healing.

Flexible chitosan-based membranes were prepared by casting/solvent evaporation method using chitosan flocks as raw material. To improve mechanical and biological properties, chitosan microspheres (CMs) were prepared and integrated to form the composite membranes. Two different anti-bacterial drugs, e.g., tetracycline hydrochloride (TH) and silver sulfadiazine (AgSD), were loaded into the CMs and composite membranes to enhance their anti-bacterial properties. Furthermore, composite membranes were alternately coated by multi-layers of oxidized alginate (OAlg) and carboxymethyl chitosan (CMCS) via the layer-by-layer self-assembly and Schiff-base cross-linking. Our results demonstrated that the microspheres and multi-layer coatings could improve the swelling, water vapor transmission and hydrophilicity of the composite membranes. The chitosan microspheres and multi-layer coatings increased the tensile strength and decreased the elongation at the break of the membranes. Our composite membrane had better mechanical properties, slow drug release, anti-bacterial properties, which could promote cell proliferation. This composite membrane has great application potential in inhibiting bacterial infection and promoting wound regeneration.