Layer-by-layer assembly using bacterial Levan adhesive polymer

Nanostructured coatings consisting of chitosan and the adhesive bacterial exopolysaccharide levan were fabricated using layer-by-layer (LbL) assembly. Taking advantage of the electrostatic self-assembly mechanism of LbL, the charges of both chitosan and a phosphonate-derivatized levan (Ph-levan) were measured and the feasibility to construct hybrid films was monitored and confirmed using a quartz crystal microbalance with dissipation monitoring (QCM-D). The adhesive properties between two identical bonded films with a total of 100 layers were compared to control films in which Ph-levan was replaced by alginate, revealing that the detachment force of the former is about 3 times higher than the control. Scanning electron microscopy of the films surface showed that the surface of Ph-levan films is smooth and homogeneous. Cell adhesion tests were conducted using a L929 cell line. Early cell adhesion is significantly higher in chitosan/Ph-levan films when compared to chitosan/alginate controls. These findings establish levan derivatives as bioinspired ingredients for conceiving medical adhesive devices that allow achieving enhanced mechanical and biological performance. In the context of biomedical and tissue engineering, these films could provide enhanced adhesiveness and protection to a new generation of wound healing bandages or to surgical sealants and also surfaces with optimized cell/substrate interactions, fabricated by a versatile and cost-effective multilayer technology.