Development of new physical gels based on chitosan for wound healing.

Purpose: To investigate the potential of new chitosan-based physical gels, alone or loaded with plant extract or growth factors, for wound healing. Methods: Chitosan (CHI) was autoclaved and then dissolved at 2% w/w in acetic acid 0.1 M; the resulting dispersion was sonicated and then placed under vacuum for 48h. CHI gels were differently loaded depending of the considered active. In particular, gels loaded with PDGF and FGF-?? were prepared by co-dissolution of the growth factors with CHI in acetic acid 0.1 M. Alternatively, Centella asiatica (CEN) or Echinacea angustifolia (ECH) were added to the preformed gel. Thermal and rheological analysis were carried out to highlight the differences due to the heat treatment on the viscoelastic properties of gels. In addition, the effects of the gels on human fetal foreskin fibroblasts (HFFF-2) viability, proliferation and migration were investigated. Finally, the effect of the different gels on wound healing was investigated on C57BL/6J mice using an experimental model of pressure ulcer. Results: The differential scanning calorimeter (DSC) analysis showed that, the thermal treatment modifies the chemical and physical characteristics of the CHI powder. Furthermore, the formulations with non-autoclaved CHI showed a rheological behavior typical of an entangled network, while gels prepared from the autoclaved CHI have a typical gel behavior. The loading of actives into the gel did not affect the rheological properties of the formulations. In vitro tests on HFFF-2 showed that CHI gels were not toxic and led to increased cell proliferation and migration. Finally, the presence of PDGF ,FGF-??, CEN or ECH in the gels shows also to enhance the migration, the proliferation without affecting the vitality of fibroblasts. In vivo, CHI gel enhanced wound healing compared to untreated mice. This effect was higher when using CHI gels containing PDGF, FGF-??, CEN or ECH. Studies are in progress to determine the gel with the highest effect on wound healing, as well as the mechanism driving the tissue regeneration. Conclusions: The rheological properties of the developed CHI gels as well as in vitro and in vivo results, demonstrated a high potential as new products for the medication of wound, i.e. pressure ulcers.