Development of antioxidant wound dressings based on functionalized and crosslinked chitosan

Tissue engineering is an interdisciplinary field that develops new methods to enhance the regeneration of damaged tissues. Skin tissue engineering takes advantage of principles of engineering, biology and chemistry for manufacturing dressings that can promote the regeneration of injured skin. Polysaccharides such as hyaluronic acid, alginate and chitosan have appropriate biological properties to be used as wound dressings [1]. Furthermore, the presence of functional groups in their backbone makes them easily modifiable both by chemical reactions and physical interactions with different molecules, allowing the development of materials with better antibacterial and/or anti-inflammatory activity. In the present work, innovative dressings based on modified chitosan were developed using the solvent casting technique. In particular, chitosan (CS), characterized by good antimicrobial activity [2] but poor dimensional stability in physiological environment, was first modified with glycidylmethacrylate (GMA) and glycerol (GLY) and then with ethylene glycol dimethacrylate (EGDMA). GMA was introduced into the polysaccharide to have a functionality (double bond) to be exploited in the subsequent crosslinking reaction with EGDMA, while GLY was taken into consideration to provide a good degree of elasticity to polymer films, which must be able to adapt to the skin. To evaluate the effect of GLY on the mechanical properties of the developed matrices, the films were obtained by varying the glycerol concentration (10, 20 and 30% w/v). For all samples, at each concentration of GLY, an increase in the elongation at break and in the dimensional stability in aqueous environment was observed, accompanied however by a considerable decrease in the elastic modulus. The matrices were then subjected to chemical crosslinking using EGDMA in order to create bridges between the GMA-modified CS chains. To evaluate how the cross-linking process affected the elasticity of the films, three different concentrations of EGDMA (0.05-0.1-0.5 mM) were tested for the same reaction time (5 min). The crosslinked matrices showed a significant increase in the value of the elastic modulus, but only in the case of the lowest EDGMA concentration the matrices maintained an elongation at break suitable for the development of dressings. With the aim of avoiding possible inflammatory reactions during the healing phase, the films were functionalized with 3,4 hydroxycinnamic acid (HCAF), an antioxidant capable of limiting the phenomenon of oxidative stress [3]. The introduction of the antioxidant into the films was carried out both by covalent bonding between CS amino groups and the ortho position of the catechol ring, using laccase as catalyst, and imbibition. In both cases the introduction of HCAF molecules increased the antioxidant properties and the elastic modulus of the films. Biological tests are underway to verify the possible application of these systems in skin tissue engineering. [1] Sahana, T.G., Rekha, P.D., «Biopolymers: Applications in wound healing and skin tissue engineering». Mol Biol Rep, vol. 45, pp. 2857–2867, 2018. [2] D. d. B. O. B. G. A. Rejane C. Goy, «A Review of the Antimicrobial Activity of Chitosan,» Polímeros: Ciência e Tecnologia, vol. 19, n. 3, pp. 241-247, 2009. [3] Tarique Hussain, Bie Tan, Yulong Yin, Francois Blachier, Myrlene C. B. Tossou, Najma Rahu, "Oxidative Stress and Inflammation: What Polyphenols Can Do for Us?", Oxidative Medicine and Cellular Longevity, vol. 2016, pp. 1-9, 2016.