Development of natural-based wound dressings impregnated with bioactive compounds and using supercritical carbon dioxide.

Film- and foam-like structures of N-carboxybutylchitosan (CBC) and of agarose (AGA) were prepared and characterized in order to evaluate their potential application as topical membrane-type wound dressing materials, mostly regarding their sustained release capacities and fluid handling properties. Polymeric biomaterials were loaded with two natural-origin bioactive compounds (quercetin and thymol, which present anti-inflammatory and anaesthetic properties, respectively), separately or as a mixture of these two substances, and using a supercritical solvent impregnation (SSI) method. Impregnation experiments were carried out with supercritical carbon dioxide (scCO₂) at 10 and 20 MPa, and at 303 and 323 K. Ethanol (10%, v/v) was employed as a co-solvent whenever quercetin was used. Release kinetic studies were performed for all prepared systems and the obtained results showed that higher amounts of quercetin and/or thymol were loaded when higher pressures and temperatures were employed. Results showed that the separated and the simultaneous SSI loading of these two bioactive substances into CBC and AGA is a feasible and advantageous process and that the relative loaded amounts of these substances can be "tuned" simply by changing the operational pressure-temperature conditions. Quercetin presented more sustained release profiles which can be justified by its higher molecular volume and by its lower water solubility as well as by the specific favourable interactions that can be established between quercetin and CBC. Obtained results showed that the employed SSI process also promoted the size reduction of loaded quercetin particles which can significantly improve the solubility of this compound in aqueous solutions. In addition, prepared systems presented adequate water sorption and water vapor sorption capacities as well as water vapor transmission rates that were in the typical and desired ranges for commercial wound dressings.