Preparation and characterization of asiaticoside-loaded alginate films and their potential for use as effectual wound dressings

A wound dressing material was successfully prepared from alginate, a natural polymer capable of forming into hydrogels, and asiaticoside (PAC), a substance from the plant Centella asiatica which has commonly been used in traditional medicine to heal wounds. Various amounts of PAC (i.e., at 2.5, 5 and 10%, based on the weight of alginate) were mixed with alginate in distilled water. The mixtures were later cast into films. The formation into solid films was achieved with the two-step cross-linking procedure with Ca2+. First, a dilute CaCl2 aqueous solution (at 0.05% (w/v), 200 mL) was added slowly into an alginate aqueous solution (at 2% (w/v), 100 mL). This step imparted the dimensional stability of the obtained “mixed” films. Secondly, the “mixed” films were cross-linked further in either 2.5 or 5% CaCl2 aqueous solution to obtain “immersed” films. This step caused the “immersed” films to be more stable in environment that requires exposure to a high humidity or contact with an aqueous medium. Due to its insolubility in water, PAC existed in the films as discrete entities. The release of PAC from the PAC-loaded alginate “immersed” films was achieved by both the swelling and the erosion of the alginate matrix in the phosphate buffer solution (PBS) that contained methanol at about 10% (v/v). The potential for use of both the neat and the PAC-loaded alginate “immersed” films as wound dressings was assessed by indirect cytotoxicity evaluation and direct cell culture, using normal human dermal fibroblasts (NHDF). The results showed that these materials were non-toxic to the skin cells.