Biomaterials based on natural substances are playing an increasingly important role in the development of new products for medical applications and therapies (Schilrreff & Alexiev, 2022). Specifically, the use of natural antioxidants integrated into innovative biomaterials holds significant potential for the development of future therapeutics, especially in wound healing. In general, wound healing is inhibited when the wound remains in the inflammatory stage for too long and thus becomes chronic (Schilrreff & Alexiev, 2022). The most common chronic wounds include pressure ulcers, diabetic ulcers, venous ulcers and chronic non-healing wounds due to trauma or surgical wounds. Chronic wounds occur at the molecular level when enzymes in the wound bed are not in balance, oxidative stress occurs, or when bacteria colonize and form biofilms. Oxidative stress is mainly due to the formation of free radicals. The body's natural antioxidant capacity, which is no longer sufficient in the context of oxidative stress in the clinical picture, can be compensated by the supply of antioxidants. Various biomaterials with integrated antioxidants have been described to promote wound healing and skin tissue regeneration (Schilrreff and Alexiev, 2022). Promising results have been shown in animal studies, leading to the first commercial wound healing products. However, clinical studies in humans are still very limited. This is mainly due to the poor water solubility and thus bioavailability/stability of natural antioxidants, which is a major obstacle to their widespread therapeutic use. Several strategies to improve these negative properties have been investigated. Mostly, these are nanoparticle-based strategies that can improve poor water solubility (Simioni, 2022). In addition to water solubility and bioavailability, the varying antioxidant activity of these substances is currently still a major problem, which also limits the success of their therapeutic use. For example, curcumin has an antioxidant capacity of n~3 (n is the number of radical molecules that can be neutralised by one molecule of antioxidant, therefore also called stoichiometry). The value for vitamin E is n=2-3. A higher antioxidant capacity is attributed to astaxanthin and the carotenoids in general (Tsuchiya, 1992), and thus also a broad effect (Schilrreff & Alexiev, 2022). However, the antioxidant capacity data for astaxanthin in particular vary greatly in the literature or are only given in relative terms (Dose, 2016).
To address this need, this research project focused on the remarkable properties of the highly antioxidative astaxanthin compound from the green microalgae Chlorella zofingiensis, its combination in a new therapeutic lipid nanoparticle together with an accurate determination of its antioxidant capacity.
