This work reports a straightforward approach for incorporation of plant-derived flavonoid-based antioxidants into an intrinsically antimicrobial chitosan platform in order to generate chitosan-based materials suitable for biomedical applications. The novelty of this approach consists in the use of thioacidolysis – a common analytical method for the characterization of proanthocyanidins – to covalently functionalize natural macromolecules such as chitosan with bioactive phenolic moieties. It is known that proanthocyanidins undergo depolymerization in acid medium, where in the presence of nucleophiles they form stable flavan-3-ol derivatives. Based on this reaction, flavan-3-ol moieties from the polyphenol extract of Hamamelis virginiana are incorporated covalently into a previously thiolated chitosan matrix. The phenolics-functionalized chitosan possesses improved antioxidant and antimicrobial properties, and inhibitory efficiency over deleterious wound enzymes in vitro.
Rocasalbas, G.; Francesko, A.; Touriño, S.; Fernandez-Francos, X.; Gübitz, G. M,.; Tzanov, T. Carbohydrate polymers Vol. 92, num. 2, p. 989-996 DOI: 10.1016/j.carbpol.2012.10.045 Data de publicació: 2012-11-02 Article en revista
Laccase-assisted simultaneous cross-linking and functionalization of chitosan/gelatin blends with phenolic compounds from Hamamelis virginiana was investigated for the development of bioactive hydrogel dressings. The potential of these hydrogels for chronic wound treatment was evaluated in vitro, assessing their antibacterial and inhibitory effect on myeloperoxidase and collagenase. Rheological studies revealed that the mechanical properties of the hydrogels were a function of the enzymatic reaction time. Stable hydrogels and resistant to lysozyme degradation were achieved after 2 h laccase reaction. The inhibitory capacity of the hydrogel for myeloperoxidase and collagenase was 32% and 79% respectively after 24 h incubation. Collagenase activity was additionally suppressed by adsorption (20%) of the enzyme onto the hydrogel. Therefore, the bioactive properties of the hydrogels were due to the effect of both released phenolic compounds and the permanently functionalized platform itself. The hydrogels showed antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus.
Díaz, M.; Rocasalbas, G.; Francesko, A.; Touriño, S.; Torres, J.; Tzanov, T. Biocatalysis and biotransformation Vol. 30, num. 1, p. 102-110 DOI: 10.3109/10242422.2012.646676 Data de publicació: 2012-01-18 Article en revista
The chronic wound environment is characterized by high concentrations of reactive oxygen species (ROS) and elevated
levels of myeloperoxidase (MPO) and collagenases, together impairing the healing process. Therefore, the management of chronic wounds at a molecular level requires the synergistic use of antioxidants, MPO and collagenase inhibitors to simultaneously target multiple factors from wound pathogenesis. In this study, a polyphenolic extract from Hamamelis virginiana plant, rich in condensed and hydrolysable oligomeric tannins, was evaluated as an inhibitor of MPO and collagenase.In addition to efficient scavengers of radical and non-radical reactive species, H. virginiana polyphenols were found to act as substrates in the MPO peroxidase cycle, preventing the accumulation of ROS in the chronic wound
site. Furthermore, it was also found that the plant exerts an irreversible inhibitory effect on collagenase activity (IC50 = 75 ± 10 μg/mL)
Francesko, A.; Rocasalbas, G.; Touriño, S.; Mattu, C.; Gentile , P.; Chiono, V.; Ciardelli , G.; Tzanov, T. International Conference on Polymer and Textile Biotechnology p. 1-26 Data de presentació: 2011-03-04 Presentació treball a congrés
Chitosan is a partially deacetylated derivative of chitin, a natural polysaccharide extracted from crustaceans, insects and certain fungi. Owing to its unique properties such as biodegradability, biocompatability, biological activity and capacity of forming polyelectrolyte complex with anionic polyelectrolytes, chitosan has been widely applied in the food and cosmetics industry, as well as the biomedical field in relation to tissue engineering, and the pharmaceutical industry relating to drug delivery. This handbook gathers current research from around the globe in the study of chitosan and its applications.