Raman spectroscopic characterisation of photo-active keratin doped with Methylene Blue for wound dressings and tissue engineering

BACKGROUND: The design of wound dressings with extraordinary functionalities that fully address the problem of wound healing is an ambitious challenge in biomedical field. Keratin is a protein most abundant in nature, being the major component of wool, feather, hair, etc., with promising applications in biomedical and regenerative medicine fields. A high level of antibacterial functionality is another desirable property for applications in biomedical field in response to the increasing resistance of bacteria to antibiotics. One of the emerging methods of disinfection and sterilization is the antimicrobial photodynamic therapy (APDT), which uses light combined to a photosensitizer and oxygen to produce phototoxic species. OBJECTIVE: Biomatrices (photo-active keratin) made of wool keratin functionalized with methylene blue, a powerful photosensitizer, have been developed and tested as systems that combine the bioactive properties with the antimicrobial photodynamic functionality. METHODS: The biomatrix resistance to photo-degradation and the formation of reactive oxygen species were evaluated by spectroscopic methods, whereas the antibacterial properties were tested towards gram-positive bacteria. RESULTS: The Raman analysis revealed that specific damages occur at sensitive amino acid sites, selectively, rather than indiscriminately. However, keratin resulted to be a suitable biomaterial for APDT, since it has enough resistance to photodegradation and the radical-induced oxidation is not able to induce strong structural changes in the protein. CONCLUSIONS: The results clearly indicate the potential use of these novel photo-active keratin biomatrices in wound dressing and tissue engineering.