Biocompatible curdlan-based biomaterials loaded with gentamicin and Zn-doped nano-hydroxyapatite as promising dressing materials for the treatment of infected wounds and prevention of surgical site infections

Abstract

A topical application of antibiotic-loaded wound dressings is recommended only for chronically infected wounds with poor vascularization. Thus, more often dressing materials loaded with antibacterial metal ions are produced. In turn, gentamicin sponges are commonly used to prevent surgical site infections. The aim of this study was to produce curdlan-based biomaterials enriched with gentamicin and zinc (Zn)-doped nano-hydroxyapatite to prevent wound and surgical site infections. Developed biomaterials were subjected to basic microstructural characterization, cytotoxicity test against human skin fibroblasts (BJ cell line), and comprehensive microbiological experiments using Staphylococcus aureus and Pseudomonas aeruginosa strains. To evaluate the in vivo healing capacity of the developed biomaterials, severely infected chronic wound in a veterinary patient was treated with the use of gentamicin-loaded dressing. Fabricated biomaterials were characterized by a highly porous microstructure with high plasma absorption capacity (approx. 7 mL/g for Zn-loaded biomaterial and 13 mL/g for gentamicin-enriched dressing) and optimal water vapor transmission rate (approx. 1700 g/m²/day). Due to the presence of bioceramics, material containing Zn showed slightly higher compressive strength (0.37 MPa) and Young's modulus (3.33 MPa) values compared to gentamicin-loaded biomaterial (0.12 MPa and 1.29 MPa, respectively). Gentamicin-enriched biomaterial showed burst release of the drug within the first 5 h, while, the zinc-loaded biomaterial exhibited a constant gradual release of the zinc ions. Conducted assays showed that developed biomaterials were non-toxic against human skin fibroblasts (cell viability in the range of 71-95 %) and revealed strong bactericidal activity (99.9 % reduction in the number of viable bacterial CFUs in direct contact test) against S. aureus. In the case of P. aeruginosa, only gentamicin-loaded biomaterial exhibited bactericidal effect. Additionally, biomaterials had the ability to uptake, lock in, and kill bacteria within their gel structure, enabling the cleansing of the wound bed at every dressing change. Finally, the treatment of severely infected wound in veterinary patient confirmed the effectiveness of gentamicin-loaded biomaterial. Biomaterial enriched with gentamicin possesses great potential to be used as a dressing material or sponge for the treatment of chronically infected wounds and surgical site infections. In turn, the zinc-loaded biomaterial may be used as a wound dressing to reduce and prevent microbial contamination.

Keywords: Cytotoxicity; Gentamicin sponge; Regenerative medicine; Wound dressing.