Bio-inspired biomaterial coating for enzyme responsive release of antimicrobial peptides

Biofilm formation and implant-associated infections, potentially leading to periprosthetic bone loss and subsequent loss of osseointegration, remain high-risk factors for failure of implants. Consequently, the prevention of bacterial colonization on implant surfaces is of high interest. The development of multi-drug-resistant bacteria led to less effective infection prophylaxis using commonly used antibiotics. Functionalization of implant surfaces with antibacterial agents like antimicrobial peptides to reduce or even prevent bacterial adhesion is a promising perspective. Here, we report on the synthesis of a new peptide-based biomaterial coating. Two antimicrobial peptides, [Nle⁵]-SHAP1 and P5, were successfully coupled to a mussel-derived carrier peptide containing l-3,4-dihydroxyphenylalanine and immobilized onto titanium and poly(ε-caprolactone) (PCL). Incorporation of specific linker sequences enabled protease-mediated release from the surface by matrix metalloproteinase 9 and 2, as well as by neutrophil elastase, enzymes that are frequently found in infected wounds. The antibacterial activity of the coating components was assessed individually as well as combined in a broth dilution assay setup. Reduction of bacterial growth has been shown after 4 h of incubation upon enzymatic release using PCL nanoparticles coated with the most promising candidate. All tested coatings were non-cytotoxic for eukaryotic osteogenic SaOS-2 and monocytic THP-1 cells. This study offers a promising approach for functionalizing biomaterial surfaces with antimicrobial peptides, potentially reducing the incidence of implant-associated infections. To overcome limitations of non-fouling and contact-killing surfaces, enzyme-sensitive sequences were incorporated that allow for triggered release of the antimicrobial peptides and thus for combating bacteria at the peri-implant site.