Scientists attached a short piece of the immune protein LL‑37 (called KR‑12) to a titanium surface using a stretchy protein that breaks down when the body’s enzymes are present. This lets the antimicrobial peptide be released on demand, killing most of the tested bacteria and helping bone cells grow on the surface.

Implant-associated infections pose significant challenges due to bacterial resistance to antibiotics. Recent research highlights the potential of immobilizing antimicrobial peptides (AMPs) onto implants as an alternative to conventional antibiotics for the prevention of bacterial infection. While various AMP immobilization methodologies have been investigated, they lack responsiveness to biological cues. This study proposes an enzyme-responsive antimicrobial coating for orthopedic devices using KR-12, an AMP derived from Cathelicidin LL-37, coupled with the Human Elastin-Like Polypeptide (HELP) as a biomimetic and stimuli-responsive linker, while mimicking the extracellular matrix (ECM). During implantation, these customized interfaces encounter the innate immune response triggering elastase release, which degrades HELP biopolymers, enabling the controlled release of KR-12. After coupling KR-12 with HELP to titanium surfaces, the antimicrobial activity against four pathogenic bacterial strains (<i>Staphylococcus aureus</i>, <i>Staphylococcus epidermidis</i>, <i>Escherichia coli</i>, and <i>Pseudomonas aeruginosa</i>) was assessed, revealing an inhibition ratio of bacterial adhesion and colonization exceeding 92% for all tested strains, compared with surfaces functionalized with KR-12 only. It is thought that the enhanced antimicrobial activity was due to the improved mobility of KR-12 when coupled with HELP. Furthermore, the prepared coatings boosted the adhesion and proliferation of human osteoblasts, confirming the cytocompatibility. These findings suggest the potential for smart coatings that combine the antimicrobial functions of AMPs with HELP's biological properties for use in a variety of settings, including medical devices.