Antimicrobial and Anti-inflammatory Gallium–Defensin Surface Coatings for Implantable Devices

Emerging and re-emerging infections are a global threat driven by the development of antimicrobial resistance due to overuse of antimicrobial agents and poor infection control practices. Implantable devices are particularly susceptible to such infections due to the formation of microbial biofilms. Furthermore, the introduction of implants into the body often results in inflammation and foreign body reactions. The antimicrobial and anti-inflammatory properties of gallium (Ga) have been recognized but not yet utilized effectively to improve implantable device integration. Furthermore, defensin (De, hBD-1) has potent antimicrobial activity in vivo as part of the innate immune system; however, this has not been demonstrated as successfully when used in vitro. Here, we combined Ga and De to impart antimicrobial activity and anti-inflammatory properties to polymer-based implantable devices. We fabricated polylactic acid films, which were modified using Ga implantation and subsequently functionalized with De. Ga-ion implantation increased surface roughness and increased stiffness. Ga implantation and defensin immobilization both independently and synergistically introduced antimicrobial activity to the surfaces, significantly reducing total live bacterial biomass. We demonstrated, for the first time, that the antimicrobial effects of De were unlocked by its surface immobilization. Ga implantation of the surface also resulted in reduced foreign body giant cell formation and expression of proinflammatory cytokine IL-1β. Cumulatively, the treated surfaces were able to kill bacteria and reduce inflammation in comparison to the untreated control. These innovative surfaces have the potential to prevent biofilm formation without inducing cellular toxicity or inflammation, which is highly desired for implantable device integration.