Tailoring the immobilization and release of chlorhexidine using dopamine chemistry to fight infections associated to orthopedic devices

Abstract A crucial factor in the pathogenesis of orthopedics associated infections is that bacteria do not only colonize the implant surface but also the surrounding tissues. This study aimed to engineer an antimicrobial release coating for stainless steel (SS) surfaces, to impart them with the ability to prevent Staphylococci colonization. Chlorhexidine (CHX) was immobilized using two polydopamine (pDA)-based approaches: a one-pot synthesis, where CHX is dissolved together with dopamine before its polymerization; and a two-step methodology, comprising the deposition of a pDA layer to which CHX is immobilized. To modulate CHX release, an additional layer of pDA was also added for both strategies. Immobilization of CHX using a one-step approach yielded surfaces with a more homogenous coating and less roughness than the other strategies. The amount of released CHX was lower for the one-step approach, as opposed to the two-step approach yielding the higher release, which could be decreased by applying an outward layer of pDA. Both one and two-step approaches provided the surfaces with the ability to prevent bacterial colonization of the surface itself and kill most of bacteria in the bulk phase up to 10 days. This long-term antimicrobial performance alluded a stable and enduring immobilization of CHX. In terms of biocompatibility, the amount of CHX released from the one-step approach did not compromise the growth of mammalian cells, contrary to the two-step strategy. Additionally, the few bacteria that managed to adhere to surfaces modified with one-step approach did not show evidence of resistance towards CHX. Overall data underline that one-step immobilization of CHX holds great potential to be further applied in the fight against orthopedic devices associated infections.