“Smart” Implant Coating Delivers Antibiotics in Presence of Bacteria

Implant_Coating_7_20_16Despite advances in sterile techniques and evidence-based use of perioperative antibiotics, periprosthetic joint infections still occur in 1% of primary and 3% to 7% of revision total joint arthroplasties. But a “smart” antimicrobial polymer coating, described in the July 20, 2016 Journal of Bone & Joint Surgery, has great potential to cut those percentages.

Stavrakis et al. devised a nontoxic, biodegradable polymer coating (called PEG-PPS for short) that locally delivers antibiotics (vancomycin and tigecycline in this study) both passively and actively, with the active release initiated by the presence of bacteria.

The authors tested the efficacy of the coating both in vitro and in vivo. In vitro, the release of antibiotics from the coating was enhanced in the presence of an oxidative environment, as would occur during a periprosthetic joint infection, demonstrating the coating’s “smartness.”

In vivo, using a mouse model of post-arthroplasty infection caused by Staphylococcus aureus, the authors showed radiographically that implants coated with PEG-PPS alone had a dramatic degree of periprosthetic osteolysis by postoperative day 7, compared with antibiotic-encapsulated PEG-PPS implants, which showed no detectable osteolysis. Similarly, the number of colony forming units of S. aureus cultured from implants on postoperative day 21 was significantly lower in the antibiotic-encapsulated implants than in the PEG-PPS-alone implants. (Interestingly, the tigecycline coating was more effective than the vancomycin coating in preventing bacterial colonization.)

While acknowledging that this proof-of-concept study needs to be replicated with other infectious organisms and in larger animals and humans, the authors conclude that PEG-PPS delivery of antibiotics has “great potential to minimize the incidence of postoperative infection following arthroplasty.”

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