Biomed. Eng.-Biomed. Tech. 2018; aop Steffi Grohmann, Manuela Menne, Diana Hesse, Sabine Bischoff, René Schiffner, Michael Diefenbeck and Klaus Liefeith* Biomimetic multilayer coatings deliver gentamicin and reduce implant-related osteomyelitis in rats https://doi.org/10.1515/bmt-2018-0044 Received March 20, 2018; accepted July 16, 2018 Abstract: Implant-related infections like periprosthetic joint infections (PJI) are still a challenging issue in ortho- pedic surgery. In this study, we present a prophylactic anti-infective approach based on a local delivery of the antibiotic gentamicin. The local delivery is achieved via a nanoscale polyelectrolyte multilayer (PEM) coating that leaves the bulk material properties of the implant unaf- fected while tuning the surface properties. The main components of the coating, i.e. polypeptides and sulfated glycosaminoglycans (sGAG) render this coating both bio- mimetic (matrix mimetic) and biodegradable. We show how adaptions in the conditions of the multilayer assem- bly process and the antibiotic loading process affect the amount of delivered gentamicin. The highest concentra- tion of gentamicin could be loaded into films composed of polypeptide poly-glutamic acid when the pH of the load- ing solution was acidic. The concentration of gentamicin on the surface could be tailored with the number of depos- ited PEM layers. The resulting coatings reveal a bacterio- toxic effect on Staphylococcus cells but show no signs of cytotoxic effects on MC3T3-E1 osteoblasts. Moreover, when multilayer-coated titanium rods were implanted into contaminated medullae of rat tibiae, a reduction in the development of implant-related osteomyelitis was observed. This reduction was more pronounced for the multifunctional, matrix-mimetic heparin-based coatings that only deliver lower amounts of gentamicin. Keywords: antibacterial effect; antibiotics; drug delivery; loading capacity; polyelectrolyte multilayers. Abbreviations: CS, chondroitin sulfate; ECM, extracellular matrix; GM, aminoglycoside gentamicin; Hep, heparin; PA, polyanion; PEM, polyelectrolyte multilayer; PGA, poly-glutamin acid; PJI, periprosthetic joint infection; PLL, poly-L-lysin; QCM-D, quartz-crystal-microbalance with dissipation; ROI, region of interest; sGAG, sulfated glycosaminoglycans. Introduction Surgical site infections are a serious complication in the field of orthopedic and trauma surgery. While their fre- quency is approximately 1–4% for primary joint replace- ment surgery [1–4], it dramatically increases for revision surgery (up to ∼40% according to Trampuz and Widmer [5]). Recently, it was further reported that the 5-year mor- tality rate for patients diagnosed with periprosthetic joint infection (PJI) was even higher than for certain types of cancer like breast cancer [6, 7]. Systemic antibiotic proph- ylaxis is the preferred therapy as a clinical standard to reduce the risk for PJI. However, a local delivery of antibi- otics is the favorable approach for the administration of antibiotics, as prophylactic systemic administration also implies a high risk of sub-inhibitory antibiotic concentra- tion at the site of implantation [8]. For this reason, recent research was focused on the development of systems that locally deliver antibiotics (reviewed in [9, 10]). Respective systems provide surgeons with the possibility of using local antibiotics, like aminoglycoside gentamicin (GM), that may usually cause side effects when administered systemically in higher doses. GM is a cheap, broad-spectrum antibiotic with a rapid, dose-dependent activity [11] but has the risk of ototoxicity when it is administered in a systemic therapy. In a recent study, the risk of cytotoxicity could be overcome by local delivery of effective concentrations where no signs of cytotoxic effects on osteoblasts were observed [12]. Due to GM’s good effectivity against staphylococci which accounts for up to 65% of all PJI [10], it is success- fully locally applied when delivered in cement spacers *Corresponding author: Klaus Liefeith, Institute for Bioprocessing and Analytical Measurement Techniques (iba) e.V., Department of Biomaterials, 37308 Heilbad Heiligenstadt, Germany, Phone: +49-3606-671500, Fax: +49-3606-671200, E-mail: Klaus.liefeith@iba-heiligenstadt.de Steffi Grohmann, Manuela Menne and Diana Hesse: Institute for Bioprocessing and Analytical Measurement Techniques (iba) e.V., Department of Biomaterials, 37308 Heilbad Heiligenstadt, Germany Sabine Bischoff: Institute for Laboratory Animal Science and Welfare, University Hospital, 07743 Jena, Germany René Schiffner: Orthopaedic Department, University Hospital, 07743 Jena, Germany Michael Diefenbeck: Scientific Consulting in Orthopaedic Surgery and Traumatology, 22081 Hamburg, Germany Brought to you by | Imperial College London Authenticated Download Date | 9/24/18 12:32 PM