Biomechanical and antibacterial properties of Tobramycin loaded hydroxyapatite coated fixation pins

Abstract

The present study investigates the use of nanoporous, biomimetic hydroxyapatite (HA) coatings deposited on TiO₂ coated fixation pins as functional implant surfaces for the local release of Tobramycin in order to prevent bacterial colonization. The impact of HA-coating thickness, coating morphology and biomechanical forces during insertion into synthetic bone on the drug loading and release properties are analyzed. The coatings are shown to exhibit bactericidal effects against Staphylococcus aureus in agar medium for a duration of 6 days after loading by adsorption with Tobramycin for only 5 min at elevated temperature and pressure. Furthermore, high performance liquid chromatography analysis shows a drug release in phosphate buffered saline for 8 days with antibiotic concentration remaining above the minimal inhibitory concentration for S. aureus during the entire release period. Biomechanical insertion tests into synthetic bone and conventional scratch testing demonstrate adhesive strength at the HA/TiO₂ interface. Biocompatibility is verified by cell viability tests. Outgrowth endothelial cells, as well as primary osteoblasts, are viable and firmly attached to both HA and TiO₂ surfaces. The results presented are encouraging and support the concept of functional HA coatings as local drug delivery vehicles for biomedical applications to treat as well as to prevent post-surgical infections.

Biomimetic Hydroxyapatite Coated Titanium Screws Demonstrate Rapid Implant Stabilization and Safe Removal <i>In-Vivo</i>

“…The results obtained in the current study demonstrated biomechanical resistance of the HA coating during insertion in-vivo. This has also been shown with the same type of biomimetic HA coatings in-vitro on external fixation pins by using different synthetic bone qualities [47] [48]. Nevertheless in-vivo proof was lacking in these studies.…”

Antifouling and antimicrobial biomaterials: an overview

“…In more recent years, grit‐blasted and mesoporous materials, such as hydroxyapatite (HA), have been also loaded with gentamicin and tobramycin . The release and efficacy of vancomycin hydrochloride, cephalothin sodium, amoxicillin and carbenicillin sodium salts have been also tested when incorporated in HA coatings .…”

Impact of Biomechanical Forces on Antibiotics Release Kinetics from Hydroxyapatite Coated Surgical Fixation Pins

“…Within the foam structure, the delaminated HA-B fragments showed a flake like morphology, which reflects the "as-deposited" coating morphology [15]. The size of delaminated HA-B fragments, Figure 2(c), is comparable to those observed during conventional scratch testing of the TiO 2 /HA-B coating system [32].…”

“…Biomechanical properties were evaluated using polyurethane (25 PU) foam blocks (20 mm × 20 mm × 4 mm) mimicking spongy bone quality. 25 PU was chosen, since preliminary tests demonstrated that this particular grade induced more severe coating wear-effects after insertion compared to higher density synthetic bone qualities reflecting cancellous bone structures [32]. Three fixation pins of each sample type were loaded with Tobramycin via adsorption at room temperature, denoted as HA-B_RT_BML, or under elevated temperature and pressure, denoted as HA-B_PHT_BML followed by biomechanical insertion.…”