Nanocrystalline hydroxyapatite and calcium sulphate as biodegradable composite carrier material for local delivery of antibiotics in bone infections

The use of polymethylmetacrylate beads for local delivery of antibiotics requires a second surgical procedure for their removal and resorbable calcium sulphate exhibits cytotoxic effects. In this work, a bioresorbable composite of calcium sulphate and nanoparticulate hydroxyapatite (PerOssal®) was studied regarding its antibiotic release properties and biocompatibility. Material characteristics of plain PerOssal® and pure calcium sulphate pellets were studied using scanning and electron microscopy and X-ray methods. Pellets were soaked with gentamicin and vancomycin, respectively. Release properties of both antibiotics from both materials were investigated over 10 days. Quantitative and qualitative cytotoxic assays were performed for biocompatibility testing. Specific surface was 106m2/g for PerOssal® and 2.2m2/g for pure calcium sulphate. Almost complete elution of gentamicin was found for both carrier materials (94.7% for PerOssal® vs. 95.8% for calcium sulphate) within 10 days, whereas vancomycin release was higher for PerOssal® (96.3% vs. 74.8%). PerOssal® showed higher initial and lower release after approximately 5 days compared to calcium sulphate. No significant in vitro cytotoxic differences were found between PerOssal® and nontoxic cell culture medium. Calcium sulphate showed cytotoxic effects in two out of four tests. PerOssal® exhibits excellent properties regarding resorption, biocompatibility, and antibiotic release.