A gentamicin-loaded hydroxyapatite/collagen bone-like nanocomposite (GNT-HAp/Col) was fabricated and evaluated for its absorption–desorption properties, antibacterial efficacy, and cytotoxicity. The hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) powder was mixed with gentamicin sulfate (GNT) in phosphate-buffered saline (PBS) at room temperature. After 6 h mixing, the GNT adsorption in all conditions reached plateau by Langmuir’s isotherm, and maximum GNT adsorption amount was 34 ± 7 μg in 250 μg/mL GNT solution. Saturated GNT-loaded HAp/Col powder of 100 mg was soaked in 10 mL of PBS at 37 °C and released all GNT in 3 days. A shaking culture method for a GNT extraction from the GNT-HAp/Col and an inhibition zone assay for the GNT-HAp/Col compact showed antibacterial efficacy to Escherichia coli (E. coli) at least for 2 days. From the release profile of the GNT from the GNT-HAp/Col powder, antibacterial efficacy would affect E. coli at least for 3 days. Further, no cytotoxicities were observed on MG-63 cells. Thus, the GNT-HAp/Col is a good candidate of bioresorbable anti-infection bone void fillers by prevention initial infections, which is the primary cause of implant-associated infection even for rapid bioresorbable materials.

Osteosarcoma has a poor survival rate due to relapse and metastasis. Zoledronic acid (ZOL), an anti-resorptive and anti-tumor agent, is used for treating osteosarcoma. Delivery of ZOL to the target region is difficult due to its high binding affinity to bone minerals. This study developed a novel treatment for osteosarcoma by delivering ZOL to the target region locally and sustainably. In this study, we fabricated a novel bone substitute by loading ZOL on β-tricalcium phosphate (β-TCP). The ZOL-loaded β-TCP (ZOL/β-TCP) would be expected to express the inhibitory effects via both bound-ZOL (bound to β-TCP) and free-ZOL (release from ZOL/β-TCP). To explore the ability to release ZOL from the ZOL/β-TCP, the amount of released ZOL was measured. The released profile indicates that a small amount of ZOL was released, and most of it remained on the β-TCP. Our data showed that ZOL/β-TCP could successfully express the effects of ZOL via both bound-ZOL and free-ZOL. In addition, we examined the biological effects of bound/free-ZOL using osteosarcoma and osteoclasts (target cells). The results showed that two states of ZOL (bound/free) inhibit target cell activities. As a result, ZOL/β-TCP is a promising candidate for application as a novel bone substitute.

Influences of combined supplementation of calcium citrate (Ca–Cit) and calcium carbonate (CaCO₃) on the hydroxyapatite/collagen (HAp/Col)–sodium alginate (Na–Alg) paste (HAp/Col paste) were investigated. Supplementation amounts of Ca–Cit and CaCO₃ were denoted as Nx, where N is a multiplication number to Ca²⁺ ion amounts for the equivalent reaction with Na–Alg obtained previously. Combined supplementation of 10x Ca–Cit and 2x CaCO₃ improved the anti-washout property at a washout ratio of 2.42 ± 0.72% and pH maintenance at 7.34 ± 0.08, these values were better than the best HAp/Col paste using Ca–Cit (5.91 ± 2.73% washout ratio and 6.72 ± 0.06 of pH). This is due to coordinate effects of initial washout inhibition by weak but rapid formation of long-range network by citric acid followed by long term anti-washout inhibition by strong but slow network formation by Ca²⁺ ions. The paste also showed good cytocompatibilty that MG63 cells proliferated with the culture time without any significant difference with the HAp/Col dense bodies. The HAp/Col paste is expected to be utilized in minimally invasive surgery of bone defect.