Brushite-based calcium phosphate cement with multichannel hydroxyapatite granule loading for improved bone...

Current bone graft materials face limitations in biodegradation rates and tissue integration. Traditional calcium phosphate cements (CPCs) often lack sufficient porosity to support tissue in-growth. While tri-calcium phosphate (TCP) is known for its osteoconductive properties, its integration into CPC systems remains underexplored. The role of micro-channels in enhancing degradation and bone infiltration is not well established. Sodium and silicon have been proposed to influence CPC setting and biodegradation, but their combined effect is unclear. Existing CPC formulations struggle to balance mechanical strength with degradation rates. The fibrous monolithic (FM) process for HAp granules has not been widely applied in CPC systems. This gap motivated the development of a CPC system with micro-channeled HAp granules to improve bone regeneration.

The aim of this study was to develop a novel brushite-based CPC system with micro-channeled hydroxyapatite (HAp) granules to improve bone regeneration. The specific problem addressed is the limited tissue integration and controlled degradation of conventional CPCs. The motivation stems from the need for implants that degrade in sync with new bone formation. The study focused on incorporating micro-channeled HAp granules to enhance degradation and tissue access. Sodium and silicon were added to modify the CPC’s setting behavior and biodegradation. The FM process was used to fabricate HAp granules with defined micro-channels. The goal was to maintain compressive strength while introducing porosity. In vivo testing was conducted to assess bone in-growth and degradation rates.

A sodium- and silicon-rich calcium phosphate powder was synthesized via a wet chemical route. The powder was combined with mono-calcium phosphate monohydrate (MCPM) to form the CPC matrix. TCP nanopowder acted as a packing filler and reaction moderator. HAp granules were produced using the fibrous monolithic (FM) process, resulting in 800 µm diameter cylinders with seven micro-channels. Acid sodium pyrophosphate and sodium citrate solution served as the liquid component, controlling setting time and homogeneity. The CPC was mixed with the micro-channeled HAp granules to introduce porosity. Compressive strength was measured to assess mechanical properties. In vivo testing involved creating critical size femoral defects in rabbits and monitoring bone regeneration over 1 and 2 months.

The CPC system with micro-channeled HAp granules showed accelerated degradation of the brushite matrix. Bone tissue infiltration was observed through the micro-channels in the CPC. The granules introduced porosity without significantly reducing compressive strength. In vivo results showed excellent bone in-growth after two months of implantation. The micro-channels provided a direct pathway for tissue access into the CPC matrix. Sodium and silicon addition influenced the setting behavior and degradation rate. The FM process allowed precise fabrication of HAp granules with defined micro-channels. The CPC retained sufficient mechanical integrity while promoting tissue integration.

The authors propose that the CPC system with micro-channeled HAp granules improves bone regeneration by enhancing degradation and tissue access. The micro-channels in the HAp granules facilitated bone in-growth into the CPC matrix. The addition of sodium and silicon modified the setting and degradation behavior of the CPC. The FM process enabled controlled fabrication of HAp granules with defined micro-channels. The CPC retained compressive strength while introducing porosity. In vivo results supported the hypothesis that the system promotes bone regeneration. The study suggests that micro-channeled granules can be used to improve CPC performance. The findings indicate that this approach may be useful in bone repair applications.