Comparative in vitro study of calcium phosphate ceramics for their potency as scaffolds for tissue engineering.

BACKGROUND: Calcium phosphate ceramics have been widely considered as scaffolds for bone tissue engineering. Selection of the best support for cultured cells, crucial for tissue engineered systems, is still required. OBJECTIVE: We examined three types of calcium phosphate compounds: α-tricalcium phosphate - the most soluble one, carbonate hydroxyapatite - chemically the most similar to the bone mineral and biphasic calcium phosphate - with the best in vivo biocompatibility in order to select the best support for osteoblastic cells for tissue engineered systems. METHODS: Human osteoblasts were tested in direct contact with both dense samples and 3D scaffolds in either static or dynamic culture. Cell viability, cell spreading, osteogenic cell capacity, and extracellular matrix production were examined. RESULTS: The obtained data indicate that biphasic calcium phosphate is the optimal cell-supporting material. In addition, dynamic culture improved cell distribution in the scaffolds, enhanced production of the extracellular matrix and promoted cells osteogenic capacity. CONCLUSIONS: Biphasic calcium phosphate should be recommended as the most suitable matrix for osteogenic cells expansion and differentiation in tissue engineered systems.

Physicochemical properties of the novel biphasic hydroxyapatite-magnesium phosphate biomaterial.

Besides high-temperature calcium phosphates (CaPs), low-temperature calcium phosphate bone cements (CPCs), due to excellent biological properties: bioactivity, biocompability and osteoconductivity, are successfully used as bone substitutes. However, some disadvantages, related mainly to their low resorption rate and poor mechanical properties result in limited range of applications of these implant materials to non-loaded places in the skeletal system. To overcome this problem, magnesium phosphate cements (MPCs) with high strength have been considered as biomaterials. The main disadvantage of MPCs is that the acid-base setting reaction is an exothermic process that must be strictly controlled to avoid tissue necrosis. In this work, a new composite bone substitute (Hydroxyapatite Magnesium Phosphate Material - HMPM) based on hydroxyapatite (HA) and magnesium phosphate cement (MPC) with sodium pyrophosphate applied as a retardant of setting reaction was obtained. Its setting time was adequate for clinical applications. Combining properties of HA and MPC has made it possible to obtain microporous (showing bimodal pore size distribution in the range of 0.005-1.700 micrometers) potential implant material showing good surgical handiness and sufficient mechanical strength. Effectiveness of sodium pyrophosphate as a retardant of exothermic setting reaction of the new cement formulation was confirmed. After setting and hardening, the material consisted of hydroxyapatite and struvite as crystalline phases. Unreacted magnesium oxide was not detected.

[Application of porous composite hydroxyapatite-TCP implants in orthopaedic surgery]. / Zastosowanie porowatych wszczepów kompozytowych hydroksyapatyt-TCP w ortopedii.

Bone grafts are the basic material in bone deficit filling. Due to difficulties to obtain bone grafts often the bone substitutes are used. Authors presents chemical, mineralogic and biologic properties of hydroxyapatite and ceramic material based on calcium phosphorate. HAp-TCP has a wide applications in bone deficit filling in knee and hip arthroplasty or revision arthroplasty, bone cysts, wrist and ankle joint arthrodesis. Bone substitutes should be mix with bone grafts, in the cases where load bearing is needed, because of their weak mechanical strength. Further clinical and experimental studies should be continued to get new generation of material on the calcium phoshorate base. This new material should present higher mechanical strength with preserving osteocondactive and osteoinductive properties of hydroxyapatite.