Formation of calcium phosphate/collagen composites through mineralization of collagen matrix

Abstract

Several types of calcium phosphate/collagen composites, including noncrystalline calcium phosphate/collagen, poorly crystalline carbonate-apatite (PCCA)/collagen, and PCCA + tetracalcium phosphate/collagen composites, were prepared through the mineralization of collagen matrix. The type I collagen was presoaked with a PO(3-)(4) containing solution and then immersed in a Ca(2+) containing solution to allow mineral deposition. The solution of 0.56 M sodium dibasic phosphate (Na(2)HPO(4)) with a pH of nearly 14 was metastable and its crystallization produced Na(2)HPO(4) and sodium tripolyphosphate hexahydrate (Na(5)P(3)O(10)). 6H(2)O), leading to a controlled release of orthophosphate ions during the subsequent mineral precipitation. The development of the composites was investigated in detail. The mineral contributed up to 60-70% of the weight of the final composites. The strength and Young's modulus of the composites in tensile tests overlapped the lower range of values reported for bone. When implanted in muscle tissue, the composite showed biodegradability that was partly through a multinucleated giant cell mediated process. In a bone explant culture model it was observed that bone-derived cells deposited mineralizing collagenous matrix on the composite.

Influence of a novel calcium-phosphate coating on the mechanical properties of highly porous collagen scaffolds for bone repair

“…However, porosities of only 60-70% (Vance et al 2005) and 80-85% (Kim et al 2005) are reported. With a similar CP process and commercially available Gelfix scaffolds, Yaylaoglu et al, Kose et al and Du et al claim similar material results to our study of precipitated CP to a collagen scaffold (Du et al 2000, Kose et al 2004, Yaylaoglu et al 1999. However no data on the mechanical properties of these scaffolds is available to support their assumption.…”

“…However, as each scaffold consists of some phase which is not found naturally in the human body, they have all exhibited drawbacks with biocompatibility, biodegradability or osteconductivity (Rezwan et al 2006). Natural collagen scaffolds coated with HA or CP have been investigated using a bi-phasic immersion process with promising results in terms of their biological performance (Du et al 2000, Yaylaoglu et al 1999. However, this study used commercially available collagen sheets with initial porosities of 50-60% which is very low compared to collagen sheets developed by O'Brien et al (2004) with a porosity of 99.5%.…”

“…Both studies use different techniques (i.e. immersion sequences and rinsing steps between coating treatments), exposure times and concentrations of the solutions (Du et al 2000, Yaylaoglu et al 1999) and the optimal process for coating collagen scaffolds with CP is yet to be elucidated.…”

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…The collagen molecules and the nanocrystals of biological apatite assembled into mineralized fibrils are approximately 6-nm-diameter and 300-nm-long [31,35,38,510,589]. Although the complete mechanisms involved in the bone building strategy are still unclear, the strengthening effect of apatite nanocrystals in calcified tissues might be explained by the fact that the collagen matrix is a load transfer medium and thus transfers the load to the intrinsically rigid inorganic nanocrystals.…”

Nanostructured Injectable Cell Microcarriers for Tissue Regeneration

“…Incorporating HAP, an important inorganic component of bone ECM, into synthetic microspheres to fabricate a composite material with enhanced osteoconductivity is one example of a composite microsphere. The nanoscale organization of HAP within a polymeric matrix provides increased hydrophilicity, future science group Review Zhang, Eyster & Ma wettability, surface area and surface roughness, which leads to enhanced osteoblast adhesion and osteoconductivity and better bonding to host bone for long-term functionality [126,127]. One approach for organizing HAP at the nanoscale is through in situ precipitation of apatite crystals within a polymer or macromolecular solution [122,123].…”