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Biocomposites prepared by alkaline phosphatase mediated mineralization of alginate microbeads

Xie, Minli, Olderøy, Magnus Ø., Zhang, Zhibing, Andreassen, Jens-Petter, Strand, Berit L., Sikorski, Pawel
RSC advances 2012 v.2 no.4 pp. 1457-1465
X-ray diffraction, alginates, alkaline phosphatase, biocomposites, biomimetics, gels, hydroxyapatite, microbeads, mineral content, mineralization, modulus of elasticity, nanocrystals, scanning electron microscopy, thermal stability, thermogravimetry, transmission electron microscopy
This study set out to develop a biomimetic scaffold by incorporating osteoinductive hydroxyapatite (HA) particles into a porous alginate gel matrix via a cell-friendly pathway. Two types of alginate/calcium phosphate (Alg/CP) composites were prepared through alkaline phosphatase (ALP) mediated mineralization and counter-diffusion precipitation. Structural characteristics were analyzed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Thermal stability and mineral content were studied by means of thermogravimetric (TG) analysis. X-ray diffraction (XRD) and Rietveld refinement showed the presence of bone-like hydroxyapatite. Our studies suggested that the gradual nature of enzymatic process together with alginate matrices provide regulation of nanocrystalline hydroxyapatite formation. The ALP-mediated mineralization process has great advantages over counter-diffusion precipitation, providing homogenous mineral distributions, smaller crystal sizes, and increased apparent Young's moduli, which creates a better structure for bone defect repair scaffolds.