NANOSTRUCTURED BIOMATERIALS: NANOHYDROXYAPATITE/COLLAGEN

SCAFFOLDS SUPPLEMENTED WITH SPARC AS FACILITATORS IN BONE ENGINEERING

A. Y. Pataquiva-Mateus1,2,3 H.-C. Wu1,4 C. Lucchesi 1 M. P. Ferraz 5 F. J. Monteiro 2,3 M.

Spector 1,6 1 Tissue Engineering, VA Boston Healthcare System, Boston, Massachusetts 2 Laboratório de Biomateriais, INEB — Instituto de Engenharia Biomédica, Porto, Portugal 3 Departamento de Engenharia Metalúrgica e Materiais, Universidade do Porto, Porto, Portugal 4 Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan 5 Universidade Fernando Pessoa, Porto, Portugal 6 Orthopaedic Research, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts

Key Words: collagen, mineralization, stem cells, biomaterials availability, bone. Abstract. Bone exhibits natural hydroxyapatite crystals with needle-like or rod-like shapes, well arranged within the polymeric matrix of collagen type I. These natural nanoparticles formed in physiological environment have a more dynamic response by bone cells when compared to synthetic material with larger particle size. Added to this, the nonstructural extracellular matrix-associated protein, SPARC (Secreted Protein Acidic and Rich in Cysteine) is known to play a role in the mineralization of collagen in bone formation. Thus, the objective of this study was to determine the degree to which SPARC supplementation of type I collagen scaffolds in vitro enhanced the uptake of calcium and phosphorus when the scaffolds were soaked in a calcium phosphate solution and a suspension of hydroxyapatite nanoparticles. For this, hydroxyapatite nanoparticles were prepared using a chemical precipitation synthesis based on H3PO4, Ca(OH)2 and a surfactant, SDS (sodium dodecylsulphate), as starting reagents; and later added to collagen type 1 sponges. The calcium and phosphorus contents of the scaffolds were evaluated by inductively coupled plasma analysis, and the elastic modulus of the scaffolds determined by unconfined compression testing. Scaffolds were seeded with goat bone marrow-derived mesenchymal stem cells and the cell-seeded constructs grown in osteogenic medium. Supplementation of the scaffolds with as little as 0.008 % by wt. of collagen resulted in a increase in the binding of hydroxyapatite nanoparticles to the scaffold, but had no effect on incorporation of calcium or phosphorus from a calcium phosphate solution. The incorporation of hydroxyapatite nanoparticles into the scaffolds did not result in an increase in modulus. Supplementation of the scaffolds with SPARC and the increase in the binding of hydroxyapatite nanoparticles did not affect the proliferation of mesenchymal stem cells. References Pataquiva-Mateus AY, Wu H-C, Lucchesi C, Ferraz MP, Monteiro FJ, Spector M. Supplementation of collagen scaffolds with SPARC to facilitate mineralization. J Biomed Mater Res B 2012;100B:862–870

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