Poly(lactide-co-glycolide)/hydroxyapatite composite scaffolds for bone tissue engineering.

Biodegradable polymer/bioceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes such as brittleness and difficulty in shaping. However, conventional methods for fabricating polymer/bioceramic composite scaffolds often use organic solvents (e.g., the solvent casting and particulate leaching (SC/PL) method), which might be harmful to cells or tissues. Furthermore, the polymer solutions may coat the ceramics and hinder their exposure to the scaffold surface, which may decrease the likelihood that the seeded osteogenic cells will make contact with the bioactive ceramics. In this study, a novel method for fabricating a polymer/nano-bioceramic composite scaffold with high exposure of the bioceramics to the scaffold surface was developed for efficient bone tissue engineering. Poly(D,L-lactic-co-glycolic acid)/nano-hydroxyapatite (PLGA/HA) composite scaffolds were fabricated by the gas forming and particulate leaching (GF/PL) method without the use of organic solvents. The GF/PL method exposed HA nanoparticles at the scaffold surface significantly more than the conventional SC/PL method does. The GF/PL scaffolds showed interconnected porous structures without a skin layer and exhibited superior enhanced mechanical properties to those of scaffolds fabricated by the SC/PL method. Both types of scaffolds were seeded with rat calvarial osteoblasts and cultured in vitro or were subcutaneously implanted into athymic mice for eight weeks. The GF/PL scaffolds exhibited significantly higher cell growth, alkaline phosphatase activity, and mineralization compared to the SC/PL scaffolds in vitro. Histological analyses and calcium content quantification of the regenerated tissues five and eight weeks after implantation showed that bone formation was more extensive on the GF/PL scaffolds than on the SC/PL scaffolds. Compared to the SC/PL scaffolds, the enhanced bone formation on the GF/PL scaffolds may have resulted from the higher exposure of HA nanoparticles at the scaffold surface, which allowed for direct contact with the transplanted cells and stimulated the cell proliferation and osteogenic differentiation. These results show that the biodegradable polymer/bioceramic composite scaffolds fabricated by the novel GF/PL method enhance bone regeneration compared with those fabricated by the conventional SC/PL method.

[1]  S. Bruder,et al.  Osteogenic differentiation of purified, culture‐expanded human mesenchymal stem cells in vitro , 1997, Journal of cellular biochemistry.

[2]  J. Planell,et al.  Effect of the particle size on the micro and nanostructural features of a calcium phosphate cement: a kinetic analysis. , 2004, Biomaterials.

[3]  M. Bonfiglio,et al.  Immunological responses to bone. , 1972 .

[4]  J. Vacanti,et al.  Tissue-engineered growth of bone and cartilage. , 1993, Transplantation proceedings.

[5]  A. Mikos,et al.  Marrow stromal osteoblast function on a poly(propylene fumarate)/beta-tricalcium phosphate biodegradable orthopaedic composite. , 2000, Biomaterials.

[6]  L. Weiss,et al.  In vitro analysis of biodegradable polymer blend/hydroxyapatite composites for bone tissue engineering. , 1999, Journal of biomedical materials research.

[7]  Peter X Ma,et al.  Structure and properties of nano-hydroxyapatite/polymer composite scaffolds for bone tissue engineering. , 2004, Biomaterials.

[8]  R. Martinetti,et al.  Resorption of composite polymer-hydroxyapatite membranes: a time-course study in rabbit. , 1997, Biomaterials.

[9]  Young Ha Kim,et al.  Tissue Engineering of Smooth Muscle under a Mechanically Dynamic Condition , 2003 .

[10]  A. Coombes,et al.  Resorbable synthetic polymers as replacements for bone graft. , 1994, Clinical materials.

[11]  F. Delannay,et al.  The influence of high sintering temperatures on the mechanical properties of hydroxylapatite , 1995 .

[12]  Byung-Soo Kim,et al.  Thermally produced biodegradable scaffolds for cartilage tissue engineering. , 2004, Macromolecular bioscience.

[13]  D J Mooney,et al.  Open pore biodegradable matrices formed with gas foaming. , 1998, Journal of biomedical materials research.

[14]  C T Laurencin,et al.  A novel amorphous calcium phosphate polymer ceramic for bone repair: I. Synthesis and characterization. , 2001, Journal of biomedical materials research.

[15]  Cato T Laurencin,et al.  Novel polymer-synthesized ceramic composite-based system for bone repair: an in vitro evaluation. , 2004, Journal of biomedical materials research. Part A.

[16]  Byung-Soo Kim,et al.  A poly(lactic acid)/calcium metaphosphate composite for bone tissue engineering. , 2005, Biomaterials.

[17]  K. Leong,et al.  The design of scaffolds for use in tissue engineering. Part I. Traditional factors. , 2001, Tissue engineering.

[18]  Y. Koyama,et al.  In Vitro and In Vivo Tests of Newly Developed TCP/CPLA Composites , 1997 .

[19]  Young Ha Kim,et al.  Smooth muscle-like tissues engineered with bone marrow stromal cells. , 2004, Biomaterials.

[20]  R. Reis,et al.  Bionert and biodegradable polymeric matrix composites filled with bioactive SiO2−3CaO·P2O5−MgO glasses and glass-ceramics , 1997 .

[21]  Lichun Lu,et al.  Synthetic bone substitutes , 2000 .

[22]  P. Ma,et al.  Poly(alpha-hydroxyl acids)/hydroxyapatite porous composites for bone-tissue engineering. I. Preparation and morphology. , 1999, Journal of biomedical materials research.

[23]  Min Wang,et al.  Developing bioactive composite materials for tissue replacement. , 2003, Biomaterials.

[24]  M. Textor,et al.  Biodegradable polymer/hydroxyapatite composites: surface analysis and initial attachment of human osteoblasts. , 2001, Journal of biomedical materials research.

[25]  H. D. Boer THE HISTORY OF BONE GRAFTS , 1988 .

[26]  Cato T. Laurencin,et al.  Advancements in tissue engineered bone substitutes , 1999 .

[27]  D. Wise,et al.  Enhanced bioactivity of a poly(propylene fumarate) bone graft substitute by augmentation with nano-hydroxyapatite. , 2003, Bio-medical materials and engineering.

[28]  Seung‐Woo Cho,et al.  Engineering of volume-stable adipose tissues. , 2005, Biomaterials.

[29]  M. Falk,et al.  Factors influencing synthesis and mineralization of bone matrix from fetal bovine bone cells grown in vitro , 1992, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[30]  L. Guan,et al.  Preparation and characterization of a highly macroporous biodegradable composite tissue engineering scaffold. , 2004, Journal of biomedical materials research. Part A.

[31]  Minna Kellomäki,et al.  Tissue reactions of subcutaneously implanted mixture of ε-caprolactone-lactide copolymer and tricalcium phosphate. An electron microscopic evaluation in sheep , 2003, Journal of materials science. Materials in medicine.