title: Self-hardening calcium phosphate composite scaffold for bone tissue engineering.
abstract: Calcium phosphate cement (CPC) sets in situ to form solid hydroxyapatite, can conform to complex cavity shapes without machining, has excellent osteoconductivity, and is able to be resorbed and replaced by new bone. Therefore, CPC is promising for craniofacial and orthopaedic repairs. However, its low strength and lack of macroporosity limit its use. This study investigated CPC reinforcement with absorbable fibers, the effects of fiber volume fraction on mechanical properties and macroporosity, and the cytotoxicity of CPC-fiber composite. The rationale was that large-diameter absorbable fibers would initially strengthen the CPC graft, then dissolve to form long cylindrical macropores for colonization by osteoblasts. Flexural strength, work-of-fracture (toughness), and elastic modulus were measured vs. fiber volume fraction from 0% (CPC Control without fibers) to 60%. Cell culture was performed with osteoblast-like cells, and cell viability was quantified using an enzymatic assay. Flexural strength (mean+/-SD; n=6) of CPC with 60% fibers was 13.5+/-4.4 MPa, three times higher than 3.9+/-0.5 MPa of CPC Control. Work-of-fracture was increased by 182 times. Long cylindrical macropores 293+/-46 microm in diameter were created in CPC after fiber dissolution, and the CPC-fiber scaffold reached a macroporosity of 55% and a total porosity of 81%. The new CPC-fiber formulation supported cell adhesion, proliferation and viability. The method of using large-diameter absorbable fibers in bone graft for mechanical properties and formation of long cylindrical macropores for bone ingrowth may be applicable to other tissue engineering materials.
authors.affiliation: Paffenbarger Research Center, American Dental Association Foundation, National Institute of Standards and Technology, Building 224, Room A-153, 100 Bureau Drive Stop 8546, Gaithersburg, MD 20899, USA. hockin.xu@nist.gov
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
authors.forename: Carl G
authors.initials: CG
authors.lastname: Simon
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000737:chemistry*; D018786:Bone Substitutes / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D002448:Cell Adhesion; D002455:Cell Division; D002470:Cell Survival; D002478:Cells, Cultured; D051379:Mice; D023822:Tissue Engineering
chemical_list: D001843:Bone Cements; D018786:Bone Substitutes; D002130:Calcium Phosphates; C020243:calcium phosphate