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 μm 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. Published by Elsevier Ltd. on behalf of Orthopuedic Research Society. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.

Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures

“…3A and C were similar to those of previous values and suitable for cell infiltration and tissue ingrowth. Furthermore, the dissolution of fibers in the strong layer would create cylindrical macropore channels about the diameter of the fibers (322 μm) as shown in previous studies [34,35].…”

“…A number of other studies investigated the setting reaction [8], in vitro aging [12], macroporous scaffolds [22][23][24][25][26][32][33][34][35], and shelf life of CPC [38]. Fast-setting and anti-washout CPC were also formulated [9,35,39].…”

“…As in that study, the suture was cut to filaments of 8 mm in length and randomly mixed into the CPC paste. A fiber volume fraction of 30% (fiber volume/specimen volume) was used following a previous study, which showed that it provided substantial reinforcement without rendering the paste too dry [34].…”

Self-Setting Calcium Orthophosphate Formulations: Cements, Concretes, Pastes and Putties

“…Another shortcoming is the lack of strength of the resulting material, especially if particulates dissolve quickly, greatly limiting its applications. An innovative approach that aims at overcoming the lack of interconnectivity and initial strength consists in using resorbable fibers [319][320][321][322][323][324][325][326]. These fibers have the function of reinforcing the cement, providing the needed short-term strength and toughness, and gradually dissolving afterwards, leaving behind macropores suitable for bone ingrowth.…”

“…In the cases, when bioresorbable reinforcement fibers are used, strength augmentation is attained at the initial stages [319][320][321][322][323][324][325][326]. For example, the initial strength of a concrete was threefold higher than that of the unreinforced cement control [319].…”