Tissue Engineered Bone Using Polycaprolactone Scaffolds Made by Selective Laser Sintering
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Tissue Engineered Bone Using Polycaprolactone Scaffolds Made by Selective Laser Sintering J.M. Williams1, A. Adewunmi2, R.M. Schek1,3, C.L. Flanagan1, P.H. Krebsbach1,3, S.E. Feinberg5, S.J. Hollister1,2,4, S. Das2 1
Biomedical Engineering, 2Mechanical Engineering, 3Dentistry, 4Surgery, 5Oral and Maxillofacial Surgery, University of Michigan, Ann Arbor, Michigan, 48109-0018, USA ABSTRACT Polycaprolactone is a bioresorbable polymer that has potential for tissue engineering of bone and cartilage. In this work, we report on the computational design and freeform fabrication of porous polycaprolactone scaffolds using selective laser sintering, a rapid prototyping technique. The microstructure and mechanical properties of the fabricated scaffolds were assessed and compared to designed porous architectures and computationally predicted properties. Compressive modulus and yield strength were within the lower range of reported properties for human trabecular bone. Finite element analysis showed that mechanical properties of scaffold designs and of fabricated scaffolds can be computationally predicted. Scaffolds were seeded with BMP-7 transduced fibroblasts and implanted subcutaneously in immunocompromised mice. Histological evaluation and micro-computed tomography (µCT) analysis confirmed that bone was generated in vivo. Finally, we have demonstrated the clinical application of this technology by producing a prototype mandibular condyle scaffold based on an actual pig condyle. INTRODUCTION Repair and reconstruction of complex joints such as the temporo-mandibular joint (TMJ) pose many challenges for bone tissue engineering. Adverse reactions to alloplastic, nonbiological materials result in compromised functional outcome in patients and autogenous grafts can lead to complications elsewhere in the patient [1,2]. Tissue engineering may overcome these limitations by the use of scaffolds that fit into anatomic defects, possess mechanical properties that will bear in vivo loads, enhance tissue in-growth, and produce biocompatible degradation byproducts [3-9]. Solid freeform fabrication techniques (SFF) enable design and fabrication of anatomically shaped scaffolds with varying internal architectures, thereby allowing precise control over pore size, porosity, permeability, and stiffness [10]. Control over these characteristics may enhance cell infiltration and cellular communications, and mass transport of nutrients and metabolic waste throughout the scaffold. One such SFF method, selective laser sintering (SLS), may be advantageous for creating bone tissue engineering scaffolds for sites such as the TMJ, because it provides a cost-effective, efficient method for constructing scaffolds matching the complex anatomical geometry of craniofacial or periodontal structures, where preformed materials might be difficult or ineffective [1]. SLS constructs scaffolds from 3-D digital data by sequentially fusing selected regions in a powder bed, layer by layer, via a computer controlled scanning laser beam [11,12]. With SLS, virtua
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