2011 IR&D Annual Report

Design and Fabrication of Multi-Component Scaffolds for Bone Tissue Engineering, 01-R8078

Principal Investigators
XingGuo Cheng
Gianny Rossini

Inclusive Dates:  07/07/09 – 01/07/11

Background — The ideal bone scaffold should have a modulus match to that of bone, while also biodegradable, tough, cheap, easily processable and biocompatible. Moreover, the scaffold itself should be able to stimulate bone-like tissue growth and accommodate intrinsic or external osteo-inductive factors. In light of these requirements and challenges to repair and regenerate bone defect, this research project aims to develop Mg alloy-based scaffolds to stimulate bone growth.

Approach — To develop an ideal bone scaffold, SwRI researchers have developed a three-dimensionally coated, cylindrical, wrapped Mg alloy scaffold with interlayer spaces and lumen (Fig. 1a); in-vitro biocompatiblity testing methods using mesenchymal stem cells (MSCs, Fig. 1b) and in-vitro corrosion testing (electrochemical corrosion, mass, pH, etc.); and in-vivo testing methods using both rat and rabbit models. X-ray radiographs and micro-CT imaging, blood CPK measurement, SEM/EDX analysis and biomechanical testing have been used to characterize the implantation outcome.

Accomplishments — Without any external osteoinductive factors (BMP2, thrombin peptide TP508, gene transfer of BMP-6, platelet-rich plasma, stem cells and anabolic drugs), SwRI's Mg alloy scaffolds resulted in partial-to-full regeneration of rabbit critical-size ulna defects within 12 weeks. The statistical analysis showed that, on average, the intact ulnae and the implant-treated ulnae exhibited a similar biomechanical performance in one group.  Radiograph (Fig. 1c-d), SEM/EDX and Micro-CT analysis (Fig. 1e) indicated that bone-like tissue grows inside and outside the scaffold. This study suggests the SwRI-designed and fabricated Mg alloy scaffold is promising for bone regeneration.

Figure 1. (a) 3D coated biocompatible Mg alloy scaffold (3.5 mm diameter x 15 mm length); 
				(b) Image of live MSCs on coated Mg alloy; (c-d) Mg alloy scaffold implantation resulted in repair of a critical sized ulna defect; 
				(e) Micro-CT image of radio-dense bone-like tissue (red arrow) in and surrounding Mg alloy scaffold.
Figure 1. (a) 3D coated biocompatible Mg alloy scaffold (3.5 mm diameter x 15 mm length); (b) Image of live MSCs on coated Mg alloy; (c-d) Mg alloy scaffold implantation resulted in repair of a critical sized ulna defect; (e) Micro-CT image of radio-dense bone-like tissue (red arrow) in and surrounding Mg alloy scaffold.

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 10 technical divisions.
04/15/14