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Co-extruded Tissue Engineering Scaffolds and Characterization of Tissue Development using Magnetic Resonance Imaging

Newell Washburn,  Polymers (854)/MSEL

Tissue engineering is a new paradigm in medicine with the goal of regenerating missing or damaged tissue. One strategy is to develop scaffolds that, after surgical implantation, will initially serve as a mechanical support but over time will coax cells into proliferating, differentiating, and organizing themselves into functional tissue. Scaffolds under consideration for such applications are generally made out of polymers and in this work a new method for producing them has been developed using techniques borrowed from polymer processing. Biocompatible polymers such as poly(caprolactone) or poly(ethyl methacrylate)  were blended with a water-soluble, biocompatible polymer such as poly(ethylene oxide) in a twin-screw extruder. Annealing the blends followed by dissolution of the poly(ethylene oxide) with water results in a porous material having a continuous network of void space with characteristic lengths scales that may be tuned to greater than 100 µm, the relevant size scale for tissue engineering.. The characteristic length scale of the void space can be controlled by varying the blend composition and annealing conditions. Cell proliferation studies indicated that the extruded polymers retain their biocompatibility. This method does not require the use of potentially toxic organic solvents and is amenable to both laboratory- and industrial-scale production.

Tissue development on the scaffolds was characterized using magnetic resonance imaging (MRI) and histological techniques. We chose to study the proliferation of osteoblasts in the scaffolds and monitored the early events in bony matrix production, namely collagen production and mineral deposition. The use of MRI permits the in situ monitoring of these important processes using standard methods such as magnetization transfer. These results compared favorably against standard histological analysis where sections of the cell-seeded scaffold were stained and photographed, suggesting MRI may be a valuable tool for investigating tissue development.