We have fabricated pliable, porous, biodegradable scaffolds with poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) blends using a solvent-casting and particulate-leaching technique. Our study investigated the effects of four different processing parameters on pliability and pore morphology of the biodegradable scaffolds. The parameters investigated were the PLGA copolymer ratio, the PLGA/PEG blend ratio, the initial salt weight fraction, and the salt particle size. A wide range of shear moduli (0.59 to 9.55 MPa), porosities (0.798 to 0.942), and median pore diameters (71 to 154 microns) was able to be achieved by varying the combination of these parameters. Our study indicates that initial salt weight fraction and PLGA/PEG blend ratio have the most significant effects on the physico-mechanical properties of the scaffolds. Enhanced pliability of the three dimensional foams made with blends of PLGA and PEG is evidenced by the ability to roll them into a tube without macroscopic damage to the scaffold. Pliable polymer substrates hold great promise for regeneration of soft tissues such as skin, or those requiring a tubular conformation such as intestine or vascular grafts.
The emerging field of tissue engineering is yielding a variety of new strategies for bone replacement. In vivo assessment of candidate bone substitutes to demonstrate biocompatibility, degradability, and the ability to produce meaningful quantities of bone is essential prior to clinical use. We present results of a large animal model using formed plastic chambers implanted adjacent to the rib periosteum in sheep to fabricate vascularized bone flaps of different shapes. Chambers packed with morcellized corticocancellous bone graft, representing the most favorable natural circumstances for bone formation, were compared to empty chambers, representing the least favorable. Implants containing bone chips yielded formed blocks of vascularized bone after 6 weeks with evidence of remodeling after 13 weeks. Histomorphometric analysis demonstrated that there was full bone penetration into shallow (5 mm) chambers and 8.8 mm (+/-0.6) penetration into deep (10 mm) implants after 6 weeks. Molded bone segments failed to grow in empty chambers. This model presents a quantifiable range of bone forming potential to which different bone substitutes may be compared for usefulness in creating tissue engineered bone flaps for reconstructive surgery.
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