Fabrication of biodegradable polymer scaffolds to engineer trabecular bone.

We present a novel method for manufacturing three-dimensional, biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) foam scaffolds for use in bone regeneration. The technique involves the formation of a composite material consisting of gelatin microspheres surrounded by a PLGA matrix. The gelatin microspheres are leached out leaving an open-cell foam with a pore size and morphology defined by the gelatin microspheres. The foam porosity can be controlled by altering the volume fraction of gelatin used to make the composite material. PLGA 50:50 was used as a model degradable polymer to establish the effect of porosity, pore size, and degradation on foam mechanical properties. The yield strengths and moduli in compression of PLGA 50:50 foams were found to decrease with increasing porosity according to power law relationships. These mechanical properties were however, largely unaffected by pore size. Foams with yield strengths up to 3.2 MPa were manufactured. From in vitro degradation studies we established that for PLGA 50:50 foams the mechanical properties declined in parallel with the decrease in molecular weight. Below a weight average molecular weight of 10,000 the foam had very little mechanical strength (0.02 MPa). These results indicate that PLGA 50:50 foams are not suitable for replacement of trabecular bone. However, the dependence of mechanical properties on porosity, pore size, and degree of degradation which we have determined will aid us in designing a biodegradable scaffold suitable for bone regeneration.