To help restore damaged bone, researchers are developing polymer scaffolds that can be implanted in the body to support the growth of new tissue. Poly(propylene fumarate), or PPF, is one of the few materials available for tissue engineering that is both compatible with three-dimensional printing and can be completely absorbed by the body. But applications for this material have been limited by a lack of production methods suitable for commercial-scale 3-D printing, says Matthew L. Becker of the University of Akron.
Becker’s team developed a scalable method to make PPF that involves a ring-opening copolymerization and a functionalized primary alcohol initiator. Using magnesium 2,6-di-tert-butyl-4-methylphenoxide as a catalyst, the researchers synthesize poly(propylene maleate), which then isomerizes to produce PPF (J. Am. Chem. Soc. 2017, DOI: 10.1021/jacs.7b09978).
Importantly, PPF produced using this method possesses reactive end groups, which engineers could use to attach molecules like peptides that help cells adhere and spread across the surface of a 3-D-printed scaffold. The end groups even survive the harsh conditions of stereolithography—a 3-D printing method that uses light to cure polymer layers—allowing the scaffold’s surface to be modified post-printing. The researchers confirmed this property by attaching peptides to small printed PPF discs and observing the growth of mouse cells on the surface.
Unlike traditional step-growth polymerization methods, this new one enables researchers to influence how fast the material degrades in the body by tailoring the polymer’s chain length, Becker says.
The PPF synthesis technology has been licensed to medical materials company 21MedTech, which Becker cofounded.