Development of a highly porous, flexible and biodegradable poly(ester urethane)urea scaffold for tissue engineering

For mechanically demanding applications in tissue engineering an ideal scaffold might possess high elastance and strength together with controllable biodegradative and cell adhesive properties. Toward this end, we have synthesized a biodegradable poly(ester-urethane)urea (PEUU) from polycaprolactone and 1,4-diisocyanatobutane, with putrescine used as a chain extender. Porous PEUU scaffolds were created by thermally induced phase separation of a polymer/solvent mixture. The formed scaffolds had open and interconnected pores with pore sizes ranging from several microns to 100 microns and porosities of 80-94%. The scaffolds were flexible with breaking strains greater than 210% and tensile strengths on the order of 1 MPa. The biodegradation rate of PEUU scaffolds was dependent on pore morphology and porosity with the highest weight loss being 21% over 8 weeks. For cellular ingrowth studies, scaffolds were modified with radio frequency glow discharge followed by surface coupling of RGDS peptide. Smooth muscle cells were cultured on scaffolds with and without adhesion peptide treatment. Cells penetrated deeper and distributed more uniformly in RGDS-modified scaffolds than in unmodified scaffolds, and cell number was consistently higher over time in RGDS-modified scaffolds. In summary, these biodegradable PEUU scaffolds offer a platform that is compatible with mechanical training of cell/scaffold constructs. Such training may prove necessary in the development of functional tissues for the cardiovascular system.