Porous hybrid structures based on P(DLLA‐ co ‐TMC) and collagen for tissue engineering of small‐diameter blood vessels

Poly ( D , L ‐lactide)‐ 7co ‐(1,3‐trimethylene carbonate) [P(DLLA‐ co ‐TMC)] (83 mol % DLLA) was used to produce matrices suitable for tissue engineering of small‐diameter blood vessels. The copolymer was processed into tubular structures with a porosity of ∼98% by melt spinning and fiber winding, thus obviating the need of organic solvents that may compromise subsequent cell culture. Unexpectedly, incubation in culture medium at 37°C resulted in disconnection of the contact points between the polymer fibers. To improve the structural stability of these P(DLLA‐ co ‐TMC) scaffolds, a collagen microsponge was formed inside the pores of the synthetic matrix by dip coating and freeze drying. Hybrid structures with a porosity of 97% and an average pore size of 102 μm were obtained. Structural stability was preserved during incubation in culture medium at 37°C. Smooth‐muscle cells (SMCs) were seeded in these hybrid scaffolds and cultured under pulsatile flow conditions in a bioreactor (120 beats/min, 80–120 mmHg). After 7 days of culture in a dynamic environment viable SMCs were homogeneously distributed throughout the constructs, which were five times stronger and stiffer than noncultured scaffolds. Values for yield stress (2.8 ± 0.6 MPa), stiffness (1.6 ± 0.4 MPa), and yield strain (120% ± 20%) were comparable to those of the human artery mesenterica. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006