POLY(L-LACTIC ACID) FOAMS WITH CELL SEEDING AND CONTROLLED-RELEASE CAPACITY

A synthetic porous three-dimensional structure that can mimic the arch itecture of actual tissues, provide sustained release of nutrients or growth factors, and serve as a template for cell seeding would be an i deal substrate for tissue engineering. Poly(l-lactic acid) (PLLA) foam s were fabricated for this purpose, based on the principle of phase se paration from homogeneous naphthalene solutions. Complex shapes could be readily fabricated, and resulting foams had relatively uniform, ope n cells throughout the matrix. Densities and total pore-surface areas were in the range of 0.05-0.1 g/cm(3) and 0.8-1.3 m(2)/g, respectively . The loss tangent of these foams ranged from 0.07 to 0.128, as measur ed by thermomechanical analysis. Naphthalene residue in the resulting foams went below 0.2 wt% after extensive vacuum sublimation. Feasibili ty of incorporating drugs or nutrients into such a highly porous struc ture was demonstrated by the dispersion of two model compounds, bromot hymol blue (BTB) and sulforhodamine B (SD), in the matrix. Sustained r elease of BTB from the foam with a porosity as high as 87% was observe d for more than 2 months. Alkaline phosphatase, as a model protein to be incorporated, lost approximately 30% of its bioactivity during the fabrication. As a cell-culture substrate, the PLLA foams performed as well as the flat PLLA surface in supporting the growth of rat osteosar coma cells (ROS 17/2.8) and in maintaining their functions such as alk aline phosphatase activity and osteocalcin synthesis. UMR-106 cells cu ltured in the foam also expressed a higher degree of mineralization th an those cultured on the flat PLLA substrate. (C) John Wiley & Sons, I nc.