A composite scaffold of PLGA microspheres/fibrin gel for cartilage tissue engineering: fabrication, physical properties, and cell responsiveness

A composite scaffold of poly(L-lactic-co-glycolic acid) (PLGA) microspheres and fibrin gel was fabricated by blending fibrinogen-immobilized PLGA microspheres with fibrinogen and thrombin solution. The PLGA microspheres with a size of 70 approximately 100 microm were aminolyzed in a hexanediamine/n-propanol solution to introduce free amino groups on their surface. The fibrinogen immobilization was achieved by glutaraldehyde coupling. When the --NH(2) content on the microsphere surface was increased from approximately 2 x 10(-8) mol/mg to approximately 4 x 10(-8) mol/mg, the fibrinogen amount was correspondingly increased from approximately 35 microg/mg to approximately 70 microg/mg. Measured by UV-VIS spectroscopy, the clotting time of the composite was less influenced by the microsphere amount, but mainly controlled by the thrombin concentration. When the thrombin concentration was higher than 15 U/mL, the gelation could be finished within 1 min and yielded a composite with evenly suspended and distributed PLGA microspheres. Blending with the microspheres could significantly improve the elastic modulus of the hydrogel as well, whereas less influence on the chondrocyte proliferation and extracellular matrix production.