Osteoblast behaviour on in situ photopolymerizable three-dimensional scaffolds based on D, L-lactide, epsilon-caprolactone and trimethylene carbonate.

Polymer networks formed by photocrosslinking of multifunctional oligomers have great potential as injectable and in situ forming materials for bone tissue engineering. Porous scaffolds varying in polyester type and crosslinking density were prepared from methacrylate-endcapped oligomers based on D,L-lactide, epsilon -caprolactone and trimethylene carbonate: LA/CL-hexanediol, LA/CL-dipentaerythritol and LA/TMC-HXD. The biocompatibility and bone formation were related with the degradation time and mechanical properties. The viability of fibroblasts was evaluated after incubation with extraction medium by MTT-assay. All scaffolds showed a good biocompatibility. Rat bone marrow cells were cultured on the scaffolds for 21 days and were able to attach and differentiate on the scaffolds. The cells expressed high alkaline phosphatase activity, have formed a mineralized extracellular matrix and secreted osteocalcin. TEM of the polymer interface revealed osteoblasts which secreted an extracellular matrix containing matrix vesicles loaded with apatite crystals.LA/TMC-HXD, LA/CL-HXD and LA/CL-DPENT had a 50% mass loss at 3,5 months respectively 6 and 7, 5 months. The mechanical properties improve by increasing the branching of the precursor methacrylates (by replacing HXD by DPENT) but do not depend on their chemical composition. Hence, scaffolds with high elastic properties and variable degradation time can be obtained, which are promising for bone tissue engineering.