Evaluation of alginate hydrogels under in vivo-like bioreactor conditions for cartilage tissue engineering

Alginate hydrogels in forms of discs and packed beds of microbeads (~800 μm) were tested in a novel bioreactor at 10% strain using two regimes: at a loading rate of 337.5 μm/s and at sequential increments of 50 μm displacement every 30 min. Compressive strength increased with the increase in alginate concentration (1.5 vs. 2% w/w) and the content of guluronic residues (38.5 vs. 67%). Packed beds of microbeads exhibited significantly higher (~1.5-3.4 fold) compression moduli than the respective discs indicating the effects of gel form and entrapped water. Short-term cultivation of microbeads with immobilized bovine calf chondrocytes (1.5% w/w, 33 × 10(6) cells/ml) under biomimetic conditions (dynamic compression: 1 h on/1 h off, 0.42 Hz, 10% strain) resulted in cell proliferation and bed compaction, so that the compression modulus slightly increased. Thus, the novel bioreactor demonstrated advantages in evaluation of biomaterial properties and cell-biomaterial interactions under in vivo-like settings.