“…P3 BMSCs (4 × 10 5 cells/ Electric field-driven building blocks for introducing multiple gradients to hydrogels RESEARCH ARTICLE well) were seeded on the hydrogel surface in 48-well plates and cultured for 24 h with low glucose DMEM (Gibco, Thermo Fisher, MO, USA) containing 10% FBS and 100 units/mL penicillin-streptomycin (Gibco, Thermo Fisher, MO, USA). Chondrogenic-osteogenic co-culture medium supplemented with high glucose DMEM (Gibco, Thermo Fisher, MO, USA), 10% FBS, 10 ng/mL recombinant human TGF-β3 (PeproTech, Newark, NJ, USA), 100 U/mL penicillin/streptomycin (Gibco, Thermo Fisher, MO, USA), 100 nmol/L dexamethasone (Sigma-Aldrich, St. Louis, MO, USA), 91.5 μg/mL ascorbic acid 2-phosphate (Sigma-Aldrich, St. Louis, MO, USA), 10 mmol/L β-sodium glycerophosphate (Sigma-Aldrich, St. Louis, MO, USA), and 40 lg/mL L-proline (Sigma-Aldrich, St. Louis, MO, USA) was used to culture the cells for 28 days (Ribeiro et al, 2018). The co-culture medium was changed every 2 days.…”