Norland optical adhesive 63 noa 63

After cleaning, the Si wafer was coated with perfluorooctyltriethoxysilane (Sigma-Aldrich, Oakville, ON, Canada) by vapor phase deposition. An accurate polymer copy of the wafer was obtained after double replication using polydimethylsiloxane (PDMS) and a UV-sensitive polyurethane as described in [14] (link). First, a 6 mm layer of 1∶10 PDMS (Dow Corning, Corning, NY, USA) was poured on the wafer inside a Petri dish, followed by degassing under vacuum in a desiccator for 10 min. Next, the PDMS was cured in an oven for 24 h at 60°C (VWR, Montreal, QC, Canada), then peeled from the wafer. To remove uncured monomers and other extractables, the PDMS replica was submersed in 70% ethanol for 24 h then baked at 60°C for 4 h. Next, a drop of UV sensitive polyurethane (Norland Optical Adhesive 63 (NOA 63), Norland Products, Cranbury, NJ) was applied to the PDMS replica and cured by 600 W of UV light (Uvitron International, Inc., West Springfield, MA) for 45 s. The PDMS was then removed yielding an NOA replica of the original Si wafer pattern with 200 nm holes [14] (link).

Poly(dimethylsiloxane) (PDMS) pre-polymer (Sylgard 184) and a curing agent were purchased from Dow Corning (Midland, MI, USA). Tris-HCl was purchased from Biosesang (Seongnam, Korea). Dopamine hydrochloride and Alizarin Red S were obtained from Sigma-Aldrich (St. Louis, MO, USA). MSCs, HUVECs, MSC growth medium (MSCM), endothelial cell growth medium (ECM), endothelial cell growth supplements (ECGS), MSC growth supplements (MSCGS), fetal bovine serum (FBS), penicillin/streptomycin (P/S) solution, trypsin-EDTA (T/E) solution, Dulbecco’s phosphate-buffered saline (DPBS), MSC chondrogenic differentiation medium (MCDM), MSC chondrogenic differentiation supplement (MCDS), MSC osteogenic differentiation medium (MODM), and MSC osteogenic differentiation supplement A and B (MODS-A and MODS-B) were purchased from ScienCell (Carlsbad, CA, USA). Transforming growth factor-β3 (TGF-β3) and live/dead viability/cytotoxicity kits were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Safranin O was obtained from Polyscience (Warrington, PA, USA). Norland optical adhesive63 (NOA63) was purchased from Norland Products (Jamesburg, NJ, USA). Polystyrene (PS) sheets and poly(ethylene terephthalate) (PET) film were obtained from Goodfellow (Pittsburgh, PA, USA).