Gfp huvec

Polydimethylsiloxane (PDMS, Sylgard 184) was obtained from Dow Corning (Midland, MI, USA). Alginate with medium viscosity was purchased from Sigma Aldrich (St. Louis, MO, USA). Calcium chloride powder was bought from Aladdin (Shanghai, China). Agarose powder with low melting temperature (87–89°C) was bought from Biowest (Spain). Green fluorescent particles with a particle size of 10 µm and red fluorescent particles with particle size of 10 µm and 3.2 µm were purchased from Base Line (Tianjin, China). Red/green/blue/yellow pigment was purchased from M and G (China). Alginate solutions with different concentration of 1%, 2%, and 3% (w/v) were prepared by dissolving Alginate powder into distilled water or culture medium. About 2% (w/v) agarose solution with 2% (w/v) calcium chloride was prepared by dissolving agarose and calcium chloride powders into distilled water at 100°C. After boiling, agarose solution was poured in a Petri dish and cooled down to form a flat agarose hydrogel with a thickness of 3 mm as the collecting substrate. For cell printing, GFP expressing human umbilical vein endothelial cells (GFP-HUVEC; ATCC, Manassas, VA, USA) and red fluorescent protein embryonic rat cardiomyocytes (H9C2, ATCC, Manassas, VA, USA) were added into 3% Alginate solution with a density of 5 × 10⁵ cells mL⁻¹.