Fig 2: Characterization of HUVECs in PIC hydrogels. (A) HUVECs were encapsulated in PIC and PIC-RGD and went through 7 days of culture (scale bar = 200 μm). (B) Number of HUVECs grown in PIC and PIC-RGD for 0, 3, and 7 days. HUVECs did not grow in the PIC gel without RGD, but the proliferation of the PIC -RGD was significant. The error bars represent the standard error of mean of four experiments. (C) HUVECs grown in PIC-RGD were subcultured to PIC and PIC-RGD in each generation. The growth characteristic of HUVECs is stable after 5 rounds of passaging in PIC and PIC-RGD (scale bar = 200 μm). (D) Fluorescence staining of P5 HUVECS in PIC-RGD after 7 days of cultures shows good maintenance of phenotype characteristics. CD31: in red, EC maker; phalloidin: in green, stains F-actin; Hoechst33342: in blue, stains cell nuclei (scale bar = 200 μm). (E) Percentage of CD31 positive cells per field of vision. (F) TUNEL assay (red) with Hoechst33342 staining (blue, cell nuclei) and bright field image of P5 HUVECs after 7 days in culture in PIC-RGD show few apoptotic cells in spheroids (scale bar = 200 μm). (G) Percentage of TUNEL negative cells per field of vision. For all samples, the PIC and PIC-RGD concentration c = 1 mg mL−1 and the initial cell density is 200,000 cells mL−1. N/A represents not applicable data, since HUVECs do not proliferate in PIC.