Vert1

After CFSE dye staining, Cal27 cells were observed for their behavior by an inverted microscope (Zeiss VERT1, United States) and LSCM (Olympus Fluoview FV1200, Tokyo, Japan). Cells encapsulated in microtubes were stained with Calcein-AM/PI Cell Live/Dead Assay Kit (Beyotime Institute of Biotechnology, Shanghai, China) to investigate the viability of cells.

The surface of hollow microtubes was observed by ordinary optics microscope and SEM. Different sizes of hydrogel microtubes could be prepared by varying the flow rate of the core and shell solution, achieving controllability of preparation.
The hollow hydrogel microtubes were suspended in water and observed under the microscope (Zeiss VERT1, United States). Then the prepared hollow microtubes were washed third in water to remove calcium chloride, and the samples were dehydrated in a freeze dryer. Glue the sample to the conductive adhesive on the sample stage, and after spraying gold on the particle sputtering instrument for 30 s, the surface and cross-section of the sample were observed by SEM (Thermo Fisher Scientific, Apreo S, United States). Microspheres with green fluorescence were added into the sodium alginate solution, and the cross-section of the hollow microtubes was viewed through LSCM (Olympus Fluoview FV1200, Tokyo, Japan).

The scratch assay was classic to analyze the cell migration in vitro. The Cal27 cells were seeded in 6-well plates at a density of 1 × 10⁶; after 24 h, a perpendicular scratch was generated on the surface of the plate using a 1,000 μL pipette tip, followed by extensive washing with PBS to remove cell debris. Then, we incubated the plates with DMEM medium containing 1% FBS and treated cells with aspirin, indomethacin, and nimesulide. The photographic images were taken by the light microscope (Zeiss VERT1, United States) at the indicated time after the drug treatment.