CCK-8 assay
On the sixth day of culture, a complete medium containing 10% CCK-8 (Meilunbio, China) was prepared. The cells were washed twice with PBS and then treated with the respective FITC-dextran solutions. After one and two hours of treatment, 100 μL of medium from the lower layer was collected to measure the fluorescence intensity using a plate reader (Infinite® 200 PRO, Tecan, Switzerland).