Evaluating rTsDPP1 Effects on Macrophage Viability

The effect of rTsDPP1 on RAW264.7 macrophage cellular viability was determined using a Cell Counting Kit-8 assay (CCK-8; Solarbio, Beijing, China) [33 (link), 34 (link)]. Briefly, the cells were seeded in a 96-well plate (approximately 1 × 10³ cells per well) and cultured under the same conditions as described above. rTsDPP1, recombinant thioredoxin (TRX) tag protein and AW ESA were added into the medium and cocultured with cells for 48 h. Then, 10 µL CCK-8 solutions were added to each well and incubated for another 2 h. The absorbance at 450 nm was measured using a multimode reader (SpectraMax i3X; Molecular Devices, USA). Cell viability was presented as the cell survival rate according to the following formulas: cell survival rate = (OD values of test group – OD values of blank control)/(OD values of PBS control group – OD values of blank control) × 100%.