Fig. 6

Force spectroscopy of the interactions between LDL/oxLDL particles functionalized on AFM probe tips and cell surfaces of endothelial cells under various acidic conditions. A Optical observation of endothelial cells under an AFM cantilever. B Statistical analysis of the interaction forces between LDL or oxLDL particles modified on AFM tips via the immersion method and cell surfaces under different acidic conditions. ^**p < 0.01 compared oxLDL with LDL; ^#p < 0.05 compared with pH 7.4 (n = 300 interactions in each group from three independent experiments). C The dynamic changes in topographical (top panels) and force (bottom panels) mapping of the same cells but under different acidic conditions (from left to right: pH 7.4, 6.4, and 5.4, respectively) detected by LDL-modified AFM tips via the micro-droplet method, respectively. D Topographical (top panels) and force (bottom panels) mapping of cells under different acidic conditions (from left to right: pH 7.4, 6.4, and 5.4, respectively) detected by oxLDL-modified AFM tips via the micro-droplet method, respectively. E, F Statistical analysis of the interaction forces between LDL (E) or oxLDL (F) particles modified on tips via the micro-droplet method and cell surfaces under different acidic conditions. The control groups represent the interactions between LDL/oxLDL-modified tips via the micro-droplet method and bare glass (i.e., the substrate of a petri dish for cell culture) at pH 7.4. ^*p < 0.05 and ^**p < 0.05 compared with pH 7.4 (n = 300 interactions in each group from three independent experiments). All AFM force spectroscopic experiments were performed in PBS buffer at different pH values