Key points are not available for this paper at this time.
Cell fixation is an essential step to preserve cell samples for a wide range of biological assays involving histochemical and cytochemical analysis. Paraformaldehyde (PFA) has been widely used as a cross-linking fixation agent. It has been empirically recognized in a gold standard protocol that the PFA concentration for cell fixation, C PFA, is 4%. However, it is still not quantitatively clear how the conventional protocol of C PFA is optimized. Here, we investigated the mechanical properties of cell fixation as a function of C PFA by using atomic force microscopy and scanning ion conductance microscopy. The goal of this study is to investigate the effect of C PFA (0–10 wt%) on the morphological and mechanical properties of live and fixed mouse fibroblast cells. We found that both Young’s modulus, E, and the fluctuation amplitude of apical cell membrane, a m, were almost constant in a lower C PFA (4%), indicating that the cell fixation is stabilized at C PFA = ca. 4%, which is consistent with the empirical concentration of cell fixation optimized in biological protocols. Taken together, these findings offer a deeper understanding of how varying PFA concentrations influence the mechanical properties of cells and suggest new avenues for establishing refined cell fixation protocols.
Kim et al. (Mon,) studied this question.