CM-DiI, lipophilic tracer (LP3513)

CM-DiI is an orange-red fluorescent carbocyanine dye containing thiol-reactive chloromethyl (CM) moiety. CM-DiI labels plasma membranes by inserting its two long hydrocarbon (C18 carbon) chains into the lipid bilayer. The dye is weakly fluorescent until incorporated into membranes. CM-DiI is used for in vivo and in vitro labeling of cells to analyze their proliferation as well as for cell tracking and motility assays. The dye is transferred to daughter cells and does not leak to adjacent cells in a population. CM-DiI staining displays bright fluorescence for at least 72 hours (around three to six cell generations). The dye shows little cytotoxicity inside the cell, with minimal effects on the proliferative ability or biology of the cell. Unlike other membrane dyes, CM-DiI has increased water solubility and can be fixed using traditional aldehyde fixatives. CM-DiI also persists in cells after permeabilization procedures. These make it feasible to detect labeled cells in combination with other histological techniques such as immunochemistry, optical clearing, etc.