Rational design of a ratiometric two-photon fluorescent probe for real-time visualization of apoptosis.

A dialdehyde-functionalized ratiometric two-photon fluorescent probe (Mito-DCHO) based on a symmetric carbazole-containing two-dimensional ICT system was rationally designed for cysteine-specific detection in mitochondria, which was utilized for real-time assessing and dual-channel visualization of the early stage of apoptosis by monitoring mitochondrial oxidative stress levels.