Mitochondrion
is one of the most important organelles and becomes
a target in many cancer therapeutic strategies. Mitochondrial microenvironments
in response to therapeutic methods are the key to understand therapeutic
mechanisms. However, they are almost rarely studied. Herein, the mitochondrial
microenvironments, including mitochondrial membrane potential (MMP)
and reactive oxygen species (ROS) after different photodynamic therapy
(PDT) dosages, were monitored by fluorescent imaging and compared
among three cell lines (HepG2, MCF-7, and LO2). Furthermore, the fluctuations
of intramitochondrial pHs were revealed via a plasmonic mitochondrion-targeting
surface-enhanced Raman scattering (SERS) pH nanosensor. Results indicate
that the MMP decreases gradually with the ROS generation and the cancerous
cells exhibit less response to excess ROS relative to normal cells.
On the other hand, the pH value in the mitochondria decreases initially
and then increases when the amount of ROS increases. The LO2 cell
is preliminarily evidenced to have a higher self-adjustment ability
due to its better tolerance to differential intra/extracellular pHs.
This study may provide a basis for an in-depth understanding of the
mechanisms of the mitochondrial targeting-based PDT therapeutic processes.
It is also helpful for more accurate and useful diagnosis according
to intramitochondrial microenvironments and improvement on therapy
efficiency of cancers.