Quantitative Mapping of the Spatial Distribution of Nanoparticles in Endo-Lysosomes by Local pH

Understanding
the intracellular distribution and trafficking of nanoparticle drug
carriers is necessary to elucidate their mechanisms of drug delivery
and is helpful in the rational design of novel nanoparticle drug delivery
systems. The traditional immunofluorescence method to study intracellular
distribution of nanoparticles using organelle-specific antibodies
is laborious and subject to artifacts. As an alternative, we developed
a new method that exploits ratiometric fluorescence imaging of a pH-sensitive
Lysosensor dye to visualize and quantify the spatial distribution
of nanoparticles in the endosomes and lysosomes of live cells. Using
this method, we compared the endolysosomal distribution of cell-penetrating
peptide (CPP)-functionalized micelles to unfunctionalized micelles
and found that CPP-functionalized micelles exhibited faster endosome-to-lysosome
trafficking than unfunctionalized micelles. Ratiometric fluorescence
imaging of pH-sensitive Lysosensor dye allows rapid quantitative mapping
of nanoparticle distribution in endolysosomes in live cells while
minimizing artifacts caused by extensive sample manipulation typical
of alternative approaches. This new method can thus serve as an alternative
to traditional immunofluorescence approaches to study the intracellular
distribution and trafficking of nanoparticles within endosomes and
lysosomes.