Digitization of Endocytic pH by Hybrid Ultra-pH-Sensitive Nanoprobes at Single-Organelle Resolution

Yiguang Wang *, Chensu Wang, Yang Li, Gang Huang, Tian Zhao, Xinpeng Ma, Zhaohui Wang, Baran D. Sumer, Michael A. White, and Jinming Gao* . Advanced Materials , 2017, 2017, 29, 1603794.  (* Corresponding author)

 Maturation of endocytic organelles, characterized by acidification of the vacuolar compartments, plays a central role in a number of cellular functions and drug/gene delivery. Currently, there is no method for quantifying the dynamic maturation process of the acidic organelles at single organelle resolution. Here we describe a multi-spectral reporter assay that allows for spatio-temporal digitization of endocytic pH in live cells. The technology capitalizes on a novel hybrid ultra pH-sensitive (HyUPS) nanotransistor design consisting of a molecular mixture of block copolymers with discrete and sharp pH transitions. The HyUPS shows binary sensing and fluorescence activation at specific pH thresholds that reflect different maturation status. Using a panel of isogenic cell lines, we demonstrate a drastic KRAS-dependent phenotypic difference in organelle acidification between normal bronchial epithelial cells and malignant lung cancer cells. This nanotechnology platform offers a new imaging method to digitize analog biological signals with improved sensitivity to study endosome/lysosome biology at single organelle resolution in various disease indications. 

Keywords: endocytosis, pH-sensitive nanoparticle, organelle maturation, acidification, hybrid nanoprobe

Pubmed link: https://www.ncbi.nlm.nih.gov/pubmed/27813172