The Establishment and Application Studies on Precise Lysosome pH Indicator Based on Self-Decomposable Nanoparticles

Acidic pH of lysosomes is closely related to autophagy; thus, well known of the precise lysosomes, pH changes will give more information on the autophagy process and status. So far, however, only pH changes in a relatively broad range could be indicated, the exact lysosomes pH detection has never arrived. In our study, we established an endo/lysosome pH indicator based on the self-decomposable SiO₂ nanoparticle system with specific synthesis parameters. The central concentrated methylene blue (MB) in the central-hollow structural nanoparticles presented sensitive release as a function of pH values from pH 4.0-4.8, which is exactly the pH range of lysosomes. The linear correlation of the optical density (OD) values and the pH values has been built up, which has been used for the detection of lysosomes pH in 6 different cell lines. Moreover, by this system, we succeeded in precisely detecting the pH average changes of lysosomes before and after black mesoporous silicon (BPSi) NP endocytosis, clarifying the mechanism of the autophagy termination after BPSi endocytosis. So, the self-decomposable nanoparticle-based luminal pH indicator may provide a new methodology and strategy to know better of the lysosome pH, then indicate more details on the autophagy process or other important signaling about metabolisms.