Highly Sensitive Two-Photon Lipid Droplet Tracker for In Vivo Screening of Drug Induced Liver Injury

Lipid droplets (LDs) are lipid-abundant organelles found in most cell lines and primarily consist of neutral lipids. They serve as a repository of various lipids and are associated with many cellular metabolic processes, includingenergy storage, membrane synthesis, and protein homeostasis. LDs are prominentin a variety of diseases related to lipid regulation, including obesity, fatty liverdisease, diabetes, and atherosclerosis. To monitor LD dynamics in live samples, we developed a highly selective two-photon fluorescent tracker for LDs (LD1). Itexhibited outstanding sensitivity with a remarkable two-photon-action crosssection (Phi delta max> 600 GM), photostability, and low cytotoxicity. In humanhepatocytes andin vivomouse liver tissue imaging,LD1showed very brightfluorescence with high LD selectivity and minimized background signal to evaluatethe stages of nonalcoholic fatty liver disease. Interestingly, we demonstrated that the liver sinusoid morphology became narrowerwith increasing LD size and visualized the dynamics including fusion of the LDsin vivo. Moreover, real-time and dual-color TPM imaging withLD1and a two-photon lysosome tracker could be a useful predictive screening tool in the drug development process to monitor impending drug-induced liver injury inducing drug candidates