Engineering a Viscosity-Gated Dual-Rotor Probe for Comprehensive Mapping of Lipid Droplet Heterogeneity.

Small, metabolically active lipid droplets (LDs) with elevated core viscosity play pivotal roles in lipid metabolism and disease yet remain underexplored due to their transient nature and the limitations of conventional probes. Here, we report , a viscosity-gated dual-rotor fluorophore optimized for fixed-cell imaging that enables high-fidelity, ratiometric imaging of LD heterogeneity across diverse cell types. integrates a red-emissive intramolecular charge transfer (ICT) scaffold with a sterically tuned pyrrole rotor system, conferring enhanced brightness, photostability, and pronounced sensitivity to local microviscosity.