Facile Cholesterol Loading with a New Probe ezFlux Allows for Streamlined Cholesterol Efflux Assays

[Image: see text] Here, we report a nanoparticle-based probe that affords facile cell labeling with cholesterol in cholesterol efflux (CE) assays. This probe, called ezFlux, was optimized through a screening of multiple nanoformulations engineered with a Förster resonance energy transfer (FRET) reporter. The physicochemical- and bio-similarity of ezFlux to standard semi-synthetic acetylated low-density lipoprotein (acLDL) was confirmed by testing uptake in macrophages, the intracellular route of degradation, and performance in CE assays. A single-step fast self-assembly fabrication makes ezFlux an attractive alternative to acLDL. We also show that CE testing using ezFlux is significantly cheaper than that performed using commercial kits or acLDL. Additionally, we analyze clinical trials that measure CE and show that ezFlux has a place in many research and clinical laboratories worldwide that use CE to assess cellular and lipoprotein function.