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ACS Nano. 2017 Nov 28;11(11):10689-10703. doi: 10.1021/acsnano.7b04743. Epub 2017 Sep 12.

A Carbon Nanotube Optical Reporter Maps Endolysosomal Lipid Flux.

Author information

1
Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.
2
Department of Chemical Engineering, University of Rhode Island , Kingston, Rhode Island 02881, United States.
3
Weill Cornell Medicine , New York, New York 10065, United States.
4
Division of Tumor Biology & Immunology, The Netherlands Cancer Institute , Amsterdam 1066 CX, The Netherlands.
5
Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States.
6
Ludwig Center for Cancer Research, University of Lausanne , Lausanne CH 1066, Switzerland.

Abstract

Lipid accumulation within the lumen of endolysosomal vesicles is observed in various pathologies including atherosclerosis, liver disease, neurological disorders, lysosomal storage disorders, and cancer. Current methods cannot measure lipid flux specifically within the lysosomal lumen of live cells. We developed an optical reporter, composed of a photoluminescent carbon nanotube of a single chirality, that responds to lipid accumulation via modulation of the nanotube's optical band gap. The engineered nanomaterial, composed of short, single-stranded DNA and a single nanotube chirality, localizes exclusively to the lumen of endolysosomal organelles without adversely affecting cell viability or proliferation or organelle morphology, integrity, or function. The emission wavelength of the reporter can be spatially resolved from within the endolysosomal lumen to generate quantitative maps of lipid content in live cells. Endolysosomal lipid accumulation in cell lines, an example of drug-induced phospholipidosis, was observed for multiple drugs in macrophages, and measurements of patient-derived Niemann-Pick type C fibroblasts identified lipid accumulation and phenotypic reversal of this lysosomal storage disease. Single-cell measurements using the reporter discerned subcellular differences in equilibrium lipid content, illuminating significant intracellular heterogeneity among endolysosomal organelles of differentiating bone-marrow-derived monocytes. Single-cell kinetics of lipoprotein-derived cholesterol accumulation within macrophages revealed rates that differed among cells by an order of magnitude. This carbon nanotube optical reporter of endolysosomal lipid content in live cells confers additional capabilities for drug development processes and the investigation of lipid-linked diseases.

KEYWORDS:

hyperspectral microscopy; live-cell imaging; near-infrared fluorescence; single-cell sensing; single-walled carbon nanotubes

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