Azoreductase-Responsive Nanoprobe for Hypoxia-Induced Mitophagy Imaging

Anal Chem. 2019 Jan 15;91(2):1360-1367. doi: 10.1021/acs.analchem.8b03492. Epub 2019 Jan 2.

Abstract

Mitophagy, as a crucial metabolic process, plays an essential role in maintaining cellular and tissue homeostasis. Various stresses especially hypoxia could improve intracellular reactive oxygen species (ROS) level to induce mitophagy. However, high-specific fluorescence imaging of mitophagy in living cells under hypoxia is still a challenge. Based on this, we report an azoreductase-responsive nanoprobe (termed Micelle@Mito-rHP@TATp, MCM@TATp) by encapsulating cationic spiropyrane derivative (Mito-rHP) to realize specific imaging of mitophagy in living cells under hypoxia. An azoreductase-responsive amphiphilic polymer, 1,2-distearoyl- sn-glycero-3-phosphoethanolamine-azo- N-[maleimide(polyethylene glycol-2000) (Mal-PEG2000-Azo-DSPE), was first self-assembled into a micelle in aqueous solution. Meanwhile, the synthetic Mito-rHP encapsulated into this formed micelle to construct MCM. By modifying the surface of MCM with cell-penetrating peptide (TATp) to form MCM@TATp, the nanoprobe could avoid endolysosomal trapping. Under hypoxic conditions, the azobenzene moiety-contained MCM@TATp would be disrupted by the highly expressed azoreductase, then the encapsulated Mito-rHP would be released. Since Mito-rHP is a mitochondria-targeted and pH-sensitive probe, thus it could target into mitochondria and displayed a desirable "off-on" fluorescence response to mitophagy during which mitochondria were regarded to undergo acidification. The results indicated that the MCM@TATp in our design could image mitophagy under hypoxia in high-specificity. As further application, we have also demonstrated that this MCM@TATp can perform well to realize mitophagy imaging under the photodynamic therapy (PDT) which can induce hypoxia in treatment of cancer. We expect this new strategy would be a powerful tool for hypoxia-related fundamental and clinical research.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Azo Compounds / chemical synthesis
  • Azo Compounds / metabolism*
  • Fluorescent Dyes / chemistry
  • Hep G2 Cells
  • Humans
  • Hypoxia / metabolism
  • Micelles
  • Microscopy, Confocal / methods
  • Microscopy, Fluorescence / methods
  • Microsomes, Liver / metabolism
  • Mitophagy / physiology*
  • NADH, NADPH Oxidoreductases / metabolism*
  • Nitroreductases
  • Phosphatidylethanolamines / chemical synthesis
  • Phosphatidylethanolamines / metabolism*
  • Photochemotherapy
  • Polyethylene Glycols / chemical synthesis
  • Polyethylene Glycols / metabolism*
  • Rats
  • Spiro Compounds / chemical synthesis
  • Spiro Compounds / metabolism*

Substances

  • Azo Compounds
  • Fluorescent Dyes
  • Micelles
  • Phosphatidylethanolamines
  • Spiro Compounds
  • Polyethylene Glycols
  • NADH, NADPH Oxidoreductases
  • Nitroreductases
  • azoreductase