Ratiometric Nanoparticle Probe Based on FRET‐Amplified Phosphorescence for Oxygen Sensing with Minimal Phototoxicity

Pichandi Ashokkumar (1) , Nagappanpillai Adarsh (1) , Andrey S Klymchenko (1)

1 LBP - Laboratoire de Bioimagerie et Pathologies

Luminescent oxygen probes enable direct imaging of hypoxic conditions in cells and tissues, which are associated with a variety of diseases, including cancer. Here, a nanoparticle probe that addresses key challenges in the field is developed, it: i) strongly amplifies room temperature phosphorescence of encapsulated oxygen‐sensitive dyes; ii) provides ratiometric response to oxygen; and iii) solves the fundamental problem of phototoxicity of phosphorescent sensors. The nanoprobe is based on 40 nm polymeric nanoparticles, encapsulating ≈2000 blue‐emitting cyanine dyes with fluorinated tetraphenylborate counterions, which are as bright as 70 quantum dots (QD525). It functions as a light‐harvesting nanoantenna that undergoes efficient Förster resonance energy transfer to ≈20 phosphorescent oxygen‐sensitive platinum octaethylporphyrin (PtOEP) acceptor dyes. The obtained nanoprobe emits stable blue fluorescence and oxygen‐sensitive red phosphorescence, providing ratiometric response to dissolved oxygen. The light harvesting leads to ≈60‐fold phosphorescence amplification and makes the single nanoprobe particle as bright as ≈1200 PtOEP dyes. This high brightness enables oxygen detection at a single‐particle level and in cells at ultra‐low nanoprobe concentration with no sign of phototoxicity, in contrast to PtOEP dye. The developed nanoprobe is successfully applied to the imaging of a microfluidics‐generated oxygen gradient in cancer cells. It constitutes a promising tool for bioimaging of hypoxia.

Mots clés: oxygen sensors; dye-loaded polymeric nanoparticles; phosphorescence; single-particle fluorescence; oxygen gradients in microfluidics

Domaines: Matériaux; Chimie analytique

Pichandi Ashokkumar, Nagappanpillai Adarsh, Andrey S Klymchenko. Ratiometric Nanoparticle Probe Based on FRET‐Amplified Phosphorescence for Oxygen Sensing with Minimal Phototoxicity. Small, 2020, 16 (32), pp.2002494. ⟨10.1002/smll.202002494⟩. ⟨hal-03085816⟩