Versatile Conjugated Polymer Nanoparticles for High-Resolution O₂Imaging in Cells and 3D Tissue Models

Abstract

High brightness, chemical and photostability, tunable characteristics, and spectral and surface properties are important attributes for nanoparticle probes designed for live cell imaging. We describe a class of nanoparticles for high-resolution imaging of O2 that consists of a substituted conjugated polymer (polyfluorene or poly(fluorene-alt-benzothiadiazole)) acting as a FRET antenna and a fluorescent reference with covalently bound phosphorescent metalloporphyrin (PtTFPP, PtTPTBPF). The nanoparticles prepared from such copolymers by precipitation method display stability, enhanced (>5-10 times) brightness under one- and two-photon excitation, compatibility with ratiometric and lifetime-based imaging modes, and low toxicity for cells. Their cell-staining properties can be modulated with positively and negatively charged groups grafted to the backbone. The "zwitter-ionic" nanoparticles show high cell-staining efficiency, while their cell entry mechanisms differ for the different 3D models. When injected in the bloodstream, the cationic and anionic nanoparticles show similar distribution in vivo. These features and tunable properties make the conjugated polymer based phosphorescent nanoparticles a versatile tool for quantitative O2 imaging with a broad range of cell and 3D tissue models.

Use of Fluorescence Lifetime Imaging Microscopy (FLIM) as a Timer of Cell Cycle S Phase

“…Combined FLIM-PLIM with multiplexing in spectral and time domains (ns and μs probes) allows imaging of oxygenation, division and localization of proliferating cells, Ca 2+ fluxes and cell death (necrosis, apoptosis) [15, 17, 38]. We performed multiplexed FLIM-PLIM of intestinal organoids loaded with BrdU for 4 h and then co-stained with HXT, O 2 -sensitive phosphorescent probe Pt-Glc [18] and Cholera Toxin-Alexa Fluor 488 (CTX) conjugate (lipid raft-specific probe).…”

Molecular Interactions in Organic Nanoparticles for Phototheranostic Applications

“…Dmitriev et al synthesized conjugated polymer nanoparticles by copolymerizing fluorene molecules with the Pt-porphyrin, platinum(II)meso-bis(pentafluorophenyl)bis(4-bromophenyl)porphyrin. 150 The polymer was stabilized in aqueous solution through the effect of charged quarternary ammonium and propionic acid moieties. The conjugated polymer nanoparticles varied in size between 35 and 112 nm.…”

Conjugated Polymer Nanoparticles for Fluorescence Imaging and Sensing of Neurotransmitter Dopamine in Living Cells and the Brains of Zebrafish Larvae

“…[29][30][31][32] pi-Conjugated polymers as fluorescence probes are being actively investigated in biological sensors and imaging. [33][34][35][36][37][38][39][40] Endogenous dopamine has been found in a concentration of 0.01 to 1 µM in the brain of bovine, rat, and human. 41 It is also present with redox active interfering biomolecules, causing considerable difficulties in dopamine analysis.…”