Ultra-Fast Fluorescence Imaging in Vivo with Conjugated Polymer Fluorophores in the Second Near-Infrared Window

TL;DR

This paper introduces novel conjugated polymer fluorophores emitting in the second near-infrared window, enabling ultrafast, deep-tissue in vivo imaging of blood flow with high spatial and temporal resolution.

Contribution

The study develops water-soluble, biocompatible polymer nanoparticles with high quantum yield for the first time, achieving ultrafast in vivo imaging at >25 fps in the second NIR window.

Findings

Deep tissue imaging of mouse blood flow at >25 fps

First in vivo ultrafast imaging in the second NIR window

Spatially and temporally resolved cardiac cycle imaging

Abstract

In vivo fluorescence imaging in the second near-infrared window (1.0-1.7 microns) can afford deep tissue penetration and high spatial resolution, owing to the reduced scattering of long-wavelength photons. Here, we synthesize a series of low-bandgap donor/acceptor copolymers with tunable emission wavelengths of 1050-1350 nm in this window. Non-covalent functionalization with phospholipid-polyethylene glycol results in water-soluble and biocompatible polymeric nanoparticles, allowing for live cell molecular imaging at > 1000 nm with polymer fluorophores for the first time. Importantly, the high quantum yield of the polymer allows for in vivo, deep-tissue and ultrafast imaging of mouse arterial blood flow with an unprecedented frame rate of > 25 frames per second. The high time resolution results in spatially and time resolved imaging of the blood flow pattern in cardiogram waveform over a single cardiac cycle (~ 200 ms) of a mouse, which has not been observed with fluorescence imaging in this window before.