Improved Fluorescence and Brightness of Near-Infrared and Shortwave Infrared Emitting Polymer Dots for Bioimaging Applications

Abstract

Development of near-infrared (NIR) and shortwave infrared (SWIR) emitting fluorophores is central to the fluorescence-based bioimaging. While conjugated polymer nanoparticles (polymer dots) are one of the promising fluorophores for this application, obtaining polymer dots that show bright fluorescence, especially in the SWIR wavelength region, has been challenging. Here, we report generalized approach to obtain bright polymer dots through a systematic characterization of photophysical properties of NIR and SWIR emitting polymer dots. Detailed photophysical characterization of a series of polymer dots fabricated using polycarbazole (PCz)based conjugated polymers that adopt bent and twisted conformation reveals that the fluorescence brightness of the PCz-based polymer dots is determined by subtle balance between fluorescence quenching due to polymer chain interaction inside the particles and the twisting between the donor and acceptor moieties of the conjugated polymers inside the particles. Our results provide important insight into the rational design of highly fluorescing SWIR-emitting polymer dots.

Biodegradable Polyimidazole Particles as Contrast Agents Produced by Direct Arylation Polymerization

“…1,2 Conjugated polymer nanoparticles have shown great potential as contrast agents in fluorescence and photoacoustic imaging. [3][4][5][6] Compared to small molecular contrast agents nanoparticles are advantageous in their high fluorescence and photostability. [7][8][9] In addition to their outstanding optical properties, nanoparticles of conjugated polymers can be used for passive targeting, where they make use of the enhanced permeation and retention (EPR) effect.…”

Millimeter-Deep Detection of Single Shortwave-Infrared-Emitting Polymer Dots through Turbid Media

“…30 We recently reported a new generalized strategy for obtaining Pdots that exhibit bright SWIR fluorescence by integrating the rational design and synthesis of CPs; we also optimized the fabrication protocol for Pdots. 34 Here, we report single-particle fluorescence imaging of SWIR-emitting Pdots. We show that ultrasmall (as small as 3.5 nm) SWIR-emitting Pdots exhibit much brighter (5× brighter) fluorescence compared with frequently used semiconductor quantum dots (e.g., PbS QDs) under typical experimental conditions for single-molecule imaging.…”

“…[27][28][29][30][31] In addition to their high biocompatibility, 32 Pdots can be reliably prepared as ultrasmall (<5 nm) NPs using proper protocols. 33,34 Thus, Pdots are promising fluorescent NPs for single-particle SWIR imaging. Researchers have developed small-bandgap CPs with a large extinction coefficient by designing DAD-type CPs that exhibit strong intramolecular charge transfer absorption and fluorescence.…”

Counterion-insulated near-infrared dyes in biodegradable polymer nanoparticles for in vivo imaging

“…Even though it is challenging to shift conjugated polymers to the NIR region, recent studies using conjugated donor–acceptor fluorophore systems showed remarkable examples exhibiting high brightness and good in vivo imaging contrast. 18,19 However, these systems owing to their structures remain essentially non-biodegradable NPs. Another approach is to use biodegradable polymeric NPs 2,20 as a nanocarrier of dyes.…”