Softness Meets with Brightness: Dye-Doped Multifunctional Fluorescent Polymer Particles via Microfluidics for Labeling

Abstract

Fluorogenic labeling strategies have emerged as powerful tools for in vivo and in vitro imaging applications for diagnostic and theranostic purposes. Free organic chromophores (fluorescent dyes) are bright but rapidly degrade. Inorganic nanoparticles (e.g., quantum dots) are photostable but toxic to biological systems. Alternatively, dye-doped polymer particles are promising for labeling and imaging due to their properties that overcome limitations of photodegradation and toxicity. This progress report, therefore, presents various synthesis techniques for the generation of dye-doped fluorescent polymer particles. Polymer particles are relatively soft compared to inorganic nanoparticles and can be synthesized with characteristics like biocompatibility and stimuli responsiveness. Also, their ability of loading fluorophores through various interactions reveals brightness. Here, a multiscale-multicolor library of bright and soft fluorescent polymer particles is generated hierarchically. Various microfluidic supported strategies have been applied where fluorophores can be linked to polymeric networks noncovalently and covalently in the interior, and at the surface of nanoparticles (60–550 nm). Besides, microfluidic strategies for hydrophilic and hydrophobic fluorescent polymer microparticles (20–800 µm) have been performed for systematic tuning in size and color combination. Furthermore, soft and bright particulate assemblies are enabled through interfacial interactions at the intermediate scale (600 nm–3 µm) between the nanometer and micrometer lengthscale.