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.

NIR FRET Luminescence in Rhenium Complex and Dye Co‐Loaded Polymer Nanoparticles

“…A general and particularly facile approach to obtain luminescent probes is to encapsulate high amounts of individual emitters in non-fluorescent nanoparticles (NPs), such as silica NPs, [14,15] and, in particular, polymer NPs. [16][17][18] Encapsulation allows to efficiently separate the emitters from the PL-quenching environment. At the same time, the NP can be used to control the size and interactions of the probe with the biological environment, allowing to decouple the photophysical properties from the surface properties and physical chemistry of the nanoprobe.…”

Assembly of Fluorescent Polymer Nanoparticles Using Different Microfluidic Mixers

“…Their surface properties can now be readily controlled, and through this their fate in biological environments. Over the last two decades, the development of polymer NPs has achieved a level, at which scale-up and reproducibility of particle assembly starts to become a focus, in order to translate this type of materials toward the clinic and commercialization. − As an example, so-called fluorescent dye-loaded polymer NPs have gained increasing interest as very bright fluorescent probes. − Thanks to different approaches for overcoming aggregation-caused quenching of the dyes inside the particles, they gave rise to fluorescent emitters several orders of magnitude brighter than fluorescent proteins, molecular dyes, or even luminescent quantum dots. These particle systems have already led to various applications, i.e.…”

“…Originally, nanoprecipitation was mainly performed through manual addition of one of the phases to the other, typically with the aqueous phase in large excess . Taking into account the fact that often relatively small amounts of valuable compounds have to be encapsulated, one possibility to better control the addition of the two phases is the use of microfluidics. ,− Microfluidics should, in principle, allow automatization of a NP assembly with high reproducibility and further scale-up through highly parallel synthesis. However, particle formation in nanoprecipitation depends strongly on the speed of mixing of the two phases, which defines the supersaturation and the homogeneity of conditions during particle formation.…”

DNA-Immobilized Fluorescent Polystyrene Nanoparticles as Probes with Tunable Detection Limits

“…The dye-loaded polymer nanoparticles reported thus far are commonly prepared by nanoprecipitation. ,, In this process, polymers are combined with dye molecules and the mixture is then co-precipitated to form dye-loaded nanoparticles. , As the dye encapsulation process is kinetically controlled, fine-tuning the number of dyes incorporated can be difficult. Additionally, as the dyes are not covalently bound to the nanoparticles, the elution of the dye over time may also be of potential concern.…”