Fluorescent Polymer Particles of Nanometer and Micrometer Lengthscales Towards Labeling Applications—Synthesis and Properties

Various types of fluorescent organic dyes of diverse characteristics are routinely utilized for labeling purposes due to their easy use, low cost, and availability of full emission wavelength range. However, organic dyes are very sensitive to their surrounding in which they rapidly degrade either via chemical degradation or photodegradation. To avoid the concern of degradability, inorganic nanoparticles, in particular, quantum dots are highly versatile and photostable. However, quantum dots are relatively toxic to biological systems, and hence their widespread and safe uses are a concern. Alternatively, dye-doped polymer particles are promising for labeling and imaging due to their properties that overcome limitations of photodegradation as well as toxicity. Fluorescent polymer particles can be prepared simply by incorporating fluorescent dyes in the polymer nanoparticle matrix. In this work, various experimental strategies for the nanoscale fluorescent polymer particles have been developed to bind the fluorophores inside the matrix covalently or non-covalently, as well as at the surface through direct adsorption or based on bio-conjugation. Besides, Hydrophilic and hydrophobic microscale fluorescent polymer particles were prepared via photopolymerization by droplet microfluidics. Highly controlled color compositions were inserted inside the fluorescent polymer microparticles, and a color combination library of the multi-colored fluorescent polymer microparticles was synthesized. Furthermore, soft and bright particulate assemblies were enabled through interfacial interactions at the intermediate scale between the nanometer and micrometer length scale. Overall in this work, various techniques for the synthesis of nanoscale fluorescent polymer particles, as well as microscale fluorescent polymer particles with hydrophobic and hydrophilic characteristics, and assembly of the fluorescent polymer particles at the multiscale level are presented.