Ultrabright Fluorescent Polymeric Nanoparticles Made from a New Family of BODIPY Monomers

Four novel BODIPY derivatives (π-) functionalized by different polymerizable groups, styrene (S), phenyl acrylate (PhA), ethyl methacrylate (EtMA) and ethyl acrylate (EtA) have been synthesized. Following a formerly established one-pot RAFT miniemulsion polymerization process (Grazon Macromol. Rapid Commun. 2011, 32, 699−705), the fluorophores were copolymerized in a controlled way at 2.6 mol % with styrene in water. On the basis of the polymerization-induced self-assembly (PISA) principle, the copolymers assembled during their formation into fluorescent nanoparticles. The distribution of the fluorescent monomers along the polymer backbone was monitored by kinetic studies of the copolymerization reaction. Fluorescent stationary and time-resolved spectroscopy was then performed on both the monomers and the nanoparticles (NPs) and the observed differences are discussed in view of the distribution of the fluorescent monomers in the polymer chain. With two of the novel fluorescent monomers (πS and πPhA), the brightness of the NPs could be significantly improved (by a factor 2) compared to particles comprising the other BODIPY monomers. The obtained particles were 200 to 2000 times brighter than usual quantum dots and 40 to 300 times brighter than most of the fluorescent polymeric nanoparticles reported in the literature

Ultrabright BODIPY-Tagged Polystyrene Nanoparticles: Study of Concentration Effect on Photophysical Properties

Fluorescent nanomaterials are invaluable tools for bioimaging. Polymeric nanoparticles labeled with organic dyes are very promising for this purpose. It is thus very important to fully understand their photophysical properties. New fluorescent core–shell nanoparticles have been prepared. The outer part is a poly­(ethylene glycol)-<i>block</i>-poly­(acrylic acid) copolymer, and the core is a copolymer of styrene and methacrylic BODIPY fluorophore. The hydrophilic and hydrophobic parts are covalently linked, ensuring both stability and biocompatibility. We prepared nanoparticles with increasing amounts of BODIPY, from 500 to 5000 fluorophores per particles. Increasing the concentration of BODIPY lowers both the fluorescence quantum yield and the lifetime. However, the brightness of the individual particles increases up to 8 × 10⁷. To understand the loss of fluorescence efficiency, fluorescence decays have been recorded and fitted with a mathematical model using a stretched exponential function. This result gives an insight into the fluorophore arrangement within the hydrophobic core

Fast, Efficient, and Stable Conjugation of Multiple DNA Strands on Colloidal Quantum Dots

A novel method for covalent conjugation of DNA to polymer coated quantum dots (QDs) is investigated in detail. This method is fast and efficient: up to 12 DNA strands can be covalently conjugated per QD in optimized reaction conditions. The QD-DNA conjugates can be purified using size exclusion chromatography and the QDs retain high quantum yield and excellent stability after DNA coupling. We explored single-stranded and double-stranded DNA coupling, as well as various lengths. We show that the DNA coupling is most efficient for short (15 mer) single-stranded DNA. The DNA coupling has been performed on QDs emitting at four different wavelengths, as well as on gold nanoparticles, suggesting that this technique can be generalized to a wide range of nanoparticles

Semiconductor Nanoplatelets: A New Class of Ultrabright Fluorescent Probes for Cytometric and Imaging Applications

Fluorescent semiconductor nanoplatelets (NPLs) are a new generation of fluorescent probes. NPLs are colloidal two-dimensional materials that exhibit several unique optical properties, including high brightness, photostability, and extinction coefficients, as well as broad excitation and narrow emission spectra from the visible to the near-infrared spectrum. All of these exceptional fluorescence properties make NPLs interesting nanomaterials for biological applications. However, NPLs are synthesized in organic solvents and coated with hydrophobic ligands that render them insoluble in water. A current challenge is to stabilize NPLs in aqueous media compatible with biological environments. In this work, we describe a novel method to disperse fluorescent NPLs in water and functionalize them with different biomolecules for biodetection. We demonstrate that ligand exchange enables the dispersion of NPLs in water while maintaining optical properties and long-term colloidal stability in biological environments. Four different colors of NPLs were functionalized with biomolecules by random or oriented conformations. For the first time, we report that our NPLs have a higher brightness than that of standard fluorophores, like phycoerythrin or Brilliant Violet 650 (BV 650), for staining cells in flow cytometry. These results suggest that NPLs are an interesting alternative to common fluorophores for flow cytometry and imaging applications in multiplexed cellular targeting