Lanthanide‐based bulky counterions against aggregation‐caused quenching of dyes in fluorescent polymeric nanoparticles

Abstract

Dye‐loaded polymeric nanoparticles (NPs) are promising bioimaging agents because of their available surface chemistry, high brightness, and tunable optical properties. However, high dye loadings can cause the aggregation‐caused quenching (ACQ) of the encapsulated fluorophores. Previously, we proposed to mitigate the ACQ inside polymeric NPs by insulating cationic dyes with bulky hydrophobic counterions. In order to implement new functionalities into dye‐loaded NPs, here, we extend the concept of bulky counterions to anionic lanthanide‐based complexes. We show that by employing Gd‐based counterions with octadecyl rhodamine B loaded NPs at 30 wt% versus polymer, the fluorescence quantum yield can be increased to 10‐fold (to 0.34). Moreover, Gd‐anion provides NPs with enhanced contrast in electron microscopy. A combination of a luminescent Eu‐based counterion with a far‐red to near‐infrared cyanine 5 dye (DiD) yields Forster resonance energy transfer NPs, where the UV‐excited Eu‐based counterion transfers energy to DiD, generating delayed fluorescence and large stokes shift of ∼340 nm. Cellular studies reveal low cytotoxicity of NPs and their capacity to internalize without detectable dye leakage, in contrast to leaky NPs with small counterions. Our findings show that the aggregation behavior of cationic dyes in the polymeric NPs can be controlled by bulky lanthanide anions, which will help in developing bright luminescent multifunctional nanomaterials.

Synergetic effect of pyrene-based fluorescent probes for trace nitroaniline sensing

“…1 H and 13 C NMR spectra were recorded on a Bruker AV 400M spectrometer using chloroform-d solvent and tetramethylsilane as an internal reference. J-values are given in Hz.…”

“…For example, compound 1 shows considerable solubility in polar solvents, such as ethyl acetate or THF, but is insoluble in non-polar solvents, while compounds 2 and 3 can dissolve in common solvents with good solubility. All intermediates and target compounds were fully characterized by 1 H/ 13 C NMR spectroscopy and high-resolution mass spectrometry (HRMS). Furthermore, the thermal stability of these compounds was investigated by thermogravimetric analysis (TGA).…”

“…For example, luminescent metal-organic frameworks (MOFs) not only can be excellent fluorescent probes for selectively recognizing p-nitroaniline with a low detection limit, [9][10][11] but also display a high photocatalytic activity for the photodegradation of contaminates. 4,12,13 Fluorescent dyes with whitelight emission utilizing dicarboxylatopillar [5]arene (DCP5)-based coordination polymers have been reported to exhibit good detection performance toward nitroaromatic pollutants. 14 Both the above-mentioned nitroaromatic detecting systems (as well as similar trace nitroaniline sensing systems) operate using mechanisms ascribed to photoinduced charge transfer (PCT), Fo ¨rster resonance energy transfer (FRET), the inner filter effect (IFE), and intramolecular charge transfer (ICT), which result in a strong fluorescence quenching.…”

Supra‐Cyanines: Ultrabright Cyanine‐Based Fluorescent Supramolecular Materials in Solution and in the Solid State

“…Strategies have been developed to minimize ACQ with the help of supramolecular isolators, including bulky fluorinated counterions, and small-molecule ionic isolation lattices. [31][32][33][34][35][36][37] Cyclic peptides, consisting of an even number of alternating D-and L-amino acids, exhibit a tendency to selfassemble into nanotubular structures. [38][39] This phenomenon can be attributed to the robust multiple hydrogen bonding interactions between the flattened ring structures.…”

Supra‐Cyanines: Ultrabright Cyanine‐Based Fluorescent Supramolecular Materials in Solution and in the Solid State

“…Strategies have been developed to minimize ACQ with the help of supramolecular isolators, including bulky fluorinated counterions, and small-molecule ionic isolation lattices. [31][32][33][34][35][36][37] Cyclic peptides, consisting of an even number of alternating D-and L-amino acids, exhibit a tendency to selfassemble into nanotubular structures. [38][39] This phenomenon can be attributed to the robust multiple hydrogen bonding interactions between the flattened ring structures.…”