Conjugates of Benzoxazole and GFP Chromophore with Aggregation‐Induced Enhanced Emission: Influence of the Chain Length on the Formation of Particles and on the Dye Uptake by Living Cells

Abstract

Six conjugates of benzoxazole and green fluorescent protein chromophore that differ by the length of their alkyl chain (from C1 to C16) are investigated. They exhibit rigidofluorochromism and clear aggregation-induced emission enhancement (AIEE) behavior with emission in the orange-red that is specific to the solid state. A preparation method based on solvent exchange is used to prepare particles. The self-association properties of these molecules depend on the length of the alkyl chain. Microfibers, platelets, and rounded microparticles are successively obtained by increasing the chain length. The same method is used to prepare nanoparticles (NPs) that are fully characterized. In particular, homogeneous populations of stable NPs measuring around 70 nm are obtained with the analogs whose chains contain four to eight carbon atoms. The behavior with respect to living cells is also influenced by the nature of the compounds. Only the dyes with intermediate hydrophobicity are efficiently uptaken by both normal and tumor cells, and fluorescence only originates from dispersed dye molecules. There is no evidence for incorporation of NPs into cells. This work shows that small variations of the chemical structure must be taken into account for making the best use of AIEE compounds in view of precise applications.

DNA mimics of red fluorescent proteins (RFP) based on G-quadruplex-confined synthetic RFP chromophores

“…A number of approaches have achieved emissive GFP analogues via mimicking the natural confined effect of GFP β-barrel to restrict the intramolecular motions of GFP chromophores. They include: structure locking by chemical linkage ( 11 – 16 ), both covalent and non-covalent; and, GFP chromophore encapsulation into a rigid environment, such as supra-molecular hosts ( 17 , 18 ), metal-organic frameworks ( 19 ), the framework of aggregation-induced emission (AIE) ( 20 , 21 ), protein assembly ( 22 , 23 ), and ribonucleic acid (RNA) aptamers. A fluorogenic RNA aptamer ‘Spinach’ developed by Jaffrey et al.…”

Modulation of Fluorescent Protein Chromophores To Detect Protein Aggregation with Turn-On Fluorescence

“…4 For instance, fluorophores have been developed to inhibit TICT of FP chromophores by structural modifications. 3 In addition, FP analogues locked in supra-molecular hosts, 4b metal−organic frameworks, 5 aggregated solids 6 and host proteins 7 have been reported to fluoresce strongly. In biological imaging, HBI analogues have been used to visualize RNA aptamers and DNA quadruplex.…”

Ca2+ Induced Crosslinking of AIE‐Active Polyarylene Ether Nitrile into Fluorescent Polymeric Nanoparticles for Cellular Bioimaging

“…On the contrary, the fluorescence emission of PEN‐TPE homopolymer is independent of Ca 2+ concentration according to Figure S7 (Supporting Information), proving the indispensability of carboxyl groups in fluorescence modulation. Although the specific reason for the formulation of nanospheres with enhanced emission is still unclear, the complexation of Ca 2+ to pendant hydrophilic group (COOH) of PEN‐TPE/PPL is likely to be the major driving force . Furthermore, additional control experiments involving the fluorescence emission of homopolymer (synthesized using PPL and DCBN) in the presence of H 2 O and Ca 2+ have been conducted.…”