Synthesis of a polymerizable aggregation-induced emission (AIE) dye with A-D structure based on benzothiadiazole for fluorescent nanoparticles and its application in bioimaging

Abstract

In recent years, fluorescent materials with aggregation-induced emission (AIE) have been receiving widespread attention in diverse fields due to their unique characteristics. In this work, a novel AIE fluorescent dye TTPA with electron acceptor–donor (A-D) structure were fabricated through Suzuki coupling and Knoevenagel condensation reaction using benzothiazole (BTA) and 4-(1,2,2-triphenylvinyl) benzaldehyde (TPB) as main components, and its maximum emission wavelength was about at 524 nm, otherwise, on the basis of the quantum calculations, the energy difference ΔE between HOMO and LUMO of TPB and TTPA were about 3.63 eV and 2.81 eV, respectively. The obtained TTPA dye with AIE feature could emit fluorescence in THF owing to the electron A-D structure and intramolecular charge transfer (ICT) effect. Subsequently, the amphiphilic fluorescent copolymers PEG-PA were synthesized through the RAFT polymerization of TTPA and PEGMA with various feeding ratios. The molecular weight (MW) and molecular weight distribution (Ð) of PEG-PA1 were about 1.8 × 104 and 1.30, respectively. According to the 1H NMR spectra, the molar proportion of TTPA in PEG-PA increased from 18.5 % to 26.6 % when the proportion of TTPA in the reactants increased from 20.0 % to 25.0 %. Moreover, the as-prepared PEG-PA copolymers would self-assemble into nanoparticles with 150–200 nm diameter in a water solution due to their amphiphilic property, which exhibited the prospective bioimaging application with many advantages such as hypotoxicity, good biocompatibility, and excellent cells penetration.