A novel AIE-active dye for fluorescent nanoparticles by one-pot combination of Hantzsch reaction and RAFT polymerization: synthesis, molecular structure and application in cell imaging

In recent years, amphiphilic AIE-active fluorescent organic materials with aggregation-induced emission (AIE) properties have been extensively investigated due to their excellent properties. This study describes the synthesis of a novel AIE-active dye of tetraphenylethylene diphenylaldehyde (TPDA). As compared with the reported fluorescent dye TPB, the fluorescence intensity of TPDA is significantly enhanced with the distinct red shift of emission wavelength. Subsequently, the corresponding novel polymers PEG-TPD were obtained through the one-pot combination of Hantzsch reaction and RAFT polymerization. The structure of PEG-TPD1 by the two-step process was similar with that of PEG-TPD2 by the one-pot method at the same feeding ratio of TPDA and PEGMA. The molecular weights (M(n)) of the polymers PEG-TPD1 and PEG-TPD2 were respectively 52 000 and 28 000 with narrow polydispersity index (PDI), and their molar fractions of TPDA were respectively about 9.5% and 14.3%, indicating that the degree of Hantzsch reaction in the one-pot process was more complete. Subsequently, the effect of feed ratio of TPDA and PEGMA on polymer structure was further studied. It can be seen that the M(n) of the polymers gradually increases as the proportion of TPDA increases. In aqueous solution, these amphiphilic PEG-TPD polymers tended to self-assemble into corresponding fluorescent polymer nanoparticles (FPNs). The diameter of PEG-TPD2 FPNs ranged from 200 to 300 nm, and their fluorescence emission spectra have maximum emission peak at 509 nm. The PEG-TPD FPNs have significant advantages such as good fluorescence intensity, high water dispersibility, good biocompatibility and easy absorption by cells, which can be attractively used in the field of bioimaging.