Ultrafast construction and biological imaging applications of AIE-active sodium alginate-based fluorescent polymeric nanoparticles through a one-pot microwave-assisted Döbner reaction

Abstract

Aggregation-induced emission (AIE) is a unique fluorescence phenomenon that has attracted great interest for various applications especially for the fabrication of AIE-active polymeric nanoparticles. The AIE-active fluorescent polymeric nanoparticles (FPNs) showed attractive optical properties, which could elegantly overcome the lousy aggregation-caused quenching (ACQ) effect of FPNs based on conventional organic fluorogens. Although great advances and progress have been achieved for the fabrication of AIE-active FPNs, the preparation of AIE-active carbohydrate polymers is still challengeable for the poor solubility of carbohydrate polymers in organic solvents. In this work, we reported the sodium alginate-based fluorescent biopolymers (OSA-PA-PhE) with AIE characteristic could be facilely fabricated via an ultrafast one-pot multicomponent reaction (named as Döbner reaction) with the assistance of microwave irradiation. Among the Döbner reaction system, the oxidized sodium alginate (OSA) and AIE-active dye (named as PhE-NH2) were conjugated using pyruvic acid (PA) as the molecular “bridge”. A number of characterization techniques, such as proton nuclear magnetic resonance (1H NMR), fourier transform infrared (FT-IR) spectroscopy, UV–Vis absorption spectroscopy, fluorescent spectroscopy and transmission electron microscopy (TEM), have been utilized to confirm the successful preparation of OSA-PA-PhE biopolymers. The biological evaluation results confirmed that the OSA-PA-PhE FPNs possessed ultrahigh biocompatibility and desirable imaging properties. Moreover, compared with the previous work about FPNs, this work had at least two obvious advantages, one was the original materials of sodium alginate are resourceful, cheaper, and compatible for human tissue and cells, and another was the novel Döbner reaction is a facile conjugation reaction under mild experimental conditions (e.g. catalyst-free, air atmosphere and in the presence of water). Considered the features of microwave-assisted Döbner reaction and OSA, the OSA-PA-PhE FPNs should be of great potential for different biomedical applications.