Effect of Element Iodine on the Cell Membrane Transportability of Fluorescent Polymers and Lysosome-Targeted Cell Imaging

Fluorescence cell staining has become an important tool in biology for sensing and imaging applications. Surprisingly, the introduction of halogen atoms, especially iodine atoms, into small molecules' framework is able to enhance the cellular uptake of fluorescent objects. However, for these iodocontaining fluorescent probes, the inherent disadvantages, such as water insolubility, high toxicity, and aggregation-caused quenching, prevent them from extensive applications. Furthermore, iodination of organic molecules is really difficult to produce. In our research work, we synthesized fluorescence probes by a copolymerization method, by which the water-soluble copolymers of P-TPE, P-TPE-I-1 P-TPE-I-2, and P-TPE-I-3 with different iodine element contents were synthesized. The study on fluorescence performances demonstrated that these polymers are of high fluorescence quantum yields and long fluorescence lifetimes (up to 15 ns). Both of these characteristics are very beneficial to fluorescence probes being used in sensing and cell imaging. Importantly, these aggregation-induced emission (AIE)-active probes were specifically lysosome-targeted. More than that, our research results supported the conclusion that introduction of iodine atoms is able to enhance the cellular uptake of fluorescent probes. Possibly, the nature of halogen bonding plays a crucial role in the plasma membrane transport in mammalian cells. Obviously, these results may provide a novel strategy to improve the cellular uptake of organic molecules for studying cellular functions and drug delivery with a more convenient manner. Our research results disclosed the potential applications of AIE materials on the plant cell staining. Due to the water solubility and biocompatiblilty, the resulting fluorescent polymers demonstrated less stress on the plant cells.