Novel Aggregation-Induced Emission Fluorescent Molecule for Platinum(IV) Ion-Selective Recognition and Imaging of Controlled Release in Cells

The loading, delivery, and release of Pt(IV) precursors in living organisms are important aspects of exploring the development of platinum drugs. In recent years, the biological application of the fluorescent sensors to platinum drugs has been insufficient to meet the study of Pt(IV) precursors. It is urgent to design and develop a biocompatible, multifunctional fluorescent sensor for the study of loading, transport, and release of Pt(IV) ions. Herein, we report a fluorescent molecule (E)-6-(diethylamino)-N'-(4-(diphenylamino) benzylidene)-2-oxo-2H-chromene-3 carbohydrazide (CHTPA). CHTPA has good sensitivity and selectivity to Pt(IV) when the water content is 5%, and significant increase of the fluorescence emission intensity of CHTPA is observed with Pt(IV) concentration. The sensing mechanism is attributed to photo-induced electron transfer, which is verified by X-ray absorption near edge spectroscopy spectra, UV-vis absorption spectroscopy, 1H NMR spectra, and Fourier transform infrared spectra. Furthermore, the CHTPA-Pt(IV) complex is able to release Pt(IV) in aqueous solution, and the green fluorescence of CHTPA based on the aggregation-induced emission effect can be observed. Inspired by these, the amphiphilic block copolymer poly(ethyloxide)-block-polystyrene (PEO-b-PS) is used to prepare the nonconjugated polymer dots (Pdots). The experimental results show that Pdots can effectively slow down the release speed of Pt(IV) in aqueous solution and it has a great monodispersity in aqueous solution. Meanwhile, Pdots show low cytotoxicity, and this is favorable for intracellular applications. The investigation of cellular imaging indicates that these Pdots can act as a carrier to deliver Pt(IV) into MCF-7 cells for visualized delivery and sustained release of platinum(IV) ions. Therefore, this study provides a new avenue to design and develop a biocompatible multifunctional fluorescent sensor for studying the loading, delivery, and release of Pt(IV) in cells.