Jinjin Zhang

Although boron dipyrromethene (BODIPY)-based metallacycles are expected to be promising candidates for imaging probes and therapeutic agents, their biomedical applications are restricted by their short absorption/emission wavelengths. In this work, we report a rhombic metallacycle M with broad absorption in the near-infrared (NIR) range and emissions at wavelengths >800 nm, which exhibits an efficient photothermal conversion capacity. Metallacycle M was encapsulated via Pluronic F127 to fit the biotic environment, resulting in the generation of F127/M nanoparticles (NPs) with high hydrophilicity and biocompatibility. In vitro studies demonstrated that the F127/M NPs underwent efficient cellular uptake and exhibited satisfactory photothermal therapeutic activity. Furthermore, in vivo experiments revealed that tumor growth was effectively inhibited, and the degree of undesirable biological damage was minimal in treatment with F127/M NPs and laser irradiation. Finally, the F127/M NPs could be visualized through NIR fluorescence imaging in living mice, thereby allowing their distribution to be monitored in order to enhance treatment accuracy during photothermal therapy. We envision that such BODIPY-based metallacycles will provide emerging opportunities for the development of novel therapeutic agents for biomedical applications.

Main observation and conclusion: Supramolecular polymer networks (SPNs) have always been the focus of research due to their novel features of good processability, stimuli‐responsiveness, self‐healing, and recyclability. Herein, we report the preparation of a metallacycle‐linked supramolecular gel via orthogonal metal‐ligand interactions and host‐guest interactions. A triangular metallacycle with three appended 21‐crown‐7 (21C7) units was obtained by the metal coordination of nickel(II)‐salen‐based dipyridyl ligands and platinum(II) acceptors. The integration of this metallacycle and traditional copolymer bearing secondary ammonium salts constructed a SPN via host‐guest recognition between 21C7 units and ammonium salts, and a supramolecular gel further formed at high concentration. Multiple stimulus responsiveness and self‐healing properties of gel were observed. The gel exhibited better stretchability compared to relative gel formed by copolymer alone owing to the synergistic effect of covalent bonds and supramolecular interactions. Moreover, compared to the model gel without metallacycles, the gel showed higher storage and loss moduli, and exhibited stronger stiffness in the self‐healing tests performed with rheometer, indicating the metallacycle played an important role in improving the stiffness and self‐healing of the gel. Therefore, the feasible approach to the formation of SPNs by the marriage of covalent polymers and metallacycles is expected to open a new way to design novel SPNs.

Conjugated polymers generally contain conjugated backbone structures with benzene, heterocycle, double bond, or triple bond, so that they have properties similar to semiconductors and even conductors. Their energy band gap is very small and can be adjusted via chemical doping, allowing for excellent photoelectric properties. To obtain prominent conjugated materials, numerous well-designed polymer backbones have been reported, such as polyphenylenevinylene, polyphenylene acetylene, polycarbazole, and polyfluorene. 4,4′-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based conjugated polymers have also been prepared owing to its conjugated structure and intriguing optical properties, including high absorption coefficients, excellent thermal/photochemical stability, and high quantum yield. Most importantly, the properties of BODIPYs can be easily tuned by chemical modification on the dipyrromethene core, which endows the conjugated polymers with multiple functionalities. In this paper, BODIPY-based conjugated polymers are reviewed, focusing on their structures and applications. The forms of BODIPY-based conjugated polymers include linear, coiled, and porous structures, and their structure–property relationship is explored. Also, typical applications in optoelectronic materials, sensors, gas/energy storage, biotherapy, and bioimaging are presented and discussed in detail. Finally, the review provides an insight into the challenges in the development of BODIPY-based conjugated polymers.