Metallacages and Covalent Cages for Biological Imaging and Therapeutics

Abstract

Due to their precise three-dimensional structures and tunable cavities, metallacages and covalent cages have been widely used in various fields, such as catalysis, separation, sensing, and biomedicine. As a result of the unique pattern of directed synthesis and modular assembly, cages can be modified in many different ways to construct stimuli-responsive cages for marker detection and imaging in biological applications. Additionally, imaging agents and drugs can be loaded into the unique cavity of the cages to achieve precise disease diagnosis and treatment. This Review summarizes recent advances in metallacages and covalent cages in biological applications and presents their representative examples in imaging and therapeutics. The problems and future development directions of cages in biological applications are emphasized, which may provide clear guidance for the design and application of precise and controllable biological diagnostic reagents.

Cage-based sensors for circular dichroism analysis

“…Covalent cages do not contain metals and bind covalently with ligands, in contrast to metallacages and their noncovalent cage-analyte interactions. [47][48][49] Because some chiral analytes are unstable in the presence of metal ions and others contain metal ions themselves, the metal-free cages have an important place in chiral sensing. This section compiles the latest examples of covalent cages for the detection of chiral analytes, including ions, small molecules, and peptides.…”

Multimodal Therapeutic Platforms Based on Self‐Assembled Metallacycles/Metallacages for Cancer Radiochemotherapy

“…The most frequently and extensively used organic ligands so far are focused on porphyrin, boron dipyrromethene (BOD-IPY) derivatives, aggregation-induced emission luminogens (AIEgens) and other second near-infrared (NIR-II) dyes. [16,17] With the assistance of different types of organic fluorophores, the efficacy of imaging-guided PTT and PDT would be significantly accelerated via regulating the photothermal conversion capacity or the cytotoxic reactive oxygen species (ROS) generating ability of ligands. Among these organic linkers, porphyrin has been exploited as a highly efficient photosensitizer since the early 1980s, which holds the capability of producing ROS under the irradiation of visible or NIR light.…”

Porous organic cages for gas separations

“…Additionally, POCs show promising potential for numerous applications such as molecular recognition, membranes, catalysis, and separation. [74][75][76][77][78][79][80][81][82][83][84][85] Despite prior reviews covering several applications, there remains an insufficient amount of coverage regarding the efficient gas-selective separation achieved by POCs. Similar to zeolites, MOFs, and COFs, POCs also exhibit gas storage and separation capabilities, fundamental attributes of porous materials.…”