Photo‐Controlled Reversible Microtubule Assembly Mediated by Paclitaxel‐Modified Cyclodextrin

The design and construction of multi‐stimuli‐responsive supramolecular nanoassemblies that can mimic and regulate the fundamental biological processes have become a focus of interest in supramolecular chemistry. In this work, a perfect combination has been achieved between naturally occurring microtubules and artificially macrocyclic receptors. The self‐assembling morphology of microtubules can be photo‐tuned by the host–guest interaction of paclitaxel‐modified β‐cyclodextrin (PTX‐CD) and photochromic arylazopyrazole (PTX‐AAP). Moreover, the supramolecularly aggregated microtubules in a cellular environment can induce a pronounced cell morphological change and cell death. This supramolecular approach based on the secondary PTX‐AAP?PTX‐CD complexation provides us a facile method to reversibly control the intertubular aggregation behaviors of microtubules, which may bring new perspectives in the treatment of diseases related to improper protein aggregation.     

Photophysical Properties of Emissive Pyrido[3,2‐c]carbazole Derivatives and Apoptosis Induction: Development towards Theranostic Agents in Response to Light Stimulus

Pyridocarbazole moieties are present in many natural products, such as olivacine and ellipticine, and their derivatives are well‐known anticancer agents. To develop functional therapeutic and diagnostic compounds, three emissive pyrido[3,2‐c]carbazole derivatives, PC‐X , containing secondary or tertiary amine groups, were synthesized from an aminoquinoline derivative using a palladium complex as the catalyst. X‐ray diffraction analyses revealed that PC‐X showed highly planar structures between the pyridine ring and the carbazole framework, exhibiting high fluorescence intensities along with solvatochromic behavior. Imaging of HeLa cells treated with PC‐X showed no specific accumulation into the organelles; however, a comparative examination showed that the accumulation in mitochondria was the highest as compared to nuclei and lysosomes. Cytotoxicity analysis using HeLa cells showed that PC‐H, containing a secondary amine group showed the highest cytotoxicity (IC₅₀≈20 μm ) as compared to another PC‐X having a tertiary amine group. Colocalization with MitoTracker, a typical mitochondrial staining dye, showed apoptosis‐like behavior with remarkable appearance of blebbing during irradiation with near UV light (403 nm), suggesting that the PC‐H may not only behave as a fluorescence probe for the imaging organelles, but also as a therapeutic agent for inducing apoptosis in HeLa cells, thereby functioning as a theranostic agent.