Masafumi Minoshima

Heterogenizing molecular photocatalysts while preserving their intact, pre‐designed structures—without redesigning the host—remains a fundamental challenge. Immobilization within porous materials offers control over reaction environments and improved recyclability; however, most host systems require catalyst‐specific structural redesign, limiting generality. We introduce a cage‐type porous organic salt (POS) as a modular host platform for homogeneous, molecularly defined photocatalysts (organic molecules and metal coordination complexes) based on a ship‐in‐a‐bottle strategy. A sodalite‐type POS constructed from adamantane‐based sulfonic acid and tri(ethynylphenyl)methylamine provides well‐defined, light‐transparent, cage‐like internal cavities. Single‐crystal X‐ray diffraction reveals that the POS accommodates diverse photocatalysts, including anthraquinone, phenanthrenequinone, and phthalocyanine, through a unified recrystallization protocol. The framework exhibits negligible absorption in the visible region, enabling selective excitation of photocatalysts without competitive light absorption. Post‐synthetic thiol–yne crosslinking of ethynyl groups on the pore surface reinforces the framework and renders it insoluble while preserving cage‐like cavities. For example, a phenanthrenequinone‐encapsulated POS functions as a reusable heterogeneous photocatalyst for visible‐light‐driven hydrogen peroxide production from isopropanol and oxygen, achieving rates of up to 4.2 mmol g ⁻¹ h ⁻¹ without catalyst leaching. Overall, cage‐type POSs serve as light‐transparent nanoreactors for intact molecular photocatalysts, providing a modular, expandable platform for photocatalyst immobilization and post‐synthetic functionalization.

Heterogenizing molecular photocatalysts while preserving their intact, pre‐designed structures—without redesigning the host—remains a fundamental challenge. Immobilization within porous materials offers control over reaction environments and improved recyclability; however, most host systems require catalyst‐specific structural redesign, limiting generality. We introduce a cage‐type porous organic salt (POS) as a modular host platform for homogeneous, molecularly defined photocatalysts (organic molecules and metal coordination complexes) based on a ship‐in‐a‐bottle strategy. A sodalite‐type POS constructed from adamantane‐based sulfonic acid and tri(ethynylphenyl)methylamine provides well‐defined, light‐transparent, cage‐like internal cavities. Single‐crystal X‐ray diffraction reveals that the POS accommodates diverse photocatalysts, including anthraquinone, phenanthrenequinone, and phthalocyanine, through a unified recrystallization protocol. The framework exhibits negligible absorption in the visible region, enabling selective excitation of photocatalysts without competitive light absorption. Post‐synthetic thiol–yne crosslinking of ethynyl groups on the pore surface reinforces the framework and renders it insoluble while preserving cage‐like cavities. For example, a phenanthrenequinone‐encapsulated POS functions as a reusable heterogeneous photocatalyst for visible‐light‐driven hydrogen peroxide production from isopropanol and oxygen, achieving rates of up to 4.2 mmol g ⁻¹ h ⁻¹ without catalyst leaching. Overall, cage‐type POSs serve as light‐transparent nanoreactors for intact molecular photocatalysts, providing a modular, expandable platform for photocatalyst immobilization and post‐synthetic functionalization.

Fluorogenic probes are invaluable tools in biology and medicine, offering high sensitivity and background-free imaging. However, achieving a high signal-to-noise ratio, target specificity, and robust cell permeability in wash-free imaging remains a significant challenge. Here, we report a new class of fluorogenic fluorophores engineered by incorporating five-membered heterocycles such as furan or thiophene at 9-position of the xanthene core. This structural modification enables precise control over intramolecular rotation, which is suppressed in viscous environments or upon interaction with biomolecular targets to allow for fluorescence activation independent of the spirolactone equilibrium characteristic of traditional rhodamine fluorophores. This rotation-based activation strategy was further extended to develop furan- and thiophene-substituted carborhodamine and silicon-rhodamine fluorophores, demonstrating the versatility and modularity of our approach. Using this design, we developed practical fluorogenic probes for self-labeling protein tags, including HaloTag, SNAP-tag, and PYP-tag, achieving high cell permeability and strong fluorescence activation under no-wash live-cell imaging conditions. The HaloTag probe enabled real-time visualization of the endoplasmic reticulum whorl formation in live cells, showcasing its utility in dynamic cellular imaging. To enhance the applicability of our design, we developed BRD4- and EGFR-targeting probes by conjugating our fluorophores with JQ1 and gefitinib/erlotinib inhibitors, utilizing a non-covalent binding strategy. The EGFR-targeting probes exhibited strong fluorescence in cells with high levels of EGFR expression, demonstrating their effectiveness for detecting EGFR overexpression. This work presents a versatile design strategy that leverages the controlled intramolecular rotation of furan/thiophene rings to create innovative OFF/ON fluorogenic probes, offering a robust platform for selective, wash-free live-cell imaging of diverse cellular targets.

The development of noninvasive, quantifiable molecular imaging probes using magnetic resonance imaging (MRI) is critical for advancing in vivo diagnostics. Previous work has demonstrated the development of perfluorocarbon (PFC)‐encapsulated silica nanoparticles named as FLAME (fluorine accumulated silica nanoparticles for MRI enhancement) for sensitive in vivo imaging using ¹⁹ F MRI. While FLAME shows excellent MR properties and application potential, its biocompatibility is yet to be enhanced. Herein, a lipid bilayer‐coated ¹⁹ F MRI nanoparticle (FLAME‐LB) is developed, which easily changes the surface components of nanoparticles by coating PFC‐loaded silica nanoparticles with a phospholipid membrane containing PEGylated lipids. Structural characterization confirmed the successful bilayer formation, and ¹⁹ F nuclear magnetic resonance (NMR)/MRI analyses demonstrated strong, concentration‐dependent fluorine signals. In vivo studies in mice reveal that FLAME‐LB accumulates in the liver shortly after intravenous injection, but exhibits significantly faster clearance than uncoated FLAME nanoparticles. This difference is attributed to the lipid bilayer and PEGylation, which promotes hepatobiliary elimination. These findings highlight the potential of the surface‐engineered FLAME‐LB as a biocompatible and tunable platform for ¹⁹ F MRI applications in biomedical imaging.

Optical regulation of transcription using chemical compounds is an effective strategy to manipulate gene expression spatiotemporally. Conventional caging approaches with photoremovable protecting groups may require intense UV‐light exposure and release potentially toxic byproducts. To address these problems, here we developed a light‐mediated transcriptional regulation system by combining a caging‐group‐free photoactivatable dye PaX ₅₆₀ and a multidrug‐binding transcriptional regulator QacR. The cationic dye generated from PaX ₅₆₀ through traceless photoconversion bound QacR and reduced its repressor function, resulting in transcriptional activation. Importantly, this system allowed transcriptional activation with a large dynamic range under mild visible light exposure and simultaneous detection of the state of the photoactivated effector. This module was integrated into the T7 RNA polymerase expression system to demonstrate light‐activated transcription in vitro and in living cells.

Optical regulation of transcription using chemical compounds is an effective strategy to manipulate gene expression spatiotemporally. Conventional caging approaches with photoremovable protecting groups may require intense UV‐light exposure and release potentially toxic byproducts. To address these problems, here we developed a light‐mediated transcriptional regulation system by combining a caging‐group‐free photoactivatable dye PaX ₅₆₀ and a multidrug‐binding transcriptional regulator QacR. The cationic dye generated from PaX ₅₆₀ through traceless photoconversion bound QacR and reduced its repressor function, resulting in transcriptional activation. Importantly, this system allowed transcriptional activation with a large dynamic range under mild visible light exposure and simultaneous detection of the state of the photoactivated effector. This module was integrated into the T7 RNA polymerase expression system to demonstrate light‐activated transcription in vitro and in living cells.

The precise control of DNA recombination enables the cell‐ or time‐dependent regulation of gene expression in studies of gene function. Caged estrogen receptor ligands combined with a Cre‐ERT2/loxP system are useful tools for light‐triggered DNA recombination. However, the photolysis of most caged compounds requires ultraviolet or blue light, which is toxic and displays low tissue penetration. Although a cyanine‐based photo‐responsive protecting group (PPG) can release estrogen receptor ligands with longer‐wavelength light, its low photolytic efficiency requires long illumination times. We developed a caged estrogen receptor ligand with improved green light‐responsive PPGs. The rational modification of Hydroxylated Thiazole Orange (HTO) photocages using electron‐donating groups (EDGs), such as dimethoxy (DiMeO)‐substituted HTO, resulted in high photolytic efficiency (up to ϵΦ ≈320 M⁻¹ cm⁻¹). Theoretical calculations demonstrated that the enhanced photolytic efficiencies were derived from the increased intramolecular charge transfer by EDGs upon excitation. The efficient uncaging of estrogen receptor ligands enabled the control of gene recombination in a ligand‐dependent Cre‐ERT2/loxP system in live cells.

To understand the function of protein in live cells, real‐time monitoring of protein dynamics and sensing of their surrounding environment are important methods. Fluorescent labeling tools are thus needed that possess fast labeling kinetics, high efficiency, and long‐term stability. We developed a versatile chemical protein‐labeling tool based on fluorophore‐conjugated diazabicyclooctane β‐lactamase inhibitors (BLIs) and wild‐type TEM‐1 β‐lactamase protein tag. The fluorescent probes efficiently formed a stable carbamoylated complex with β‐lactamase, and the labeled proteins were visualized over a long period of time in live cells. Moreover, use of an α‐fluorinated carboxylate ester‐based BLI prodrug enabled the probe to permeate cell membranes and stably label intracellular proteins after unexpected spontaneous ester hydrolysis. Lastly, combining the labeling tool with a pH‐activatable fluorescent probe allowed visual monitoring of lysosomal protein translocation during autophagy.

To understand the function of protein in live cells, real‐time monitoring of protein dynamics and sensing of their surrounding environment are important methods. Fluorescent labeling tools are thus needed that possess fast labeling kinetics, high efficiency, and long‐term stability. We developed a versatile chemical protein‐labeling tool based on fluorophore‐conjugated diazabicyclooctane β‐lactamase inhibitors (BLIs) and wild‐type TEM‐1 β‐lactamase protein tag. The fluorescent probes efficiently formed a stable carbamoylated complex with β‐lactamase, and the labeled proteins were visualized over a long period of time in live cells. Moreover, use of an α‐fluorinated carboxylate ester‐based BLI prodrug enabled the probe to permeate cell membranes and stably label intracellular proteins after unexpected spontaneous ester hydrolysis. Lastly, combining the labeling tool with a pH‐activatable fluorescent probe allowed visual monitoring of lysosomal protein translocation during autophagy.

Adapting MRI to the field of molecular imaging is a challenge that continues to attract considerable attention. The detection of a given biomolecular analyte requires the availability of a molecular probe that is able to respond with a sufficient signal gap in order to overcome the low sensitivity of MRI. To this end, ¹⁹F MRI has yielded promising results due to its negligible endogenous background signals. Several small molecular probes have been reported; however, the low sensitivity of ¹⁹F MRI render the detection of biomarkers in vivo difficult, in view of their sub‐nanomolar concentration on site. Researchers have thus directed their attention toward larger chemical objects containing large numbers of ¹⁹F nuclei as smart platforms that allow a stimuli‐induced response. This article discusses the recent advances and future directions in the design of nano‐probes that respond to chemical or physical stimuli recognized as biomarkers for life and disease.