Bio-orthogonally Activatable Fluorescent Probe for Specific Imaging of Myeloid Cell Leukemia 1 Protein.

The antiapoptotic protein myeloid cell leukemia 1 (Mcl-1) has been increasingly identified as a promising potential therapeutic target attributed to its critical regulation effect in diverse cellar physiopathological events. Current fluorescence imaging strategies tend to be susceptible to the cellular microenvironment, and straightforward mapping of Mcl-1's level variation remains challenging. In this paper, an activatable "off-on" fluorescence strategy for Mcl-1 specific labeling was presented based on bio-orthogonal chemistry by introducing tetrazine-functionalized borondipyrromethene (TB) as a fluorescent reporter and trans-cyclooctyne-derived indole-2-carboxylic acid (TI) as an Mcl-1 targeting moiety. With the click pair of TB and TI, the Mcl-1 expression level in vitro and in vivo was successfully mapped straightforward. Also, the level changes of Mcl-1 upon drug challenge were demonstrated. This work provides a robust fluorescence strategy for Mcl-1 in situ imaging, and the results would further facilitate the comprehensive revelation of the Mcl-1 biological effect.

Exploration of Thermally Activated Delayed Fluorescence (TADF)-Based Photoredox Catalyst To Establish the Mechanisms of Action for Photodynamic Therapy.

The mechanisms of action (MoA) have been proposed to further reduce the O2 dependence of photodynamic therapy (PDT) significantly. However, the triplet states of traditional photosensitizers are relatively short and also are easily deactivated by the quenching of H2O or O2. This is not conducive for the electron transfer in the photocatalytic process and poses a great obstacle to establish the MoA. Therefore, we selected and synthesized a zirconium(IV) complex (Zr(MesPDPPh)2) reported by Milsmann to address this issue. The specific symmetric and intact geometry endowed Zr(MesPDPPh)2 NPs with long-lived triplet excited state (τ = 350 µs), desired sensitized ability, and improved anti-interfering performance on O2, which was matched with the requirements of photoredox catalyst significantly. The results showed that while PDT (I) and PDT (II) could be achieved simultaneously by leveraging Zr(MesPDPPh)2 NPs, it also could be served as a rare example of thermally activated delayed fluorescence (TADF)-based photoredox catalyst to implement the MoA of PDT. It involved the oxidation of NADH and the establishment of catalytic cycle collaborating by O2 and cytochrome c (cyt c) in normoxia and hypoxia, respectively. As a result, the oxygen-free PDT and tumor-growth inhibition was realized.

In Situ Fluorescence Imaging Reveals Contribution of Cerebral Hydroxyl Radicals in Hyperhomocysteinemia-Induced Alzheimer-like Dementia.

Elevated plasma level of homocysteine, also termed as hyperhomocysteinemia, is acknowledged as a significant and independent risk factor of Alzheimer's disease. However, the mechanistic insight has not been thoroughly elucidated yet. In this work, 3,5-dihydroxybenzyloxy was explored as the unique reaction trigger and integrated into the naphthalimide fluorophore via a carbamate linker to afford a new probe for •OH imaging. •OH treatment induced aromatic hydroxylation and subsequent elimination reaction to release the caged fluorophore, accompanied with a highly specific and sensitive turn-on fluorescence response. Cell imaging results revealed that excess homocysteine triggered overwhelming •OH production, which was mediated by N-methyl-d-aspartate receptor and NADPH oxidase, and the resultant •OH stress further initiated neuronal ferroptosis, also confirmed by western blot analyses. Additionally, hyperhomocysteinemic mouse models were established, and Alzheimer-like dementia of the mice was observed from behavioral tests. Most importantly, with this probe, cerebral •OH fluctuation was in situ visualized in live mice, which positively correlated with the severity of Alzheimer-like dementia induced by hyperhomocysteinemia. These results reveal that cerebral •OH stress may be the critical nexus linking hyperhomocysteinemia and Alzheimer's disease. This work provides a robust fluorescence probe for in situ visualizing the cerebral •OH fluctuations and illuminating critical insights into •OH contributions in brain disorders.

Endoplasmic Reticulum-Targeted Carbon Monoxide Photoreleaser for Drug-Induced Hepatotoxicity Remediation.

The alleviation of drug-induced liver injury has been a long-term public health concern. Growing evidence suggests that endoplasmic reticulum (ER) stress plays a critical role in the pathogenesis of drug-induced hepatotoxicity. Therefore, the inhibition of ER stress has gradually become one of the important pathways to alleviate drug-induced liver injury. In this work, we developed an ER-targeted photoreleaser, ERC, for controllable carbon monoxide (CO) release with a near-infrared light trigger. By employing peroxynitrite (ONOO-) as an imaging biomarker of hepatotoxicity, the remediating effect of CO was mapped upon drug acetaminophen (APAP) challenge. The direct and visual evidence of suppressing oxidative and nitrosative stress by CO was obtained both in living cells and in mice. Additionally, the ER stress inhibiting the effect of CO was verified during drug-induced hepatotoxicity. This work demonstrated that CO may be employed as a potent potential antidote for APAP-related oxidative and nitrative stress remediation.

Modified preparation of Si@C@TiO2 porous microspheres as anodes for high-performance lithium-ion batteries.

Microscale porous silicon materials have shown great application potential as anodes for next-generation lithium-ion batteries (LIBs); however, they face significant challenges, including mechanical structure instability, low intrinsic conductivity, and uncontrollable processing. In this study, a modified etching strategy combined with a facile sol-gel method is demonstrated to prepare microscale porous Si microspheres encapsulated by an inner amorphous carbon shell (≈10 nm) and an outer rigid anatase titanium oxide (TiO2) shell (≈20 nm) (PSi@C@TiO2), with the intact porous framework and core-shell-shell spherical structure. The interconnected pores can sufficiently accommodate the expansion of the Si core during lithiation. Moreover, the double shells can not only enhance the kinetic behavior of the PSi@C@TiO2 microspheres, but can act as a compact fence to force the Si core to expand toward the internal pores during lithiation, ensuring the integrity of the porous spherical structure. As a result, the PSi@C@TiO2 anodes show greatly superior high specific capacity, excellent rate capability, stable solid-electrolyte interphase (SEI) films and steady mechanical structure. It delivers a high reversible capacity of 1004 mA h g-1 after 250 cycles at 0.5 A g-1. This study provides a modified method to prepare microscale porous Si anodes with a stable mechanical structure and long cycle life for LIBs.

Real-time visualization of the fluctuations in HOBr with AIE fluorescent probes during myocardial ischemia-reperfusion injury.

Two fluorescent probes (QM-S and QM-Se) featuring AIE properties were developed. The increased intracellular hypobromous acid (HOBr) in cardiomyocytes during MIRI was revealed with these probes. It was also observed that MIRI might be alleviated by combating oxidative stress, as well as inhibiting inflammation and ferroptosis, which could mediate oxidative stress.

Cyano-substituted stilbene (CSS)-based conjugated polymers: Photophysical properties exploration and applications in photodynamic therapy.

Conjugated polymers (CPs) have attracted great attention due to their excellent optical properties (such as large absorption cross section, signal amplification, high photostability etc.). As representative electron acceptors and organic small molecules which are easy to be synthesized and modified, cyano-substituted stilbene (CSS) derivatives are widely used to construct photoelectrical materials. Despite donor-acceptor (D-A) conjugated polymers based on CSS have been applied in sensing and super-resolution imaging, systematic studies about the effects of different CSS structures on the photophysical properties of CPs have rarely been reported. Therefore, we have synthesized a series of D-A conjugated polymer nanoparticles (CP NPs) based on different CSS units, and found that the photophysical properties of CP NPs including the bandgap and ΔES-T were closely associated with the structure of CSS derivatives. Moreover, the introduction of tetraphenylethylene (TPE) can relieve the aggregation-caused quenching (ACQ) effects of CSS conjugated polymers to varying degrees. The theoretical calculation further corroborated that by regulating the number and distribution of cyanide groups in the repeating units, the stronger D-A strength resulted in a redshift in the emission spectrum and the more efficient capacity of total ROS (1O2, O2•- and •OH) generation. We then selected CP6-TAT NPs, with the near infrared (NIR) emission and best ФPS, to characterize its performance in photodynamic therapy (PDT). It was revealed that CP6-TAT NPs can be regarded as an ideal candidate for PDT. The results provided a new reference for regulating the structure-effect relationship of CPs and a comprehensive method for constructing photosensitizers based on CPs.

Identification of 1,4-Benzodiazepine-2,5-dione Derivatives as Potential Protein Synthesis Inhibitors with Highly Potent Anticancer Activity.

In this study, a random multiple human tumor cell line screening of an in-stock small-molecule chemical library was performed, and a hit compound, 1,4-benzodiazepine-2,5-dione (BZD, 11a; average 50% growth inhibitory concentration (GI50 = 0.24 µM)) to 60 tumor cell lines of nine types of human cancers, was identified. Subsequent structure-activity relationship (SAR) investigation disclosed a highly potent antitumor compound, 52b, that was shown to exert promising effects against lung cancer cells by inducing cell cycle arrest and apoptosis. Further polysome profile analysis revealed that 52b inhibited protein synthesis in cancer cells. Moreover, 52b significantly prevented tumor growth in a human non-small-cell lung cancer (NCI-H522) xenograft mouse model with no observable toxic effects. These findings are the first report of the synthetic compound 52b with a 1,4-benzodiazepine-2,5-dione skeleton that acts as a potential protein synthesis inhibitor to effectively inhibit tumor growth.

Photocontrollable Fluorescence Imaging of Mitochondrial Peroxynitrite during Ferroptosis with High Fidelity.

Ferroptosis, a new regulatory cell death modality, underlies the pathogenesis of a broad range of disorders. Although much efforts have been made to uncover the molecular mechanisms, some mechanistic details of ferroptosis still remain poorly understood. Particularly, the functional relevance of mitochondrial reactive oxygen species (ROS) in ferroptosis is still highly controversial, which is partially due to the fact that it still remains puzzled how the mitochondrial ROS level varies during ferroptosis. The conventional mitochondria-targeted probes may react with cytosolic ROS and show fluorescence variation before entering mitochondria, thus probably giving a false result on the mitochondrial ROS level and leading to the misjudgment on its biofunction. To circumvent this issue, we rationally designed a photocontrollable and mitochondria-targeted fluorescent probe to in situ visualize the mitochondrial peroxynitrite (ONOO-), which is the ROS member and mediator of ferroptosis. The photoactivated probe was endowed with a highly specific and sensitive fluorescence response to ONOO-. Notably, the response activity could be artificially regulated with light irradiation, which ensured that all the probe molecules passed through the cytosol in the locked status and were then photoactivated after reaching mitochondria. This photocontrolled fluorescence imaging strategy eliminated the interference of ONOO- outside the mitochondria, thus potentially afforded improved fidelity for mitochondrial ONOO- bioimaging in live cells and animal models. With this probe, for the first time, we revealed the mitochondrial ONOO- flux and its probable biological source during erastin-induced ferroptosis. These results suggest a tight correlation between mitochondrial ONOO-/ROS and ferroptotic progression, which will further facilitate the comprehensive exploration and manipulation of ferroptosis.

Two-photon fluorescence imaging of the cerebral peroxynitrite stress in Alzheimer's disease.

We designed and synthesized an oxindole-functionalized two-photon fluorescent probe based on a naphthalimide fluorophore, which enabled in situ visualization of the overwhelming peroxynitrite flux during amyloid-ß-induced neuronal ferroptosis and cerebral peroxynitrite stress in live mice with Alzheimer's disease.

Fabricating and Modulating Robust Multi-Photoaddressable Systems with the Derivatives of Diarylethylene and Donor-Acceptor Stenhouse Adducts.

Multi-photoaddressable systems (MPSs) belong to complex systems, which are comprised of more than one photoswitching molecule and can respond to different wavelengths of light simultaneously. While MPSs have been extensively applied in various fields, there are also some challenges, such as the deficiency of the wavelength-selective control and the interference from the poor thermodynamic stability of used photoswitching molecules. Herein, we reported two robust MPSs (MPS1/2) consisting of diarylethylene derivative (DAE) and different donor-acceptor Stenhouse adducts (DASAs), in which both opened and closed forms of DAE and opened forms of DASAs are thermodynamically stable. MPS1/2 enable fully reversible cyclic photoswitching with improved thermal interference resistance. Moreover, MPS2 also shows a favorable property in PMMA films and has been applied in multicolor display. It is expected that the prepared MPSs could be used in more fields such as information storage and reading and encoding light.

Harnessing SeN to develop novel fluorescent probes for visualizing the variation of endogenous hypobromous acid (HOBr) during the administration of an immunotherapeutic agent.

By means of the formation of SeN, the ABT-Se and NDI-Se were developed to detect and visualize endogenous hypobromous acid (HOBr) in live cells. Specifically, the upregulation of HOBr was monitored by NDI-Se during the administration of an immunotherapeutic agent.

Dual-Channel Imaging of Amyloid-ß Plaques and Peroxynitrite To Illuminate Their Correlations in Alzheimer's Disease Using a Unimolecular Two-Photon Fluorescent Probe.

Alzheimer's disease (AD) involves multiple pathological factors that mutually cooperate and closely contact to form interaction networks for jointly promoting the AD progression. Therefore, the comonitoring of different factors is particularly valuable for elucidating their level dynamics and complex interactions. However, such significant investigations remain a major challenge due to the lack of unimolecular fluorescent probes capable of simultaneous and discriminative visualization of multiple targets. To address this concern, as proof of principle, we rationally designed a unimolecular fluorescent probe to discriminate and simultaneously profile amyloid-ß (Aß) plaques and peroxynitrite (ONOO-), which are both the pronounced AD pathological factors. Herein, a novel ONOO- reaction trigger was installed onto an Aß plaque binding fluorophore to generate a dual functional fluorescent probe, displaying completely separate spectral responses to Aß plaques and ONOO- with high selectivity and sensitivity. With this probe, for the first time, we comonitored the distribution and variation of Aß plaques and ONOO- through two independent fluorescence channels, demonstrating their close apposition and tight correlation during AD course in live cell and mouse models through two-photon imaging mode. Notably, Aß aggregates induce the neuronal ONOO- generation, which conversely facilitates Aß aggregation. The two critical events, ONOO- stress and Aß aggregation, mutually amplify each other through positive feedback mechanisms and jointly promote the AD onset and progression. Furthermore, by coimaging of the level dynamics of Aß plaques and ONOO-, we found that the cerebral ONOO- is a potential biomarker, which emerges earlier than Aß plaques in transgenic mouse models. Overall, the dual-channel responsive performance renders this probe as a powerful imaging tool to decipher Aß plaque-ONOO- interactions, which will facilitate AD-associated molecular pathogenesis elucidation and multitarget drug discovery.

A light-activatable photosensitizer for photodynamic therapy based on a diarylethene derivative.

Herein, a light-activatable photosensitizer based on a diarylethene derivative, DAE-TPE, was developed for photodynamic therapy. Upon UV exposure, the "opened" form (OF) of DAE-TPE NPs was converted to the "closed" form (CF), and photosensitization was activated. The CF of DAE-TPE NPs exhibited sufficient photodynamic therapy effects upon HeLa cells.

A near-infrared fluorogenic probe for nuclear thiophenol detection.

Based on the thiolysis of dinitrophenyl ethers, a nucleus-targeted fluorescent probe, AQD, with bisalkylaminoanthraquinone as the fluorophore, was prepared for the near-infrared mapping of thiophenol in live cells, zebrafish, and mice.

Near-infrared photocontrolled therapeutic release via upconversion nanocomposites.

Photocontrolled therapeutic release holds great promise due to its versatile manipulability, superb spatiotemporal precision and minimal tissue invasiveness in biomedical purposes. However, most of light-responsive platforms thus far have relied on UV or visible light which substantially limit the potential applicability in living animals. In recent decades, near-infrared (NIR) light-mediated theranostic upconversion nanocomposites (UCNCs) that integrate conventional UV/Vis-sensitive materials and classic lanthanide-doped upconversion nanoparticles (UCNPs) have significantly promoted the development of deep-tissue photoreleasable therapeutics in vivo. Herein, we seek to review current NIR upconversion triggered photorelease techniques and their diverse applications in the biological regulation, as well as diseases therapy. In addition, the future perspectives and challenges for advancing UCNCs based NIR photoreleasable nanotherapeutics into clinical translations are proposed.

Visualizing peroxynitrite fluxes in myocardial cells using a new fluorescent probe reveals the protective effect of estrogen.

A tetraphenyl ethylene (TPE)-based fluorescent probe specific for ONOO- was developed to evaluate and verify the protective effect of estrogen on myocardial cells during OGD/R.

An H2S-activated ratiometric CO photoreleaser enabled by excimer/monomer conversion.

Based on the excimer-monomer conversion of a pyrene-flavone hybrid, a ratiometric CO photoreleaser, PFN, was constructed for simultaneous H2S quantification and CO release in inflammatory cells.

A Facile, Versatile, and Highly Efficient Strategy for Peroxynitrite Bioimaging Enabled by Formamide Deformylation.

Peroxynitrite (ONOO-) is attracting increasing attention due to its involvement in multiple facets of pathophysiological processes. However, ONOO- bioimaging is still challenging due to (1) the lack of highly specific reaction triggers, (2) the tedious and low-yielding synthesis of current sophisticated probes, and (3) the lack of availability of a versatile chemical strategy. To address these challenges, on the basis of amine formylation/deformylation chemistry, we have developed a novel strategy for ONOO- bioimaging. As proof of principle, we designed, synthesized, and evaluated four novel fluorescent probes equipped with the formamide functionality. Although they feature distinctly different fluorophore classes, all probes can be synthesized in one step in high yields and exhibit particularly specific, highly sensitive, and rapid responses to ONOO-. The bioimaging capability is well demonstrated by successfully visualizing ONOO- fluctuation in live cells and major organs of mice suffering from paraquat poisoning. The proposed strategy has proved to be a facile, versatile, and highly efficient methodology for ONOO- visualization, which will greatly facilitate ONOO- biochemistry and pathophysiology.

Reactivity Modulation of Benzopyran-Coumarin Platform by Introducing Electron-Withdrawing Groups: Specific Detection of Biothiols and Peroxynitrite.

A variety of fluorophores have been designed and created to fabricate organic fluorescent probes. Among these fluorophores, benzopyran-coumarin (BC) based fluorescent platform has attracted increasing attention as it shows multiple appropriate fluorescent and imaging capacities. Nevertheless, the analytical potential of BC is still urgently needed to be further excavated as its detection performance is hindered by the inherent drawbacks of current BC skeleton, that is, limited number of reactive sites. As such, in this work, by simply introducing electron-withdrawing (EW) substituent groups, we reconstructed BC skeleton to afford two fluorescent probes, BCB (-Br substitued) and BCN (-NO2 substitued), both of which featured two highly reactive sites. These two probes were capable of detecting peroxynitrite (ONOO-) and biothiols (hydrogen sulfide, glutathione, cysteine, and homocysteine) through naked eye and UV-vis absorption analysis in buffer solution. In addition, BCB was able to specifically sense biothiols with fluorescent analysis while BCN, with - NO2 instead of -Br, displayed more prominent fluorescent specificity toward ONOO-. This work provided a new strategy for the reactivity regulation of fluorophore through EW group introduction, as well as an alternative approach and method for the construction of fluorescent probes for other important biological species.