Rationally Designed Fluorescence . OH Probe with High Sensitivity and Selectivity for Monitoring the Generation of . OH in Iron Autoxidation without Addition of H2 O2

Flammulina velutipes-derived carbon dots for fluorescence detection and imaging of hydroxyl radical

Monitoring hydroxyl radical (•OH) fluctuation is of great importance to study some relative pathological processes and to predict early diagnosis of diseases. Efficient •OH-responsive fluorescent sensors based on carbon dots (CDs) have been reported, but most researches have focused on the new strategies for the synthesis and doping of the CDs. Herein, a kind of biomass CDs (F-CDs) with Flammulina velutipes (F. velutipes) as the carbon source was prepared by a one-step hydrothermal method without any additional modification. The prepared F-CDs have remarkable sensitivity and selectivity and there is a good linear relationship from 0 to 12 μM with a low detection limit of 95 nM for quantitative •OH assay. With excitation-independent emission, favourable biocompatibility and low toxicity, the F-CDs can penetrate cell membranes as •OH-responsive fluorescent sensors to detect intracellular •OH in A549 cells stimulated by phorbol 12-myristate 13-acetate (PMA) and successfully monitor the •OH concentration levels by the corresponding fluorescence change. Given the combined benefits of the green and eco-friendly approach, the F-CDs show promise as novel theranostics tools for early detection and treatment of related diseases.

Design of Smart Aggregates: Toward Rapid Clinical Diagnosis of Hyperlipidemia in Human Blood

Molecular aggregates with environmental responsive properties are desired for their wide practical applications such as bioprobes. Here, a series of smart near-infrared (NIR) luminogens for hyperlipidemia (HLP) diagnosis is reported. The aggregates of these molecules exhibit a twisted intramolecular charge-transfer effect in aqueous media, but aggregation-induced emission in highly viscous media due to the restriction of the intramolecular motion. These aggregates, which can autonomously respond to different environments via switching the aggregation state without changing their chemical structures are described, as "smart aggregates". Intriguingly, these luminogens demonstrate NIR-II and NIR-III luminescence with ultralarge Stokes shifts (>950 nm). Both in vitro detection and in vivo imaging of HLP can be realized in a mouse model. Linear relationships exist between the emission intensity and multiple pathological parameters in blood samples of HLP patients. Thus, the design of smart aggregate facilitates rapid and accurate detection of HLP and provides a promising attempt in aggregate science.

Rational Design of a Two-Photon Fluorescent Probe for Human Cytochrome P450 3A and the Visualization of Mechanism-Based Inactivation

Mechanism-based inactivation (MBI) can mediate adverse reactions and hepatotoxicity from drugs, which is a result of their conversion into highly reactive metabolites catalyzed by enzymes such as cytochrome P450 3A (CYP3A). In the present research, we optimized the key interaction domain of the fluorophore with the target protein to develop a two-photon fluorescent probe for CYP3A that is involved in the metabolism of more than half of all clinical drugs. The developed BN-1 probe exhibited appropriate selectivity and sensitivity for the semi-quantitative detection and imaging of endogenous CYP3A activity in various living systems, thereby providing a high-throughput screening system enabling evaluation of MBI-associated hepatotoxicity by CYP3A. Using BN-1 as a fluorescent molecular tool facilitates the efficient discovery and characterization of CYP3A-induced MBI in natural systems.

Harnessing Hypoxia-Dependent Cyanine Photocages for In Vivo Precision Drug Release

Photocaging holds promise for the precise manipulation of biological events in space and time. However, current near-infrared (NIR) photocages are oxygen-dependent for their photolysis and lack of timely feedback regulation, which has proven to be the major bottleneck for targeted therapy. Herein, we present a hypoxia-dependent photo-activation mechanism of dialkylamine-substituted cyanine (Cy-NH) accompanied by emissive fragments generation, which was validated with retrosynthesis and spectral analysis. For the first time, we have realized the orthogonal manipulation of this hypoxia-dependent photocaging and dual-modal optical signals in living cells and tumor-bearing mice, making a breakthrough in the direct spatiotemporal control and in vivo feedback regulation. This unique photoactivation mechanism overcomes the limitation of hypoxia, which allows site-specific remote control for targeted therapy, and expands the photo-trigger toolbox for on-demand drug release, especially in a physiological context with dual-mode optical imaging under hypoxia.

Visualizations of Mercury Methylation and Dynamic Transformations by In Vivo Imaging

Visualization of Hg(II) and MeHg in their native contexts is significant for examining mercury poisoning, while it is challenging because of indistinguishable fluorescent (FL) signals during FL imaging. Herein, visualizations of mercury methylation and dynamic transformations of Hg(II) and MeHg are achieved in living biological systems. Well distinguishable FL responses (blue emission for Hg(II), yellow emission for MeHg) are obtained by a double-response FL probe (DPAHB) without any interference. As demonstrated by experimental and computational studies, the distinguishable signals are attributed to selective binding with DPAHB and different inhibition of excited-state proton transfer. Through control tests for live-dead markers, mercury methylation is demonstrated to be employed in living biological systems. Therefore, the methylation and dynamic transformations of both ions are monitored in zebrafish by imaging, and these results are confirmed by traditional high-performance liquid chromatography-based methods. The methylation of Hg(II) to MeHg, dynamic transformations and final accumulations of both species in zebrafish tissues are visualized successfully. This method is also convenient for fast evaluation of detoxification reagents. This is the first visualization of in vivo mercury methylation and dynamic transformation of both species and is effective for studying pathological processes in their native contexts.

Accelerated photoelectron transmission by carboxymethyl β-cyclodextrin for organic contaminants removal: An alternative to noble metal catalyst

Applications of noble metal decorated photocatalytic nanomaterials are restricted by its high cost. In this study, carboxymethyl β-cyclodextrin (CM-β-CD), as an alternative to gold nanoparticle, was used to modified titanium dioxide (CM-β-CD-P25) to accelerate photoelectron transmission and enhance the organic contaminants removal from water. Several of emerging organic contaminants, such as bisphenol A (BPA), phenol and sulphanilamide (SA), were used to evaluate their photocatalytic activities. Carboxymethyl-β-cyclodextrin not only provide hydrophobic sites to entrap organic contaminants but also provide a "bridge" for accelerated transmission of photogenerated charges without introducing the recombination interface. Consequently, 91.6 % of BPA, 71.9 % of phenol and 97.1 % of SA could be removed by CM-β-CD-P25(2:1) under 1 h UV light irradiation. The photooxidation rate constant of BPA, phenol and SA by CM-β-CD-P25(2:1) were 0.039 min^-1, 0.021 min^-1 and 0.062 min^-1, respectively, which are much higher than that of pristine P25 and Au-P25. Moreover, the photocatalytic activity of CM-β-CD-P25(2:1) remains almost unchanged in repeated cycle test owing to its high stability. The reasonable mechanism of CM-β-CD-P25 were investigated. CM-β-CD-P25 hybrid nanoparticles completely surpasses Au-P25 in organic contaminants removal, and shows great potential to replace noble metal as mediator.

Imaging of hydrogen peroxide (H2O2) during the ferroptosis process in living cancer cells with a practical fluorescence probe

Hydrogen peroxide (H₂O₂) plays an important role in intracellular signal transduction pathway. It has been closely associated with the occurrence and development of tumors as well as the recent studied ferroptosis. In this work, monitoring the H₂O₂ level during the ferroptosis process in living cancer cells was achieved by using a new practical fluorescence probe, HP, accompanying with a series of property evaluation and model construction. As a practical tool, HP indicated high sensitivity (LOD 0.77 μM), high selectivity and low toxicity. Most satisfactorily, it could realize the applications of mapping the variation of intracellular H₂O₂ level regulated by the inducer or activator and visualizing the H₂O₂ release event as a significant feature during the ferroptosis process. This work was a challenging trial to monitor dynamic parameters of ferroptosis, and offered crucial information about the role of H₂O₂ for investigating further physiological or pathological processes.

Bioimaging of Glutathione with a Two-Photon Fluorescent Probe and Its Potential Application for Surgery Guide in Laryngeal Cancer

As the most abundant nonprotein biothiol in living cells, glutathione (GSH) prevents cellular components from oxidative damage and maintains the intracellular redox homeostasis. For further exploring whether GSH can be employed as a bioindicator to discriminate tumor lesion at a cellular level, the highly selective detection and accurate quantification of GSH under pathological conditions are critical. Herein, we design a coumarin derivative-based two-photon fluorescent probe Cou-Br for the detection of GSH in living cells, mice models, and clinical specimens. The prepared probe is capable of sensitively and selectively detecting GSH in complex biological systems. Cou-Br displays a good linear relationship in response to GSH and a low limit of detection. With the fluorescence signal positively associated with intracellular GSH levels, the probe enables real-time imaging of GSH in various cell lines. Under the condition of CS₂ stimulation, Cou-Br can rapidly respond to the fluctuation of intracellular GSH induced by oxidative damage. Furthermore, the in situ and in vivo bioimaging performances of Cou-Br are demonstrated. Typically, relying on the different cellular concentrations of GSH, the probe is successfully employed to identify the human laryngeal cancer lesion with outstanding capabilities of deep tissue imaging and tumor margin recognition. We assume that the abnormal expression level of GSH may be utilized as a potential bioindicator to discriminate tumor tissues from the surrounding disease-free tissues. To conclude, the proposed probe Cou-Br may potentially serve as a powerful chemical tool for the surgical navigation of cancer in clinic.

Sensitive and Selective Measurement of Hydroxyl Radicals at Subcellular Level with Tungsten Nanoelectrodes

Hydroxyl radical (^•OH) is an essential reactive oxygen species involved in critical cell functions. However, the mechanisms controlling its subcellular localization and intracellular level during health and disease remain poorly understood. This is due to the challenge of detecting ^•OH that are highly reactive and consequently short-lived (in vivo half-life of ∼10^-9 s). Herein, we present tungsten nanoelectrodes functionalized with stable 1-hexanethiol (HAT) for selective and sensitive detection of ^•OH at the subcellular level via the destruction of the self-assembled monolayer of HAT on the nanoelectrode tip. Taking advantage of the ultrasmall nanotip and the super mechanical toughness, the tungsten nanoelectrode could easily penetrate a single living cell without inducing any observable damage. Controlled by a high precision micromanipulator, the ^•OH level in RAW 264.7 murine macrophages under amyloid β (Aβ) induced oxidative stress were first investigated by the nanoelectrodes at the subcellular level. Moreover, the results revealed the cordycepin-mediated cytoprotection of macrophages through modulation of PI3K/Akt pathway activity and introduction of heme oxygenase-1 (HO-1). We believe that the developed nanoelectrochemical method has shown great capacities for the study of potential drugs for therapeutic intervention of Alzheimer's disease.

Renal-clearable Molecular Semiconductor for Second Near-Infrared Fluorescence Imaging of Kidney Dysfunction

Real-time imaging of kidney function is important to assess the nephrotoxicity of drugs and monitor the progression of renal diseases; however, it remains challenging because of the lack of optical agents with high renal clearance and high signal-to-background ratio (SBR). Herein, a second near-infrared (NIR-II) fluorescent molecular semiconductor (CDIR2) is synthesized for real-time imaging of kidney dysfunction in living mice. CDIR2 not only has a high renal clearance efficiency (≈90 % injection dosage at 24 h post-injection), but also solely undergoes glomerular filtration into urine without being reabsorbed and secreted in renal tubules. Such a unidirectional renal clearance pathway of CDIR2 permits real-time monitoring of kidney dysfunction in living mice upon nephrotoxic exposure. Thus, this study not only introduces a molecular renal probe but also provides useful molecular guidelines to increase the renal clearance efficiency of NIR-II fluorescent agents.