A Polymeric Nanobeacon for Monitoring the Fluctuation of Hydrogen Polysulfides during Fertilization and Embryonic Development

Molecular Engineering of a Doubly Quenched Fluorescent Probe Enables Ultrasensitive Detection of Biothiols in Highly Diluted Plasma and High-Fidelity Imaging of Dihydroartemisinin-Induced Ferroptosis

The occurrence and development of diseases are accompanied by abnormal activity or concentration of biomarkers in cells, tissues, and blood. However, the insufficient sensitivity and accuracy of the available fluorescence probes hinder the precise monitoring of associated indexes in biological systems, which is generally due to the high probe intrinsic fluorescence and false-negative signal caused by the reactive oxygen species (ROS)-induced probe decomposition. To resolve these problems, we have engineered a ROS-stable, meso-carboxylate boron dipyrromethene (BODIPY)-based fluorescent probe, which displays quite a low background fluorescence due to the doubly quenched intrinsic fluorescence by a combined strategy of the photoinduced electron transfer (PET) effect and "ester-to-carboxylate" conversion. The probe achieved a high S/N ratio with ultrasensitivity and good selectivity toward biothiols, endowing its fast detection capability toward the biothiol level in 200×-diluted plasma samples. Using this probe, we achieved remarkable distinguishing of liver injury plasma from normal plasma even at 80× dilution. Moreover, owing to its good stability toward ROS, the probe was successfully employed for high-fidelity imaging of the negative fluctuation of the biothiol level in nonsmall-cell lung cancer (NSCLC) during dihydroartemisinin-induced ferroptosis. This delicate design of suppressing intrinsic fluorescence reveals insights into enhancing the sensitivity and accuracy of fluorescent probes toward the detection and imaging of biomarkers in the occurrence and development of diseases.

Integration of Hybridization Chain Reaction and Protein-Binding Amplification for Long-Term Imaging of Intracellular mRNA: Avoiding Signal Fluctuation

Amplified nanoprobes based on hybridization chain reaction (HCR) have been widely developed for the detection of intracellular low abundance mRNA. However, the formed chain-like assembly decorated with fluorophore would be degraded rapidly by endogenous enzyme, resulting in failure of the long-term fluorescence imaging. To address this issue, herein, a composite signal-amplifying strategy that integrates HCR into protein-binding signal amplification (HPSA) was communicated for the in situ imaging of mRNA by avoiding signal fluctuation. Different from conventional HCR-based nanoprobes (HCR-nanoprobe), the HCR was used as the signal-triggered mode and the amplifying signal generated from in situ fluorophore-protein binding in cells, which can maintain high stability of the signal for a long time. As a proof-of-principle, a nanobeacon based on HPSA (HPSA-nanobeacon) was constructed to detect TK1 mRNA. Taking advantage of the double signal-amplifying mode, the endogenous TK1 mRNA was sensitively detected and the fluorescence signal was maintained for more than 8 h in HepG2 cells. The attempt in this work provides a new option to the current signal-amplifying strategy for sensing nucleic acid targets with high stability, significantly enhancing the acquisition of intracellular molecular information.

Chemo-Selective Single-Cell Metabolomics Reveals the Spatiotemporal Behavior of Exogenous Pollutants During Xenopus Laevis Embryogenesis

In-depth profiling of embryogenesis-associated endogenous and exogenous metabolic changes can reveal potential bio-effects resulting from human-made chemicals and underlying mechanisms. Due to the lack of potent tools for monitoring spatiotemporal distribution and bio-transformation behavior of dynamic metabolites at single-cell resolution, however, how and to what extent environmental chemicals may influence or interfere embryogenesis largely remain unclear. Herein, a zero-sample-loss micro-biopsy-based mass spectrometric platform is presented for quantitative, chemo-selective, high-coverage, and minimal-destructive profiling of development-associated cis-diol metabolites, which are critical for signal transduction and epigenome regulation, at both cellular level and tissue level of Xenopus laevis. Using this platform, three extraordinary findings that are otherwise hard to achieve are revealed: 1) there are characteristically different cis-diol metabolic signatures among oocytes, anterior and posterior part of tailbud-stage embryos; 2) halogenated cis-diols heavily accumulate at the posterior part of tailbud-stage embryos of Xenopus laevis; 3) dimethachlon, a kind of exogenous fungicide that is widely used as pesticide, may be bio-transformed and accumulated in vertebrate animals in environment. Thus, this study opens a new avenue to simultaneously monitoring intercellular and intraembryonic heterogeneity of endogenous and exogenous metabolites, providing new insights into metabolic remolding during embryogenesis and putting a warning on potential environmental risk.

A near-infrared light-activated nanoprobe for simultaneous detection of hydrogen polysulfide and sulfur dioxide in myocardial ischemia-reperfusion injury

Ischemia-reperfusion-induced cardiomyocyte mortality constitutes a prominent contributor to global morbidity and mortality. However, early diagnosis and preventive treatment of cardiac I/R injury remains a challenge. Given the close relationship between ferroptosis and I/R injury, monitoring their pathological processes holds promise for advancing early diagnosis and treatment of the disease. Herein, we report a near-infrared (NIR) light-activated dual-responsive nanoprobe (UCNP@mSiO2@SP-NP-NAP) for controllable detection of hydrogen polysulfide (H2Sn) and sulfur dioxide (SO2) during ferroptosis-related myocardial I/R injury. The nanoprobe's responsive sites could be activated by NIR and Vis light modulation, reversibly alternating for at least 5 cycles. We employed the nanoprobe to monitor the fluctuation levels of H2Sn and SO2 in H9C2 cardiomyocytes and mice, revealing that H2Sn and SO2 levels were up-regulated during I/R. The NIR light-activated dual-responsive nanoprobe could be a powerful tool for myocardial I/R injury diagnosis. Moreover, we also found that inhibiting the initiation of the ferroptosis process contributed to attenuating cardiac I/R injury, which indicated great potential for treating I/R injury.

Molecular Engineering of Luminogens for High-Integrity Imaging of Hydrogen Polysulfides via Activatable Aggregation-Induced Dual-Color Fluorescence

Understanding biological events associated with H2Sn rather than mediated by H2S is of great significance but remains to be solved due to a lack of high-integrity imaging tools. In this study, we report a chemoselective probe for H2Sn over H2S through the molecular engineering of luminogens. Based on our search for H2Sn-activatable probes with high selectivity, we fabricate water-soluble and biocompatible nanoprobes. Such a designed nanoprobe shows rare aggregation-induced dual-color fluorescence responses to H2Sn, lighting up bright emissions at 588 and 750 nm, respectively. By use of this activatable dual-color fluorescence, high-integrity identification of intracellular H2Sn was successfully realized. Thus, our approach to H2Sn-activated multicolor fluorescent probes could provide valuable insight into interrogating H2Sn-mediated biological events.

Rigidity-Dependent Emission: Inspired Selection of an ATP-Specific Polyvalent Hydrogen Binding-Lighted Fluorophore for Intracellular Amplified Imaging

ATP, a small molecule with high intracellular concentration (mM level), provides a fuel to power signal amplification, which is meaningful for biosensing. However, traditional ATP-powered amplification is based on ATP/aptamer recognition, which is susceptible to the complex biological microenvironment (e.g., nuclease). In this work, we communicate a signaling manner termed as ATP-specific polyvalent hydrogen binding (APHB), which is mimetic to ATP/aptamer binding but can avoid interference from biomolecules. The key in APHB is a functional fluorophore that can selectively bind with ATP via polyvalent hydrogen, and the fluorescence was lighted with the changes of the molecular structure from flexibility to rigidity. By designing, synthesizing, and screening a series of compounds, we successfully obtained an ATP-specific binding-lighted fluorophore (ABF). Experimental verification and a complex analogue demonstrated that two melamine brackets in the ABF dominate the polyvalent hydrogen binding between the ABF and ATP. Then, to achieve amplification biosensing, fibroblast activation protein (FAP) in activated hepatic stellate cells was taken as a model target, and a nanobeacon consisting of an ABF, a quencher, and an FAP-activated polymer shell was constructed. Benefiting from the ATP-powered amplification, the FAP was sensitively detected and imaged, and the potential relationship between differentiation of hepatocytes and FAP concentration was first revealed, highlighting the great potential of APHB-mediated signaling for intracellular sensing.

Visualization of Mitochondria During Embryogenesis in Zebrafish by Aggregation-Induced Emission Molecules

PURPOSE

Aggregation-induced emission (AIE) molecules have been widely utilized for fluorescence imaging in many biomedical applications, benefited from large Stokes shift, high quantum yield, good biocompatibility, and resistance to photobleaching. And visualization of mitochondria is almost investigated in vitro and ex vivo, but in vivo study of mitochondria is more essential for systematic biological research, especially during embryogenesis. Therefore, suitable and time-saving alternatives with simple operation based on AIE molecules are urgently needed compared with traditional transgenic approach.

PROCEDURES

Five tetraphenylethylene isoquinolinium (TPE-IQ)-based molecules with AIE characteristics and their ability of mitochondrial visualization in vitro and in vivo and mitochondrial tracking during embryogenesis on zebrafish model were investigated. The biosafety of these AIE molecules was also evaluated systematically in vitro and in vivo.

RESULTS

All these five AIE molecules could image mitochondria in vitro with good biocompatibility. In them, TPE-IQ1 exhibited excellent imaging quality for in vivo visualization and tracking of mitochondria during the 4-day embryogenesis in zebrafish, in comparison with the conventional transgenic fluorescent protein. Furthermore, TPE-IQ1 could visualize mitochondrial damage induced by chemicals in real time on 24-h post fertilization (hpf) embryos.

CONCLUSIONS

This study indicated TPE-IQ-based AIE molecules had the potential for mitochondrial imaging and tracking during embryogenesis and mitochondrial damage visualization in vivo.

Brain-targeted Near-Infrared Nanobeacon for In Situ Monitoring H2S Fluctuation during Epileptic Seizures

Epilepsy is a neurological brain disease, and its recurrent seizures are related to the reductive substance-powered antioxidant defense system (ADS). However, until now, there has been no report on the study of in situ antioxidant fluctuation during epilepsy of varying severity. In this work, hydrogen sulfide (H₂S) was selected as the model target, a H₂S-responsive near-infrared fluorophore was designed and synthesized, and an amphiphilic molecule was synthesized and modified with angiopep-2 peptide at its hydrophilic terminus. A nanobeacon termed as BFPP was prepared by the formation of micelles with the package of the fluorophore. The nanobeacon was sensitive to H₂S, with a low detection limit of 17 nM. The H₂S fluctuation in cells can be monitored by fluorescence imaging. In addition, angiopep-2 peptide at the surface of BFPP helps it cross the blood-brain barrier, and near-infrared fluorescence improves in vivo imaging. BFPP revealed that H₂S was at a moderate level in the normal brain, but its level was obviously elevated during mild epilepsy because of the activation of the ADS while significantly suppressed during severe epilepsy due to neuronal damage. This approach is generally accessible for other targets by altering the responsive fluorophore, with significance for in situ analysis of brain pathology.

Direct C(sp)-H/Si-H Cross-Coupling via Copper Salts Photocatalysis

Reported herein is the first example of C(sp)-H/Si-H cross-coupling by photocatalysis. In terms of cheap and readily available starting materials, a series of alkynylsilanes are prepared in good to excellent yields upon visible-light irradiation of CuCl and alkynes with silane. The large scale reaction with flow chemistry and late-stage functionalization of natural products shows the potential of the transformation in practical organic synthesis of the alkynylsilanes intermediates.