The development of logic gate-based fluorescent probes that respond to intracellular hydrogen peroxide and pH in tandem.

Logic gate-based fluorescent probes are powerful tools for the discriminative sensing of multiple signaling molecules that are expressed in concert during the progression of many diseases such as inflammation, cancer, aging, and other disorders. To achieve logical sensing, multiple functional groups are introduced to the different substitution sites of a single fluorescent dye, which increases the complexity of chemical synthesis. Herein, we report a simple strategy that incorporates just one responsive unit into a hemicyanine dye achieving the logic gate-based sensing of two independent analytes. We introduce boronic acid to hemicyanine to quench the fluorescence, and in the presence of hydrogen peroxide (H2O2), the fluorescence is recovered due to removal of the boronate. Interestingly, the subsequent decrease in pH turned the red fluorescence of hemicyanine to green emissive because of protonation of the phenolic alcohol. This unique feature of the probe enables us to construct "INHIBIT" and "AND" logical gates for the accurate measuring of intracellular H2O2 and acidic pH in tandem. This study offers insight into the simple construction of logic-gate based fluorescent probes for the tandem sensing of multiple analytes that are correlatively produced during disease progression.

A Highly Sensitive and Selective Near-Infrared Fluorescent Probe for Imaging Peroxynitrite in Living Cells and Drug-Induced Liver Injury Mice.

Drug-induced liver injury (DILI) is a major clinical issue associated with the majority of commercial drugs. During DILI, the peroxynitrite (ONOO-) level is upregulated in the liver. However, traditional methods are unable to timely monitor the dynamic changes of the ONOO- level during DILI in vivo. Therefore, ONOO--activated near-infrared (NIR) fluorescent probes with high sensitivity and selectivity are key to the early diagnosis of DILI in situ. Herein, we report a novel ONOO--responsive NIR fluorescent probe, QCy7-DP, which incorporates a donor-dual-acceptor π-electron cyanine skeleton with diphenyl phosphinate. The ONOO--mediated highly selective hydrolytic cleavage via an addition-elimination pathway of diphenyl phosphinate produced the deprotonated form of QCy7 in physiological conditions with a distinctive extended conjugated π-electron system and ∼200-fold enhancement in NIR fluorescence emission at 710 nm. Moreover, the probe QCy7-DP was successfully used for the imaging of the endogenous and exogenous ONOO- concentration changes in living cells. Importantly, in vivo fluorescence imaging tests demonstrated that the probe can effectively detect the endogenous generation of ONOO- in an acetaminophen (APAP)-induced liver injury mouse model. This study provides insight into the design of highly selective NIR fluorescent probes suitable for spatiotemporal monitoring of ONOO- under different pathological conditions.

Progress in the Foaming of Polymer-based Electromagnetic Interference Shielding Composites by Supercritical CO2.

As a critical action plan formulated for peaking carbon dioxide emissions, polymeric electromagnetic interference (EMI) shielding materials based on CO2 foaming technology have recently been attracting widespread attention in both research and industry, attributable to their efficient use of CO2 , high specific strength, corrosion resistance and low-cost characteristics. In the past decade, the emergence of novel design concepts and preparation techniques for CO2 foaming technology has led to the development of new high-performance EMI shielding materials in this field. This review summarizes the research progress made to date on the fabrication of EMI shielding composite foams by supercritical carbon dioxide (scCO2 ) foaming. We also explore the structure-activity relationships between the component/distribution and EMI shielding properties. Additionally, the application prospects and development challenges of new EMI shielding composite foams are described.

Photochromic Fluorescent Probe Strategy for the Super-resolution Imaging of Biologically Important Biomarkers.

Here, we report a ß-galactosidase (ß-Gal)-responsive photochromic fluorescent probe, NpG, that was designed to prebind to human serum albumin (HSA) to form the probe/protein hybrid, NpG@HSA. The formation of NpG@HSA led to an increase in fluorescence emission (520 nm) corresponding to the binding of the fluorescent naphthalimide unit with HSA. In addition, this enabled visualization of the spiropyran fluorescence emission in aqueous media. Our probe/protein hybrid approach afforded a unique imaging platform with enhanced cell permeability and solubility that was capable of visualizing the cellular uptake of NpG@HSA before its activation by ß-Gal. The ß-Gal-mediated cleavage of the galactose unit within the NpG@HSA hybrid resulted in the formation of NpM@HSA and an increase in red fluorescence emission (620 nm). The resultant merocyanine unit was then able to undergo photoisomerization (merocyanine ↔ spiropyran) to facilitate STORM (i.e., stochastic optical reconstruction microscopy) imaging with minimal phototoxicity and excellent photostability/reversibility. Using STORM, NpG@HSA was able to determine the subcellular distribution of ß-Gal activity between cell lines with nanoscale precision. We believe that this system represents a versatile imaging platform for the design of photochromic fluorescent probes suitable for illuminating the precise location of disease-specific biomarkers in various cellular processes.

Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor.

The development of photochromic fluorescence sensors with dynamic and multiple-signaling is beneficial to the improvement of biosensing/imaging precision. However, elaborate designs with complicated molecular structures are always required to integrate these functions into one molecule. By taking advantages of both redox-active/high loading features of two-dimensional (2D) manganese dioxide (MnO2) and dynamic fluorescence photoswitching of photochromic sensors, we here design a hybrid photochromic MnO2 glycosheet (Glyco-DTE@MnO 2 ) to achieve the photoswitchable imaging of intracellular glutathione (GSH). The photochromic glycosheet manifests significantly turn-on fluorescence and dynamic ON/OFF fluorescence signals in response to GSH, which makes it favorable for intracellular GSH double-check in targeted human hepatoma cell line (HepG2) through the recognition between ß-D-galactoside and asialoglycoprotein receptor (ASGPr) on cell membranes. The dynamic fluorescence signals and excellent selectivity for detection and imaging of GSH ensure the precise determination of cell states, promoting its potential applications in future disease diagnosis and therapy.

Fluorogenic probes for disease-relevant enzymes.

Traditional biochemical methods for enzyme detection are mainly based on antibody-based immunoassays, which lack the ability to monitor the spatiotemporal distribution and, in particular, the in situ activity of enzymes in live cells and in vivo. In this review, we comprehensively summarize recent progress that has been made in the development of small-molecule as well as material-based fluorogenic probes for sensitive detection of the activities of enzymes that are related to a number of human diseases. The principles utilized to design these probes as well as their applications are reviewed. Specific attention is given to fluorogenic probes that have been developed for analysis of the activities of enzymes including oxidases and reductases, those that act on biomacromolecules including DNAs, proteins/peptides/amino acids, carbohydrates and lipids, and those that are responsible for translational modifications. We envision that this review will serve as an ideal reference for practitioners as well as beginners in relevant research fields.

Photochromism and molecular logic gate operation of a water-compatible bis-glycosyl diarylethene.

We report the synthesis of a water-compatible bis-glycosyl diarylethene using click chemistry that undergoes photochromism and functions as a molecular logic gate.