Simultaneous Fluorescence Imaging Reveals N-Methyl-d-aspartic Acid Receptor Dependent Zn2+/H+ Flux in the Brains of Mice with Depression

A novel di-functional fluorescent probe for ONOO- and Zn2+ imaging in cells

Peroxynitrite (ONOO-) is one of the most significant reactive oxygen species (ROS) in living cells. Zn2+ in living cells plays an essential part in different physiological processes. The abnormal concentration of ONOO- and Zn2+ in living cells are related to many kinds of diseases, such as anemia, epilepsy, diarrhea, Alzheimer's disease, and so on. The relationship of ONOO- and Zn2+ in living cells when the relative disease occurs remains unknown. So we develop the first probe H-1 for detecting ONOO- and Zn2+ at the same time. The probe H-1 shows high selectivity, good anti-interference capability, low detection limit and short response time to ONOO- and Zn2+. When the probe was applied to detect ONOO- and Zn2+ in HeLa cells, we could observe the fluorescence changing in the green and blue channels separately without interference in real time. It has the potential to employ the relation of ONOO- and Zn2+ in some disease mechanism research.

Fluorescent Probes for Disease Diagnosis

The identification and detection of disease-related biomarkers is essential for early clinical diagnosis, evaluating disease progression, and for the development of therapeutics. Possessing the advantages of high sensitivity and selectivity, fluorescent probes have become effective tools for monitoring disease-related active molecules at the cellular level and in vivo. In this review, we describe current fluorescent probes designed for the detection and quantification of key bioactive molecules associated with common diseases, such as organ damage, inflammation, cancers, cardiovascular diseases, and brain disorders. We emphasize the strategies behind the design of fluorescent probes capable of disease biomarker detection and diagnosis and cover some aspects of combined diagnostic/therapeutic strategies based on regulating disease-related molecules. This review concludes with a discussion of the challenges and outlook for fluorescent probes, highlighting future avenues of research that should enable these probes to achieve accurate detection and identification of disease-related biomarkers for biomedical research and clinical applications.

Progress in the application of molecular imaging in psychiatric disorders

Psychiatric disorders have always attracted a lot of attention from researchers due to the difficulties in their diagnoses and treatments. Molecular imaging, as an emerging technology, has played an important role in the researchers of various diseases. In recent years, molecular imaging techniques including magnetic resonance spectroscopy, nuclear medicine imaging, and fluorescence imaging have been widely used in the study of psychiatric disorders. This review will briefly summarize the progression of molecular imaging in psychiatric disorders.

Recent advances in Zn2+ imaging: From organelles to in vivo applications

Zn2+ is involved in various physiological and pathological processes in living systems. Monitoring the dynamic spatiotemporal changes of Zn2+ levels in organelles, cells, and in vivo is of great importance for the investigation of the physiological and pathological functions of Zn2+. However, this task is quite challenging since Zn2+ in living systems is present at low concentrations and undergoes rapid dynamic changes. In this review, we summarize the design and application of fluorescent probes for Zn2+ imaging in organelles, cells, and live organisms reported over the past two years. We aim to provide inspiration for the design of novel Zn2+ probes for multi-level monitoring and deepen the understanding of Zn2+ biology.

Terbium-based metal-organic frameworks through energy transfer modulation for visual logical sensing zinc and fluorine ions

Zinc is the second most abundant trace element in the human central nervous system, which is closely related to various physiological activities in the human body. Fluoride ion is one of the most harmful elements in drinking water. Excessive intake of F^- may cause dental fluorosis, renal failure, or DNA damage. Therefore, it is urgent to develop sensors with high sensitivity and selectivity for the detection of Zn²⁺ and F^- ions at the same time. In this work, a series of mixed lanthanide metal-organic frameworks (Ln-MOFs) probes are synthesized using a simple method of in situ doping. The luminous color can be finely modulated by changing the molar ratio of Tb³⁺ and Eu³⁺ during synthesis. Benefiting from the unique energy transfer modulation mechanism, the probe has the continuous detection capability of zinc ions and fluoride ions. The detection of Zn²⁺ and F^- in a real environment shows that the probe has a good practical application prospect. The as-designed sensor at 262 nm excitation can sequentially detect Zn²⁺ concentrations ranging from 10^-8 to 10^-3 M (LOD = 4.2 nM) and F^- levels ranging from 10^-5 to 10^-3 M (LOD = 3.6 μM) with high selectivity. Based on different output signals, a simple Boolean logic gate device is constructed to realize intelligent visualization of Zn²⁺ and F^- monitoring.

Extracellular Alkalosis Reduces the Neurotoxicity of Zinc Ions in Cultured Cerebellar Granule Neurons

Zn²⁺ is known to be important for the normal brain functions. Disruption of zinc homeostasis and zinc-induced neurotoxicity has been shown to play a role in the development of neurodegenerative diseases. In this work, we investigated the effect of extracellular alkalosis on the zinc ions neurotoxicity in the cultured rat cerebellar granule neurons. Zinc chloride (0.03-0.06 mM, 24 h) added to the culture medium of rat cerebellar granule neurons caused the dose-dependent death of these cells. According to ultrastructural morphological features, the process of cell death could be attributed to necrosis, since it was accompanied by swelling of intracellular organelles and disruption of cell membranes against the background of relatively intact nuclear membranes. Neuronal death was associated with an increase in the level of intracellular free zinc. The toxic effect of zinc ions was significantly decreased when ionotropic glutamate NMDA-receptors were blocked by MK-801 or when the extracellular pH was increased from 7.3 to 7.8, due to a decrease in the zinc overload of the cytoplasm of these cells. The presented results demonstrate that NMDA channels are one of the Zn ion entry pathways in the cultured cerebellar granule neurons. Extracellular alkalosis reduces the zinc overload of the cytoplasm and, consequently, promotes the survival of neurons. Probably, zinc's neurotoxicity is inextricably linked with changes in the intracellular concentration of protons.

Dual-Ligand Near-Infrared Luminescent Lanthanide-Based Metal-Organic Framework Coupled with In Vivo Microdialysis for Highly Sensitive Ratiometric Detection of Zn2+ in a Mouse Model of Alzheimer's Disease

Zinc, which is the second most abundant trace element in the human central nervous system, is closely associated with Alzheimer's disease (AD). However, attempts to develop highly sensitive and selective sensing systems for Zn²⁺ in the brain have not been successful. Here, we used a one-step solvothermal method to design and prepare a metal-organic framework (MOF) containing the dual ligands, terephthalic acid (H₂BDC) and 2,2':6',2″-terpyridine (TPY), with Eu³⁺ as a metal node. This MOF is denoted as Eu-MOF/BDC-TPY. Adjustment of the size and morphology of Eu-MOF/BDC-TPY allowed the dual ligands to produce multiple luminescence peaks, which could be interpreted via ratiometric fluorescence to detect Zn²⁺ using the ratio of Eu³⁺-based emission, as the internal reference, and ligand-based emission, as the indicator. Thus, Eu-MOF/BDC-TPY not only displayed higher selectivity than other metal cations but also offered a highly accurate, sensitive, wide linear, color change-based technique for detecting Zn²⁺ at concentrations ranging from 1 nM to 2 μM, with a low limit of detection (0.08 nM). Moreover, Eu-MOF/BDC-TPY maintained structural stability and displayed a fluorescence intensity of at least 95.4% following storage in water for 6 months. More importantly, Eu-MOF/BDC-TPY sensed the presence of Zn²⁺ markedly rapidly (within 5 s), which was very useful in practical application. Furthermore, the results of our ratiometric luminescent method-based analysis of Zn²⁺ in AD mouse brains were consistent with those obtained using inductively coupled plasma mass spectrometry.

Novel Copper Complexes as Visible Light Photoinitiators for the Synthesis of Interpenetrating Polymer Networks (IPNs)

This work is devoted to the study of two copper complexes (Cu) bearing pyridine ligands, which were synthesized, evaluated and tested as new visible light photoinitiators for the free radical photopolymerization (FRP) of acrylates functional groups in thick and thin samples upon light-emitting diodes (LED) at 405 and 455 nm irradiation. These latter wavelengths are considered to be safe to produce polymer materials. The photoinitiation abilities of these organometallic compounds were evaluated in combination with an iodonium (Iod) salt and/or amine (e.g., N-phenylglycine—NPG). Interestingly, high final conversions and high polymerization rates were obtained for both compounds using two and three-component photoinitiating systems (Cu1 (or Cu2)/Iodonium salt (Iod) (0.1%/1% w/w) and Cu1 (or Cu2)/Iod/amine (0.1%/1%/1% w/w/w)). The new proposed copper complexes were also used for direct laser write experiments involving a laser diode at 405 nm, and for the photocomposite synthesis with glass fibers using a UV-conveyor at 395 nm. To explain the obtained polymerization results, different methods and characterization techniques were used: steady-state photolysis, real-time Fourier transform infrared spectroscopy (RT-FTIR), emission spectroscopy and cyclic voltammetry.

Improvement of synaptic plasticity by nanoparticles and the related mechanisms: Applications and prospects

Synaptic plasticity is an important basis of learning and memory and participates in brain network remodelling after different types of brain injury (such as that caused by neurodegenerative diseases, cerebral ischaemic injury, posttraumatic stress disorder (PTSD), and psychiatric disorders). Therefore, improving synaptic plasticity is particularly important for the treatment of nervous system-related diseases. With the rapid development of nanotechnology, increasing evidence has shown that nanoparticles (NPs) can cross the blood-brain barrier (BBB) in different ways, directly or indirectly act on nerve cells, regulate synaptic plasticity, and ultimately improve nerve function. Therefore, to better elucidate the effect of NPs on synaptic plasticity, we review evidence showing that NPs can improve synaptic plasticity by regulating different influencing factors, such as neurotransmitters, receptors, presynaptic membrane proteins and postsynaptic membrane proteins, and further discuss the possible mechanism by which NPs improve synaptic plasticity. We conclude that NPs can improve synaptic plasticity and restore the function of damaged nerves by inhibiting neuroinflammation and oxidative stress, inducing autophagy, and regulating ion channels on the cell membrane. By reviewing the mechanism by which NPs regulate synaptic plasticity and the applications of NPs for the treatment of neurological diseases, we also propose directions for future research in this field and provide an important reference for follow-up research.

A Bioluminescent Probe for Detecting Norepinephrine in Vivo

As a neurotransmitter, norepinephrine (NE) is critical for psychiatric conditions, neurodegenerative diseases, and pheochromocytoma. A real-time and noninvasive method for the detection of NE as a tracer to investigate the NE-relevant disease treatment process is urgently desirable. Herein, we successfully developed a turn-on NE bioluminescent probe (NBP), which was grounded on p-toluenethiol deprotectrf by nucleophilic substitution. Compared with other analytes, the NBP exhibited high sensitivity and selectivity in vitro. More importantly, the NBP provides a promising strategy for in vivo imaging of NE in living animals with noninvasive visualization and real-time features.

Naphthyl-Naphthalimides as High-Performance Visible Light Photoinitiators for 3D Printing and Photocomposites Synthesis

In this article, five new organic dyes based on the naphthalimide scaffold (Napht-1–Napht-5) were synthesized and tested as high-performance photoinitiators for both the Free Radical Photopolymerization (FRP) of acrylates and the Cationic Polymerization (CP) of epoxides using blue Light-Emitting Diodes (LEDs) as a safe irradiation source (LED @405 nm and 455). In fact, very good photopolymerization profiles (high final conversions and high polymerization rates) were obtained once these photoinitiators were combined with an Iodonium salt (Iod) or Iod/amine NPG and NVK). Remarkably, these dyes were able to generate interpenetrating polymer networks (IPN) by polymerization of a blend of monomers. These experiments were carried out to improve the polymerization profiles as well as the mechanical properties of the obtained materials. Due to their high photoinitiation abilities, these compounds were used in some applications such as photocomposite synthesis, direct laser write, and 3D printing experiments. To determine the chemical mechanisms, the photochemical/photophysical properties of these compounds were studied using different characterization techniques such as UV–visible absorption spectroscopy, steady-state photolysis, Fluorescence quenching, time-resolved fluorescence spectroscopy, FTIR spectroscopy, and cyclic voltammetry

Small-molecule fluorescence-based probes for interrogating major organ diseases

Chemical tools that allow the real-time monitoring of organ function and the visualisation of organ-related processes at the cellular level are of great importance in biological research. The upregulation/downregulation of specific biomarkers is often associated with the development of organ related diseases. Small-molecule fluorescent probes have the potential to create advances in our understanding of these disorders. Viable probes should be endowed with a number of key features that include high biomarker sensitivity, low limit of detection, fast response times and appropriate in vitro and in vivo biocompatibility. In this tutorial review, we discuss the development of probes that allow the targeting of organ related processes in vitro and in vivo. We highlight the design strategy that underlies the preparation of various promising probes, their optical response to key biomarkers, and proof-of-concept biological studies. The inherent drawbacks and limitations are discussed as are the current challenges and opportunities in the field. The hope is that this tutorial review will inspire the further development of small-molecule fluorescent probes that could aid the study of pathogenic conditions that contribute to organ-related diseases.

3-Carboxylic Acid and Formyl-Derived Coumarins as Photoinitiators in Photo-Oxidation or Photo-Reduction Processes for Photopolymerization upon Visible Light: Photocomposite Synthesis and 3D Printing Applications

In this paper, nine organic compounds based on the coumarin scaffold and different substituents were synthesized and used as high-performance photoinitiators for free radical photopolymerization (FRP) of meth(acrylate) functions under visible light irradiation using LED at 405 nm. In fact, these compounds showed a very high initiation capacity and very good polymerization profiles (both high rate of polymerization (Rp) and final conversion (FC)) using two and three-component photoinitiating systems based on coum/iodonium salt (0.1%/1% w/w) and coum/iodonium salt/amine (0.1%/1%/1% w/w/w), respectively. To demonstrate the efficiency of the initiation of photopolymerization, several techniques were used to study the photophysical and photochemical properties of coumarins, such as: UV-visible absorption spectroscopy, steady-state photolysis, real-time FTIR, and cyclic voltammetry. On the other hand, these compounds were also tested in direct laser write experiments (3D printing). The synthesis of photocomposites based on glass fiber or carbon fiber using an LED conveyor at 385 nm (0.7 W/cm²) was also examined.

Two-photon small-molecule fluorescence-based agents for sensing, imaging, and therapy within biological systems

In this tutorial review, we will explore recent advances for the design, construction and application of two-photon excited fluorescence (TPEF)-based small-molecule probes.

Specific Fluorescent Probe Based on "Protect-Deprotect" To Visualize the Norepinephrine Signaling Pathway and Drug Intervention Tracers

In recent years, increased social pressure and other factors have led to a surge in the number of people suffering from depression: studies show that quite a few people will experience major depression in their lifetime. Currently, it is widely believed that the internal cause of major depression is reduced levels of norepinephrine (NE) in brain tissue. Norepinephrine is very similar in structure and chemical properties to the other two catecholamine neurotransmitters, epinephrine (EP) and dopamine (DA). These three neurotransmitters are synthesized sequentially through enzymatic reactions in the biological system. Therefore, design of a norepinephrine-specific fluorescent probe is very challenging. In this work, we utilized a "protect-deprotect" strategy: longer emission wavelength cyanine containing water-soluble sulfonate was protected by a carbonic ester linking departing group thiophenol; the β-hydroxy ethyl amine moiety of norepinephrine may react with the carbonic ester via nucleophilic substitution and intramolecular nucleophilic cyclization to release the fluorophore. The process realized the specific red fluorescence detection of norepinephrine. Imaging of the norepinephrine nerve signal transduction stimulated by potassium ion was studied. More importantly, real-time fluorescence imaging of norepinephrine levels in the brain of rats stimulated by antidepressant drugs was studied for the first time.