Alkyne-tagged SERS nanoprobe for understanding Cu+ and Cu2+ conversion in cuproptosis processes.

Simultaneously quantifying mitochondrial Cu+ and Cu2+ levels is crucial for evaluating the molecular mechanisms of copper accumulation-involved pathological processes. Here, a series of molecules containing various diacetylene derivatives as Raman reporters are designed and synthesized, and the alkyne-tagged SERS probe is created for determination Cu+ and Cu2+ with high selectivity and sensitivity. The developed SERS probe generates well-separated distinguishable Raman fingerprint peaks with built-in corrections in the cellular silent region, resulting in accurate quantification of Cu+ and Cu2+. The present probe demonstrates high tempo-spatial resolution for real-time imaging and simultaneously quantifying mitochondrial Cu+ and Cu2+ with long-term stability benefiting from the probe assembly with designed Au-C≡C groups. Using this powerful tool, it is found that mitochondrial Cu+ and Cu2+ increase during ischemia are associated with breakdown of proteins containing copper as well as conversion of Cu+ and Cu2+. Meanwhile, we observe that parts of Cu+ and Cu2+ are transported out of neurons by ATPase. More importantly, cuproptosis in neurons is found including the oxidative stress process caused by the conversion of Cu+ to Cu2+, which dominates at the early stage (<9 h), and subsequent proteotoxic stress. Both oxidative and proteotoxic stresses contribute to neuronal death.

A two-photon ratiometric fluorescent probe for real-time imaging and quantification of NO in neural stem cells during activation regulation.

Developing a novel tool capable of real-time monitoring and accurate quantification of NO is critical to understanding its role in physiological and pathological processes. Herein, a two-photon ratiometric fluorescent probe (NOP) was developed for real-time imaging and quantification of NO based on fluorescence resonance energy transfer-photoinduced electron transfer (FRET-PET). In this developed probe, coumarin (CM) and naphthalimide with o-phenylenediamine (NPM) were rationally designed as a fluorescent donor and acceptor, respectively, to enable a ratiometric fluorescence response to NO. The developed NO probe demonstrated good detection linearity with the concentration of NO in the range of 0.100-200 µM, with a detection limit of 19.5 ± 1.00 nM. Considering the advantages of high selectivity, good accuracy and rapid dynamic response (<15 s), the developed NO probe was successfully applied for real-time imaging and accurate quantification of NO in neural stem cells (NSCs) and different regions of mouse brain tissue with a penetration depth of 350 µm. Using this powerful tool, it was found that NO regulated the activation and differentiation of quiescent NSCs (qNSCs). In addition, NO-induced differentiation of qNSCs into neurons was found to be dose-dependent: 50.0 µM NO caused about 50.0% of qNSCs to differentiate into neurons. Moreover, different regions of the mouse brain were observed to be closely related to the concentration of NO, and the concentration of NO in the DG region was found to be lower than that in the S1BF, CA1, LD and CPu of the Alzheimer's disease (AD) mouse brain. The symptoms of AD mice were significantly improved through the treatment with NO-activated NSCs in the DG region.

Two-photon fluorescence imaging and ratiometric quantification of mitochondrial monoamine oxidase-A in neurons.

Herein, we designed and developed a single two-photon ratiometric fluorescence probe (TMF2P) for selective and accurate determination of mitochondrial MAO-A in live neurons. It was discovered that the increases in MAO-A levels under oxidative stress resulted in an elevated influx of Ca2+ flow into mitochondria through the transient receptor potential melastatin 2 (TRPM2) channels.

Raman Fiber Photometry for Understanding Mitochondrial Superoxide Burst and Extracellular Calcium Ion Influx upon Acute Hypoxia in the Brain of Freely Moving Animals.

Developing a novel tool capable of real-time monitoring and simultaneous quantitation of multiple molecules in mitochondria across the whole brain of freely moving animals is the key bottleneck for understanding the physiological and pathological roles that mitochondria play in the brain events. Here we built a Raman fiber photometry, and created a highly selective non-metallic Raman probe based on the triple-recognition strategies of chemical reaction, charge transfer, and characteristic fingerprint peaks, for tracking and simultaneous quantitation of mitochondrial O2.- , Ca2+ and pH at the same location in six brain regions of free-moving animal upon hypoxia. It was found that mitochondrial O2.- , Ca2+ and pH changed from superficial to deep brain regions upon hypoxia. It was discovered that hypoxia-induced mitochondrial O2.- burst was regulated by ASIC1a, leading to mitochondrial Ca2+ overload and acidification. Furthermore, we found the overload of mitochondrial Ca2+ was mostly attributed to the influx of extracellular Ca2+ .

Pillar[5]arene-Based Fluorescent Sensor Array for Biosensing of Intracellular Multi-neurotransmitters through Host-Guest Recognitions.

Neurotransmitters are very important for neuron events and brain diseases. However, effective probes for analyzing specific neurotransmitters are currently lacking. Herein, we design and create a supramolecular fluorescent probe (CN-DFP5) by synthesizing a dual-functionalized fluorescent pillar[5]arene derivative with borate naphthalene and aldehyde coumarin recognition groups to identify large-scale neurotransmitters. The developed probe can detect seven model neurotransmitters by generating different fluorescence patterns through three types of host-guest interactions. The obtained signals are statistically processed by principal component analysis, thus the high-throughput analysis of neurotransmitters is realized under dual-channel fluorescence responses. The present probe combines the advantages of small-molecule-based probes to easily enter into living neurons and cross-reactive sensor arrays. Thus, the selective binding enables this probe to identify specific neurotransmitters in biofluids, living neurons, and tissues. High selectivity and sensitivity further demonstrate that the molecular device could extend to more applications to detect and image neurotransmitters.

A ratiometric electrochemical sensor for selectively monitoring monoamine oxidase A in the live brain.

Herein, an electrochemical method for selectively sensing and accurately quantifying monoamine oxidase A (MAO-A) in the cortex and thalamus of a live mouse brain was reported. Using this tool, it was found that MAO-A increased Ca2+ entry into neurons via the TPRM2 channel in the live mouse brain of an AD model.

Chiral Selective Adhesion of Protein Droplets on Calix[4]arene-Enantiomer-Modified Surfaces.

Chiral-specific assembly is involved in many biochemical processes, such as DNA hybridization, protein adhesion, and sugar recognition. However, the signals of chiral interaction are usually very weak, and it is difficult to investigate the enantioselective behaviors. Therefore, it is necessary to construct the functional materials to regulate the selective behaviors of protein droplets via weak chiral interaction, which is also significant for the biological process of protein adhesive behaviors and proteinic drug delivery. Here, S- and R-amino alcohol derivative of calix[4]arene enantiomers (R/S-AC4) were synthesized and modified onto Au-surfaces to fabricate the enantiomer's materials and investigate the chiral selective adhesion of protein droplets. Through the experiment of fluorescence titration and molecular docking simulation, bovine serum albumin (BSA) showed the stronger interaction with R-amino alcohol-calix[4]arene than S-amino alcohol-calix[4]arene on the molecular level. Notably, the sliding angle showed that the droplet of BSA selectively adhered to the R-amino alcohol-calix[4]arene-modified surface, while it released rapidly from S-amino alcohol-calix[4]arene-modified surface by virtue of chiral selectivity. This result not only provides an easy and convenient model to regulate the selective adhesion and release of protein from chemical view, but also realizes the signal transduction through the weak chiral interaction.

Construction of a Switchable Nanochannel for Protein Transport via a Pillar[5]arene-Based Host-Guest System.

Modulating protein selective translocation is a significant process, which has great potential for mimicking and understanding complex biological activities. As such, how to construct a nanochannel that can accomplish well gating protein transport is vital and challenge. Herein, inspired by nature, we presented a robust strategy to construct a switchable nanochannel by introducing a pH responsive binary host-guest system into a nanochannel. Benefiting from the novel design of the pillar[5]arene as gatekeeper, the functional nanochannel can well facilitate histone transport. Under pH regulation, the host-guest assembled nanochannel is capable of switching "on" and "off" to manipulate the histone translocation process. This study exemplifies the importance of molecular switch mediated protein transport in this process and provides a new theoretical model for biological research, which will open a new avenue for better understanding of some physiological and pathological behaviors.

A light-regulated host-guest-based nanochannel system inspired by channelrhodopsins protein.

The light-controlled gating of ion transport across membranes is central to nature (e.g., in protein channels). Herein, inspired by channelrhodopsins, we introduce a facile non-covalent approach towards light-responsive biomimetic channelrhodopsin nanochannels using host-guest interactions between a negative pillararene host and a positive azobenzene guest. By switching between threading and dethreading states with alternating visible and UV light irradiation, the functional channels can be flexible to regulate the inner surface charge of the channels, which in turn was exploited to achieve different forms of ion transport, for instance, cation-selective transport and anion-selective transport. Additionally, the pillararene-azobenzene-based nanochannel system could be used to construct a light-activated valve for molecular transport. Given these promising results, we suggest that this system could not only provide a better understanding of some biological processes, but also be applied for drug delivery and various biotechnological applications.Light-controlled gating of ion transport across membranes occurs in nature via channelrhodopsin nanochannels. Here, the authors show facile non-covalent approach towards light-responsive biomimetic nanochannels using host-guest interactions between a negative pillararene host and a positive azobenzene guest.

Correction: The macroscopic wettable surface: fabricated by calix[4]arene-based host-guest interaction and chiral discrimination of glucose.

Correction for 'The macroscopic wettable surface: fabricated by calix[4]arene-based host-guest interaction and chiral discrimination of glucose' by Yue Sun et al., Chem. Commun., 2016, 52, 14416-14418.

The macroscopic wettable surface: fabricated by calix[4]arene-based host-guest interaction and chiral discrimination of glucose.

Herein, we reported a new strategy based on self-assembly chemistry for chiral discrimination of glucose on a new S-mandelic acid-appended calix[4]arene (S-MC4) modified nanostructure, which exhibits macroscopic chiral preference for d-glucose via contact angle measurements (CA). The proposed macroscopic chiral device displays rapidly remarkable specificity and is convenient to use, which should be suitable for diagnostic purposes, nanomedical applications, etc.