Homeostasis inside Single Activated Phagolysosomes: Quantitative and Selective Measurements of Submillisecond Dynamics of Reactive Oxygen and Nitrogen Species Production with a Nanoelectrochemical Sensor

An Opto-electrophysiology Neural Probe with Photoelectric Artifact-Free for Advanced Single-Neuron Analysis

Opto-electrophysiology neural probes targeting single-cell levels offer an important avenue for elucidating the intrinsic mechanisms of the nervous system using different physical quantities, representing a significant future direction for brain-computer interface (BCI) devices. However, the highly integrated structure poses significant challenges to fabrication processes and the presence of photoelectric artifacts complicates the extraction and analysis of target signals. Here, we propose a highly miniaturized and integrated opto-electrophysiology neural probe for electrical recording and optical stimulation at the single-cell/subcellular level. The design of a total internal reflection layer addresses the photoelectric artifacts that are more pronounced in single-cell devices compared to conventional implantable BCI devices. Finite element simulations and electrical signal tests demonstrate that the opto-electrophysiology neural probe eliminates the photoelectric artifacts in the time domain, which represents a significant breakthrough for optoelectrical integrated BCI devices. Our proposed opto-electrophysiology neural probe holds substantial potential for promoting the development of in vivo BCI devices and developing advanced therapeutic strategies for neurological disorders.

Real-time monitoring of intracellular biochemical response in locally stretched single cell by a nanosensor

Mechanotransduction is the essential process that cells convert mechanical force into biochemical responses, and electrochemical sensor stands out from existing techniques by providing quantitative and real-time information about the biochemical signals during cellular mechanotransduction. However, the intracellular biochemical response evoked by mechanical force has been poorly monitored. In this paper, we report a method to apply local stretch on single cell and simultaneously monitor the ensuing intracellular biochemical signals. Specifically, a ferromagnetic micropipette was fabricated to locally stretch a single cell labeled with Fe3O4 nanoparticles under the external magnetic field, and the SiC@Pt nanowire electrode (SiC@Pt NWE) was inserted into the cell to monitor the intracellular hydrogen peroxide (H2O2) production induced by the local stretch. As a proof of concept, this work quantitatively investigated the elevated amount of H2O2 levels in single endothelial cell under different stretching amplitudes. This work puts forward a new research modality to manipulate and monitor the mechanotransduction at the single-cell level.

Dynamic Monitoring of Time-Dependent Evolution of Biomolecules Using Quantum Dots-Based Biosensors Assemblies

The dynamic monitoring of biomolecules that are part of cell membranes generally constitutes a challenge. Electrochemiluminescence (ECL) biosensor assemblies provide clear advantages concerning microscopic imaging. Therefore, this paper proposes and analyzes a quantum dots-based biosensor assembly. Thus, particular attention is granted to biomolecules that are part of cell membranes. Additionally, this paper describes and analyzes a quantum dots-based biosensor assembly, which is used to implement a fully functional color ECL visualization system that allows for cellular and biomolecular structures to be accurately visualized. The related nano-emitter allows the implementation of real-time bioimaging scenarios. Consequently, the proposed approach is thoroughly evaluated relative to the time-dependent evolution of biomolecules. It has been demonstrated that traditionally problematic structures, like the biomolecules that are part of cell membranes, can be studied and monitored relative to their time-dependent dynamic evolution using the proposed solution. The reported research process has been conducted in the realm of cooperation with a specialized biomedical engineering company, and the described results are expected to substantially support a better understanding of the biomolecules' time-dependent dynamic evolution.

Microelectrochemical Sensor Reveals Tunneling Nanotube-Mediated Intercellular Communication of Endothelial Mechanotransduction

The intercellular communication of mechanotransduction has a significant impact on various cellular processes. Tunneling nanotubes (TNTs) have been documented to possess the capability of transmitting mechanical stimulation between cells, thereby triggering an influx of Ca2+ ions. However, the related kinetic information on the TNT-mediated intercellular mechanotransduction communication is still poorly explored. Herein, we developed a classic and sensitive Pt-functionalized carbon fiber microelectrochemical sensor (Pt/CF) to study the intercellular communication of endothelial mechanotransduction through TNTs. The experimental findings demonstrate that the transmission of mechanical stimulation from stimulated human umbilical vein endothelial cells (HUVECs) to recipient HUVECs connected by TNTs occurred quickly (<100 ms) and effectively promoted nitric oxide (NO) production in the recipient HUVECs. The kinetic profile of NO release exhibited remarkable similarity in stimulated and recipient HUVECs. But the production of NO in the recipient cell is significantly attenuated (16.3%) compared to that in the stimulated cell, indicating a transfer efficiency of approximately 16.3% for TNTs. This study unveils insights into the TNT-mediated intercellular communication of mechanotransduction.

In situ self-referenced intracellular two-electrode system for enhanced accuracy in single-cell analysis

Since the emergence of single-cell electroanalysis, the two-electrode system has become the predominant electrochemical system for real-time behavioral analysis of single-cell and multicellular populations. However, due to the transmembrane placement of the two electrodes, cellular activities can be interrupted by the transmembrane potentials, and the test results are susceptible to influences from factors such as intracellular solution, membrane, and bulk solution. These limitations impede the advancement of single-cell analysis. Here, we propose a highly miniaturized and integrated in situ self-referenced intracellular two-electrode system (IS-SRITES), wherein both the working and reference electrodes are positioned inside the cell. Additionally, we demonstrated the stability (0.28 mV/h) of the solid-contact in situ Ag/AgCl reference electrode and the ability of the system to conduct standard electrochemical testing in a wide pH range (pH 6.0-8.0). Cell experiments confirmed the non-destructive performance of the electrode system towards cells and its capacity for real-time monitoring of intra- and extracellular pH values. Moreover, through equivalent circuits, finite element simulations, and drug delivery experiments, we illustrated that the IS-SRITES can yield more accurate test results and exhibit enhanced resistance to interference from the extracellular environment. Our proposed system holds the potential to enable the precise detection of intracellular substances and optimize the existing model of the electrode system for intracellular signal detection, thereby spearheading advancements in single-cell analysis.

Nanoelectrochemistry monitoring of intracellular reactive oxygen and nitrogen species induced by nanoplastic exposure

Airborne nanoplastics can enter alveolar cells and trigger intracellular oxidative stress primarily. Herein, taking advantage of the high electrochemical resolution of SiC@Pt nanoelectrodes, we achieved the quantitative discrimination of the major ROS/RNS within A549 cells, disclosed the sources of their precursors, and observed that the NO (RNS precursor) level significantly increased, whereas O2˙- (ROS precursor) remained relatively stable during the nanoplastics exposure. This establishes that iNOS or mitochondrion-targeted treatment may be a preventive or therapeutic strategy for nanoplastic-induced lung injury.

Aggregation-Enabled Electrochemistry in Confined Nanopore Capable of Complementary Faradaic and Non-Faradaic Detection

Electrochemistry that empowers innovative nanoscopic analysis has long been pursued. Here, the concept of aggregation-enabled electrochemistry (AEE) in a confined nanopore is proposed and devised by reactive oxygen species (ROS)-responsive aggregation of CdS quantum dots (QDs) within a functional nanopipette. Complementary Faradaic and non-Faradaic operations of the CdS QDs aggregate could be conducted to simultaneously induce the signal-on of the photocurrents and the signal-off of the ionic signals. Such a rationale permits the cross-checking of the mutually corroborated signals and thus delivers more reliable results for single-cell ROS analysis. Combined with the rich biomatter-light interplay, the concept of AEE can be extended to other stimuli-responsive aggregations for electrochemical innovations.

Nanosensor detection of reactive oxygen and nitrogen species leakage in frustrated phagocytosis of nanofibres

Exposure to widely used inert fibrous nanomaterials (for example, glass fibres or carbon nanotubes) may result in asbestos-like lung pathologies, becoming an important environmental and health concern. However, the origin of the pathogenesis of such fibres has not yet been clearly established. Here we report an electrochemical nanosensor that is used to monitor and quantitatively characterize the flux and dynamics of reactive species release during the frustrated phagocytosis of glass nanofibres by single macrophages. We show the existence of an intense prolonged release of reactive oxygen and nitrogen species by single macrophages near their phagocytic cups. This continued massive leakage of reactive oxygen and nitrogen species damages peripheral cells and eventually translates into chronic inflammation and lung injury, as seen during in vitro co-culture and in vivo experiments.

A Potentiometric Dual-Channel Microsensor Reveals that Fluctuation of H2 S is Less pH-Dependent During Spreading Depolarization in the Rat Brain

Spreading depolarization (SD) is one of the most common neuropathologic phenomena in the nervous system, relating to numerous diseases. However, real-time monitoring the rapid chemical changes during SD to probe the molecular mechanism remains a great challenge. We develop a potentiometric dual-channel microsensor for simultaneous monitoring of H2 S and pH featuring excellent selectivity and spatiotemporal resolution. Using this microsensor we first observe real time changes of H2 S and pH in the rat brain induced by SD. This changes of H2 S are completely suppressed when the rat pre-treats with aminooxyacetic acid (AOAA), a blocker to inhibit the H2 S-producing enzyme, indicating H2 S fluctuation might be related to enzyme-dependent pathway during SD and less pH-dependent. This study provides a new perspective for studying the function of H2 S and the molecular basis of SD-associated diseases.

An ultra-sensitive platinized nanocavity electrode for analysis of cytosolic catecholamines in one living cell

The catecholamines, mainly dopamine (DA), are present in the cellular cytosol with low abundance, while, play key roles in various neurodegenerative disorders. Here, platinized nanocavity carbon electrodes are employed to analyze cytosolic catecholamines in a single living PC12 cell, which is not easily quantified using the classic electrodes. The confined structure and excellent conductivity in the platinized nanocavity accelerate the electron transfer of the DA, resulting in a low detection limit down to 50 nM. The sensitivity of DA detection is improved to be 10.73 pA mM-1 nm-1 in the response range of 50 nM-100 μM, which guarantees quantitative analysis of cytosolic catecholamines with low abundance. Eventually, the platinized nanocavity electrode is employed to detect cytosolic catecholamines in a single PC12 cell without an obvious interruption of cellular catecholamine level. The cytosolic catecholamines in a single PC12 cell is measured in situ to be 0.1 μM, which is achieved for the first time at the single cell level using the electrochemical method. The results demonstrate that the nanocavity electrode with a high sensitivity could offer a promising means to dynamically track catecholamines in a single cell.

Enzymatic Galvanic Redox Potentiometry for In Vivo Biosensing

Redox potentiometry has emerged as a new platform for in vivo sensing, with improved neuronal compatibility and strong tolerance against sensitivity variation caused by protein fouling. Although enzymes show great possibilities in the fabrication of selective redox potentiometry, the fabrication of an enzyme electrode to output open-circuit voltage (EOC) with fast response remains challenging. Herein, we report a concept of novel enzymatic galvanic redox potentiometry (GRP) with improved time response coupling the merits of the high selectivity of enzyme electrodes with the excellent biocompatibility and reliability of GRP sensors. With a glucose biosensor as an illustration, we use flavin adenine dinucleotide-dependent glucose dehydrogenase as the recognition element and carbon black as the potential relay station to improve the response time. We find that the enzymatic GRP biosensor rapidly responds to glucose with a good linear relationship between EOC and the logarithm of glucose concentration within a range from 100 μM to 2.65 mM. The GRP biosensor shows high selectivity over O2 and coexisting neurochemicals, good reversibility, and sensitivity and can in vivo monitor glucose dynamics in rat brain. We believe that this study will pave a new platform for the in vivo potentiometric biosensing of chemical events with high reliability.

θ-Nanopore Ratiometry

Developing nanoscale ratiometric techniques capable of biochemical response should prove of significance for precise applications with stringent spatial and biological restrictions. Here we present and devise the concept of θ-nanopore ratiometry, which uses ratiometric signals that could well address the serious concerns about device deviation in fabrication and nonspecific adsorption in the detection. As exemplified by a 200 nm θ-nanopore toward miRNA detection, the ±20 nm aperture drift could be mitigated and the issue of nonspecific adsorption could be minimized in the complex cytosolic environment. Practical application of this θ-nanopore ratiometry realizes the measurements of cytosolic miRNA-10b. This work has not only established a nanoscopic ratiometric technique but also enriched the extant armory of nanotools for single-cell studies and beyond.

Ratiometric electrochemical determination of hydroxyl radical based on graphite paper modified with metal-organic frameworks and impregnated with salicylic acid

Hydroxyl radical (•OH) detection is pivotal in medicine, biochemistry and environmental chemistry. Yet, electrochemical method-specific detection is challenging because of hydroxyl radicals' high reactivity and short half-life. In this study, we aimed to modify the electrode surface with a specific recognition probe for •OH. To achieve this, we conducted a one-step hydrothermal process to fabricate a CoZnMOF bimetallic organic framework directly onto conductive graphite paper (Gp). Subsequently, we introduced salicylic acid (SA) and methylene blue (MB), which easily penetrated the pores of CoZnMOF. By selectively capturing •OH by SA and leveraging the electrochemical signal generated by the reaction product, we successfully developed an electrochemical sensor Gp/CoZnMOF/SA + MB. The prepared sensor exhibited a good linear relationship with •OH concentrations ranging from 1.25 to 1200 nM, with a detection limit of 0.2 nM. Additionally, the sensor demonstrated excellent reproducibility and accuracy due to the incorporation of an internal reference. It exhibited remarkable selectivity for •OH detection, unaffected by other electrochemically active substances. The establishment of this sensor provides a way to construct MOF-modified sensors for the selective detection of other reactive oxygen species (ROS), offering a valuable experimental basis for ROS-related disease research and environmental safety investigations.

Bisphenol A Induces Reactive Oxygen Species Production and Apoptosis-Related Gene Expression in Pacific Red Snapper Lutjanus peru Leukocytes

Bisphenol A is one of the most used components of the polycarbonate plastic industry in the word. This contaminant has disrupting effect in cells in in vitro and in vivo in fish. This study evaluated for the first time the cytotoxicity, oxidative stress and apoptosis induced by bisphenol A (BPA) in head-kidney and spleen leukocytes isolated from Pacific red snapper Lutjanus peru. Head-kidney and spleen leukocytes were exposed to 100, 1000 and 10,000 µg/mL of BPA at 2 and 24 h. Results showed cytotoxicity of BPA at 1000 and 10,000 µg/mL. Cell viability > 80% was observed in leukocytes exposed to 100 µg/mL for 2 h; thus, this concentration was selected for the remainder of the study. Reactive oxygen species (ROS) production, analyzed by DCF-DA and NBT assays, significantly increased in those leukocytes exposed to BPA compared to controls after 2 or 24 h. Superoxide dismutase and catalase activities increased in head-kidney leukocytes after 24 h of BPA exposure. Apoptosis was inferred from caspase (casp-1 and casp-3), granzyme A (granz-A) and perforin 1 (perf-1) gene expression, which was significantly up-regulated, at 2 h BPA exposure in head-kidney leukocytes, and from granz-A and perf-1, which were up-regulated, after 24 h BPA exposure in spleen leukocytes. Short cytoplasmic prolongations and membrane blebs, suggestive of apoptosis, were observed by scanning electron microscopy. These data suggest that BPA at 100 µg/mL induces cytotoxicity, oxidative stress, apoptosis in Pacific red snapper head-kidney and spleen leukocytes.

Fast Antioxidation Kinetics of Glutathione Intracellularly Monitored by a Dual-Wire Nanosensor

The glutathione (GSH) system is one of the most powerful intracellular antioxidant systems for the elimination of reactive oxygen species (ROS) and maintaining cellular redox homeostasis. However, the rapid kinetics information (at the millisecond to the second level) during the dynamic antioxidation process of the GSH system remains unclear. As such, we specifically developed a novel dual-wire nanosensor (DWNS) that can selectively and synchronously measure the levels of GSH and ROS with high temporal resolution, and applied it to monitor the transient ROS generation as well as the rapid antioxidation process of the GSH system in individual cancer cells. These measurements revealed that the glutathione peroxidase (GPx) in the GSH system is rapidly initiated against ROS burst in a sub-second time scale, but the elimination process is short-lived, ending after a few seconds, while some ROS are still present in the cells. This study is expected to open new perspectives for understanding the GSH antioxidant system and studying some redox imbalance-related physiological.

Application and outlook of electrochemical technology in single-cell analysis

Cellular heterogeneity, especially in some important diseased cells like tumor cells, acts as an invisible driver for disease development like cancer progression in the tumor ecosystem, contributing to differences in the macroscopic and microscopic detection of disease lesions like tumors. Traditional analysis techniques choose group information masked by the mean as the analysis sample, making it difficult to achieve precise diagnosis and target treatment, on which could be shed light via the single-cell level determination/bioanalysis. Hence, in this article we have reviewed the special characteristic differences among various kinds of typical single-cell bioanalysis strategies and electrochemical techniques, and then focused on the recent advance and special bio-applications of electrochemiluminescence and micro-nano electrochemical sensing mediated in single-cell bioimaging & bioanalysis. Especially, we have summarized the relevant research exploration of the possibility to establish the in-situ single-cell electrochemical methods to detect cell heterogeneity through determination of specific biomolecules and bioimaging of some important biological processes. Eventually, this review has explored some important advances of electrochemical single-cell detection techniques for the real-time cellular bioimaging and diagnostics of some disease lesions like tumors. It raises the possibility to provide the specific in-situ platform to exploit the versatile, sensitive, and high-resolution electrochemical single-cell analysis for the promising biomedical applications like rapid tracing of some disease lesions or in vivo bioimaging for precise cancer theranostics.

Vasculature-on-a-Chip with a Porous Membrane Electrode for In Situ Electrochemical Detection of Nitric Oxide Released from Endothelial Cells

Vasculature-on-a-chip is a microfluidic cell culture device used for modeling vascular functions by culturing endothelial cells. Porous membranes are widely used to create cell culture environments. However, in situ real-time measurements of cellular metabolites in microchannels are challenging. In this study, a novel microfluidic device with a porous membrane electrode was developed for the in situ monitoring of nitric oxide (NO) released by endothelial cells in real time. In this system, a porous Au membrane electrode was placed directly beneath the cells for in situ and real-time measurements of NO, a biomarker of endothelial cells. First, the device was electrochemically characterized to construct a calibration plot for NO. Next, NO released by human umbilical vein endothelial cells under l-arginine stimulation was successfully quantified. Furthermore, the changes in NO release with culture time (in days) using the same sample were successfully recorded by exploiting minimally invasive measurements. This is the first report on the combination of a microfluidic device and porous membrane electrode for the electrochemical analysis of endothelial cells. This device will contribute to the development of organ-on-a-chip technology for real-time in situ cell analyses.

In situ monitoring of ROS secretion from single cells with a dual-nanopore biosensor

We report here a dual-nanopore biosensor based on modulation of surface charge density coupled with a microwell array chip for in situ monitoring of ROS secretion from single MCF-7 cells.

High-Precision Single-Cell microRNA Therapy by a Functional Nanopipette with Sensitive Photoelectrochemical Feedback

This work proposes the concept of single-cell microRNA (miR) therapy and proof-of-concept by engineering a nanopipette for high-precision miR-21-targeted therapy in a single HeLa cell with sensitive photoelectrochemical (PEC) feedback. Targeting the representative oncogenic miR-21, the as-functionalized nanopipette permits direct intracellular drug administration with precisely controllable dosages, and the corresponding therapeutic effects can be sensitively transduced by a PEC sensing interface that selectively responds to the indicator level of cytosolic caspase-3. The experimental results reveal that injection of ca. 4.4 × 10-20  mol miR-21 inhibitor, i.e., 26488 copies, can cause the obvious therapeutic action in the targeted cell. This work features a solution to obtain the accurate knowledge of how a certain miR-drug with specific dosages treats the cells and thus provides an insight into futuristic high-precision clinical miR therapy using personalized medicine, provided that the prerequisite single-cell experiments are courses of personalized customization.

Tumour-associated macrophages: versatile players in the tumour microenvironment

Tumour-Associated Macrophages (TAMs) are one of the pivotal components of the tumour microenvironment. Their roles in the cancer immunity are complicated, both pro-tumour and anti-cancer activities are reported, including not only angiogenesis, extracellular matrix remodeling, immunosuppression, drug resistance but also phagocytosis and tumour regression. Interestingly, TAMs are highly dynamic and versatile in solid tumours. They show anti-cancer or pro-tumour activities, and interplay between the tumour microenvironment and cancer stem cells and under specific conditions. In addition to the classic M1/M2 phenotypes, a number of novel dedifferentiation phenomena of TAMs are discovered due to the advanced single-cell technology, e.g., macrophage-myofibroblast transition (MMT) and macrophage-neuron transition (MNT). More importantly, emerging information demonstrated the potential of TAMs on cancer immunotherapy, suggesting by the therapeutic efficiency of the checkpoint inhibitors and chimeric antigen receptor engineered cells based on macrophages. Here, we summarized the latest discoveries of TAMs from basic and translational research and discussed their clinical relevance and therapeutic potential for solid cancers.

A High-Density Raman Photometry for Tracking and Quantifying of AchE Activity in The Brain of Freely Moving Animals with Network

A high-density Raman photometry based on a dual-recognition strategy is created for accurately quantifying acetylcholinesterase (AchE) activity in 24 brain regions of free-moving animals with network. A series of 5-ethynyl-1,2,3,3-tetramethyl-based molecules with different conjugated structures and substitute groups are designed and synthesized for specific recognition of AchE by Raman spectroscopy. After systematically evaluating the recognition ability toward AchE, 2-(4-((4-(dimethylamino)benzoyl)oxy)styryl)-5-ethynyl-1,3,3-trimethyl-3H-indol-1-ium (ET-5) is finally optimized for AchE determination, which shows the highest selectivity, the greatest sensitivity, and the fastest response time among the investigated seven molecules. More interestingly, using the developed probe for AchE with high accuracy and sensitivity, the optimized AchE regulated by nitric oxide (NO) is discovered for promoting the neurogenesis of neural stem cells (NSCs). Benefiting from the high-density photometry, it is found that the activity and distribution of AchE varied in 24 brain regions, and the levels of AchE activity in 24 brain regions of Alzheimer's mice (AD) are lower than those of normal mice. It is the first time that a functional network of AchE in 24 brain regions is established. It is also found that the loss of AchE functional network in AD mice is restored and reconstructed by the controlled release of AchE regulated by NO.

Enhancing electrochemical properties of a two-dimensional zeolitic imidazole framework by incorporating a conductive polymer for dopamine detection

The zeolitic imidazole framework with a leaf-shaped morphology (ZIF-L) has a wide range of promising applications in gas storage, battery materials, catalytic reactions, and optoelectronic devices due to its planar leaf-like structure and large surface area. However, the low conductivity, weak catalytic activity, and poor stability in the water dielectric medium of ZIF-L limit its further practical application. To solve these problems, we added the conductive polymer heterocyclic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to ZIF-L for the sensitive detection of dopamine (DA). The synthesized composite ZIF-L/PEDOT:PSS (ZIF-L/PEDOT) not only retained the surface morphology of ZIF-L but also exhibited excellent electrochemical properties. The higher electrical conductivity of ZIF-L/PEDOT than that of ZIF-L was due to the enhanced electron transfer at the interface between ZIF-L and PEDOT:PSS. As a result, we developed an electrochemical biosensor based on the ZIF-L/PEDOT composite, which has a limit of detection of 7 nM for DA and a wide linear range from 25 nM to 500 μM. Furthermore, the current drop was negligible after 28 days, proving that the biosensor has excellent stability. Based on the above-mentioned outstanding performance, the ZIF-L/PEDOT-based biosensor was successfully used to detect DA in human serum samples. These results demonstrated that ZIF-L/PEDOT is expected to play an essential role in disease detection.

Mycobacterium tuberculosis and its clever approaches to escape the deadly macrophage

Mycobacterium tuberculosis (Mt.b), a deadly disease causer, is a facultative parasite. This microorganism has developed several methods to defend itself, once internalized within specialised vacuoles in the macrophages. A wide array of receptors like the complement receptor mannose receptors, scavenger receptor assists the entry of the microbe within the phagocytic macrophages. However, Mt.b is clever enough to protect itself from the hostile environment of the macrophage thereby prevailing within it. The microbe can efficiently inhibit processes like phagosome-lysosome fusion, acidification of phagosomes, release of proinflammatory cytokines and stop crucial events like apoptosis. Additionally, it also adopts resistance to killing by reactive oxygen intermediates and reactive nitrogen intermediates. There are multiple genes both in host and the pathogen which are involved in this successful survival of Mt.b. The regulation of phagolysosome fusion is mediated by proteins such as Coronin, TlyA, SapM, PnkG, EsxH. The microbe has certain mechanisms to even acquire iron from the host cell, to withstand iron deprivation as a mode of host's defence mechanism. This review focuses on the various defensive adaptations acquired by Mt.b for fighting against the deprived conditions existing within the macrophages and their capability of proliferating successfully within it, thereby resulting in a diseased condition.

Click-Chemistry-Enabled Nanopipettes for the Capture and Dynamic Analysis of a Single Mitochondrion inside One Living Cell

The in-depth study of single cells requires the dynamically molecular information in one particular nanometer-sized organelle in a living cell, which is difficult to achieve using current methods. Due to high efficiency of click chemistry, a new nanoelectrode-based pipette architecture with dibenzocyclooctyne at the tip is designed to realize fast conjugation with azide group-containing triphenylphosphine, which targets mitochondrial membranes. The covalent binding of one mitochondrion at the tip of the nanopipette allows a small region of the membrane to be isolated on the Pt surface inside the nanopipette. Therefore, the release of reactive oxygen species (ROS) from the mitochondrion is monitored, which is not interfered by the species present in the cytosol. The dynamic tracking of ROS release from one mitochondrion reveals the distinctive "ROS-induced ROS release" within the mitochondria. Further study of RSL3-induced ferroptosis using nanopipettes provides direct evidence for supporting the noninvolvement of glutathione peroxidase 4 in the mitochondria during RSL3-induced ROS generation, which has not previously been observed at the single-mitochondrion level. Eventually, this established strategy should overcome the existing challenge of the dynamic measurement of one special organelle in the complicated intracellular environment, which opens a new direction for electroanalysis in subcellular analysis.

Profiling H2O2 from single COS-7 cells by means of scanning electrochemical microscopy

We report quantitative determination of extracellular H₂O₂ released from single COS-7 cells with high spatial resolution, using scanning electrochemical microscopy (SECM). Our strategy of depth scan imaging in vertical x-z plane was conveniently utilized to a single cell for obtaining probe approach curves (PACs) to any positions on the membrane of a live cell by simply drawing a vertical line on one depth SECM image. This SECM mode provides an efficient way to record a batch of PACs, and visualize cell topography simultaneously. The H₂O₂ concentration at the membrane surface in the center of an intact COS-7 cell was deconvoluted from apparent O₂, and determined to be 0.020 mM by overlapping the experimental PAC with the simulated one having a known H₂O₂ release value. The H₂O₂ profile determined in this way gives insight into physiological activity of single live cells. In addition, intracellular H₂O₂ profile was demonstrated using confocal microscopy by labelling the cells with a luminomphore, 2',7'-dichlorodihydrofluorescein diacetate. The two methodologies have illustrated complementary experimental results of H₂O₂ detection, indicating that H₂O₂ generation is centered at endoplasmic reticula.

Dual-emissive carbonized polymer dots for the ratiometric fluorescence imaging of singlet oxygen in living cells

Singlet oxygen (¹O₂) is a type of reactive oxygen species (ROS), playing a vital role in the physiological and pathophysiological processes. Specific probes for monitoring intracellular ¹O₂ still remain challenging. In this study, we develop a ratiometric fluorescent probe for the real-time intracellular detection of ¹O₂ using o-phenylenediamine-derived carbonized polymer dots (o-PD CPDs). The o-PD CPDs possessing dual-excitation-emission properties (blue and yellow fluorescence) were successfully synthesized in a two-phase system (water/acetonitrile) using an ionic liquid tetrabutylammonium hexafluorophosphate as a supporting electrolyte through the electrolysis of o-PD. The o-PD CPDs can act as a photosensitizer to produce ¹O₂ upon white LED irradiation, in turn, the generated ¹O₂ selectively quenches the yellow emission of the o-PD CPDs. This quenching behavior is ascribed to the specific cycloaddition reaction between ¹O₂ and alkene groups in the polymer scaffolds on o-PD CPDs. The interior carbon core can be a reliable internal standard since its blue fluorescence intensity remains unchanged in the presence of ¹O₂. The ratiometric response of o-PD CPDs is selective toward ¹O₂ against other ROS species. The developed o-PD CPDs have been successfully applied to monitor the ¹O₂ level in the intracellular environment. Furthermore, in the inflammatory neutrophil cell model, o-PD CPDs can also detect the ¹O₂ and other ROS species such as hypochlorous acid after phorbol 12-myristate 13-acetate (PMA)-induced inflammation. Through the dual-channel fluorescence imaging, the ratiometric response of o-PD CPDs shows great potential for detecting endogenous and stimulating ¹O₂in vivo.

An Electrochemical Nanosensor for Monitoring the Dynamics of Intracellular H2 O2 Upon NADH Treatment

Reactive oxygen species (ROS)-based therapeutic strategies play an important role in cancer treatment. However, in situ, real-time and quantitative analysis of intracellular ROS in cancer treatment for drug screening is still a challenge. Herein we report one selective hydrogen peroxide (H₂ O₂ ) electrochemical nanosensor, which is prepared by electrodeposition of Prussian blue (PB) and polyethylenedioxythiophene (PEDOT) onto carbon fiber nanoelectrode. With the nanosensor, we find that the level of intracellular H₂ O₂ increases with NADH treatment and that increase is dose-dependent to the concentration of NADH. High-dose of NADH (above 10 mM) can induce cell death and intratumoral injection of NADH is validated for inhibiting tumor growth in mice. This study highlights the potential of electrochemical nanosensor for tracking and understanding the role of H₂ O₂ in screening new anticancer drug.

Potentiometric nanosensor for real-time measurement of hydrogen sulfide in single cell

One potentiometric nanosensor for monitoring intracellular hydrogen sulfide (H₂S) with fast potential response, high selectivity and excellent antifouling properties was developed. This study constructs a powerful tool to real-time track the changes of intracellular H₂S in situ, promoting the future studies of physiologically relevant processes.

Organic Molecular Probe Enabled Ionic Current Rectification toward Subcellular Detection of Glutathione with High Selectivity, Sensitivity, and Recyclability

Single-cell interrogation with the solid-state nanoprobes enables understanding of the linkage between cellular behavior and heterogeneity. Herein, inspired by the charge property of the organic molecular probe (OMP), a generic ionic current rectification (ICR) single-cell methodology is established, exemplified by subcellular detection of glutathione (GSH) with high selectivity, sensitivity, and recyclability. The as-developed nanosensor can transduce the subcellular OMP-GSH interaction via a sensitive ionic response, which stems from the superior specificity of OMP and its essential charge property. In addition, the nanosensor exhibits good reversibility, since the subsequent tandem reaction after the recognition can well recover the sensing surface. Given the diverse structures and tailorable charge properties of OMP, this work underpins a new and general method of OMP-based ICR single-cell analysis.

Tailoring Silica-Based Nanoscintillators for Peroxynitrite-Potentiated Nitrosative Stress in Postoperative Radiotherapy of Colon Cancer

The development of a manageable reactive nitrogen species-potentiated nitrosative stress induction system for cancer therapy has remained elusive. Herein, tailored silica-based nanoscintillators were reported for low-dosage X-ray boosting for the in situ formation of highly cytotoxic peroxynitrite (ONOO^-). Significantly, cellular nitrosative stress revolving around the intracellular protein tyrosine nitration through ONOO^- pathways was explored. High-energy X-rays were directly deposited on silica-based nanoscintillators, forming the concept of an open source and a reduced expenditure-aggravated DNA damage strategy. Moreover, the resultant ONOO^-, along with the released nitric oxide, not only can act as "oxygen suppliers" to combat tumor hypoxia but also can induce mitochondrial damage to initiate caspase-mediated apoptosis, further improving the therapeutic efficacy of radiotherapy. Thus, the design of advanced nanoscintillators with specific enhanced nitrosative stress offers promising potential for postoperative radiotherapy of colon cancer.