A Highly Selective and Sensitive Chemiluminescent Probe for Real-Time Monitoring of Hydrogen Peroxide in Cells and Animals

V4O7 microcubes as an alternative to peroxidase/TMB for colorimetric detection of H2O2: Development of glucose sensing method

The study focuses on the synthesis of V4O7 microcubes for the non-enzymatic colorimetric determination of H2O2.Vanadium oxide nanostructures are known for their redox activity and layered structures, making V4O7 a valuable material for sensing applications. The characterization of the prepared sample was done using XPS, XRD, Raman spectroscopy, and SEM techniques. The V4O7 microcube showed a rapid response to H2O2 through direct color change without the need for peroxidase enzymes or TMB. Upon exposure to H2O2, the mixed valence V4O7 oxidized to produce V2O5, enabling sensitive detection of H2O2. The V4O7 sensing system exhibited a wide linear response range from 0.025 to 300 µM with a low detection limit of 7.6 nM for H2O2 detection. When combined with glucose oxidase, the system could detect glucose levels as low as 18 nM within a linear range of 0.05 µM to 300 µM. The proposed sensor demonstrated high selectivity and robust potential for sensing H2O2 in biological samples. The system offers advantages such as fast response, simple operation, naked-eye observation, and cost-effectiveness. The novel sensing system holds promise for visual detection in H2O2 diagnostic clinics, highlighting its potential for practical applications in healthcare settings.

Diverse Fluorescent Probe Concepts for Detection and Monitoring of Reactive Oxygen Species

World-wide research on reactive oxygen species (ROS) continues to reveal new information about the role and impact of ROS on human health and disease. ROS are generated in live cells as a byproduct of aerobic metabolism. Physiological concentrations of cellular ROS are important for signaling and homeostasis, but excessive generation of ROS causes apoptotic and necrotic cell death and various health disorders. Fluorescence technology is a powerful tool to detect, monitor, and image cellular ROS. The present review provides an overview of diverse organic dye-based fluorescent probe concepts that involve modifications of traditional fluorescent dyes utilizing basic principles of dye chemistry and photophysics. Fluorescence responses of the probes and their specificity towards ROS are discussed through analyses of their photophysical and photochemical parameters. We also provide an outlook on future directions of ROS-responsive fluorescent dyes, which could enable the design and development of advanced probes for gaining deeper insights into redox biology.

Near-Infrared Chemiluminophore Switches Photodynamic Processes via Protein Complexation for Biomarker-Activatable Cancer Therapy

Despite the potential in cancer therapy, phototheranostic agents often face two challenges: limited diagnostic sensitivity due to tissue autofluorescence and suboptimal therapeutic efficacy due to the Type-II photodynamic process with the heavy oxygen reliance. In contrast, chemiluminescent theranostic agents without the requirement of real-time light excitation can address the issue of tissue autofluorescence, which however have been rarely reported for photodynamic therapy (PDT), not to mention less oxygen-dependent Type-I PDT. In this work, we synthesize near-infrared (NIR) chemiluminophores with the specific binding towards human serum albumin (HSA) to form chemiluminophore-protein complex for cancer detection and photodynamic therapy. Interestingly, after the complexation with HSA, the chemiluminescence (CL) intensities of chemiluminophores are enhanced by over 10-fold; meanwhile, the photodynamic process switches from Type-II (singlet-oxygen-generation dominated) to Type-I (superoxide anion and hydroxyl radical dominated), while the previously reported activated chemiluminophore with non-specific HSA binding can't switch photodynamic process. Based on the optimal chemiluminophore, a nitroreductase-activatable CL probe-protein complex is synthesized, which specially turns on its CL and Type-I PDT in hypoxic tumors for precision therapy. Thus, this study provides a complexation strategy to improve phototheranostic performance of chemiluminophores.

Near-Infrared Chemiluminescent Theranostics

Molecular chemiluminescence probes with near-infrared (NIR) emission offer promising benefits in deciphering complex pathological processes in a living system, as NIR chemiluminescence minimizes autofluorescence, enhances deep-tissue penetration, and improves signal-to-noise ratio. Molecular engineering using single-luminophore design and dual-luminophore design with intramolecular energy transfer provides ways to develop conventional chemiluminophore scaffolds into NIR chemiluminescence probes with ideal chemiluminescence quantum yield and half-life. By virtue of the structural diversity, 1,2-dioxetane-based NIR chemiluminophores with biomarker activity have been developed. This review summarizes the molecular design strategies of NIR chemiluminescence theranostic probes (NCTPs), followed by introducing activatable NCTPs with their biomedical applications for disease theranostics. Lastly, future perspectives and potential challenges of NIR chemiluminescence imaging in preclinical research and clinical translational potential are discussed.

Unprecedented Photoinduced-Electron-Transfer Probe with a Turn-ON Chemiluminescence Mode-of-Action

PeT-based fluorescent probes were demonstrated to be powerful tools for detection and imaging, owing to their significant fluorescence enhancement in response to specific targets. While numerous examples of fluorescence-based PeT have been frequently reported, there is not even a single example of a PeT probe that operates via a chemiluminescence mode. Here we report the first PeT-based turn-on probe that acts via a chemiluminescent operation mode. We designed, synthesized, and evaluated a novel chemiluminescent probe, featuring a PeT-based turn-on mechanism. The probe consists of a phenoxy-1,2-dioxetane, linked to an azide unit that acts as a PeT quencher. Upon cycloaddition of a strained cycloalkyne with the azide, a triazole-dioxetane is formed, which undergoes relatively slow chemiexcitation, resulting in a measurement window with an exceptionally high signal-to-noise ratio (over 5000-fold). The PeT-dioxetane probe could effectively detect and image two model proteins labeled with strained cycloalkyne units (Myc-DBCO and Max-DBCO) through either NHS or maleimide conjugations. Comparative analysis shows that our PeT-based chemiluminescent probe significantly outperforms a commercially available fluorescent analog. We anticipate that the insights gained from this study will facilitate the development of additional chemiluminescent probes utilizing various PeT-quenching pathways.

HClO-Activated Near-Infrared Chemiluminescent Probes with a Malononitrile Group for In-Vivo Imaging

Chemiluminescence (CL) imaging has emerged as a powerful approach to molecular imaging that allows exceptional sensitivity with virtually no background interference because of its unique capacity to emit photons without an external excitation source. Despite its high potential, the application of this nascent technique faces challenges because the current chemiluminescent agents have limited reactive sites, require complex synthesis, are insufficiently bright, and lack near-infrared emission. Herein, a series of HClO-activated chemiluminescent probes that exhibit robust near-infrared emission are studied. Specifically engineered to respond to HClO, a known biomarker of acute inflammation, these probes achieve high-contrast in vivo imaging by eliminating the need for constant external excitation. Comprehensive experimental and theoretical investigations demonstrate that the CL of the probes depends on the reactivity of the vinylene bonds, following a concerted decomposition of the oxidized chemiluminescent molecule. The application of these chemiluminescent nanoparticles in vivo facilitates high-contrast imaging of acute inflammation, providing real-time, high-contrast visualization of inflammatory conditions. This advancement signifies a leap forward for chemiluminescent nanoplatforms in biomedical imaging and expands the available methodologies in this field.

An activatable "AIE + ESIPT" fluorescent probe for dual-imaging of lipid droplets and hydrogen peroxide in drug-induced liver injury model

BACKGROUND

Drug-induced liver injury (DILI) is one of the most common liver diseases. The crucial role of lipid droplets (LDs) and hydrogen peroxide (H2O2), two important biomarkers in the pathophysiology of DILI, has spurred considerable efforts to accurately visualize H2O2 and LDs for elucidating their functions in the progression of DILI. However, construction of a single fluorescent probe that is able to simultaneously image H2O2 and LDs dynamics remains to be a challenging task. Therefore, it is of great demand to develop a novel fluorescent probe for tracking the LDs status and H2O2 fluctuation in drug-induced liver injury.

RESULTS

We developed an "AIE + ESIPT" fluorescent probe TPEHBT for dual-imaging of LDs and H2O2 during DILI process. TPEHBT displayed greatly enhanced fluorescent response to H2O2 by generating an excited state intramolecular proton transfer (ESIPT) fluorophore TPEHBT-OH with aggregation induced emission (AIE) properties. TPEHBT exhibits high selectivity, sensitivity (LOD = 4.73 nM) and large Stokes shift (320 nm) to H2O2. Interestingly, TPEHBT can light up LDs with high specificity. The probe was favorably applied in the detection of endogenous and exogenous H2O2 in living cells, and notably in the simultaneous real-time visualization of H2O2 generation and LDs accumulation during DILI process. Moreover, TPEHBT was able to image H2O2 generation in zebrafish animal model with APAP-induced liver injury.

SIGNIFICANCE

For the first time, probe TPEHBT was applied in the dual-imaging of H2O2 fluctuation and LDs status in APAP-induced liver injury model in vitro and in vivo. The present findings strongly suggest that TPEHBT is a promising tool for monitoring H2O2 and LDs dynamics in DILI progression.

A-D-A Molecular Design Strategy Enabling Ultrasensitive NIR Vapor Sensing

Thin-film fluorescent chemosensors, characterized by their tunable design, high selectivity, and exceptional sensitivity, hold significant promise for gas detection applications. However, the simultaneous realization of the 3S attributes (sensitivity, selectivity, and stability) remains a formidable challenge, particularly in the underexplored field of near-infrared (NIR) gas detection. In this work, we employ an acceptor-donor-acceptor (A-D-A) molecular design strategy to drive the development of an organic semiconductor fluorescent material with a progressive red shift in the emission wavelength. As a result, we synthesized C8-IDTT-IC, a NIR fluorescent thin film with a peak emission at 790 nm. In contrast to conventional visible fluorescent materials, this NIR material demonstrates excellent resistance to background light interference and optical damage, particularly in the detection of biogenic amines. Systematic evaluations reveal that the material achieves remarkable selectivity, with a detection limit as low as 116 ppb, a rapid response time of less than 30 s, and an optical damage rate of only 3% over 1800 s. The practical utility of this material is further exemplified by its integration into a hand-held detector, enabling real-time monitoring of spoilage in beef and fish samples, showcasing its potential for real-world applications.

A novel fluorescence platform for portable and visual monitoring of meat freshness

Biogenic amines (BAs) are crucial markers of meat spoilage. Developing practical and effective BAs detection methods is essential for monitoring meat freshness and ensuring daily consumption safety. This study prepared several naphthalene-based fluorescent compounds to visually monitor meat freshness in real-time. These probes show a colorimetric fluorescence response to putrescine and cadaverine (typical spoilage indicators) through nucleophilic addition/elimination reaction. The detectability of these probes can be optimized by altering the electronegativity and substitution position of the recognition group. Among these compounds, 2-((6-(4-(diphenylamino)phenyl)naphthalen-2-yl)methylene)malono nitrile (TNMA) demonstrated exceptional sensing performance toward putrescine and cadaverine, including high-contrast fluorescence color transition (red to blue), rapid response times (∼30 s), high selectivity and sensitivity (detection limit for putrescine: 2.69 ppm, cadaverine: 6.11 ppm). Furthermore, the B/R values of TNMA test strips output by RGB analysis presented a linear correlation with total volatile basic nitrogen (TVBN, an international standard for evaluating food spoilage) values in pork. Based on this correlation, we utilized smartphone applications to construct an intelligent evaluation system, enabling visual monitoring of pork, chicken, and shrimp freshness under various storage conditions. The TNMA-based system offers a reliable platform for real-time, portable and visual monitoring of meat freshness for consumers and suppliers in the food industry.

Chemiexcitation Acceleration of 1,2-Dioxetanes by Spiro-Fused Six-Member Rings with Electron-Withdrawing Motifs

The chemiluminescent light-emission pathway of phenoxy-1,2-dioxetane luminophores attracts growing interest within the scientific community. Dioxetane probes undergoing rapid flash-type chemiexcitation exhibit higher detection sensitivity than those with a slow glow-type chemiexcitation rate. We discovered that dioxetanes fused to non-strained six-member rings, with hetero atoms or inductive electron-withdrawing groups, present both accelerated chemiexcitation rates and elevated chemical stability compared to dioxetanes fused to four-member strained rings. DFT computational simulations supported the chemiexcitation acceleration observed by spiro-fused six-member rings with inductive electron-withdrawing groups of dioxetanes. Specifically, a spiro-dioxetane with a six-member sulfone ring exhibited a chemiexcitation rate 293-fold faster than that of spiro-adamantyl-dioxetane. A turn-ON dioxetane probe for the detection of the enzyme β-galactosidase, containing the six-member sulfone unit, exhibited a S/N value of 108 in LB cell growth medium. This probe demonstrated a substantial increase in detection sensitivity towards E. coli bacterial cells expressing β-galactosidase, with an LOD value that is 44-fold more sensitive than that obtained by the adamantyl counterpart. The accelerated chemiexcitation and the elevated chemical stability presented by dioxetane containing a spiro-fused six-member ring with a sulfone inductive electron-withdrawing group, make it an ideal candidate for designing efficient turn-on chemiluminescent probes with exceptionally high detection sensitivity.

Monodispersed Au nanoparticles decorated MoS2 nanosheets with enhanced peroxidase-like activity based electrochemical H2O2 sensing for anticancer drug evaluations

BACKGROUND

The unique size, physical and chemical properties, and ultra-high stability of nanozymes have attracted extensive attentions in sensing, but improvement of catalytic activity of the nanozymes is still an urgent issue. Given the ultra-high simulated enzyme activity of metal nanoparticles and the advantage of multi-enzyme catalysis, an Au-decorated MoS2 nanosheets (MoS2/Au NS) integrating the double peroxidase-like (POD) activity is developed.

RESULTS

By optimizing and adjusting the density of AuNPs, as well as its morphology and other parameters, a monodisperse and high-density distribution of AuNPs on MoS2 nanosheets was obtained, which can greatly improve the POD-like activity of MoS2/Au NS. Nafion solution was applied to assist the modification of MoS2/Au NS on the electrode surface so as to improved its stability. An electrochemical H2O2 detection platform was constructed by modifying MoS2/Au NS nanozyme on the SPCE using the conductive Nafion solution. And the negatively charged sulfonic acid group can eliminate negatively charged electroactive substances to improve the specificity. Then ascorbic acid was used to stimulate tumor cells to produce H2O2 as therapeutic model, an ultrasensitive chronocoulometry detection for H2O2 in cell lysate was established. The logarithmically of ΔQ and the logarithmically of H2O2 concentration showed a good linear relationship between 1 μM and 500 mM, with a LOD value of 0.3 μM.

SIGNIFICANCE

The developed H2O2 sensor has excellent stability, reproducibility (RSD = 2.3 %, n = 6) and selectivity, realized the quantitative detection of H2O2 in cell lysate. Compared with commercial fluorescence detection kits for H2O2 in cell lysate, it is worth mentioning that the electrochemical H2O2 sensor developed in this study is simpler and faster, with higher sensitivity and lower cost. This provides a potential substitute for disease diagnosis and treatment evaluation based on accurate detection of H2O2.

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals. This review focuses specifically on small molecule probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide, and peroxynitrite that provide a luminescent or photoacoustic signal. Important background information on general photophysical phenomena, common probe designs, mechanisms, and imaging modalities will be provided, and then, probes for each analyte will be thoroughly evaluated. A discussion of the successes of the field will be presented, followed by recommendations for improvement and a future outlook of emerging trends. Our objectives are to provide an informative, useful, and thorough field guide to small molecule probes for reactive oxygen and nitrogen species as well as important context to compare the ecosystem of chemistries and molecular scaffolds that has manifested within the field.

Human NQO1 as a Selective Target for Anticancer Therapeutics and Tumor Imaging

Human NAD(P)H-quinone oxidoreductase1 (HNQO1) is a two-electron reductase antioxidant enzyme whose expression is driven by the NRF2 transcription factor highly active in the prooxidant milieu found in human malignancies. The resulting abundance of NQO1 expression (up to 200-fold) in cancers and a barely detectable expression in body tissues makes it a selective marker of neoplasms. NQO1 can catalyze the repeated futile redox cycling of certain natural and synthetic quinones to their hydroxyquinones, consuming NADPH and generating rapid bursts of cytotoxic reactive oxygen species (ROS) and H2O2. A greater level of this quinone bioactivation due to elevated NQO1 content has been recognized as a tumor-specific therapeutic strategy, which, however, has not been clinically exploited. We review here the natural and new quinones activated by NQO1, the catalytic inhibitors, and the ensuing cell death mechanisms. Further, the cancer-selective expression of NQO1 has opened excellent opportunities for distinguishing cancer cells/tissues from their normal counterparts. Given this diagnostic, prognostic, and therapeutic importance, we and others have engineered a large number of specific NQO1 turn-on small molecule probes that remain latent but release intense fluorescence groups at near-infrared and other wavelengths, following enzymatic cleavage in cancer cells and tumor masses. This sensitive visualization/quantitation and powerful imaging technology based on NQO1 expression offers promise for guided cancer surgery, and the reagents suggest a theranostic potential for NQO1-targeted chemotherapy.

Mitochondria-Targetable Near-Infrared Fluorescent Probe for Visualization of Hydrogen Peroxide in Lung Injury, Liver Injury, and Tumor Models

Hydrogen peroxide (H2O2) overexpressed in mitochondria has been regarded as a key biomarker in the pathological processes of various diseases. However, there is currently a lack of suitable mitochondria-targetable near-infrared (NIR) probes for the visualization of H2O2 in multiple diseases, such as PM2.5 exposure-induced lung injury, hepatic ischemia-reperfusion injury (HIRI), nonalcoholic fatty liver (NAFL), hepatic fibrosis (HF), and malignant tumor tissues containing clinical cancer patient samples. Herein, we conceived a novel NIR fluorescent probe (HCy-H2O2) by introducing pentafluorobenzenesulfonyl as a H2O2 sensing unit into the NIR hemicyanine platform. HCy-H2O2 exhibits good sensitivity and selectivity toward H2O2, accompanied by a remarkable "turn-on" fluorescence signal at 720 nm. Meanwhile, HCy-H2O2 has stable mitochondria-targetable ability and permits monitoring of the up-generated H2O2 level during mitophagy. Furthermore, using HCy-H2O2, we have successfully observed an overproduced mitochondrial H2O2 in ambient PM2.5 exposure-induced lung injury, HIRI, NAFL, and HF models through NIR fluorescence imaging. Significantly, the visualization of H2O2 has been achieved in both tumor-bear mice as well as surgical specimens of cancer patients, making HCy-H2O2 a promising tool for cancer diagnosis and imaging-guided surgery.

DNA Walker-Driven Mass Nanotag Assembly System for Simultaneously Profiling Dual Markers of Oxidative Stress at Different Cellular Locations

Simultaneous profiling of redox-regulated markers at different cellular sublocations is of great significance for unraveling the upstream and downstream molecular mechanisms of oxidative stress in living cells. Herein, by synchronizing dual target-triggered DNA machineries in one nanoentity, we engineered a DNA walker-driven mass nanotag (MNT) assembly system (w-MNT-AS) that can be sequentially activated by oxidative stress-associated mucin 1 (MUC1) and apurinic/apyrimidinic endonuclease 1 (APE1) from plasma membrane to cytoplasm and induce recycled assembly of MNTs for multiplex detection of the two markers by matrix-assisted laser desorption ionization mass spectrometry (MALDI MS). In the working cascade, the sensing process governs the separate activation of w-MNT-AS by MUC1 and APE1 in diverse locations, while the assembly process contributes to the parallel amplification of the ion signal of the characteristic mass tags. In this manner, the differences between MCF-7, HeLa, HepG2, and L02 cells in membrane MUC1 expression and cytoplasmic APE1 activation were fully characterized. Furthermore, the oxidative stress level and dynamics caused by exogenous H2O2, doxorubicin, and simvastatin were comprehensively demonstrated by tracking the fate of the two markers across different cellular locations. The proposed w-MNT-AS coupled MS method provides an effective route to probe multiple functional molecules that lie at different locations while participating in the same cellular event, facilitating the mechanistic studies on cellular response to oxidative stress and other disease-related cellular processes.

A Tandem-Locked Chemiluminescent Probe for Imaging of Tumor-Associated Macrophage Polarization

Tumor-associated macrophages (TAMs) play a role in both pro- and anti-tumor functions; and the targeted polarization from M2 to M1 TAMs has become an effective therapy option. Although detection of M1 TAMs is imperative to assess cancer immunotherapeutic efficacy, existing optical probes suffer from shallow tissue penetration depth and poor specificity toward M1 TAMs. Herein, we report a tandem-locked NIR chemiluminescent (CL) probe for specific detection of M1 TAMs. Through a combined molecular engineering approach via both atomic alternation and introduction of electron-withdrawing groups, near-infrared (NIR) chemiluminophores are screened out to possess record-long emission (over 800 nm), record-high CL quantum yield (2.7 % einstein/mol), and prolonged half-life (7.7 h). Based on an ideal chemiluminophore, the tandem-locked probe (DPDGN) is developed to only activate CL signal in the presence of both tumour (γ-glutamyl transpeptidase) and M1 macrophage biomarkers (nitric oxide). Such a tandem-lock design ensures its high specificity towards M1 macrophages in the tumor microenvironment over those in normal tissues or peripheral blood. Thus, DPDGN permits noninvasive imaging and tracking of M1 TAM in the tumor of living mice during R837 treatment, showing a good correlation with ex vivo methods. This study not only reports a new molecular approach towards highly efficient chemiluminophores but also reveals the first tandem-locked CL probes for enhanced imaging specificity.

Efficient Electrochemical Microsensor for the Simultaneous Measurement of Hydrogen Peroxide and Ascorbic Acid in Living Brains

Hydrogen peroxide (H2O2) and ascorbic acid (AA), acting as two significant indicative species, correlate with the oxidative stress status in living brains, which have historically been considered to be involved mainly in neurodegenerative disorders such as Alzheimer's disease, Huntington's disease, and Parkinson's disease (PD). The development of efficient biosensors for the simultaneous measurement of their levels in living brains is vital to understand their roles played in the brain and their interactive relationship in the progress of these diseases. Herein, a robust ratiometric electrochemical microsensor was rationally designed to realize the determination of H2O2 and AA simultaneously. Therefore, a specific probe was designed and synthesized with both recognition units responsible for reacting with H2O2 to produce a detectable signal on the microsensor and linkage units helping the probe modify onto the carbon substrate. A topping ingredient, single-walled carbon nanotubes (SWCNTs) was added on the surface of the electrode, with the purpose of not only facilitating the oxidation of AA but also absorbing methylene blue (MB), prompting to read out the inner reference signal. This proposed electrochemical microsensor exhibited a robust ability to real-time track H2O2 and AA in linear ranges of 0.5-900 and 10-1000 μM with high selectivity and accuracy, respectively. Eventually, the efficient electrochemical microsensor was successfully applied to the simultaneous measurement of H2O2 and AA in the rat brain, followed by microinjection, and in the PD mouse brain.

A H2O2-specific fluorescent probe for evaluating oxidative stress in pesticides-treated cells, rice roots and zebrafish

Hydrogen peroxide (H2O2) plays an irreplaceable role in the evaluation of the redox status in versatile circumstances. The levels of H2O2 can be affected by both internal and external stimuli, including environmental hazards. Abnormal production of H2O2 is a common characteristic of pesticide-caused damage. Therefore, H2O2 levels can intuitively and conveniently reflect the oxidative stress caused by various pesticides in cells and organisms. However, reliable and convenient monitoring of H2O2 in living cells is still limited by the lack of specific imaging probes. In this study, a fluorescent probe (HBTM-HP) was developed for in situ observation of H2O2 fluctuations caused by pesticide treatment over time in mammalian cells, rice roots and zebrafish. HBTM-HP showed high sensitivity and selectivity for H2O2. Fluorescence imaging results confirmed that HBTM-HP could be applied to reveal H2O2 production induced by multiple pesticides. This study revealed that HBTM-HP could serves as a versatile tool to monitor the redox status related to H2O2 both in vitro and in vivo upon exposure to pesticides, and also provides a basis for clarifying the mechanisms of pesticides in physiological and pathological processes.

Near-Infrared Chemiluminescence Imaging of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) has a high prevalence but is poorly managed for cancer patients due to the lack of reliable and sensitive diagnostic techniques. Molecular optical imaging can provide a noninvasive way for real-time monitoring of CIPN; However, this is not reported, likely due to the absence of optical probes capable of imaging deep into the spinal canal and possessing sufficient sensitivity for minimal dosage through local injection into the dorsal root ganglia. Herein, a near-infrared (NIR) chemiluminophore (MPBD) with a chemiluminescence quantum yield higher than other reported probes is synthesized and a NIR activatable chemiluminescent probe (CalCL) is developed for in vivo imaging of CIPN. CalCL is constructed by caging MPBD with calpain-cleavable peptide moiety while conjugating polyethylene glycol chain to endow water solubility. Due to the deep-tissue penetration of chemiluminescence and specific turn-on response of CalCL toward calpain (a hallmark of CIPN), it allows for sensitive detection of paclitaxel-mediated CIPN in living mice, which is unattainable by fluorescence imaging. This study thus not only develops a highly efficient chemiluminescent probe, but also presents the first optical imaging approach toward high-throughput screening of neurotoxic drugs.

Enzymatic Activity Profiling Using an Ultrasensitive Array of Chemiluminescent Probes for Bacterial Classification and Characterization

Identification and characterization of bacterial species in clinical and industrial settings necessitate the use of diverse, labor-intensive, and time-consuming protocols as well as the utilization of expensive and high-maintenance equipment. Furthermore, while cutting-edge identification technologies such as mass spectrometry and PCR are highly effective in identifying bacterial pathogens, they fall short in providing additional information for identifying bacteria not present in the databases upon which these methods rely. In response to these challenges, we present a robust and general approach to bacterial identification based on their unique enzymatic activity profiles. This method delivers results within 90 min, utilizing an array of highly sensitive and enzyme-selective chemiluminescent probes. Leveraging our recently developed technology of chemiluminescent luminophores, which emit light under physiological conditions, we have crafted an array of probes designed to rapidly detect various bacterial enzymatic activities. The array includes probes for detecting resistance to the important and large class of β-lactam antibiotics. The analysis of chemiluminescent fingerprints from a diverse range of prominent bacterial pathogens unveiled distinct enzymatic activity profiles for each strain. The reported universally applicable identification procedure offers a highly sensitive and expeditious means to delineate bacterial enzymatic activity fingerprints. This opens new avenues for characterizing and identifying pathogens in research, clinical, and industrial applications.

High Contrast Bioimaging of Tumor and Inflammation with a Bicyclic Dioxetane Chemiluminescent Probe

The link between inflammation and the evolution of cancer is well established. Visualizing and tracking both tumor proliferation and the associated inflammatory response within a living organism are vital for dissecting the nexus between these two processes and for crafting precise treatment modalities. We report the creation and synthesis of an advanced NIR chemiluminescence probe that stands out for its exceptional selectivity, extraordinary sensitivity at nanomolar concentrations, swift detection capabilities, and broad application prospects. Crucially, this probe has been successfully utilized to image endogenous ONOO- across different inflammation models, including abdominal inflammation triggered by LPS, subcutaneous inflammatory conditions, and tumors grafted onto mice. These findings highlight the significant promise of chemiluminescence imaging in enhancing our grasp of the intricate interplay between cancer and inflammation and in steering the development of potent, targeted therapeutic strategies.

Activatable Near-Infrared Versatile Fluorescent and Chemiluminescent Dyes Based on the Dicyanomethylene-4H-pyran Scaffold: From Design to Imaging and Theranostics

Activatable fluorescent and chemiluminescent dyes with near-infrared emission have indispensable roles in the fields of bioimaging, molecular prodrugs, and phototheranostic agents. As one of the most popular fluorophore scaffolds, the dicyanomethylene-4H-pyran scaffold has been applied to fabricate a large number of versatile activatable optical dyes for analytes detection and diseases diagnosis and treatment by virtue of its high photostability, large Stokes shift, considerable two-photon absorption cross-section, and structural modifiability. This review discusses the molecular design strategies, recognition mechanisms, and both in vitro and in vivo bio-applications (especially for diagnosis and therapy of tumors) of activatable dicyanomethylene-4H-pyran dyes. The final section describes the current shortcomings and future development prospects of this topic.

Sensitive and Selective Dual-Mode Responses to Reactive Oxygen Species by Chiral Manganese Dioxide Nanoparticles for Antiaging Skin

Excessive accumulation of reactive oxygen species (ROS) can lead to oxidative stress and oxidative damage, which is one of the important factors for aging and age-related diseases. Therefore, real-time monitoring and the moderate elimination of ROS is extremely important. In this study, a ROS-responsive circular dichroic (CD) at 553 nm and magnetic resonance imaging (MRI) dual-signals chiral manganese oxide (MnO2 ) nanoparticles (NPs) are designed and synthesized. Both the CD and MRI signals show excellent linear ranges for intracellular hydrogen peroxide (H2 O2 ) concentrations, with limits of detection (LOD) of 0.0027 nmol/106 cells and 0.016 nmol/106 cells, respectively. The lower LOD achieved with CD detection may be attributable to its higher anti-interference capability from the intracellular matrix. Importantly, ROS-induced cell aging is intervened by chiral MnO2 NPs via redox reactions with excessive intracellular ROS. In vivo experiments confirm that chiral MnO2 NPs effectively eliminate ROS in skin tissue, reduce oxidative stress levels, and alleviate skin aging. This approach provides a new strategy for the diagnosis and treatment of age-related diseases.

Chemical Reactions in Living Systems

The term "in vivo ("in the living") chemistry" refers to chemical reactions that take place in a complex living system such as cells, tissue, body liquids, or even in an entire organism. In contrast, reactions that occur generally outside living organisms in an artificial environment (e.g., in a test tube) are referred to as in vitro. Over the past decades, significant contributions have been made in this rapidly growing field of in vivo chemistry, but it is still not fully understood, which transformations proceed efficiently without the formation of by-products or how product formation in such complex environments can be characterized. Potential applications can be imagined that synthesize drug molecules directly within the cell or confer new cellular functions through controlled chemical transformations that will improve the understanding of living systems and develop new therapeutic strategies. The guiding principles of this contribution are twofold: 1) Which chemical reactions can be translated from the laboratory to the living system? 2) Which characterization methods are suitable for studying reactions and structure formation in complex living environments?

Spirostrain-Accelerated Chemiexcitation of Dioxetanes Yields Unprecedented Detection Sensitivity in Chemiluminescence Bioassays

Chemiluminescence is a fascinating phenomenon that involves the generation of light through chemical reactions. The light emission from adamantyl-phenoxy-1,2-dioxetanes can glow from minutes to hours depending on the specific substituent present on the dioxetane molecule. In order to improve the light emission properties produced by these chemiluminescent luminophores, it is necessary to induce the chemiexcitation rate to a flash mode, wherein the bulk of light is emitted instantly rather than slowly over time. We report the realization of this goal through the incorporation of spirostrain release into the decomposition of 1,2-dioxetane luminophores. DFT computational simulations provided support for the hypothesis that the spiro-cyclobutyl substituent accelerates chemiexcitation as compared to the unstrained adamantyl substituent. Spiro-linking of cyclobutane and oxetane units led to greater than 100-fold and 1000-fold emission enhancement, respectively. This accelerated chemiexcitation rate increases the detection sensitivity for known chemiluminescent probes to the highest signal-to-noise ratio documented to date. A turn-ON probe, containing a spiro-cyclobutyl unit, for detecting the enzyme β-galactosidase exhibited a limit of detection value that is 125-fold more sensitive than that for the previously described adamantyl analogue. This probe was also able to instantly detect and image β-gal activity with enhanced sensitivity in E. coli bacterial assays.

π-π Interaction-Induced Organic Long-wavelength Room-Temperature Phosphorescence for In Vivo Atherosclerotic Plaque Imaging

Room-temperature phosphorescent (RTP) materials have great potential for in vivo imaging because they can circumvent the autofluorescence of biological tissues. In this study, a class of organic-doped long-wavelength (≈600 nm) RTP materials with benzo[c][1,2,5] thiadiazole as a guest was constructed. Both host and guest molecules have simple structures and can be directly purchased commercially at a low cost. Owing to the long phosphorescence wavelength of the doping system, it exhibited good tissue penetration (10 mm). Notably, these RTP nanoparticles were successfully used to image atherosclerotic plaques, with a signal-to-background ratio (SBR) of 44.52. This study provides a new approach for constructing inexpensive red organic phosphorescent materials and a new method for imaging cardiovascular diseases using these materials.

Ultrasensitive Detection of Hydrogen Peroxide Using Methylene Blue Grafted on Molecular Wires as Nanozyme with Catalase-like Activity

In this study, we present the development of an electrochemical sensor designed for ultrasensitive detection of endogenous H2O2. This sensor relies on signal amplification achieved through nanozyme activity exhibited by methylene blue (MB) grafted onto a peptide support. The sensor exhibited excellent selectivity and sensitivity, with a limit of detection of 18 nM and a linear detection range of 20-200 nM. Thus, we have validated the concept of the MB-peptide system, serving as both an electroactive label and a catalyst for H2O2 decomposition under electrochemical conditions. The implemented signal amplification system enables the rapid detection of H2O2, with an overall assay time of 1-2 min, a significant improvement compared to amperometric detection using surface-immobilized enzymes.

Unexcited Light Source Imaging for Biomedical Applications

Optical imaging has a wide range of applications in the biomedical field, allowing the visualization of physiological processes and helping in the diagnosis and treatment of diseases. Unexcited light source imaging technologies, such as chemiluminescence imaging, bioluminescence imaging and afterglow imaging have attracted great attention in recent years because of the absence of excitation light interference in their application and the advantages of high sensitivity and high signal-to-noise ratio. In this review, the latest advances in unexcited light source imaging technology for biomedical applications are highlighted. The design strategies of unexcited light source luminescent probes in improving luminescence brightness, penetration depth, quantum yield and targeting, and their applications in inflammation imaging, tumor imaging, liver and kidney injury imaging and bacterial infection imaging are introduced in detail. The research progress and future prospects of unexcited light source imaging for medical applications are further discussed.

Emission Wavelength-Tunable Bicyclic Dioxetane Chemiluminescent Probes for Precise In Vitro and In Vivo Imaging

Chemiluminescent probes have become increasingly popular in various research areas including precise tumor imaging and immunofluorescence analysis. Nevertheless, previously developed chemiluminescence probes are mainly limited to studying oxidation reaction-associated biological events. This study presents the first example of bioimaging applicable bicyclic dioxetane chemiluminescent probes with tunable emission wavelengths that range from 525 to 800 nm. These newly developed probes were able to detect the analytes of β-Gal, H2O2, and superoxide with high specificity and a limit of detection of 77 mU L-1, 96, and 28 nM, respectively. The bioimaging application of the probes was verified in ovarian and liver cancer cells and macrophage cells, allowing the detection of the content of β-Gal, H2O2, and superoxide inside the cells. The high specificity allowed us to image the xenografted tumor in mice. We expect that our probes will receive extensive applications in recording complex biomolecular events using noninvasive imaging techniques.

Emergency Treatment and Photoacoustic Assessment of Spinal Cord Injury Using Reversible Dual-Signal Transform-Based Selenium Antioxidant

Spinal cord injury (SCI), following explosive oxidative stress, causes an abrupt and irreversible pathological deterioration of the central nervous system. Thus, preventing secondary injuries caused by reactive oxygen species (ROS), as well as monitoring and assessing the recovery from SCI are critical for the emergency treatment of SCI. Herein, an emergency treatment strategy is developed for SCI based on the selenium (Se) matrix antioxidant system to effectively inhibit oxidative stress-induced damage and simultaneously real-time evaluate the severity of SCI using a reversible dual-photoacoustic signal (680 and 750 nm). Within the emergency treatment and photoacoustic severity assessment (ETPSA) strategy, the designed Se loaded boron dipyrromethene dye with a double hydroxyl group (Se@BDP-DOH) is simultaneously used as a sensitive reporter group and an excellent antioxidant for effectively eliminating explosive oxidative stress. Se@BDP-DOH is found to promote the recovery of both spinal cord tissue and locomotor function in mice with SCI. Furthermore, ETPSA strategy synergistically enhanced ROS consumption via the caveolin 1 (Cav 1)-related pathways, as confirmed upon treatment with Cav 1 siRNA. Therefore, the ETPSA strategy is a potential tool for improving emergency treatment and photoacoustic assessment of SCI.

Fast and Visual Detection of Biogenic Amines and Food Freshness Based on ICT‐Induced Ratiometric Fluorescent Probes

Biogenic amines (BAs) are important indicators for the evaluation of food spoilage and disease diagnosis. Thus, the detection of BAs with high practical potential is of great importance. In this work, a new BAs fluorescent probe design strategy is proposed by the intramolecular charge transfer (ICT) enhancement of the fluorescent probes, which is induced by the hydrogen bond interaction between probes and analyte. The probes T1 and T2 with donor–acceptor structure not only present a 140 nm bathochromic‐shifted emission, ultrafast responses (15 s for T1 and 25 s for T2), and high sensitivity (detection limit of 1.3 ppm for T1 and 2.6 ppm for T2) to cadaverine (the typical representative of BAs) but also discriminate a series of BAs and simply reused at least 30 times after air blowing. Further, a quantitative evaluation system is obtained based on T1 and T2 films. Through the Red/Green/Blue analysis with a smartphone, the total volatile basic nitrogen (an international standard to assess food spoilage) value can be output to quantitatively evaluate the freshness of food. The system is fast, visual, accurate, and non‐destructive, enabling consumers and all stakeholders in the food supply chain to monitor food freshness.

Chemiluminescent duplex analysis using phenoxy-1,2-dioxetane luminophores with color modulation

Multiplex technology is an important emerging field, in diagnostic sciences, that enables the simultaneous detection of several analytes in a single sample. The light-emission spectrum of a chemiluminescent phenoxy-dioxetane luminophore can be accurately predicted by determining the fluorescence-emission spectrum of its corresponding benzoate species, which is generated during the chemiexcitation process. Based on this observation, we designed a library of chemiluminescent dioxetane luminophores with multicolor emission wavelengths. Two dioxetane luminophores that have different emission spectra, but similar quantum yield properties, were selected from the synthesized library for a duplex analysis. The selected dioxetane luminophores were equipped with two different enzymatic substrates to generate turn-ON chemiluminescent probes. This pair of probes exhibited a promising ability to act as a chemiluminescent duplex system for the simultaneous detection of two different enzymatic activities in a physiological solution. In addition, the pair of probes were also able to simultaneously detect the activities of the two enzymes in a bacterial assay, using a blue filter slit for one enzyme and a red filter slit for the other enzyme. As far as we know, this is the first successful demonstration of a chemiluminescent duplex system composed of two-color phenoxy-1,2-dioxetane luminophores. We believe that the library of dioxetanes presented here will be beneficial for developing chemiluminescence luminophores for multiplex analysis of enzymes and bioanalytes.

Electrochemical H2O2 sensor based on a Au nanoflower-graphene composite for anticancer drug evaluation

Reliable H₂O₂ sensors for in situ cellular monitoring under drug stimulation can be developed as a powerful and versatile tool for drug evaluation. Herein, a novel electrochemical biosensor capable of detecting and quantifying H₂O₂ was fabricated by graphene and shape-controlled gold nanostructures. With the help of polyelectrolytes, gold exhibited hierarchical flower-like nanostructures. This kind of nanozyme material exhibited a prominent electrochemical response for H₂O₂. Electrocatalytic activity for H₂O₂ reduction with high sensitivity (5.07◊10^-4 mA μmol L^-1 cm^-2) and good detection capability (the lowest detection limit is 4.5 μmol L^-1 (S/N = 3)) were achieved. This electrochemical biosensor was successfully used to measure the concentration of H₂O₂ released from HepG2 hepatoma cells. Ascorbic acid (AA) and Camellia nitidissima Chi saponins (CNCS) were selected as model drugs, and their anticancer activities were compared by in situ monitoring of H₂O₂. Interestingly, the electrochemical sensor showed remarkable sensitivity, accuracy, and rapidity compared with the traditional enzymatic detection kit. In brief, the as-synthesized nanostructured H₂O₂ sensors can be applied to assess the antitumor properties of candidate drugs and inspire developments for personalized health care monitoring and cancer treatment.

Specific and Long-Term Luminescent Monitoring of Hydrogen Peroxide in Tumor Metastasis

Luminescent monitoring of endogenous hydrogen peroxide (H₂ O₂ ) in tumors is conducive to understanding metastasis and developing novel therapeutics. The clinical transformation is obstructed by the limited light penetration depth, toxicity of nano-probes, and lack of long-term monitoring modes of up to days or months. New monitoring modes are introduced via specific probes and implantable devices, which can achieve real-time monitoring with a readout frequency of 0.01 s or long-term monitoring for months to years. Near-infrared dye-sensitized upconversion nanoparticles (UCNPs) are fabricated as the luminescent probes, and the specificity to reactive oxygen species is subtly regulated by the self-assembled monolayers on the surfaces of UCNPs. Combined with the passive implanted system, a 20-day monitoring of H₂ O₂ in the rat model of ovarian cancer with peritoneal metastasis is achieved, in which the limited light penetration depth and toxicity of nano-probes are circumvented. The developed monitoring modes show great potential in accelerating the clinical transformation of nano-probes and biochemical detection methods.

Semiconducting Polymer Nanoparticles-Manganese Based Chemiluminescent Platform for Determining Total Antioxidant Capacity in Diabetic Mice

The total antioxidant capacity (TAC) is a key indicator of the body's resistance to oxidative stress injury in diabetic patients. The measurement of TAC is important for effectively evaluating the redox state to prevent and control the occurrence of diabetes complications. However, there is a lack of a simple, convenient, and reliable method to detect the total antioxidant capacity in diabetes. Herein, we design a novel chemiluminescent platform based on semiconducting polymer nanoparticles-manganese (SPNs-Mn^VII) to detect the total antioxidant capacity of urine in diabetic mice. We synthesize semiconducting polymer nanoparticles with four different structures and discover the ability of Mn^VII to produce singlet oxygen (¹O₂) that is employed to excite thiophene-based SPNs (PFODBT) to emit near-infrared chemiluminescence. Notably, the chemiluminescent intensity has a good linear relationship with the concentration of Mn^VII (detection limit: 2.8 μM). Because antioxidants (e.g., glutathione or ascorbic acid) can react with Mn^VII, such a chemiluminescent tool of SPNs (PFODBT)-Mn^VII can detect the glutathione or ascorbic acid with a larger responsive range. Furthermore, the total antioxidant capacity of urine from mice is evaluated via SPNs (PFODBT)-Mn^VII, and there are statistically significant differences between diabetic and healthy mice. Thus, this new chemiluminescent platform of SPNs (PFODBT)-Mn^VII is convenient, efficient, and sensitive, which is promising for monitoring antioxidant therapy of diabetes.

NIR-II Self-Luminous Molecular Probe for In Vivo Inflammation Tracking and Cancer PDT Effect Self-Evaluating

Optical imaging in the second near-infrared (NIR-II, 900-1700 nm) window has been extensively investigated for bioimaging. However, a strong autofluorescence background from real-time excitation light significantly reduces the images' quality of NIR-II fluorescence (FL) imaging. To resolve this issue, a NIR-II self-luminous small molecule (CLPD) based on bioluminescence (BL) resonance energy transfer (BRET) mechanism is first developed. The reactive oxygen species (ROS) can trigger NIR-II BL and reduce the NIR-II FL signals of the CLPD simultaneously, enabling ROS-correlated ratiometric BL/FL imaging. CLPD is used for high-contrast NIR-II BL imaging of osteoarthritis as well as guiding the treatment process by ratiometric BL/FL imaging. Moreover, CLPD is applied for NIR-II BL imaging of tumor triggered by the generated ROS during PDT. A correlation between the ratiometric NIR-II BL/FL signal and tumor size is constructed, providing a trustworthy tool for early assessment of PDT effect. Overall, this study presents a novel NIR-II self-luminous small molecular probe for in vivo imaging and provides a strategy for design a self-evaluation system of therapeutic effect.

Horseradish Peroxidase-Encapsulated Fluorescent Bio-Nanoparticle for Ultra-Sensitive and Easy Detection of Hydrogen Peroxide

Hydrogen peroxide (H₂O₂) has been a fascinating target in various chemical, biological, clinical, and industrial fields. Several types of fluorescent protein-stabilized gold nanoclusters (protein-AuNCs) have been developed for sensitive and easy detection of H₂O₂. However, its low sensitivity makes is difficult to measure negligible concentrations of H₂O₂. Therefore, to overcome this limitation, we developed a horseradish peroxidase-encapsulated fluorescent bio-nanoparticle (HEFBNP), comprising bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and horseradish peroxidase-stabilized gold nanoclusters (HRP-AuNCs). The fabricated HEFBNP can sensitively detect H₂O₂ owing to its two properties. The first is that HEFBNPs have a continuous two-step fluorescence quenching mechanism, which comes from the heterogenous fluorescence quenching mechanism of HRP-AuNCs and BSA-AuNCs. Second, the proximity of two protein-AuNCs in a single HEFBNP allows a reaction intermediate (•OH) to rapidly reach the adjacent protein-AuNCs. As a result, HEFBNP can improve the overall reaction event and decrease the loss of intermediate in the solution. Due to the continuous quenching mechanism and effective reaction event, a HEFBNP-based sensing system can measure very low concentrations of H₂O₂ up to 0.5 nM and show good selectivity. Furthermore, we design a glass-based microfluidic device to make it easier use HEFBNP, which allowed us to detect H₂O₂ with the naked eye. Overall, the proposed H₂O₂ sensing system is expected to be an easy and highly sensitive on-site detection tool in chemistry, biology, clinics, and industry fields.

Dual Chemiexcitation by a Unique Dioxetane Scaffold Gated by an OR Logic Set of Triggers

Chemiexcitation of phenoxy-1,2-dioxetane chemiluminescent luminophores is initiated by electron transfer from a meta-positioned phenolate ion to the peroxide-dioxetane bond. Here we report the development of a unique 1,2-dioxetane chemiluminescent scaffold with chemiexcitation gated by an OR logic dual-set of triggering events. This scaffold is composed of meta-dihydroxyphenyl-1,2-dioxetane-adamantyl molecules, equipped with acrylic acid and chlorine substituents, that chemiexcitation under physiological conditions. A dual-mode chemiluminescent probe, armed with two different triggering substrates designed for activation by the enzymes β-galactosidase and alkaline phosphatase, was synthesized. The probe emitted intense light signals in the response to each enzyme, demonstrating its ability to serve as a single-component chemiluminescent sensor for dual-analyte detection. We also demonstrated the ability of the probe to detect β-galactosidase and phosphatase activities in bacteria. This is the first 1,2-dioxetane scaffold capable of responding to two different chemiexcitation events from two different positions on the same dioxetane molecule. We anticipate that the OR-gated mode of chemiexcitation, described herein, will find utility in the preparation of chemiluminescent probes with a dual-analyte detection/imaging mode.

A dual-site multifunctional fluorescent probe for selective detection of endogenous H2O2 and SO2 derivatives based on ICT process and its bioimaging application

In this paper, we reported a coumarin-based fluorescent probe for selective detection of H₂O₂/SO₂ derivatives via ICT process. To the best of our knowledge, it was few reported with the same probe to enable visual detection of H₂O₂/SO₂ derivatives in vivo and in vitro. H₂O₂ and SO₃^2- were selectively sensed over other analytes, and the probe displayed 20-fold and 220-fold relative fluorescence intensity respectively, as well as the good linear relationship and the excellent detection limits of 2.7 * 10³ nM and 19.3 nM. Furthermore, the probe was successfully used for fluorescence imaging of the HeLa cells and the mice to monitor exogenous and endogenous H₂O₂ and SO₃^2-, suggesting its potential biomedical application for investigation and detection the intermediate indicator of oxidative stress in vitro and in vivo.

Exploring the Structural Space of Chemiluminescent 1,2-Dioxetanes

Chemiluminescent molecules which emit light in response to a chemical reaction are powerful tools for the detection and measurement of biological analytes and enable the understanding of complex biochemical processes in living systems. Triggerable chemiluminescent 1,2-dioxetanes have been studied and tuned over the past decades to advance quantitative measurement of biological analytes and molecular imaging in live cells and animals. A crucial determinant of success for these 1,2-dioxetane based sensors is their chemical structure, which can be manipulated to achieve desired chemical properties. In this Perspective, we survey the structural space of triggerable 1,2-dioxetane and assess how their design features affect chemiluminescence properties including quantum yield, emission wavelength, and decomposition kinetics. Based on this appraisal, we identify some structural modifications of 1,2-dioxetanes that are ripe for exploration in the context of chemiluminescent biological sensors.

Real-Time Detection and Visualization of Amyloid-β Aggregates Induced by Hydrogen Peroxide in Cell and Mouse Models of Alzheimer's Disease

Oxidative stress, caused by an imbalance between the production and the accumulation of reactive oxygen species (ROS), is a prominent cause of the neurotoxicity induced by aggregated amyloid-β (Aβ) in Alzheimer's disease (AD). Tools that can directly detect and monitor the presence and amount of Aβ-induced ROS are still lacking. We report herein the first Aβ-targeted ratiometric H₂O₂-responsive fluorescent probe for real-time detection and monitoring of the Aβ-induced H₂O₂ level in cell and AD mouse models. The H₂O₂-responsive probe is constructed based on a methylamino-substituted quinolinium-based cyanine as the fluorescence moiety and a phenylboronate ester as the sensing reaction site. This sensing probe exhibits a large emission wavelength shift of ∼87 nm upon reacting with H₂O₂, a high binding selectivity for Aβ, and a faster response toward H₂O₂ in the presence of Aβ, concomitant with an enhanced fluorescence intensity, hence greatly boosting the sensitivity of in-situ H₂O₂ detection. This biocompatible and nontoxic probe is capable of ratiometrically detecting and imaging endogenous H₂O₂ induced by Aβ in a neuronal cell model. Remarkably, this Aβ-targeted H₂O₂-responsive probe is also able to detect, monitor, and differentiate different Aβ-induced H₂O₂ levels in real time in different age groups of transgenic AD mice in which the cerebral H₂O₂ level increases age dependently concomitant with the plaque contents. Therefore, this smart probe can act as a powerful tool to diagnose high-risk subjects and diseased brains of AD and to further study the role of ROS in AD pathology.

Superparamagnetic Iron Oxide Nanoparticles (SPION): From Fundamentals to State-of-the-Art Innovative Applications for Cancer Therapy

Despite significant advances in cancer therapy over the years, its complex pathological process still represents a major health challenge when seeking effective treatment and improved healthcare. With the advent of nanotechnologies, nanomedicine-based cancer therapy has been widely explored as a promising technology able to handle the requirements of the clinical sector. Superparamagnetic iron oxide nanoparticles (SPION) have been at the forefront of nanotechnology development since the mid-1990s, thanks to their former role as contrast agents for magnetic resonance imaging. Though their use as MRI probes has been discontinued due to an unfavorable cost/benefit ratio, several innovative applications as therapeutic tools have prompted a renewal of interest. The unique characteristics of SPION, i.e., their magnetic properties enabling specific response when submitted to high frequency (magnetic hyperthermia) or low frequency (magneto-mechanical therapy) alternating magnetic field, and their ability to generate reactive oxygen species (either intrinsically or when activated using various stimuli), make them particularly adapted for cancer therapy. This review provides a comprehensive description of the fundamental aspects of SPION formulation and highlights various recent approaches regarding in vivo applications in the field of cancer therapy.

Hybridization of Co3S4 and Graphitic Carbon Nitride Nanosheets for High-performance Nonenzymatic Sensing of H2O2

The development of efficient H₂O₂ sensors is crucial because of their multiple functions inside and outside the biological system and the adverse effects that a higher concentration can cause. This work reports a highly sensitive and selective non-enzymatic electrochemical H₂O₂ sensor achieved through the hybridization of Co₃S₄ and graphitic carbon nitride nanosheets (GCNNS). The Co₃S₄ is synthesized via a hydrothermal method, and the bulk g-C₃N₄ (b-GCN) is prepared by the thermal polycondensation of melamine. The as-prepared b-GCN is exfoliated into nanosheets using solvent exfoliation, and the composite with Co₃S₄ is formed during nanosheet formation. Compared to the performances of pure components, the hybrid structure demonstrates excellent electroreduction towards H₂O₂. We investigate the H₂O₂-sensing performance of the composite by cyclic voltammetry, differential pulse voltammetry, and amperometry. As an amperometric sensor, the Co₃S₄/GCNNS exhibits high sensitivity over a broad linear range from 10 nM to 1.5 mM H₂O₂ with a high detection limit of 70 nM and fast response of 3 s. The excellent electrocatalytic properties of the composite strengthen its potential application as a sensor to monitor H₂O₂ in real samples. The remarkable enhancement of the electrocatalytic activity of the composite for H₂O₂ reduction is attributed to the synergistic effect between Co₃S₄ and GCNNS.

Activity-Based Sensing for Chemistry-Enabled Biology: Illuminating Principles, Probes, and Prospects for Boronate Reagents for Studying Hydrogen Peroxide

Activity-based sensing (ABS) offers a general approach that exploits chemical reactivity as a method for selective detection and manipulation of biological analytes. Here, we illustrate the value of this chemical platform to enable new biological discovery through a case study in the design and application of ABS reagents for studying hydrogen peroxide (H2O2), a major type of reactive oxygen species (ROS) that regulates a diverse array of vital cellular signaling processes to sustain life. Specifically, we summarize advances in the use of activity-based boronate probes for the detection of H2O2 featuring high molecular selectivity over other ROS, with an emphasis on tailoring designs in chemical structure to promote new biological principles of redox signaling.

Organic persistent luminescence imaging for biomedical applications

Persistent luminescence is a unique visual phenomenon that occurs after cessation of excitation light irradiation or following oxidization of luminescent molecules. The energy stored within the molecule is released in a delayed manner, resulting in luminescence that can be maintained for seconds, minutes, hours, or even days. Organic persistent luminescence materials (OPLMs) are highly robust and their facile modification and assembly into biocompatible nanostructures makes them attractive tools for in vivo bioimaging, whilst offering an alternative to conventional fluorescence imaging materials for biomedical applications. In this review, we give attention to the existing limitations of each class of OPLM-based molecular bioimaging probes based on their luminescence mechanisms, and how recent research progress has driven efforts to circumvent their shortcomings. We discuss the multifunctionality-focused design strategies, and the broad biological application prospects of these molecular probes. Furthermore, we provide insights into the next generation of OPLMs being developed for bioimaging techniques.

A chemical timer approach to delayed chemiluminescence

Although the onset time of chemical reactions can be manipulated by mechanical, electrical, and optical methods, its chemical control remains highly challenging. Herein, we report a chemical timer approach for manipulating the emission onset time of chemiluminescence (CL) reactions. A mixture of Mn²⁺, NaHCO₃, and a luminol analog with H₂O₂ produced reactive oxygen species (ROS) radicals and other superoxo species (superoxide containing complex) with high efficiency, accompanied by strong and immediate CL emission. Surprisingly, the addition of thiourea postponed CL emission in a concentration-dependent manner. The delay was attributed to a slow-generation-scavenging mechanism, which was found to be generally applicable not only to various types of CL reagents and ROS radical scavengers but also to popular chromogenic reactions. The precise regulation of CL kinetics was further utilized in dynamic chemical coding with improved coding density and security. This approach provides a powerful platform for engineering chemical reaction kinetics using chemical timers, which is of application potential in bioassays, biosensors, CL microscopic imaging, microchips, array chips, and informatics.

Electrostimulus-triggered reactive oxygen species level in organelles revealed by organelle-targeting SERS nanoprobes

Electrostimulation (ES) is an important therapeutic method for diseases caused by abnormal intracellular electrical activity. Also, it can induce apoptosis of cells, which is a potential tumor treatment method. At present, there are no relevant studies on changes in intracellular reactive oxygen species (ROS) levels produced in the process of ES, or on the effects of simultaneous implementation of conventional antioxidant inhibitor drugs and ES therapy. To reveal these, two organelle-targeting core-shell plasmonic probes were designed for measuring ROS produced during ES. The probes were delivered into target organelles (nucleus and mitochondrion) before the cells were electrically stimulated for different periods of time. Surface-enhanced Raman scattering (SERS) signals were detected in situ, and the sensing mechanism for the quantitative analysis of ROS is based on the signal reduction of SERS caused by the ROS-etching effect on the silver shell. The detection results revealed that ES could trigger ROS generation in cells, and the ROS levels localized around organelles were assessed by SERS. This study has great potential for exploring abnormal organelle microenvironments via organelle-targeting probes combined with SERS technology.