Conjugated Oligoelectrolytes for Long-Term Tumor Tracking with Incremental NIR-II Emission

The design and synthesis of the near-infrared (NIR)-II emissive conjugated oligoelectrolyte COE-BBT are reported. COE-BBT has a solubility in aqueous media greater than 50 mg mL^-1 , low toxicity, and a propensity to intercalate lipid bilayers, wherein it exhibits a higher emission quantum yield relative to aqueous media. Addition of COE-BBT to cells provides two emission channels, at ≈500 and ≈1020 nm, depending on the excitation wavelength, which facilitates in vitro confocal microscopy and in vivo animal imaging. The NIR-II emission of COE-BBT is used to track intracranial and subcutaneous tumor progression in mice. Of relevance is that the total NIR-II intensity increases over time. This phenomenon is attributed to a progressive attenuation of a COE-BBT self-quenching effect within the cells due to the expected dye dilution per cell as the tumor proliferates.

Fluorescent probes for the detection of disease-associated biomarkers

Fluorescent probes have emerged as indispensable chemical tools to the field of chemical biology and medicine. The ability to detect intracellular species and monitor physiological processes has not only advanced our knowledge in biology but has provided new approaches towards disease diagnosis. In this review, we detail the design criteria and strategies for some recently reported fluorescent probes that can detect a wide range of biologically important species in cells and in vivo. In doing so, we highlight the importance of each biological species and their role in biological systems and for disease progression. We then discuss the current problems and challenges of existing technologies and provide our perspective on the future directions of the research area. Overall, we hope this review will provide inspiration for researchers and prove as useful guide for the development of the next generation of fluorescent probes.

Glow and Flash Adjustable Chemiluminescence with Tunable Waveband from the Same CuInS2@ZnS Nanocrystal Luminophore

All commercial chemiluminescence (CL) assays are conducted with either glow or flash CL of eye-visible waveband from chemical luminophores. Herein, glow and flash, as well as waveband adjustable CL from the same nanoparticle luminophore of thiol-capped CuInS₂@ZnS nanocrystals (CIS@ZnS-Thiol), are proposed via extensively exploiting the differed redox nature of CL triggering reagents. Taking thiosalicylic acid (TSA) as the model thiol-capping agent, the electron-injection-initiated charge transfer between CIS@ZnS-TSA and reductant can bring out efficient glow CL while the hole-injection-initiated charge transfer between CIS@ZnS-TSA and oxidant can give off obvious flash CL under optimum conditions. The maximum emission wavelength for CL of CIS@ZnS-TSA is adjustable from 730 nm to 823 nm via employing different triggering agents. Promisingly, the coexistent reductant of N₂H₄·H₂O and oxidant of H₂O₂ can be employed as dual triggering reagents to trigger eye-visible and highly efficient flash CL from CIS@ZnS-TSA. The maximum emission intensity for flash CL of CIS@ZnS-TSA/N₂H₄-H₂O₂ is 101-fold greater than the glow CL of CIS@ZnS-TSA/N₂H₄ and 22-fold greater than the flash CL of CIS@ZnS-TSA/H₂O₂, respectively. The flash CL from CIS@ZnS-TSA/N₂H₄-H₂O₂ is qualified for highly sensitive and selective CL immunoassay in a commercialized typical procedure with the entire operating process manually terminated within 35 min.

Early diagnosis of breast cancer lung metastasis by nanoprobe-based luminescence imaging of the pre-metastatic niche

BACKGROUND

Early detection of breast cancer lung metastasis remains highly challenging, due to few metastatic cancer cells at an early stage. Herein we propose a new strategy for early diagnosis of lung metastasis of breast cancer by luminescence imaging of pulmonary neutrophil infiltration via self-illuminating nanoprobes.

METHODS

Luminescent nanoparticles (LAD NPs) were engineered using a biocompatible, neutrophil-responsive self-illuminating cyclodextrin material and an aggregation-induced emission agent. The chemiluminescence resonance energy transfer (CRET) effect and luminescence properties of LAD NPs were fully characterized. Using mouse peritoneal neutrophils, in vitro luminescence properties of LAD NPs were thoroughly examined. In vivo luminescence imaging and correlation analyses were performed in mice inoculated with 4T1 cancer cells. Moreover, an active targeting nanoprobe was developed by surface decoration of LAD NPs with a neutrophil-targeting peptide, which was also systemically evaluated by in vitro and in vivo studies.

RESULTS

LAD NPs can generate long-wavelength and persistent luminescence due to the CRET effect. In a mouse model of 4T1 breast cancer lung metastasis, we found desirable correlation between neutrophils and tumor cells in the lungs, demonstrating the effectiveness of early imaging of the pre-metastatic niche by the newly developed LAD NPs. The active targeting nanoprobe showed further enhanced luminescence imaging capability for early detection of pulmonary metastasis. Notably, the targeting nanoprobe-based luminescence imaging strategy remarkably outperformed PET/CT imaging modalities in the examined mouse model. Also, preliminary tests demonstrated good safety of LAD NPs.

CONCLUSIONS

The neutrophil-targeting imaging strategy based on newly developed luminescence nanoparticles can serve as a promising modality for early diagnosis of lung metastasis of breast cancers.

Chemiluminescent 1,2-Dioxetane Iridium Complexes for Near-Infrared Oxygen Sensing

Chemiluminescent iridium-based sensors which demonstrate oxygen dependent responses have been developed. The molecular probes, named IrCL-1, IrCL-2 and IrCL-3 consist of oxygen-sensitive iridium complexes attached to a spiroadamantane 1,2 dioxetane and operate via energy transfer from the chemiexcited benzoate to the corresponding iridium(III) complex. Complexing the iridium(III) center with π-extended ligands results in emission in the biologically relevant, near-infrared (NIR) region. All probes demonstrate varying oxygen tolerance, with IrCL-1 being the most oxygen sensitive. These probes have been further utilized for in vitro ratiometric imaging of oxygen, as well as for intraperitoneal, intramuscular and intratumoral imaging in live mice. To our knowledge, these are the first iridium-based chemiluminescent probes that have been employed for in vitro ratiometric oxygen sensing, and for in vivo tumor imaging.

Semiconducting Polymer Nanoparticles for Photoactivatable Cancer Immunotherapy and Imaging of Immunoactivation

Immunotherapy that stimulates the body's own immune system to kill cancer cells has emerged as a promising cancer therapeutic method. However, some types of cancer exhibited a low response rate to immunotherapy, and the high risk of immune-related side effects has been aroused during immunotherapy, which greatly restrict its broad applications in cancer therapy. Phototherapy that uses external light to trigger the therapeutic process holds advantages including high selectivity and efficiency, and low side effects. Recently, it has been proven to be able to stimulate immune response in the tumor region by inducing immunogenic cell death (ICD), the process of which was termed photo-immunotherapy, dramatically improving therapeutic specificity over conventional immunotherapy in several aspects. Among numerous optical materials for photo-immunotherapy, semiconducting polymer nanoparticles (SPNs) have gained more and more attention owing to their excellent optical properties and good biocompatibility. In this review, we summarize recent developments of SPNs for immunotherapy and imaging of immunoactivation. Different therapeutic modalities triggered by SPNs including photo-immunotherapy and photo-immunometabolic therapy are first introduced. Then, applications of SPNs for real-time monitoring immunoactivation are discussed. Finally, the conclusion and future perspectives of this research field are given.

Recent development of a magneto-optical nanoplatform for multimodality imaging of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. Given its inconspicuous and atypical early symptoms and hidden location, most patients have already reached the terminal stage before diagnosis. At present, the diagnosis of PDAC mainly depends on serological and imaging examinations. However, serum tests cannot identify specific tumor locations and each imaging technology has its own defects, bringing great challenges to the early diagnosis of PDAC. Therefore, it is of great significance to find new strategies for the early and accurate diagnosis of PDAC. In recent years, a magneto-optical nanoplatform integrating near infrared fluorescence, photoacoustic, magnetic resonance imaging, etc. has attracted widespread attention, giving full play to the complementary advantages of each imaging modality. Herein, we summarize the recent advances of imaging modalities in the diagnosis of pancreatic cancer, and then discuss in detail the construction and modification of magneto or/and optical probes for multimodal imaging, and advances in early diagnosis using the combination of various imaging modalities, which can provide potential tools for the early diagnosis or even intraoperative navigation and post-treatment follow-up of PDAC patients.

Near-infrared chemiluminescence imaging of superoxide anion production in kidneys with iron3+-nitrilotriacetate-induced acute renal oxidative stress in rats

Iron-catalyzed oxidative stress generates reactive oxygen species in the kidney and induces oxidative damage including lipid, protein, and DNA modifications which induces renal injury and may lead to cancer. An analysis of oxidative stress dynamics by reactive oxygen species has not been performed non-invasively in real time in intact kidneys and is a significant challenge in biology and medicine. Here, I report that MCLA-800 is a near-infrared chemiluminescent probe that visualizes the dynamics of superoxide anion (O₂^•-) production and the upstream generation of reactive oxygen species in living rat kidneys suffering acute renal oxidative stress induced by intraperitoneal administration of iron³⁺-nitrilotriacetate (Fe³⁺-NTA) as a representative Fe³⁺ chelate. MCLA-800 was intravenously injected at 250 nmol/kg body weight and immediately transported to the kidneys with the emitting light dependent on O₂^•- production. The magnitude of O₂^•- production correlated with the Fe³⁺-NTA dose. O₂^•- was continuously produced in the blood stream following Fe³⁺-NTA injection at 0.15 mmol/kg body weight, while peak production in the renal cortex occurred at 24 h, then decreased to the background level at 72 h. This study clearly revealed the dynamics of Fe³⁺-NTA-mediated O₂^•- production in the living kidney by chemiluminescent imaging of O₂^•- production using MCLA-800.

Modulation by Phosphonium Ions of the Activity of Mitotropic Agents Based on the Chemiluminescence of Luminols

Mitochondria-targeting drugs and diagnostics are used in the monitoring and treatment of mitochondrial pathologies. In this respect, a great number of functional compounds have been made mitotropic by covalently attaching the active moiety onto a triphenylphosphonium (TPP) cation. Among these compounds, a number of molecular detectors for reactive oxygen species (ROS) are based on fluorescent and chemiluminescent probes. In this regard, luminol (probably the most widely known chemiluminescent molecule) has been employed for a number of biological applications, including ROS detection. Its oxidation under specific conditions triggers a cascade of reactions, ultimately leading to the excited 3-aminophthalate (3AP *), which emits light upon deactivation. Hence, the photophysical interaction between the light-emitting species 3AP * and TPP cations needs to be evaluated, as it can add valuable information on the design of novel emission-based mitotropic systems. We herein investigate the quenching effect of ethyltriphenylphosphonium cation onto substituted 3-aminophthalates. These were prepared in situ upon hydrolysis of the corresponding anhydrides, which were synthesized from 3-aminophthalimides. Steady-state fluorescence and time-resolved experiments were employed for the evaluation of a possible electron transfer quenching by phosphonium ions. Our experimental results confirmed such quenching, suggesting it is mainly dynamic in nature. A minor contribution of static quenching that was also detected is attributed to complex formation in the ground state. Accordingly, the chemiluminescence of luminol was indeed strongly reduced in the presence of phosphonium ions. Our results have to be taken into account during the design of new chemiluminescent mitotropic drugs or diagnostic agents of the luminol family.

Activity-based NIR fluorescent probes based on the versatile hemicyanine scaffold: design strategy, biomedical applications, and outlook

The discovery of a near-infrared (NIR, 650-900 nm) fluorescent chromophore hemicyanine dye with high structural tailorability is of great significance in the field of detection, bioimaging, and medical therapeutic applications. It exhibits many outstanding advantages including absorption and emission in the NIR region, tunable spectral properties, high photostability as well as a large Stokes shift. These properties are superior to those of conventional fluorogens, such as coumarin, fluorescein, naphthalimides, rhodamine, and cyanine. Researchers have made remarkable progress in developing activity-based multifunctional fluorescent probes based on hemicyanine skeletons for monitoring vital biomolecules in living systems through the output of fluorescence/photoacoustic signals, and integration of diagnosis and treatment of diseases using chemotherapy or photothermal/photodynamic therapy or combination therapy. These achievements prompted researchers to develop more smart fluorescent probes using a hemicyanine fluorogen as a template. In this review, we begin by describing the brief history of the discovery of hemicyanine dyes, synthetic approaches, and design strategies for activity-based functional fluorescent probes. Then, many selected hemicyanine-based probes that can detect ions, small biomolecules, overexpressed enzymes and diagnostic reagents for diseases are systematically highlighted. Finally, potential drawbacks and the outlook for future investigation and clinical medicine transformation of hemicyanine-based activatable functional probes are also discussed.

Highly Sensitive Chemiluminescent Immunoassay of Mycotoxins Using ZIF-8-Derived Yolk-Shell Co Single-Atom Site Catalysts as Superior Fenton-like Probes

Superior to traditional nanoscale catalysts, single-atom site catalysts (SASCs) show such merits as maximal catalysis efficiency and outstanding catalytic activity for the construction of analytical methodological platforms. Hereby, an in situ etching strategy was designed to prepare yolk-shell Co SASCs derived from ZIF-8@SiO₂ nanoparticles. On the basis of direct chemical interactions between precursors and supports, the Co element with isolated atomic dispersion was anchored on ZIF-8@SiO₂ nanoparticles. The Co SASCs possess high Fenton-like activity and thus can catalyze the decomposition of H₂O₂ to produce massive superoxide radical anions instead of singlet oxygen and hydroxyl radicals. With the activity for producing superoxide radical anion, Co SASCs can greatly improve the chemiluminescent (CL) response of a luminol system by 3133.7 times. Furthermore, the SASCs with active sites of Co-O₅ moieties were utilized as the CL probes for establishment of an immunoassay method for sensitive detection of mycotoxins by adopting aflatoxin B1 as a mode analyte. The quantitation range is 10-1000 pg/mL, and the limit of detection is 0.44 pg/mL (3σ) for aflatoxin B1. The proof-of-principle work elucidates the practicability of direct chemical interactions between precursors and supports for forming SASCs with ultrahigh CL response, which can be extended to the exploitation of more sorts of SASCs for tracing biological binding events.

Chemiluminescent Probes Based on 1,2-dioxetane Structures For Bioimaging

Chemiluminescent probes based on 1,2-dioxetane scaffold are one of the most sensitive imaging modalities for detecting disease-related biomarkers and can obtain more accurate biological information in cells and in vivo . Due to the elimination of external light excitation, the background autofluorescence problem in fluorescence technology can be effectively avoided, providing ultra-high sensitivity and signal-to-noise ratio for various applications. In this minireview, we highlight a comprehensive but concise overview of activatable 1,2-dioetxane-based chemiluminescent probes by reporting significant advances in accurate detection and bioimaging. The design principles and applications for reactive species, enzymes, and other disease-related biomarkers are systematically discussed and summarized. The challenges and potential prospects of chemiluminescent probes are also discussed to further promote the development of new chemiluminescence methods for biological analysis and diagnosis.

A H2O2-responsive theranostic platform for chemiluminescence detection and synergistic therapy of tumor

Chemiluminescence substances that respond to hydrogen peroxide (H2O2) in the tumor microenvironment have the potential to achieve accurate tumor imaging. Here, Pluronic F-127 (PF127) and polymers containing oxalate ester (POE)...

State-of-the-art self-luminescence: a win–win situation

The working principles, luminescent mechanisms, versatile integrated approaches and advantages, and future perspectives of AIE-assisted “enhanced” self-luminescence systems are reviewed.

Highly Selective and Sensitive Chemiluminescent Probe for Leucine Aminopeptidase Detection in Vitro, in Vivo and in human Liver Cancer Tissue

Leucine aminopeptidase (LAP) is involved in tumor cell proliferation, invasion, and angiogenesis, and is a well-known tumor marker. In recent years, chemiluminescence has been widely used in the field of biological imaging, due to it resulting in a high sensitivity and excellent signal-to-noise ratio. Here, we report the design, synthesis, and evaluation of the first LAP-activated chemiluminescent probe for LAP detection and imaging. The probe initially had no chemiluminescence but produced an extremely strong chemiluminescence after the release of the dioxetane intermediate in the presence of LAP. The probe had high selectivity over other proteases and higher signal-to-noise ratios than commercial fluorophores. Real-time imaging results indicated that the chemiluminescence was remarkably enhanced at the mice tumor site after the probe was injected. Furthermore, the chemiluminescence of this probe in the cancerous tissues of patients was obviously improved compared to that of normal tissues. Taken together, this study has developed the first LAP-activable chemiluminescent probe, which could be potentially used in protein detection, disease diagnosis, and drug development.

The first chemiluminescent probe for the detection of LAP is described. It shows a highly selective, sensitive and rapid chemiluminescence response for the detection of LAP in vitro and in vivo, and enables the differentiation of liver cancer.

Trimetallic AuPtCo Nanopolyhedrons with Peroxidase- and Catalase-Like Catalytic Activity for Glow-Type Chemiluminescence Bioanalysis

Chemiluminescence (CL) with stable and glowing light emission is vital for the accurate detection of biomarkers. Moreover, the catalyst plays an important role in CL systems. Herein, the trimetallic AuPtCo nanopolyhedrons with peroxidase- and catalase-like catalytic activities are readily synthesized via a one-step reduction method. After reaction with the substrate ABEI and oxidant H₂O₂, the AuPtCo nanozyme can catalyze the CL emission in a flash type. Interestingly, it has been found that the biofunctionalization of the AuPtCo surface can endow the catalytic interface with a slow-diffusion effect, thereby prolonging the emission of glow-type CL. On this basis, two biofunctionalized AuPtCo nanocomposites, named as AuPtCo@Cys and AuPtCo@Ab, are prepared, achieving sensitive and selective detection of H₂O₂ and lipoprotein-associated phospholipase A₂ (Lp-PLA₂), respectively. Further, the proposed glow-type CL assays are successfully applied for the determination of H₂O₂ and Lp-PLA₂ in female vaginal discharge and human serum samples, respectively, which exhibit good correlation with the clinical results. Overall, the trimetallic AuPtCo nanozyme-based glow-type CL analysis has demonstrated as a powerful and robust tool for biomarker analysis, which holds great promise in clinical applications.

Direct and Indirect Chemiluminescence: Reactions, Mechanisms and Challenges

Emission of light by matter can occur through a variety of mechanisms. When it results from an electronically excited state of a species produced by a chemical reaction, it is called chemiluminescence (CL). The phenomenon can take place both in natural and artificial chemical systems and it has been utilized in a variety of applications. In this review, we aim to revisit some of the latest CL applications based on direct and indirect production modes. The characteristics of the chemical reactions and the underpinning CL mechanisms are thoroughly discussed in view of studies from the very recent bibliography. Different methodologies aiming at higher CL efficiencies are summarized and presented in detail, including CL type and scaffolds used in each study. The CL role in the development of efficient therapeutic platforms is also discussed in relation to the Reactive Oxygen Species (ROS) and singlet oxygen (1O2) produced, as final products. Moreover, recent research results from our team are included regarding the behavior of commonly used photosensitizers upon chemical activation under CL conditions. The CL prospects in imaging, biomimetic organic and radical chemistry, and therapeutics are critically presented in respect to the persisting challenges and limitations of the existing strategies to date.

Dynamic Visualization of Free Radicals at Single Oxygen Bubbles using Chemiluminescence

The generation of free radicals is a key process in the formation and the collapse of the bubbles in water, however, the direct and dynamic observation of the radicals in this process at single bubbles has never been achieved. Here, the hydroxyl (OH^. ) and oxygen (O₂ ^.- ) radicals at single oxygen bubbles are continuously traced using chemiluminescence (CL), in which these radicals at the bubble react with the surrounding luminol in the solution emitting the light. Varied increase trends of luminescence are observed in the generation of a bubble, floating, short parking at the water/air interface and the final explosion, revealing the complexity in the distribution of radicals at the bubble unprecedentedly. Despite more radicals are observed at the bubble generated at a deep position under the water for the stabilization, almost the same amount of radicals are included in the bubbles that is independent on the water pressure during the production of the bubble. This rich information collected from the dynamic study of bubbles illustrates the complicated generation and distribution process of radicals at the bubbles, and will facilitate the understanding of the function about the bubbles.

Aggregation-induced emission (AIE)-guided dynamic assembly for disease imaging and therapy

The phenomenon of aggregation-induced emission (AIE) is inseparable from molecular aggregation and self-assembly. Therefore, the combination of AIE and supramolecular self-assembly is well-matched. AIE-guided dynamic assembly (AGDA) could effectively respond to the endogenous stimuli (such as pH, enzymes, redox molecules) and exogenous stimuli (temperature, light, ultrasound) in the disease microenvironment, so as to achieve specific imaging and diagnosis of the disease lesions. Moreover, AGDA also dynamically adjust the intramolecular motions of AIE molecules, thereby adjusting the energy dissipation pathways and realizing the switch between photodynamic therapy and photothermal therapy for superior therapeutic effects. In this review, we aim to give an overview of the constructing strategies, stimuli-responsive imaging, regulation of intramolecular motion of AGDA in recent years, which is expected to grasp the research status and striving directions of AGDA for imaging and therapy.

Molecular Probes for Autofluorescence-Free Optical Imaging

Optical imaging is an indispensable tool in clinical diagnostics and fundamental biomedical research. Autofluorescence-free optical imaging, which eliminates real-time optical excitation to minimize background noise, enables clear visualization of biological architecture and physiopathological events deep within living subjects. Molecular probes especially developed for autofluorescence-free optical imaging have been proven to remarkably improve the imaging sensitivity, penetration depth, target specificity, and multiplexing capability. In this Review, we focus on the advancements of autofluorescence-free molecular probes through the lens of particular molecular or photophysical mechanisms that produce long-lasting luminescence after the cessation of light excitation. The versatile design strategies of these molecular probes are discussed along with a broad range of biological applications. Finally, challenges and perspectives are discussed to further advance the next-generation autofluorescence-free molecular probes for in vivo imaging and in vitro biosensors.

Aggregation of Gold Nanoparticles Triggered by Hydrogen Peroxide-Initiated Chemiluminescence for Activated Tumor Theranostics

Developing endogenous photo-activated theranostic platforms to overcome the limitation of low tissue-penetration from external light sources is highly significant for cancer diagnosis and treatment. We report a H₂ O₂ -initiated chemiluminescence (CL)-triggered nanoparticle aggregation strategy to activate theranostic functions of gold nanoparticles (AuNPs) for effective tumor imaging and therapy. Two types of AuNPs (tAuNP & mAuNP) were designed and fabricated by conjugating 2,5-diphenyltetrazole and methacrylic acid onto the surface of AuNPs, respectively. Luminol was adsorbed onto the mAuNPs to afford self-illuminating mAuNP/Lu NPs that could produce strong CL by reaction with H₂ O₂ in the tumor microenvironment, which triggers significant aggregation of AuNPs resulting in enhanced accumulation and retention of AuNPs for activated photoacoustic imaging and photothermal therapy of tumors. We thus believe that this approach may offer a promising tool for effective tumor treatment.

Rigidity Bridging Flexibility to Harmonize Three Excited-State Deactivation Pathways for NIR-II-Fluorescent-Imaging-Guided Phototherapy

Small organic phototherapeutic molecules of the second near-infrared (NIR-II) window (1000-1700 nm) serve as promising candidates for theranostics. However, developing such versatile agents for fluorescence-guided photodynamic/photothermal therapy remains a demanding task stirred by competitive energy dissipation pathways, including radiative decay, internal conversion, and intersystem crossing. To the best of current knowledge, the current paradigm for addressing the issue has deliberately approached the optimum balance among three deactivation processes through offsetting from each other, possibly leading to a comprehensively compromised theranostic efficacy. Few reports aim to modulate the three deactivation pathways excluding sacrificing any one of them. Herein, a molecular design strategy to construct a phototherapeutic organic fluorophore CCNU-1060, armed with NIR-II luorescence-guided phototherapeutic properties, is rationally developed. With a flexible motor, tetraphenylethene, bridged to the rigidified coplanar core boron-azadipyrromethene, the desired CCNU-1060 is subsequently encapsulated into an amphiphilic matrix to form CCNU-1060 nanoparticles (NPs), which match or transcend its precursor NJ-1060 NPs in the three energy dissipation processes. CCNU-1060 NPs are utilized to realize high-spatial vessel imaging and effective NIR-II fluorescence-guided phototherapeutic tumor ablation. This study unlocks a viewpoint of molecular engineering that simultaneously regulates multiple energy dissipation pathways for the construction of versatile phototherapy agents.

Non-invasive and accurate readout of superoxide anion in biological systems by near-infrared light

Infectious and inflammatory diseases involve superoxide anion (O₂^•-) production. Real-time and non-invasive evaluation of O₂^•- in intact biological systems has been a significant challenge in biology and medicine. Here, I report that an advanced near-infrared chemiluminescent probe, MCLA-800, enables reliable non-invasive optical readout of O₂^•-ex vivo and in vivo. MCLA-800 allowed highly selective and sensitive monitoring of O₂^•- in undiluted human whole blood ex vivo. For the first time, the use of MCLA-800 revealed two reproducible types of O₂^•- production in response to stimulation by unopsonized zymosan particles of Saccharomyces cerevisiae, that is, slow response (S-type) and fast response (F-type), specific to each individual. O₂^•- production was synchronized with myeloperoxidase (MPO) activation in the former type but not in the latter. Moreover, as new findings, MCLA-800 chemiluminescence demonstrated that the chemiluminescence intensity-time properties of formyl-methionyl-leucyl-phenylalanine (fMLP)- or phorbol 12-myristate 13-acetate (PMA)-induced O₂^•- production and MPO activity were independent of S- and F-type zymosan-induced MCLA-800 chemiluminescence whole blood and that PMA-induced MPO activation synchronized with PMA-induced O₂^•- production in S- and F-type zymosan-induced MCLA-800 chemiluminescence whole blood, but fMLP-induced MPO activation did not synchronize with fMLP-induced O₂^•- production in both of S- and F-type blood. Furthermore, MCLA-800 spatiotemporally allowed non-invasive and clear in vivo imaging of O₂^•- in animal models of acute dermatitis and focal arthritis. Therefore, MCLA-800 could be possibly applied in various advanced diagnostic techniques.

Building a Functionalizable, Potent Chemiluminescent Agent: A Rational Design Study on 6,8-Substituted Luminol Derivatives

Luminol is a prominent chemiluminescent (CL) agent, finding applications across numerous fields, including forensics, immunoassays, and imaging. Different substitution patterns on the aromatic ring can enhance or decrease its CL efficiency. We herein report a systematic study on the synthesis and photophysics of all possible 6,8-disubstituted luminol derivatives bearing H, Ph, and/or Me substituents. Their CL responses are monitored at three pH values (8, 10, and 12), thus revealing the architecture with the optimum CL efficiency. The most efficient pattern is used for the synthesis of a strongly CL luminol derivative, bearing a functional group for further, straightforward derivatization. This adduct exhibits an unprecedented increase in chemiluminescence efficiency at pH = 12, pH = 10, and especially at pH = 8 (closer to the biologically relevant conditions) compared to luminol. Complementary work on the fluorescence of the emissive species as well as quantum chemistry computations are employed for the rationalization of the observed results.

Cyclic Peroxidic Carbon Dioxide Dimer Fuels Peroxyoxalate Chemiluminescence

Peroxyoxalate chemiluminescence is used in self-contained light sources, such as glow sticks, where oxidation of aromatic oxalate esters produces a high-energy intermediate (HEI) that excites fluorescence dyes via electron transfer chemistry, mimicking bioluminescence for efficient chemical energy-to-light conversion. The identity of the HEI and reasons for the efficiency of the peroxyoxalate reaction remain elusive. We present here unequivocal proof that the HEI of the peroxyoxalate system is a cyclic peroxidic carbon dioxide dimer, namely, 1,2-dioxetanedione. Oxalic peracids bearing a substituted phenyl group were unable to directly excite fluorescent dyes; hence, they could be ruled out as the HEI. However, base-catalyzed cyclization of these species results in bright chemiluminescence, with decay rates and chemiexcitation quantum yields that are influenced by the electronic phenylic substituent properties. Hammett (ρ = +2.2 ± 0.1) and Brønsted (β = -1.1 ± 0.1) constants for the cyclization step preceding chemiexcitation imply that the loss of the phenolate-leaving group and intramolecular nucleophilic attack of the percarboxylate anion occur in a concerted manner, generating 1,2-dioxetanedione as the unique outcome. The presence of better leaving groups influences the reaction mechanism, favoring the chemiluminescent reaction pathway over the nonemissive formation of aryl-1,2-dioxetanones.

Construction of DCM-based NIR fluorescent probe for visualization detection of H2S in solution and nanofibrous film

Hydrogen sulfide (H₂S) played crucial roles in biological processes and daily life, and the abnormal level of H₂S was associated with many physiological processes. In this paper, we designed and developed a dicyanomethylene-4H-chromene (DCM)-based near-infrared (NIR) fluorescent probe DCM-NO guided by theoretical calculation. The probe displayed excellent selectivity towards H₂S with a fast response time (3 min) and low detection limit (fluorescence 25.3 nM/absorption 6.61 nM) in Hela cells and real water samples. Furthermore, the probe-doped solid sensing materials (test strips and nanofibrous films) exhibited specific visualization of H₂S under ambient light or hand-held UV lamp, providing great potential for on-site and real-time application in environmental and biological systems.

A novel metal organic gel with superior oxidase-like activity for efficient and sensitive chemiluminescence detection of uric acid

It is found that MIL-100(Fe) gels, as a kind of metal-organic gels (MOGs), constitutting of iron (Fe³⁺) and trimesic acid (H₃BTC), has been regarded as the efficient catalyst of luminol chemiluminescence (CL) system without the presence of extra oxidants in the present work. MIL-100(Fe) gels that have possessed mimicking oxidase-like activity can excellently enhanced luminol CL intensity by accelerating the generation of reactive oxygen species. Furthermore, with the addition of uric acid (UA), the CL signal has been dramatically inhibited under alkaline condition. Hence, the CL intensity inhibiting ratio (I₀/I_S) was proportional to the increasing concentration of UA in the rang from 10 nM to 4000 nM with the detection limit of 5.9 nM. This method has been successfully applied for analysis of UA with acceptable recoveries ranging from 97.0% to 107.9% in urine sample. These results indicates that this study open up a novel, sensitive and convenient method to detect UA in biological samples.

Photoactivatable Red Chemiluminescent AIEgen Probe for In Vitro/Vivo Imaging Assay of Hydrazine

Here, we have developed a novel photoactivatable red chemiluminescent AIEgen probe (ACL), based on the combination of the red-emission AIEgen fluorophore (TPEDC) that shows excellent singlet oxygen (¹O₂)-generation ability and the precursor of Schaap's dioxetane (the linker connected to adamantane is the C═C bond) that can be modified to target various analytes, for in vitro and in vivo measurement of hydrazine. Prior to applying for sensing detection, the C═C bond connected to adamantane in ACL was first converted into dioxetane by irradiation to form the activated chemiluminescent AIEgen probe (ACLD). Then, the self-immolative reaction was triggered upon the deprotection of the acylated phenolic hydroxyl group in ACLD in the presence of hydrazine, resulting in the release of the high energy held in the 1,2-dioxetanes, and then, the chemiexcitation was triggered, thereby producing red chemiluminescence through the intramolecular chemiluminescence resonance energy transfer from Schaap's dioxetane to TPEDC. This chemiluminescent AIEgen probe was evaluated in a clean buffer environment as well as using living cells and mouse models.

Modified Indulines: From Dyestuffs to In Vivo Theranostic Agents

The efficient, versatile, and straightforward synthesis of the first N-alkyl analogues of induline 3B (8a and 8b) is reported. Thanks to the introduction of lipophilic substituents and their attractive photophysical properties (far-red emission and production of singlet oxygen), phenazinium 8b can be used as a theranostic agent and shows, at very low concentrations (100 nM), a remarkable ability to (i) image cells and zebrafish embryos with high quality under both mono- (514 nm) and biphotonic (790 and 810 nm) excitations, (ii) efficiently and quickly penetrate cancer cells rather than healthy fibroblasts, and (iii) induce a total or almost total cancer cell death in vitro and in vivo after illumination (λ_exc = 540-560 nm). The molecular structure of 8b is based on a triamino-phenazinium core only, with no need for additional components, highlighting the emergence of a minimalistic and versatile class of fluorescent probes for targeted photodynamic cancer therapy.

Y2O3:Yb3+, Tm3+/ZnO composite with a heterojunction structure and upconversion function for the photocatalytic degradation of organic dyes

Endowing photocatalytic materials with a broader range of light responses is important for improving their performance and solar energy utilization. In this study, a simple sol-gel method was used to prepare Yb³⁺/Tm³⁺-co-doped Y₂O₃ upconversion materials and Y₂O₃:Yb³⁺, Tm³⁺/ZnO (Y/Z) composite photocatalysts for the photocatalytic degradation of dyes. The Y/Z composite photocatalyst achieved degradation rates of 38%, 95%, and 89% for methyl orange, methylene blue (MB), and acid chrome blue K dye solutions, respectively, within 30 minutes. The degradation efficiency for MB after three cycles of degradation was 86%. The spherical Y₂O₃:Yb³⁺, Tm³⁺ particles had diameters of 20-50 nm and attached to the ZnO nanosheets, forming a heterojunction structure with ZnO. Fluorescence spectroscopy showed that Y₂O₃:Yb³⁺, Tm³⁺ could convert near-infrared (NIR) light into three sets of ultraviolet light (290, 320, and 360 nm) under NIR excitation. Photoluminescence spectroscopy demonstrated that the photogenerated electron-hole pair recombination probability of the composite photocatalyst was significantly lower than that of ZnO nanosheets, thereby reducing the energy loss during the migration process. Furthermore, the addition of Y₂O₃:Yb³⁺, Tm³⁺ to ZnO substantially improved the absorption capacity for ultraviolet light, which enhanced the photocatalytic activity. A possible mechanism for the enhanced photocatalytic performance of the Y/Z composites was proposed based on the synergistic effect of heterojunction formation and the photoconversion process. The composite photocatalyst with upconversion characteristics and heterogeneous structure provides a new strategy for removing organic pollutants from water.

Hydrazine Hydrate and Dissolved Oxygen-Triggered Near-Infrared Chemiluminescence from CuInS2@ZnS Nanocrystals for Bioassays

The overwhelming majority of commercially available chemiluminescence (CL) assays are conducted in the eye-visible region. Herein, a near-infrared (NIR) aqueous CL strategy was proposed with CuInS₂@ZnS nanocrystals (CIS@ZnS NCs) as emitters. Hydrazine hydrate (N₂H₄·H₂O) could inject electrons into the conduction band of the CIS@ZnS NCs and simultaneously transformed to the intermediate radical N₂H₃^•. N₂H₃^• reduced dissolved oxygen (O₂) to O₂^-•, while the O₂^-• could inject holes into the valence band of the CIS@ZnS NCs. The recombination of electrons and holes at Cu⁺ defects in CIS@ZnS NCs eventually yielded efficient NIR CL at around 824.1 nm, which is the longest waveband for NCs CL to the best of our knowledge. The NIR CL could be conveniently performed in the neutral aqueous medium (pH 7.0) with a quantum yield of 0.0155 Einstein/mol and was successfully employed for constructing a signal-off CL biosensor with ascorbic acid as the analyte as well as a signal-on CL biosensor for determining ascorbate oxidase, which indicates that this NIR CL system has a promising potential for bioassays in diverse ways.

Emission from the working and counter electrodes under co-reactant electrochemiluminescence conditions

We present a new approach to explore the potential-dependent multi-colour co-reactant electrochemiluminescence (ECL) from multiple luminophores. The potentials at both the working and counter electrodes, the current between these electrodes, and the emission over cyclic voltammetric scans were simultaneously measured for the ECL reaction of Ir(ppy)₃ and either [Ru(bpy)₃]²⁺ or [Ir(df-ppy)₂(ptb)]⁺, with tri-n-propylamine as the co-reactant. The counter electrode potential was monitored by adding a differential electrometer module to the potentiostat. Plotting the data against the applied working electrode potential and against time provided complementary depictions of their relationships. Photographs of the ECL at the surface of the two electrodes were taken to confirm the source of the emissions. This provided a new understanding of these multifaceted ECL systems, including the nature of the counter electrode potential and the possibility of eliciting ECL at this electrode, a mechanism-based rationalisation of the interactions of different metal-complex luminophores, and a previously unknown ECL pathway for the Ir(ppy)₃ complex at negative potentials that was observed even in the absence of the co-reactant.

Exploration of potential-dependent, multi-colour co-reactant electrochemiluminescence from multiple luminophores at the working and counter electrodes reveals new pathways to emission.

AuNP array coated substrate for sensitive and homogeneous SERS-immunoassay detection of human immunoglobulin G

Owing to the high sensitivity, fast responsiveness and high specificity, immunoassays using surface-enhanced Raman scattering (SERS) as the readout signal displayed great potential in disease diagnosis. In this study, we developed a SERS-immunoassay method for the detection of human immunoglobulin G (HIgG). Upon involving well-ordered AuA on a SERSIA substrate, the LSPR effect was further enhanced to generate a strong and uniform Raman signal through the formation of sandwich structure with the addition of target HIgG and SERSIA tag. Optimization of the assay provided a wide linear range (0.1–200 μg mL⁻¹) and low limit of detection (0.1 μg mL⁻¹). In addition, the SERS-immunoassay method displayed excellent specificity and was homogeneous, which guaranteed the practical use of this method in the quantitative detection of HIgG. To validate this assay, human serum was analysed, which demonstrated the potential advantages of SERS-immunoassay technology in clinical diagnostics.

An AuNP array coated substrate was developed for the SERS-immunoassay detection of human immunoglobulin G.

A comprehensive survey upon diverse and prolific applications of chitosan-based catalytic systems in one-pot multi-component synthesis of heterocyclic rings

Heterocyclic compounds are among the most prestigious and valuable chemical molecules with diverse and magnificent applications in various sciences. Due to the remarkable and numerous properties of the heterocyclic frameworks, the development of efficient and convenient synthetic methods for the preparation of such outstanding compounds is of great importance. Undoubtedly, catalysis has a conspicuous role in modern chemical synthesis and green chemistry. Therefore, when designing a chemical reaction, choosing and or preparing powerful and environmentally benign simple catalysts or complicated catalytic systems for an acceleration of the chemical reaction is a pivotal part of work for synthetic chemists. Chitosan, as a biocompatible and biodegradable pseudo-natural polysaccharide is one of the excellent choices for the preparation of suitable catalytic systems due to its unique properties. In this review paper, every effort has been made to cover all research articles in the field of one-pot synthesis of heterocyclic frameworks in the presence of chitosan-based catalytic systems, which were published roughly by the first quarter of 2020. It is hoped that this review paper can be a little help to synthetic scientists, methodologists, and catalyst designers, both on the laboratory and industrial scales.

On paper synthesis of metal-organic framework as a chemiluminescence enhancer for estimating the total phenolic content of food samples using a smartphone readout

Herein, a novel paper-based chemiluminescence (CL) assay is reported using a smartphone readout for on-site and reliable analytical applications. The CL system was based on the high-performance improving effect of cobalt-imidazole metal-organic framework (CoMOF) on luminol-hydrogen peroxide (H₂O₂) CL emission. The CoMOF was grown on paper and used as a support for the CL reaction, which led to an intense CL emission and good reproducibility. More importantly, the stability of luminol, as the CL reagent, was greatly improved in the presence of CoMOF. This high stability, along with the high-yield CL emission, makes the device highly suitable for commercialization. Furthermore, using a smartphone as the detector for the developed device made the process easier and more accessible for public usage. In this work, the new paper-based CL smartphone device was used for the detection of the total phenolic content of food samples. Phenolic compounds (PC) are hydroxyl radical scavengers that can effectively quench the CL emission of the luminol-H₂O₂-CoMOF system. After optimizing the reaction conditions, the system could detect PC at the μg mL^-1 level. Detection limits of 0.12, 0.28, 0.46, 0.85, and 1.23 μg mL^-1 were obtained for gallic acid, quercetin, catechin, kaempferol, and caffeic acid, respectively. This work is the first report on the practical application of smartphone CL assays for the estimation of PC. The proposed assay is an easy-to-use, low-cost, portable, and suitable assay for on-site screening purposes.

Disordered Assembly of Donors and Acceptors on Layered Double Hydroxides for High-Efficiency Chemiluminescence Resonance Energy Transfer

High-efficiency chemiluminescence (CL) resonance energy transfer (CRET) can be obtained by shortening the donor-acceptor distance and/or improving the luminescence efficiency of CRET acceptors. However, careful design and stringent experimental conditions are usually required for the ordered assembly of CRET acceptors on support materials to avoid aggregation-caused quenching problems. In this work, an aggregation-induced emission (AIE)-active fluorophore was disorderly adsorbed on the surface of layered double hydroxides (LDHs), which could exhibit high-efficiency luminescence. On the other hand, the positively charged LDHs can further adsorb peroxynitrite (ONOO^-) on the surface of LDHs. Therefore, the LDH-supported AIE fluorophore could dramatically amplify weak CL signals from ONOO^- donors as a result of ultra-high CRET efficiency by coupling the shorter donor-acceptor distance with efficient CRET acceptors. The proposed CL system has been successfully applied for the detection of NaNO₂ in the concentration range from 1.0 to 100 μM with a detection limit as low as 0.5 μM. Satisfactory recoveries (98-106%) and good accuracy were achieved for sausage samples. Our success will open new avenues for the convenient design of high-efficiency CRET systems.

Ultrasound-Enhanced Self-Exciting Photodynamic Therapy Based on Hypocrellin B

Peroxalate CL as an energy source to excite photosensitizers has attracted tremendous attention in photodynamic therapy (PDT). In this work, peroxyoxalate CPPO and hypocrellin B (HB)-based nanoparticles (CBNPs) for ultrasound (US)-enhanced self-exciting PDT were designed and prepared. CBNPs showed an excellent therapeutic effect against cancer cells with the assistance of US. This US-enhanced-chemiluminescence system avoids the dependence on external light and provides an example for inspiring more effective and precise strategies for cancer treatment.

A Novel Chemiluminescence Probe for Sensitive Detection of Fibroblast Activation Protein-Alpha In Vitro and in Living Systems

Fibroblast activation protein-alpha (FAPα) is a key modulator of the microenvironment in multiple pathologies and is becoming the next pan-cancer target for cancer diagnostics and therapeutics. Chemiluminescence (CL) luminophores are considered as one of the most sensitive families of probes for detection and imaging applications due to their high signal-to-noise ratio. Until now, however, no such effective CL probe was reported for FAPα detection. Herein, we developed a novel CL probe for the detection of endogenous FAPα activity by incorporating FAPα-specific dipeptide substrates (glycine-proline) to the improved Schaap's adamantylidene-dioxetane. In this manner, we designed three CL probes (CFCL, BFCL, and QFCL) with the dipeptide substrate blocked by N-terminal benzyloxycarbonyl, N-tert-butoxycarbonyl or N-quinoline-4-carboxylic acid, respectively, which was used as the masking group to restrain the chemiexcitation energy. Probe CFCL exhibited the optimal specificity for the discrimination of FAPα from dipeptidase IV and prolyl oligopeptidase, which was elucidated by molecular docking simulation. Upon FAPα cleavage, CFCL was turned on for the highly selective and sensitive detection of FAPα with a limit of detection of 0.785 ng/mL. Furthermore, the ability of CFCL to image FAPα was effectively demonstrated in vitro, including various biological samples (plasma and tissue preparations), and in living systems (tumor cells and tumor-bearing mice). Furthermore, this newly established probe could be easily extended to evaluate FAPα inhibitors. Overall, we anticipate that probe CFCL will offer a facile and cost-effective alternative in the early detection of pathologies, individual tailoring of drug therapy, and drug screening.