Seeking Illumination: The Path to Chemiluminescent 1,2-Dioxetanes for Quantitative Measurements and In Vivo Imaging

A novel dual-activatable ultrasensitive chemiluminescent probe for mercury (II) monitoring: From rational design to multiple application

Real-time optical sensing of mercury has been developed rapidly in recent years but remains challenging such as bearing background interference. Herein, a Hg2+ and base dual-activatable ultrasensitive chemiluminescent probe CL-Hg based on benzothiazole-phenoxyl-dioxetane with profits of excitation light-free and minimal interference is presented. The photophysical properties study and sensing performance verified CL-Hg is coupled with unique advantages of long-term detection (more than 400 min), ultrahigh sensitivity (LOD = 0.52 nM), and high specificity to Hg2+, and visualization detection by the paper-based test strips. More importantly, CL-Hg showed the qualitative and quantitative detection capability for Hg2+ with great recyclability in real samples of water, seafood, and beverages, holding great potential for on-site monitoring of Hg2+ levels in the actual samples. To our knowledge, this is the first work achieving the detection of Hg2+ by chemiluminescence. Overall, the Hg2+-activated visualization platform offers a practical method for detecting Hg2+ in various application scenarios.

Realization of high-performance biosensor through sandwich analysis utilizing weak value amplification

A label-free optical sandwich immunoassay sensor, utilizing weak value amplification and total internal reflection, was devised for real-time, high-sensitivity analysis and detection of low-concentration targets. 3D printed channels and sodium chloride solution were employed to ensure reproducibility, reliability, and stability of the measurements for calibration. The sandwich structure demonstrated enhanced responsiveness in the proposed optical biosensor through a comparative analysis of the direct assay and sandwich assay for detecting alpha-fetoprotein (AFP) at the same concentration. By optimizing the binding sequences of the coating antibody, target, and detection antibody in the sandwich method, a more suitable sandwich sensing approach based on weak value amplification was achieved. With this approach, the limit of detection (LOD) of 6.29 ng/mL (pM level) for AFP in PBS solution was achieved. AFP testing and regeneration experiments in human serum have proved the feasibility of our methods in detecting complex samples and the reusability of sensing chips. Additionally, the method demonstrated excellent selectivity for unpaired antigens. The efficacy of this methodology was evaluated by simultaneously detecting AFP, carcinoembryonic antigen (CEA), and CA15-3 on a singular sensor chip. In conclusion, the label-free sandwich immunoassay sensing scheme holds promise for advancing the proposed optical sensors based on weak value amplification in early diagnosis and prevention applications. Compared to other biomarker detection methods, it will be easier to promote in practical applications.

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.

Near-infrared Fluorescent Probes with Long-acting Cyclic Monitoring and Effectively Eliminating Peroxynitrite

Two through-bond energy transfer fluorescent probes with a dihydroxyl naphthyl-pyrenyl conjugated system were synthesized for long-acting cyclic monitoring and eliminating peroxynitrite (ONOO- ). The probes exhibit large Stokes shifts (230 or 280 nm) and the fluorescence at 620 or 652 nm rapidly change in response to continuously variable concentrations of ONOO- under physiological conditions. The probes show good reversibility and can rapidly monitor the concentration changes of ONOO- in real time. In addition, with the additions of the probes, the decomposition of ONOO- is greatly accelerated. Therefore, the probes can effectively eliminate the excess ONOO- as well as sensing it. The biological studies showed that the probes can effectively and reversibly eliminate both exogenous and endogenous ONOO- in-situ as well as sensing its changes in cells, which can help to maintain the normal physiological concentration of ONOO- in organisms. This is the first system that a probe achieves multifunction including real-time detection, long-acting cyclic monitoring and in-situ elimination, thereby maintaining a normal physiological balance for ONOO- .

Vanin-1-Activated Chemiluminescent Probe: Help to Early Diagnosis of Acute Kidney Injury with High Signal-to-Noise Ratio through Urinalysis

Acute kidney injury (AKI) is a common medical condition with high morbidity and mortality. Although urinalysis provides a noninvasive and convenient diagnostic method for AKI at the molecular level, the low sensitivity of current chemical probes used in urinalysis hinders the time diagnosis of AKI. Herein, we achieved the sensitive and early diagnosis of AKI by the development of a chemiluminescent probe CL-Pa suitable for detection of urinary Vanin-1. Vanin-1 is considered as an early and sensitive biomarker for AKI, while few chemical probes have been applied to for its efficient detection. By virtue of the low autofluorescence interference during urine imaging in the chemiluminescence model, CL-Pa could realize the monitoring of the up-regulated urinary Vanin-1 with a high signal-to-noise ratio (∼588). Importantly, under the help of CL-Pa, the up-regulation of urinary Vanin-1 of cisplatin-induced AKI mice at 12 h post cisplatin injection was detected, which was much earlier than clinical biomarkers (sCr and BUN) and change of kidney histology (48 h post cisplatin injection). Furthermore, using this probe, the fluctuation of urinary Vanin-1 of mice with different degrees of AKI was monitored. This study demonstrated the ability of CL-Pa in sensitively detecting drug-induced AKI through urinalysis and suggested the great potential of CL-Pa for early diagnosis of AKI and evaluate the efficiency of anti-AKI drugs clinically.

Circularly polarized chemiluminescence from planar chiral bis(adamantylidene-1,2-dioxetane)s

Bis(adamantylidene-1,2-dioxetane), upon conjugation to a planar chiral scaffold of [2.2]paracyclophane, gave chemical-triggerable circularly polarized chemiluminescence with a dissymmetry factor of 1.1 × 10-3 scale, to which exciton chirality upon chemiexcitation was assigned as the origin.

Recent Progress of Activity-Based Fluorescent Probes for Imaging Leucine Aminopeptidase

Leucine aminopeptidase (LAP) is an important protease that can specifically hydrolyze Leucine residues. LAP occurs in microorganisms, plants, animals, and humans and is involved in a variety of physiological processes in the human body. In the physiological system, abnormal levels of LAP are associated with a variety of diseases and pathological processes, such as cancer and drug-induced liver injury; thus, LAP was chosen as the early biochemical marker for many physiological processes, including cancer. Considering the importance of LAP in physiological and pathological processes, it is critical that high-efficiency and dependable technology be developed to monitor LAP levels. Herein, we summarize the organic small molecule fluorescence/chemiluminescence probes used for LAP detection in recent years, which can image LAP in cancer, drug-induced liver injury (DILI), and bacteria. It can also reveal the role of LAP in tumors and differentiate the serum of cirrhotic, drug-induced liver injury and normal models.

Thiol-Chromene "Click" Reaction-Activated Chemiluminescent Probe for Thiol Detection In Vitro and In Vivo

Biothiols are biomolecules found in a higher content in cancer cells compared to normal cells, marking them useful cancer biomarkers. Chemiluminescence is widely used in biological imaging due to its excellent sensitivity and signal-to-noise ratio (SNR). In this study, we designed and prepared a chemiluminescent probe that is activated by a thiol-chromene "click" nucleophilic reaction. This probe is initially chemiluminescent but turned off and releases extremely strong chemiluminescence in the presence of thiols. It has high selectivity to thiol compared with other analytes. Real-time imaging of mice tumor sites showed significant chemiluminescence after the probe was injected, and the chemiluminescence of osteosarcoma tissues was also significantly stronger than that in adjacent tissues. We conclude that this chemiluminescent probe has potential to detect thiol, diagnose cancer, especially in its early stages, and aid in the development of related cancer drugs.

A highly selective and sensitive endoplasmic reticulum-targeted probe reveals HOCl- and cisplatin-induced H2S biogenesis in live cells

Reactive oxygen species (ROS) and reactive sulfur species (RSS) are involved in many physiological processes and act as collaborators with crosstalk. As an important member of gasotransmitters and RSS, hydrogen sulfide (H₂S) carries out signaling functions at submicromolar levels because of its high reactivity. Mechanisms of dynamic regulation of ROS and H₂S production are poorly understood, and the development of a highly selective and organelle-targeted chemical tool will advance the further understanding of H₂S chemical biology and ROS/RSS crosstalk. Herein, we report a highly selective and sensitive, endoplasmic reticulum (ER)-targeted fluorescent probe (ER-BODIPY-NBD) for revealing cisplatin-induced H₂S biogenesis for the first time. The probe demonstrates a 152-fold fluorescence enhancement at 520 nm after reaction with H₂S to release a bright BODIPY product (quantum yield 0.36). The probe is highly selective toward H₂S over biothiols, ER-targeted, and biocompatible. In addition, the probe was successfully employed to track H₂S biogenesis in live cells via stimulation from exogenous hypochlorous acid and the drug cisplatin.

The Molecular Basis of Organic Chemiluminescence

Bioluminescence (BL) and chemiluminescence (CL) are interesting and intriguing phenomena that involve the emission of visible light as a consequence of chemical reactions. The mechanistic basis of BL and CL has been investigated in detail since the 1960s, when the synthesis of several models of cyclic peroxides enabled mechanistic studies on the CL transformations, which led to the formulation of general chemiexcitation mechanisms operating in BL and CL. This review describes these general chemiexcitation mechanisms-the unimolecular decomposition of cyclic peroxides and peroxide decomposition catalyzed by electron/charge transfer from an external (intermolecular) or an internal (intramolecular) electron donor-and discusses recent insights from experimental and theoretical investigation. Additionally, some recent representative examples of chemiluminescence assays are given.

Design and synthesis of a small molecular NIR-II chemiluminescence probe for in vivo-activated H2S imaging

Chemiluminescence (CL) with the elimination of excitation light and minimal autofluorescence interference has been wieldy applied in biosensing and bioimaging. However, the traditional emission of CL probes was mainly in the range of 400 to 650 nm, leading to undesired resolution and penetration in a biological object. Therefore, it was urgent to develop CL molecules in the near-infrared window [NIR, including NIR-I (650 to 900 nm) and near-infrared-II (900 to 1,700 nm)], coupled with unique advantages of long-time imaging, sensitive response, and high resolution at depths of millimeters. However, no NIR-II CL unimolecular probe has been reported until now. Herein, we developed an H2S-activated NIR-II CL probe [chemiluminiscence donor 950, (CD-950)] by covalently connecting two Schaap's dioxetane donors with high chemical energy to a NIR-II fluorophore acceptor candidate via intramolecular CL resonance energy transfer strategy, thereby achieving high efficiency of 95%. CD-950 exhibited superior capacity including long-duration imaging (~60 min), deeper tissue penetration (~10 mm), and specific H2S response under physiological conditions. More importantly, CD-950 showed detection capability for metformin-induced hepatotoxicity with 2.5-fold higher signal-to-background ratios than that of NIR-II fluorescence mode. The unimolecular NIR-II CL probe holds great potential for the evaluation of drug-induced side effects by tracking its metabolites in vivo, further facilitating the rational design of novel NIR-II CL-based detection platforms.

Hydrogen-bond-driven self-assembly of chemiluminophore affording long-lasting in vivo imaging

Developing chemiluminescence probe with a slow kinetic profile, even a constant emission within analytical time, would improve the analytical sensitivity, but still remains challenging. This work reports a novel strategy to afford long-lasting in vivo imaging by developing a self-assembled chemiluminophore HPQCL-Cl via the introduction of the hydrogen-bond-driven self-assembled dye HPQ to Schaap's dioxetane. Compared with classical chemiluminophore HCL, self-assembled HPQCL-Cl was isolated from the physiological environment, thereby lowering its deprotonation and prolonging its half-life. Based on HPQCL-Cl, the long-lasting in vivo imaging of 9L-lacz tumor was achieved by developing a β-gal-responsive probe. Its signals remained constant (<5% change) for about 20 min, which may provide a wide time window for the determination of β-gal. This probe also showed high tumor-to-normal tissue ratio throughout tumor resection, highlighting its potential in image-guided clinical surgery.

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.

Oxygen-Sensing Chemiluminescent Iridium(III) 1,2-Dioxetanes: Unusual Coordination and Activity

Next generation chemiluminescent iridium 1,2-dioxetane complexes have been developed which consist of the Schaap's 1,2-dioxetane scaffold directly attached to the metal center. This was achieved by synthetically modifying the scaffold precursor with a phenylpyridine moiety, which can act as a ligand. Reaction of this scaffold ligand with the iridium dimer [Ir(BTP)2(μ-Cl)]2 (BTP = 2-(benzo[b]thiophen-2-yl)pyridine) yielded isomers which depict ligation through either the cyclometalating carbon or, interestingly, the sulfur atom of one BTP ligand. Their corresponding 1,2-dioxetanes display chemiluminescent responses in buffered solutions, exhibiting a single, red-shifted peak at 600 nm. This triplet emission was effectively quenched by oxygen, yielding in vitro Stern-Volmer constants of 0.1 and 0.009 mbar-1 for the carbon-bound and sulfur compound, respectively. Lastly, the sulfur-bound dioxetane was further utilized for oxygen sensing in muscle tissue of living mice and xenograft models of tumor hypoxia, depicting the ability of the probe chemiluminescence to penetrate biological tissue (total flux ~ 106 p/s).

Kinetics-Based Quantification of Peroxynitrite Using the Oxidative Decarbonylation of Isatin

Peroxynitrite and its radical decomposition products are highly reactive nitrogen and oxygen species that can influence the balance between health and disease in multiple organ systems. Despite vigorous research activity, real-time quantitative monitoring of peroxynitrite generated by donor compounds remains challenging. Here, we report a kinetics-based fluorescence method for quantitative tracking of peroxynitrite generation using the oxidative decarbonylation of isatin to form anthranilic acid as a fluorescent probe. This method relies on knowledge of the rate of the reaction of peroxynitrite with the probe, which we measure using stopped-flow fluorescence techniques. To the best of our knowledge, this is the first optical method capable of providing real-time quantitative measures of peroxynitrite concentrations generated from donor compounds, as demonstrated herein for SIN-1 and Angeli's salt.

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.

Recent advances in optical imaging through deep tissue: imaging probes and techniques

Optical imaging has been essential for scientific observations to date, however its biomedical applications has been restricted due to its poor penetration through tissues. In living tissue, signal attenuation and limited imaging depth caused by the wave distortion occur because of scattering and absorption of light by various molecules including hemoglobin, pigments, and water. To overcome this, methodologies have been proposed in the various fields, which can be mainly categorized into two stategies: developing new imaging probes and optical techniques. For example, imaging probes with long wavelength like NIR-II region are advantageous in tissue penetration. Bioluminescence and chemiluminescence can generate light without excitation, minimizing background signals. Afterglow imaging also has high a signal-to-background ratio because excitation light is off during imaging. Methodologies of adaptive optics (AO) and studies of complex media have been established and have produced various techniques such as direct wavefront sensing to rapidly measure and correct the wave distortion and indirect wavefront sensing involving modal and zonal methods to correct complex aberrations. Matrix-based approaches have been used to correct the high-order optical modes by numerical post-processing without any hardware feedback. These newly developed imaging probes and optical techniques enable successful optical imaging through deep tissue. In this review, we discuss recent advances for multi-scale optical imaging within deep tissue, which can provide reseachers multi-disciplinary understanding and broad perspectives in diverse fields including biophotonics for the purpose of translational medicine and convergence science.

Chemiluminescence in Combination with Organic Photosensitizers: Beyond the Light Penetration Depth Limit of Photodynamic Therapy

Photodynamic therapy (PDT) is a promising noninvasive medical technology that has been approved for the treatment of a variety of diseases, including bacterial and fungal infections, skin diseases, and several types of cancer. In recent decades, many photosensitizers have been developed and applied in PDT. However, PDT is still limited by light penetration depth, although many near-infrared photosensitizers have emerged. The chemiluminescence-mediated PDT (CL-PDT) system has recently received attention because it does not require an external light source to achieve targeted PDT. This review focuses on the rational design of organic CL-PDT systems. Specifically, PDT types, light wavelength, the chemiluminescence concept and principle, and the design of CL-PDT systems are introduced. Furthermore, chemiluminescent fraction examples, strategies for combining chemiluminescence with PDT, and current cellular and animal applications are highlighted. Finally, the current challenges and possible solutions to CL-PDT systems are discussed.

An Update on General Chemiexcitation Mechanisms in Cyclic Organic Peroxide Decomposition and the Chemiluminescent Peroxyoxalate Reaction in Aqueous Media

Four-membered ring peroxides are intimately linked to chemiluminescence and bioluminescence transformations, as high-energy intermediates responsible for electronically excited state formation. The synthesis of 1,2-dioxetanes and 1,2-dioxetanones enabled mechanistic studies on their decomposition occurring with the formation of electronically excited carbonyl products in the singlet or triplet state. The third member of this family, 1,2-dioxetanedione, has been postulated as the intermediate in the peroxyoxalate reaction, recently confirmed by kinetic studies on peroxalic acid derivatives. Several general chemiexcitation mechanisms have been proposed as model systems for the chemiexcitation step in efficient bioluminescence and chemiluminescence transformations. In this review article, we discuss the validity and efficiency of the most important chemiexcitation mechanisms, extended to aqueous media, where the efficiency is known to be drastically reduced, specifically in the peroxyoxalate reaction, highly efficient in anhydrous environment, but much less efficient in aqueous media. Mechanistic studies of this reaction will be discussed in diverse aqueous environments, with special attention to the catalysis involved in the thermal reaction leading to the formation of the high-energy intermediate and to the chemiexcitation mechanism, as well as emission quantum yields. Finally, several recent analytical and bioanalytical applications of the peroxyoxalate reaction in aqueous media will be given.

An NBD tertiary amine is a fluorescent quencher and/or a weak green-light fluorophore in H2S-specific probes

The thiolysis of NBD piperazinyl amine (NBD-PZ) is highly selective for H₂S over GSH and has been widely used for the development of many H₂S fluorescent probes. Whether the NBD amine in H₂S-specific probes could be a fluorescent quencher should be further clarified, because NBD amines have been used as environment-sensitive fluorophores for many years. Here, we compared the properties of NBD-based secondary and tertiary amines under the same conditions. For example, the emission of NBD-N(Et)2 is much smaller in water and less responsive to changes in polarity than that of NBD-NHEt. The emission of NBD-PZ-TPP is also smaller than that of NBD-NH-TPP both in aqueous buffer and in live cells. In addition, confocal bioimaging signals of NBD-PZ-TPP with excitation at 405 nm and 454 nm are much weaker than that at 488 nm. Based on these results as well as the previous work on NBD-based probes, we discuss and summarize the design strategies and sensing mechanisms for different NBD-based H₂S probes. Moreover, NBD-PZ-TPP may be a useful tool for reaction with and imaging of mitochondrial H₂S in live cells. This work should be useful for clarification of the roles of NBD in H₂S-specific fluorescent probes as well as for facilitating the development of future NBD-based probes.

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.

Recent progress in small-molecule fluorescent probes for endoplasmic reticulum imaging in biological systems

Endoplasmic reticulum (ER) is an indispensable organelle in eukaryotic cells involved in protein synthesis and processing, as well as calcium storage and release. Therefore, maintaining the quality of ER is of great importance for cellular homeostasis. Aberrant fluctuations of bioactive species in the ER will result in homeostasis disequilibrium and further cause ER stress, which has evolved to contribute to the pathogenesis of various diseases. Therefore, the real-time monitoring of various bioactive species in the ER is of high priority to ascertain the mysterious roles of ER, which will contribute to unveiling the corresponding mechanism of organism disturbances. Recently, fluorescence imaging has emerged as a robust technique for the direct visualization of molecular events due to its outstanding sensitivity, high temporal-spatial resolution and noninvasive nature. In this review, we comprehensively summarize the recent progress in design strategies, bioimaging applications, potential directions and challenges of ER-targetable small-molecular fluorescent probes.

Cell-Trappable BODIPY-NBD Dyad for Imaging of Basal and Stress-Induced H2S in Live Biosystems

H₂S is a gaseous signaling molecule that is involved in many physiological and pathological processes. In general, the level of intracellular H₂S (<1 μM) is much lower than that of GSH (∼1-10 mM), leading to the remaining challenge of selective detection and differentiation of endogenous H₂S in live biosystems. To this end, we quantitatively demonstrate that the thiolysis of NBD amine has much higher selectivity for H₂S over GSH than that of the reduction of aryl azide. Subsequently, we developed the first NBD-based cell-trappable probe 1 (AM-BODIPY-NBD) for highly selective and ultrasensitive imaging of intracellular H₂S. Probe 1 demonstrates a 207-fold fluorescence enhancement at 520 nm after reaction with H₂S/esterase to produce a bright BODIPY (quantum yield 0.42) and a detection limit of 15.7 nM. Probe 1 is water-soluble, cell-trappable, and not cytotoxic. Based on this excellent chemical tool, relative levels of basal H₂S in different cell lines were measured to reveal a positive correlation between endogenous H₂S and the metastatic potential of colon and breast cancer cells. In addition, H₂S biogenesis in vivo was also validated by probe 1 both in tobacco leaves under viral infection and in zebrafish after tail amputation. It is anticipated that probe 1 will have widespread applications in imaging and for investigating different H₂S-related biological processes and diseases.

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.

Ultrasensitive chemiluminescent neuraminidase probe for rapid screening and identification of small-molecules with antiviral activity against influenza A virus in mammalian cells

Influenza A virus is the most virulent influenza subtype and is associated with large-scale global pandemics characterized by high levels of morbidity and mortality. Developing simple and sensitive molecular methods for detecting influenza viruses is critical. Neuraminidase, an exo-glycosidase displayed on the surface of influenza virions, is responsible for the release of the virions and their spread in the infected host. Here, we present a new phenoxy-dioxetane chemiluminescent probe (CLNA) that can directly detect neuraminidase activity. The probe exhibits an effective turn-on response upon reaction with neuraminidase and produces a strong emission signal at 515 nm with an extremely high signal-to-noise ratio. Comparison measurements of our new probe with previously reported analogous neuraminidase optical probes showed superior detection capability in terms of response time and sensitivity. Thus, as far as we know, our probe is the most sensitive neuraminidase probe known to date. The chemiluminescence turn-on response produced by our neuraminidase probe enables rapid screening for small molecules that inhibit viral replication through different mechanisms as validated directly in influenza A-infected mammalian cells using the known inhibitors oseltamivir and amantadine. We expect that our new chemiluminescent neuraminidase probe will prove useful for various applications requiring neuraminidase detection including drug discovery assays against various influenza virus strains in mammalian cells.

A new chemiluminescence neuraminidase probe enables rapid screening of small molecules that inhibit viral replication, directly in influenza A-infected mammalian cells.

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.