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.

A novel ROS-Related chemiluminescent semiconducting polymer nanoplatform for acute pancreatitis early diagnosis and severity assessment.

Acute pancreatitis (AP) is a common and potentially life-threatening inflammatory disease of the pancreas. Reactive oxygen species (ROS) play a key role in the occurrence and development of AP. With increasing ROS levels, the degree of oxidative stress and the severity of AP increase. However, diagnosing AP still has many drawbacks, including difficulties with early diagnosis and undesirable sensitivity and accuracy. Herein, we synthesized a semiconducting polymer nanoplatform (SPN) that can emit ROS-correlated chemiluminescence (CL) signals. The CL intensity increased in solution after optimization of the SPN. The biosafety of the SPN was verified in vitro and in vivo. The mechanism and sensitivity of the SPN for AP early diagnosis and severity assessment were evaluated in three groups of mice using CL intensity, serum marker evaluations and hematoxylin and eosin staining assessments. The synthetic SPN can be sensitively combined with different concentrations of ROS to produce different degrees of high-intensity CL in vitro and in vivo. Notably, the SPN shows an excellent correlation between CL intensity and AP severity. This nanoplatform represents a superior method to assess the severity of AP accurately and sensitively according to ROS related chemiluminescence signals. This research overcomes the shortcomings of AP diagnosis in clinical practice and provides a novel method for the clinical diagnosis of pancreatitis in the future.

Specific Chemiluminescence Imaging and Enhanced Photodynamic Therapy of Bacterial Infections by Hemin-Modified Carbon Dots.

Antibacterial photodynamic therapy (aPDT) is a promising antibiotics-alternative strategy for bacterial infectious diseases, which features broad-spectrum antibacterial activity with a low risk of inducing bacterial resistance. However, clinical applications of aPDT are still hindered by the hydrophobicity-caused inadequate photodynamic activity of conventional photosensitizers and the hypoxic microenvironment of bacterial infections. To address these problems, herein, a promising strategy is developed to achieve specific chemiluminescence (CL) imaging and enhanced PDT of bacterial infections using hemin-modified carbon dots (H-CDs). The H-CDs can be facilely prepared and exhibit favorable water solubility, augmented photodynamic activity, and unique peroxidase-mimicking capacity. Compared with the free CDs, the photodynamic efficacy of H-CDs is significantly augmented due to the increased electron-hole separation efficiency. Moreover, the peroxidase catalytic performance of H-CDs enables not only infection identification via bacterial infection microenvironment-responsive CL imaging but also oxygen self-supplied aPDT with hypoxia-relief-enhanced bacteria inactivation effects. Finally, the enhanced aPDT efficiencies of H-CDs are validated in both in vivo abscess and infected wound models. This work may provide an effective antibacterial platform for the selective imaging-guided treatment of bacterial infections.

Highly Bright Near-Infrared Chemiluminescent Probes for Cancer Imaging and Laparotomy.

Near-infrared (NIR) chemiluminescence imaging holds potential for sensitive imaging of cancer due to its low background; however, few NIR chemiluminophores are available, which share the drawback of low chemiluminescence quantum yields (ΦCL ). Herein, we report the synthesis of NIR chemiluminophores for cancer imaging and laparotomy. Molecular engineering of the electron-withdrawing group at the para-position of the phenol-dioxetane leads to a highly bright NIR chemiluminophore (DPT), showing the ΦCL (4.6×10-2  Einstein mol-1 ) that is 3 to 5-fold higher than existing NIR chemiluminophores. By caging the phenol group of DPT with a cathepsin B (CatB) responsive moiety, an activatable chemiluminescence probe (DPTCB ) is developed for real-time turn-on detection of deeply buried tumor tissues in living mice. Due to its high brightness, DPTCB permits accurate chemiluminescence-guided laparotomy.

Near-infrared chemiluminescent nanoprobes for deep imaging and synergistic photothermal-nitric-oxide therapy of bacterial infection.

Bacterial infection is the leading cause of many serious inflammation diseases threatening human health. Existing theranostic options for bacterial infection are always complicated and unsatisfactory. There is an increasing interest in developing a more effective theranostic approach for the treatment of infections. Herein, we report the development of a near-infrared (NIR) chemiluminescent (CL) nanoparticles ALPBs containing luminol, AIE dye (TTDC), PCPDTBT, and nitric oxide (NO) donor (BNN6), which could achieve a deep CL imaging-guided photothermal-NO gas therapy of bacterial infection. After intravenous injection, ALPBs could be largely accumulated in the infected site and then activated by oversecreted reactive oxygen species (ROS) to produce near-infrared chemiluminescence, which could precisely track infection-induced local inflammation. Under the guidance of imaging, synergistic photothermal-NO therapy was further performed by 808 nm laser irradiation, leading to active bacterial eradication and rapid recovery of infected tissues. The utility of ALPBs provides a powerful and controllable "all-in-one" platform for combating bacterial infection.

Reactive Oxygen Species-Responsive and Self-Illuminating Nanoparticles for Inflammation and Tumor Imaging.

Reactive oxygen species (ROS) play a key role in various physiological and pathological processes. Abnormally elevated ROS levels are generally related to the pathogenesis of inflammatory diseases and tumors. Real-time imaging and quantification of ROS can not only provide new insight into mechanistic understanding of diseases associated with ROS but also facilitate high-throughput and high-content drug screening for these diseases. Here, the present protocol introduces ROS-responsive and self-illuminating nanoparticles with chemiluminescence (CL) and fluorescence (FL) properties that can serve as an effective nanoprobe for imaging of pathophysiology, including inflammation and tumor.

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 ultrahigh sensitivity and signal-to-noise ratio for various applications. In this review, we highlight a comprehensive but concise overview of activatable 1,2-dioxetane-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.

Near-Infrared Chemiluminescent Probe for Real-Time Monitoring Singlet Oxygen in Cells and Mice Model.

Singlet oxygen (1O2) plays a vital role in metabolism. However, because of its extremely high reactivity and short-lived state, the in vivo detection of 1O2 is challenging. To address this issue, for the first time, we herein constructed a near-infrared (NIR) chemiluminescent probe (CL-SO) by caging the precursor of phenoxy-dioxetane scaffolds and a dicyanomethylchromone acceptor for selective 1O2 detection. This probe can detect 1O2in vitro with a tremendous turn-on chemiluminescence signal in the NIR region (700 nm) and image intracellular 1O2 produced by the photosensitizer during the simulated action of photodynamic therapy (PDT). Notably, 1O2 level changes in the abdominal cavity and tumor of the various mice model under different stimulations and PDT action were effectively monitored by CL-SO, providing a novel chemiluminescence imaging platform to explore 1O2 generation in PDT-associated applications.

NIR-II Chemiluminescence Molecular Sensor for In†Vivo High-Contrast Inflammation Imaging.

Chemiluminescence (CL) sensing without external excitation by light and autofluorescence interference has been applied to high-contrast in vitro immunoassays and in vivo inflammation and tumor microenvironment detection. However, conventional CL sensing usually operates in the range of 400-850 nm, which limits the performance of in vivo imaging due to serious light scattering effects and signal attenuation in tissue. To address this challenge, a new type of CL sensor is presented that functions in the second near-infrared window (NIR-II CLS) with a deep penetration depth (≈8 mm). Successive CL resonance energy transfer (CRET) and Förster resonance energy transfer (FRET) from the activated CL substrate to two rationally designed donor-acceptor-donor fluorophores BTD540 and BBTD700 occurs. NIR-II CLS can be selectively activated by hydrogen peroxide over other reactive oxygen species (ROSs). Moreover, NIR-II CLS is capable of detecting local inflammation in mice with a 4.5-fold higher signal-to-noise ratio (SNR) than that under the NIR-II fluorescence modality.

Chemiluminescence imaging immunoassay for simultaneous determination of TBBPA-DHEE and TBBPA-MHEE in aquatic environments.

The environmental concentration of tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) and tetrabromobisphenol A mono(hydroxyethyl) ether (TBBPA-MHEE), as some of the main derivatives and byproducts of tetrabromobisphenol A (TBBPA), are obscure due to lacking available analytical methods. In the present study, a multiplexed competitive chemiluminescent imaging immunoassay (CLIIA) based on specific monoclonal antibody respectively against TBBPA-MHEE and TBBPA-DHEE has been developed for the simultaneous detection of the two targets. To improve the sensitivity of immunoassay, Au nanoparticles (AuNPs) were utilized as solid support for loading horseradish peroxidase, labeled to obtain the multi-enzyme particles. Under the optimized conditions, the limits of detection (LODs) for TBBPA-MHEE and TBBPA-DHEE were 1.85 ng/mL and 2.05 ng/mL, respectively. After estimating its accuracy and precision, the established method was applied for investigation of the contaminants at the inner rivers in Zhenjiang, Jiangsu Province. Our results indicated that no TBBPA-MHEE was found in all 11 water samples and two samples of TBBPA-DHEE were detected up to 6.34 ng/mL, possibly ascribed to the dense population and slow flow rate around the sampling site. Graphical abstract.

Semiconducting Polymer Nanoreporters for Near-Infrared Chemiluminescence Imaging of Immunoactivation.

Real-time in vivo imaging of immunoactivation is critical for longitudinal evaluation of cancer immunotherapy, which, however, is rarely demonstrated. This study reports semiconducting polymer nanoreporters (SPNRs) with superoxide anion (O2 •- )-activatable chemiluminescence signals for in vivo imaging of immunoactivation during cancer immunotherapy. SPNRs are designed to comprise an SP and a caged chemiluminescence phenoxy-dioxetane substrate, which respectively serve as the chemiluminescence acceptor and donor to enable intraparticle chemiluminescence resonance energy transfer. SPNRs are intrinsically fluorescent but only become chemiluminescent upon activation by O2 •- . Representing the first O2 •- -activatable near-infrared chemiluminescent reporter, SPNR3 sensitively differentiates higher O2 •- levels in immune cells from other cells including cancer and normal cells. Following systemic administration, SPNR3 passively accumulates into tumors in living mice and activates the chemiluminescence signals responding to the concentration of O2 •- in the tumor microenvironment. Moreover, the enhancement of in vivo chemiluminescence signal after cancer immunotherapy is correlated with increased population of T cells in the tumor, proving its feasibility in tracking of T cell activation. Thus, SPNRs represent the first kind of chemiluminescent reporters competent for in vivo imaging of immunoactivation.

Target-Catalyzed Self-Growing Spherical Nucleic Acid Enzyme (SNAzyme) as a Double Amplifier for Ultrasensitive Chemiluminescence MicroRNA Detection.

Portable chemiluminescence (CL) imaging with a smartphone has shown a great promise for point-of-care testing of diseases, especially for acute myocardial infarction (AMI), which may occur abruptly. A challenge remains how to improve the imaging sensitivity that usually is several orders of magnitude lower than those of counterpart methodologies using the sophisticated equipment. Toward this goal, here, we report the target-triggered in situ growth of AuNP@hairpin-DNA nanoprobes into spherical nucleic acid enzymes (SNAzymes), which serve as both nanolabels and amplifiers for portable CL imaging of microRNAs (miRNAs) with an ultrahigh sensitivity comparable to that of the instrumental measurement under same conditions. A G-quadruplex (G4) DNA dense layer is dynamically produced on the gold nanocore via a DNAzyme machine-driven hairpin cleaving and captures the cofactor hemin to form the SNAzymes with higher peroxidase activity and stronger nuclease resistance than the commonly used G4 DNAzymes. The matured SNAzymes are then utilized as catalytic labels in a luminol-artesunate CL system for miRNA imaging with a smartphone as the portable detector. In this way, two AMI-related miRNAs, miRNA-499 and miRNA-133a, are successfully detected in real patients' serum with a naked eye-visualized CL change at 10 fM, showing a 5 order of magnitude improvement on the sensitivity of visualizing the same disease markers in clinical circulating blood as compared to the reported strategy. In addition, a good selectivity of our developed CL imaging platform is demonstrated. These unique features make it promising to employ this portable imaging platform for clinical AMI diagnosis.

Multiplex immunoassay of chicken cytokines via highly-sensitive chemiluminescent imaging array.

Quantitative detection of multiple chicken cytokines is a good evaluation of cell-mediated immunity in chickens after disease infection or vaccination. However, current assay methods for chicken cytokines cannot meet the needs of clinical diagnosis due to unsatisfactory sensitivity and low assay throughput. Herein, a sensitive chemiluminescence (CL) imaging immunosensor array has been developed for high-throughput detection of multiple chicken cytokines. The chicken cytokines immunosensor array was prepared by assembling different cytokine capture antibodies onto a disposable silanized glass chip, where horseradish peroxidase and antibody-conjugated gold nanoparticles were used as multienzymatic amplification probe for CL imaging signal amplification. By using a sandwich assay mode, the amplified CL signals from each sensing array cell were collected for quantitation. Using chicken interleukin-4 and chicken interferon-γ as model cytokines, this novel multiplexed and amplified method demonstrated simultaneous measurement of the two chicken cytokines in the linear ranges of 0.008-0.12 ng/mL and 0.005-0.20 ng/mL, respectively, which yields limits of detection down to 2 pg/mL and 3 pg/mL. The CL imaging array method reported here also demonstrated high specificity, good repeatability, and high stability and accuracy, providing a novel multiplex immunoassay strategy for highly sensitive and high-throughput detection of chicken cytokines and further disease diagnosis in poultry.

Simultaneous detection of three biomarkers related to acute myocardial infarction based on immunosensing biochip.

An immunosensing biochip for simultaneous detection of three biomarkers related to acute myocardial infarction (AMI) was developed based on anionic soybean peroxidase (SBP) functionalized nanoprobe and chemiluminescent imaging. The nanoprobes (Ab2-SiO2-SBP) were fabricated by co-immobilization of SBP and one of the detection polyclonal antibodies, anti-cardiac troponin I antigen (anti-cTnI), anti-creatine kinase-MB (anti-CK-MB) and anti-myoglobin (anti-Myo), on the silica nanoparticle surface. The detection sensitivity was enhanced since the large surface area of silica carriers increased the loading of SBP for per sandwiched immunoreaction. The immunosensing biochip designed as 3 × 8 wells array was constructed by simultaneously immobilizing three capture monoclonal antibodies on the same one microtiter well with 2 × 3 active spots. In the presence of target protein, the nanoprobes will be attached onto the spots with high specificity through the sandwiched immunoreactions, which triggered the chemiluminescence (CL) signals on each sensing site of the microtiter plates and allowed to CL imaging of three biomarkers in one well at the same time. Therefore, the proposed biochip was a promising convenient strategy for simultaneous detection of cTnI, CK-MB and Myo, which showed potential application for multianalyte determination in clinical diagnostics.

Multiplexed chemiluminescence imaging assay of protein biomarkers using DNA microarray with proximity binding-induced hybridization chain reaction amplification.

A multiplexed chemiluminescence (CL) imaging assay was designed for sensitive screen detection of a panel of protein biomarkers by integrating DNA microarray with proximity binding-induced hybridization chain reaction (HCR) amplification. The DNA microarray was manufactured by printing hairpin DNAs for different analytes detection in an array format onto the sensing cells arranged on an aldehyde-functionalized glass chip. The existence of target proteins induced the formation of sandwich immunocomplexes along with the hybridization of DNA strands labeled on the pair of antibodies via proximity effect, which subsequently unfolded their corresponding spotting hairpin DNAs to expose prelocked primer and trigger HCR assembly. Through the streptavidin-biotin conjugation, numerous horseradish peroxidase (HRP) was coupled on the HCR assemblies to catalyze H2O2-luminol reaction and produce amplified CL signals for sensitive CL imaging assay of protein targets. As a proof of concept, the DNA microarray was used to CL imaging assay of carcinoembryonic antigen, α-fetoprotein and carcinoma antigen 125 in ranges of 0.05-500 ng mL-1, 0.06-600 ng mL-1 and 0.02-200 U mL-1, respectively. The CL microarray imaging assay could also be extended to screen detect other biomarker groups by printing different hairpin DNAs on the microarray and using corresponding antibody-DNA pairs. The proposed CL microarray imaging assay showed advantages of small sample consumption, good cost effectiveness, and multiplex detection performance, exhibiting good applicability in clinical diagnosis.

Chemiluminescence imaging of Duox2-derived hydrogen peroxide for longitudinal visualization of biological response to viral infection in nasal mucosa.

Rationale: Hydrogen peroxide (H2O2) provides an important mechanism for resisting infectious pathogens within the respiratory tract, and accordingly, the in situ analysis of H2O2 generation in real time provides a valuable tool for assessing immune response. Methods: In this study, we applied a chemiluminescent nanoparticle-based real-time imaging approach to noninvasive evaluation of the Duox2-mediated H2O2 generation after viral infection, and assessed its usefulness for analytical purposes in mouse nasal mucosa. The chemiluminescent nanoprobe employed herein (BioNT) possesses appropriate physicochemical properties, such as high sensitivity and selectivity toward H2O2, no background noise, deliverability to the respiratory tract, and capability of multiple injections to a single animal subject for long-term repetitive imaging. Results: The favorable characteristics of BioNT allowed for a longitudinal study with the same mice to noninvasively evaluate the long-term evolution of endogenous H2O2 in the nasal epithelium after infection with influenza A virus (WS/33/H1N1). We found that nasal epithelial cells by themselves respond to viral infection by generating H2O2, and that the in vivo cumulative H2O2 level in the nasal mucosa peaks at day 3 post-infection. Such in vitro and in vivo temporal behaviors of the endogenous H2O2 generation showed a good correlation with those of Duox2 expression after infection. This correlation could be further confirmed with Duox2-deficient subjects (Duox2-knockdown NHNE cells and Duox2-knockout mutant mice) where no H2O2-induced chemiluminescence was detectable even after viral infection. Importantly, upon knock-down of Duox2 expression, the condition of mice caused by viral infection in the upper airway was significantly aggravated, evidencing the involvement of Duox2 in the immune defense. Conclusion: All these results reveal a critical role of Duox2 in the infection-induced H2O2 production and the H2O2-mediated immune response to infection in the respiratory tract, well elucidating the potential of BioNT as a noninvasive tool for fundamental in vivo studies of infectious diseases.

Programmable strand displacement-based magnetic separation for simultaneous amplified detection of multiplex microRNAs by chemiluminescence imaging array.

High throughput analysis of miRNAs is of great significance to clinical and biomedical applications. In this work, we have developed a highly sensitive and selective chemiluminescence imaging array (CLIA) for simultaneous detection of three miRNAs with high throughput, easy operation and low cost. In this assay, three kinds of hairpins that can specially recognize respective miRNAs (miR-155, miR-let-7a and miR-141) are parallel modified on the magnetic beads (MBs). The employment of MBs enables quick sorting of multiplex targets in high yield and purity with high throughput. Upon introduction of the target miRNAs, they hybridize to the corresponding hairpins and initiate the DNA machines with the assistance of Klenow fragment exo- DNA polymerase and Nb.BbvCI NEase, achieving exponential amplification of targets. After that, the toehold-mediated strand displacement (TMSD) reactions are performed through sequential addition of displacement probes under magnetic separation, resulting in the release of HRP-tagged DNA hybrids in solution for CL imaging and recovery of MBs for repetitive use. This CLIA method demonstrates ultrahigh sensitivity with detection limits down to fM level, wide linear range over 5 orders of magnitude, excellent selectivity to distinguish one-base mismatched target miRNA, and good performance in real sample analysis. Together with the advantages of high throughput, easy operation, acceptable accuracy, and good recyclability and reproducibility, the proposed multiplex CLIA method holds great potential in practical applications, such as profiling the pattern of miRNA expression, disease screening, biomedical research, and so on.

Chemiluminescence imaging for microRNA detection based on cascade exponential isothermal amplification machinery.

A novel G-quadruplex DNAzyme-driven chemiluminescence (CL) imaging method was developed for ultrasensitive and specific detection of miRNA based on the cascade exponential isothermal amplification reaction (EXPAR) machinery. A structurally tailored hairpin probe switch was designed to selectively recognise miRNA and form hybridisation products to trigger polymerase and nicking enzyme machinery, resulting in the generation of product I, which was complementary to a region of the functional linear template. Then, the response of the functional linear template to the generated product I further activated the exponential isothermal amplification machinery, leading to synthesis of numerous horseradish peroxidase mimicking DNAzyme units for CL signal transduction. The amplification paradigm generated a linear response from 10 fM to 100 pM, with a low detection limit of 2.91 fM, and enabled discrimination of target miRNA from a single-base mismatched target. The developed biosensing platform demonstrated the advantages of isothermal, homogeneous, visual detection for miRNA assays, offering a promising tool for clinical diagnosis.

A portable chemiluminescence imaging immunoassay for simultaneous detection of different isoforms of prostate specific antigen in serum.

A multianalyte chemiluminescence (CL) imaging immunoassay strategy for sensitive detection of different isoforms of prostate specific antigen (PSA) was developed. The microtiter plates were fabricated by simultaneously immobilizing of free-PSA (f-PSA) and total-PSA (t-PSA) capture antibody on nitrocellulose (NC) membrane. Each of the array were spotted in replicates of six spots within a spacing of 2mm. 16 or 48 detection wells were integrated on a single NC membrane and each well could be used as a microreactor and microanalysis chamber. Under a sandwiched immunoassay, the CL signals on each sensing site were collected by a charge-coupled device (CCD), presenting an array-based chemiluminescence imaging. Soybean peroxidase (SBP) was used to label f-PSA or t-PSA monoclonal antibody. With the amplification effects of two enhancers, 3-(10'-phenothiazinyl) propane-1-sulfonate (SPTZ) and 4-morpholinopyridine (MORP), the CL intensity could significantly enhanced, which improved the sensing sensitivity and detection limit. Under the optimal conditions, the linear response to the analyte concentration ranged from 0.01-36.7ng/mL and 0.02-125ng/mL for f-PSA and t-PSA, respectively. The results for the detection of forty serum samples from prostate cancer patients and cancer-free patients showed good agreement with the clinical data, suggesting that the proposed assay had acceptable accuracy. The proposed CL imaging immunoassay possess high throughput and acceptable reproducibility, stability and accuracy, which made it great potential to available to distinguish different isoforms of PSA in serum samples.

Quercetin protects gastric epithelial cell from oxidative damage in vitro and in vivo.

Epithelial injury caused by reactive oxygen species (ROS) including H2O2 plays a critical role in the pathogenesis of gastric disorders. Therefore, pharmacological intervention targeting reactive oxygen species elimination has highly clinical values in therapy of gastric diseases. Although quercetin has been found to possess gastroprotective activity, whether it has a protective activity againress related injury to gastric epithelial cells remains unknown. The aim of the study is herein to investigate a possible protective effect of quercetin against oxidative stress in vitro and vivo. Human gastric epithelial GES-1 cells were pretreated with quercetin and then challenged with H2O2. In vivo reactive oxygen species production in acute gastric mocosa injury was assessed using a chemiluminescent probe L-012 (8-amino-5-chloro-7-phenylpyrido [3,4-d]pyridazine-1,4-(2H,3H)dione) after quercetin was administered to mice. In GES-1 cells, pretreatment of quercetin can significantly diminish H2O2-induced cell viability loss; decrease intracellular reactive oxygen species and Ca(2+) influx; restore H2O2-induced ΔΨm dissipation. It also upregulates peroxisome proliferator-activated receptor-γ coactivator (PGC-1α) expression under the state of oxidative stress, and the downstream cell apoptosis significantly decreased. In vivo, chemiluminescence imaging shows that quercetin attenuates reactive oxygen species production and gastric damages in acute gastric mucosal injury. We first reported the evidence that quercetin can protect gastric epithelial GES-1 cells from oxidative damage and ameliorate reactive oxygen species production during acute gastric mucosal injury in mice. This might be ascribed to its inhibition of oxidative stress, regulation of mitochondrial dysfunction, initiation of antioxidant defense and inhibition of apoptosis.