Rapid Analysis of Estrogens in Meat Samples by High Performance Liquid Chromatography with Fluorescence Detection.

A novel reagent named 4-(N-methyl-1,3-dioxo-benzoisoquinolin-6-yl-oxy)benzene sulfonyl chloride (MBIOBS-Cl) for the determination of estrogens in food samples by high-performance liquid chromatography (HPLC) with fluorescence detection has been developed. Estrogens could be easily labeled by MBIOBS-Cl in Na2CO3-NaHCO3 buffer solution at pH 10.0. The complete labeling reaction for estrogens could be accomplished within five minutes, the corresponding derivatives exhibited strong fluorescence with the maximum excitation and emission wavelengths at 249 nm and 443 nm, respectively. The derivatization conditions, such as the molar ratio of reagent to estrogens, derivatization time, pH, temperature, and buffers were optimized. Derivatives were sufficiently stable to be efficiently analyzed by HPLC with a reversed-phase Agilent ZORBAX 300SB-C18 column with a good baseline resolution. Excellent linear correlations were obtained for all estrogen derivatives with correlation coefficients greater than 0.9998. Ultrasonic-Assisted extraction was used to optimize the extraction of estrogens from meat samples with a recovery higher than 82%. The detection limits (LOD, S/N = 3) of the method ranged from 0.95 to 3.3 µg· kg-1. The established method, which is fast, simple, inexpensive, and environment friendly, can be successfully applied for the detection of four steroidal estrogens from meat samples with little matrix interference.

Polarity-Ultrasensitive and Lipophilicity-Enhanced Structurally Modified Hemicyanine for Two-Color Staining to Reveal Cell Apoptosis during Chemotherapy.

Programmed cell death (PCD) is a precisely controlled physiological process to sustain tissue homeostasis. Even though the PCD pathways have been explicitly subdivided, the individual cell death process seems to synergistically operate to eliminate cells rather than separately execute signal transduction. Apoptosis is the dominant intracellular PCD subtype, which is intimately regulated and controlled by mitochondria, thus tracing mitochondrial actions could reveal the dynamic changes of apoptosis, which may provide important tools for screening preclinical therapeutic agents. Herein, we exploited an innovative fluorophore Cy496 based on the light-initiated cleavage reaction. Cy496 bears the typical D-π-A structure and serves as a versatile building block for chemosensor construction through flexible side chains. By regulating lipophilicity and basicity through bis-site substitution, we synthesized a series of fluorescence probes and screened a novel mitochondria-targeted ratiometric probe Cy1321, which can real-time evaluate the dynamic changes of mitochondrial micropolarity mediated by bis-cholesterol anchoring. Cy1321 has realized two-color quantification and real-time visualization of polarity fluctuations on chemotherapy agent (cisplatin)-induced apoptosis through flow cytometry and confocal imaging and also achieved the purpose of detecting mitochondria-related apoptosis at the level of tissues. It is envisioned that Cy1321 has sufficient capability as a promising and facile tool for the evaluation of apoptosis and contributing to therapeutic drug screening.

NIR Light-Activated Mitochondrial RNA Cross-Linking Strategy for H2S Monitoring and Prolonged Colorectal Tumor Imaging.

Molecular diffusion and leakage impede the long-term retention of probes/drugs and may cause potential adverse effects in theranostic fields. Spatiotemporally manipulating the organelle-immobilization behavior of probes/drugs for prolonged tumor retention is indispensable to achieving effective cancer diagnosis and therapy. Herein, we propose a rational strategy that could realize near-infrared light-activated ribonucleic acids (RNAs) cross-linking for prolonged tumor retention and simultaneously endogenous hydrogen sulfide (H2S) monitoring in colorectal tumors. Profiting from efficient singlet oxygen (1O2) generation from Cy796 under 808 nm light irradiation, the 1O2-animated furan moiety in Cy796 could covalently cross-link with cytoplasmic RNAs via a cycloaddition reaction and realize organelle immobilization. Subsequently, specific thiolysis of Cy796 assisted with H2S resulted in homologous product Cy644 with reduced 1O2 generation yields and enhanced absolute fluorescence quantum yields (from 7.42 to 27.70%) with blue-shifted absorption and emission, which avoided the molecular oxidation fluorescence quenching effect mediated by 1O2 and validated fluorescence imaging. Furthermore, studies have demonstrated that our proposed strategy possessed adequate capacity for fluorescence imaging and endogenous H2S detection in HCT116 cells, particularly accumulated at the tumor sites, and retained long-term imaging with excellent biocompatibility. The turn-on fluorescence mode and turn-off 1O2 generation efficiency in our strategy successfully realized a diminished fluorescence cross-talk and oxidation quenching effect. It is adequately envisioned that our proposed strategy for monitoring biomarkers and prolonged tumor retention will contribute tremendous dedication in the clinical, diagnostic, and therapeutic fields.

Homocysteine-specific fluorescence detection and quantification for evaluating S-adenosylhomocysteine hydrolase activity.

Studies have shown that homocysteine (Hcy) levels are closely related to cardiovascular and cerebrovascular diseases. In this work, we have developed and synthesized three copper complexes, F542-Cu2+, F508-Cu2+, and F465-Cu2+ for Hcy detection. The different binding constants (Ks) of the copper complexes endow them with dramatic reactivity toward biothiols. The pyridine-containing tetraazacycle was employed in the construction of F542-Cu2+, which renders the medium Ks value for the copper complex compared with cyclen and TACN and effectively prevented the disintegration of the complexes. Pyridine-containing tetraazacycle provided the basis and possibility for the hypothesis for the reduction of Cu2+ by biothiols to shape into a stable six-membered ring structure. The obtained results verified that F542-Cu2+ could be utilized to specifically probe Hcy in a switched-on fluorescence mode. F542-Cu2+ exhibited excellent environmental stability, superior sensitivity, and outstanding selectivity toward Hcy under physiological conditions. The mechanism of Hcy specificity was confirmed to be related to the generation of Hcy-induced six-membered ring by fluorescence imaging, time-dependent fluorescence spectra, ESI-MS, and electron paramagnetic resonance (EPR) analyses. Furthermore, we exploited the application of F542-Cu2+ and developed a strategy for evaluating the activity of S-adenosylhomocysteine hydrolase (AHCY) in vitro by fluorescence analysis. More importantly, real-time in vivo evaluation of the enzymatic activity of AHCY was realized and assisted by our probe, providing the possibility of opening up a new avenue for enzymatic reaction assessment.

Nonoxidative Strategy for Monitoring Peroxynitrite Fluctuations in Immune Responses of Tumorigenesis.

Phagocyte respiratory burst in immune responses generates enormous amounts of reactive oxygen species (ROS) to fulfill primary defense against neoplasia. However, the beneficial functions associated with ROS, especially the potent oxidant/nucleophile peroxynitrite, in an immunological process are still ambiguous. Herein, we report the construction and biological assessment of cyanine-based fluorescent biosensors, which are based on a nonoxidative strategy for peroxynitrite detection. The established nonoxidative strategy is composed of nucleophilic substitution and nanoaggregate formation initiated by peroxynitrite. The proposed nonoxidative strategy in this study could maintain cellular oxidative stress in the critical process of detection and preserve homeostasis of cell metabolism. The remarkable detection sensitivity, reaction selectivity, and spectral photostability of our biosensors enabled us to visualize endogenous peroxynitrite levels in immune-stimulated phagocytes. With the aid of basal peroxynitrite imaging in an acute peritonitis model, the visualization of peroxynitrite level variations in immune responses of tumorigenesis was accomplished assisted by our biosensors. It is envisioned that our strategy provides a promising tool for early tumor diagnosis and evaluation of tumor suppression in the process of immune responses without disturbing the functions of ROS signaling transduction.

A novel fluorescent labeling reagent, 2-(9-acridone)-ethyl chloroformate, and its application to the analysis of free amino acids in honey samples by HPLC with fluorescence detection and identification with online ESI-MS.

In this study, a novel fluorescent labeling reagent 2-(9-acridone)-ethyl chloroformate (AEC-Cl) was designed, synthesized and applied for the determination of free amino acids by high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). The free amino acids were rapidly and efficiently labeled by AEC-Cl in the presence of basic catalyst (pH 9.0) within 5 min at room temperature (25 °C). The derivatives exhibited excellent stability and fluorescence properties, with maximum excitation and emission wavelengths at 268 nm and 438 nm, respectively. Derivatives of 22 kinds of natural amino acids were completely separated by gradient elution on a Hypersil ODS C18 column. Under the optimal conditions, the calibration curves exhibited excellent linear responses, with correlation coefficients of R2 > 0.9994. The detection and quantification limits were in the range of 0.61-2.67 µg kg-1 and 2.07-8.35 µg kg-1, respectively. Therefore, AEC-Cl was successfully applied for the detection of trace levels of free amino acids in honey samples. Graphical abstract A novel fluorescent labeling reagent was applied for the determination of free amino acids in honey by high-performance liquid chromatography with a fluorescence detector.

A novel active mitochondrion-selective fluorescent probe for the NIR fluorescence imaging and targeted photodynamic therapy of gastric cancer.

The annual morbidity and mortality due to gastric cancer are still high across the world, posing a serious threat to public health. Improving the diagnosis rate of gastric cancer and exploring new treatments are urgent issues in the clinical field. In recent years, photosensitizer (PS)-based photodynamic therapy (PDT) has proven to be an effective cancer treatment strategy and can be used to treat a variety of cancers. Developing PSs with tumor-targeting ability and high singlet oxygen yield (Φ(1O2)) is the key to improving the PDT effect. Herein, we developed a novel diagnosis and treatment system (Cy1395-NPs). Our active thio-photosensitizer is based on the sulfur substitution strategy as it can reduce the S1-T1 energy gap, which can promote the process of intersystem crossing (ISC), thus resulting in high ROS generation efficiency. Cy1395-NPs exhibited stable spectral characteristics, satisfactory biocompatibility and high 1O2 yield under laser irradiation due to the introduction of the sulfur atom. In cellular studies, Cy1395-NPs could specifically target MKN45 cells via integrin αvß3-mediated cRGD endocytosis and selectively aggregate in the mitochondria. Cy1395-NPs had no obvious cytotoxicity for MKN45 cells and exerted obvious phototoxicity due to the production of 1O2 under laser irradiation. The in vivo results showed that the fluorescence signal from the tumor site was obviously enhanced in 16-48 h, and Cy1395-NPs could selectively target solid tumors with a retention time of about 32 h. Under laser irradiation, Cy1395-NPs significantly inhibited tumor growth and led to significant tumor suppression and apoptosis. In summary, the developed Cy1395-NPs could actively target tumors and exert mitochondrial selectivity, showing an excellent fluorescence imaging effect. Under the irradiation of an 808 nm laser, Cy1395-NPs achieved good inhibition of gastric cancer cells both in vitro and in vivo, thus displaying the functions of tumor targeting, mitochondrial selectivity, fluorescence imaging and tumor inhibition. Our strategy provides a new diagnostic and treatment method for gastric cancers in clinical settings.

A rapid response near-infrared ratiometric fluorescent probe for the real-time tracking of peroxynitrite for pathological diagnosis and therapeutic assessment in a rheumatoid arthritis model.

Peroxynitrite (ONOO-) is a potent bio-oxidant involved in many physiological and pathological processes; however, most of the pathological effects associated with ONOO-in vivo are still ambiguous. Herein, we designed and synthesized two near-infrared ratiometric fluorescent probes, Ratio-A and Ratio-B, for the detection and biological evaluation of ONOO-. The recognition unit diene in the probes could be specifically cleaved by ONOO- with a 94-fold enhancement in the ratiometric fluorescence signal. By imaging ONOO- in immune stimulated cells and acute inflammation mice model using Ratio-A, we investigated the fluctuations of ONOO- levels in a rheumatoid arthritis (RA) model of mice. Ratio-A could be applied for the effective imaging of RA and could rapidly evaluate the response of the RA treatment with methotrexate (MTX). Thus, Ratio-A can be considered as a promising tool for pathological diagnosis and the therapeutic assessment of a wide range of diseases including RA.