Development of a NIR fluorescent probe for the detection of intracellular cysteine and glutathione and the monitoring of the drug resistance

Long-Term Imaging of Cys in Cells and Tumor Mice by a Solid-State Fluorescence Probe

Cysteine is an important biological thiol and is closely related to cancer. It remains a challenge to develop a probe that can provide long-term fluorescence detection and imaging of Cys in cells as well as in living organisms. Here, a solid-state fluorophore HTPQ is combined with an acrylate group to construct a solid-state fluorescent probe HTPQC for Cys recognition. The fluorescence of the probe is quenched when the photoinduced electron transfer (PET) process is turned on and the excited-state intramolecular proton transfer (ESIPT) process is turned off. In the presence of Cys, an obvious solid-state fluorescence signal can be observed. The double quenching mechanism makes the probe HTPQC have the advantages of high sensitivity, good selectivity, and high contrast of biological imaging. Due to low cytotoxicity, the probe HTPQC can be used to detect exogenous and endogenous Cys in living cells and is capable of imaging over long periods of time. By making full use of long wavelengths, the probe can be applied for the detection of Cys levels in tumor mice and equipped with the ability to conduct long-term imaging in vivo.

Development of a NIR fluorescent probe for fluorescence-assisted EGFR-TKI applicable patients screening and drug resistance monitoring

EGFR tyrosine kinase inhibitor exerts significant benefits to non-small cell lung cancer patient, but was also limited by the applicable patient screening and drug resistance. Here we presented with an EGFR-targeted and reactive oxygen species-responsive NIR probe (LX) to achieve both patient screening and drug resistance monitoring for EGFR-tyrosine kinase inhibitor. LX inherited EGFR selectivity and preference from EGFR-tyrosine kinase inhibitor, which only showed specificity to tumor with EGFR mutation. Meanwhile, the near-infrared fluorescence of LX was initially inhibited and could be turned on by intratumoral reactive oxygen species. When LX could bind to tumor EGFR, reactive oxygen species-responsive specific fluorescence was generated to indicate the applicability of tumors to EGFR-tyrosine kinase inhibitor. However, no specific LX fluorescence could be observed in inapplicable tumors due to the lack of specificity between tumor EGFR and LX. Meanwhile, when drug resistance was developed during treatments, obvious intratumoral reactive species oxygen decrease happened, which was also deemed as a significant signal of the drug resistance. By visualizing intratumoral reactive oxygen species fluctuation by responsive fluorescence, drug resistance could be monitored and reported.

2-Mercaptobenzimidazole Functionalized Copper Nanoparticles Fluorescence Probe for Sensitivity and Selectivity Detection of Cys in Serum

In this paper, a 2-mercaptobenzimidazole-copper nanoparticles (MBI-CuNPs) fluorescent probe with high performance based on 2-mercaptobenzimidazole functionalized copper nanoparticles was synthesized by a hydrothermal method and used for cysteine (Cys) detection in serum. The MBI-CuNPs probe exhibits strong fluorescence emission at 415 nm under the excitation at 200 nm, which is attributed to the metal-ligand charge transfer (MLCT) transition through the coordination of an MBI ligand and monovalent copper. Furthermore, the MBI-CuNPs probe has a high quenching fluorescence response to Cys, and shows a good linearity relationship with Cys in 0.05-65 µM, with a detection limit of 52 nM. Moreover, the MBI-CuNPs probe could eliminate the interference of biological mercaptan Hcy and GSH with a similar structure and reaction properties, due to the strong electron-donating ability of Cys, which can quench the fluorescence of the MBI-CuNPs probe. The MBI-CuNPs probe was applied to the analysis of Cys in real serum, and the absolute recovery rate was as high as 90.23-97.00%. Such a fluorescent probe with high sensitivity and selectivity has potential applications for the early prevention of various diseases caused by abnormal Cys levels.

A high-performance fluorescent probe for detection of cysteine in plasma constructed by combining Cu(I) and 2,5-dimercapto-1,3,4-thiadiazole

A high-performance fluorescent probe 2,5-dimercapto-1,3,4-thiadiazole copper nanoparticles (DMTD-CuNPs) was synthesized by hydrothermal method based on monovalent copper (Cu(I)) and 2,5-dimercapto-1,3,4-thiadiazole (DMTD), and it can effectively detect cysteine (Cys) in plasma. Experiments show that DMTD can reduces band gap of Cu(I) in DMTD-CuNPs, promote charge transfer transition from DMTD to Cu(I) and significantly enhance fluorescence intensity of DMTD-CuNPs at 515 nm. The large Stokes shift of DMTD-CuNPs is 315 nm, which can reduce the self-quenching of probe fluorescence and improves detection accuracy of the probe. In the presence of Cys, fluorescence of DMTD-CuNPs at 515 nm is significantly quenched because Cys reacts with Cu(I) in DMTD-CuNPs through Cu-S bond to form reduced charge transfer, which can be successfully used for the detection of Cys. Linear range and detection limit for Cys detection are 25-65 µM and 50 nM, respectively. Furthermore, feasibility of detecting Cys in plasma using DMTD-CuNPs probe was evaluated by standard addition method, and the absolute recovery is 96-99%. Such a DMTD-CuNPs probe shows high sensitivity, good selectivity and low detection limit for Cys, which is expected to be used for the practical analysis of Cys in plasma.

A gold-silver bimetallic nanocluster-based fluorescent probe for cysteine detection in milk and apple

Noble metal nanoclusters have attracted much attention due to their excellent optical properties. In the present work, a silver-doped gold-based bimetallic nanoclusters (Au/Ag NCs) were reasonably designed and prepared through a one-pot method by using 5-mercapto-1-tetrazolea-acetic acid sodium salt (MTAS) as a protector and capping agent. In comparison with the monometallic nanoclusters, Ag-doped metallic nanoclusters show better performance. The particle size of the MTAS-Au/Ag NCs is slightly larger than that of the undoped Au NCs by about 1.86 ± 0.5 nm, and the MTAS-Au/Ag NCs exhibit an emission peak at 635 nm with a quantum yield (QY) of 3.05%. The presence of cysteine (Cys) induces efficient quenching of the photoluminescence of the obtained Au/Ag NCs, achieving the sensitive detection of Cys with a detection limit of 16 nM. The fluorescence quenching rate of the nano fluorescent probe has a linear relationship with the cysteine concentration. Under the best detection conditions, the linear range for Cys detection with MTAS-Au/Ag NCs as a probe is 0.05-25.0 μM. Moreover, this probe has been successfully applied to the analysis of Cys in milk and apples, and a satisfactory recovery rate has been obtained, indicating the effectiveness and reliability of the sensor system for the detection of actual samples.

Research Progress on Multifunctional Fluorescent Probes for Biological Imaging, Food and Environmental Detection

There has been rapid progress in the development of fast, sensitive, cheap and low-cytotoxicity micro-molecule fluorescent probes for application in various fields, including disease diagnosis, food safety and environmental safety. As an analytical tool, dual-function fluorescent probes with dual-emission responses have attracted considerable attention due to their cost-effectiveness and efficiency over single-function sensors. This review primarily describes research progress on multifunctional probes in terms of the reaction type and coordination type, as well as the general design principles of probes. The analytes include reactive oxygen species (ROS), reactive sulfur species (RSS), harmful cations and anions, etc. Multifunctional probes for food, medical and environmental applications are listed for future research. To improve the development of rapid detection methods, trends and strategies in the development of multifunctional fluorescent probes are also discussed.

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.