A unique triple-channel fluorescent probe for discriminative detection of cyanide, hydrazine, and hypochlorite

Herein, the first triple-channel fluorescent probe, TTB, excited at the same wavelength (λ_ex = 360 nm) in the same sensing medium for the detection and discrimination of cyanide, hydrazine, and hypochlorite, is disclosed. While a fluorescent white color appeared (λ_em = 470 nm) with the addition of cyanide ion into the probe solution, upon addition of hydrazine and hypochlorite, green (λ_em = 503 nm) and orange (λ_em = 585 nm) fluorescent colors, respectively, were observed. A naked-eye detection for the three ions was documented. With the appearance of orange color, a mega Stokes shift of 175 nm was observed. The probe exhibited excellent selectivity and lower detection limits of 0.24 μM, 4.1 nM and 0.27 μM, and dynamic ranges of 0.0-2.0 μM, 0.0-0.05 μM and 0.0-2.0 μM for cyanide, hydrazine and hypochlorite, respectively. The sensing mechanism was investigated through computational studies before and after the addition of cyanide, hypochlorite, and hydrazine, applying density functional theory (DFT), along with the calculation of optical properties by time-dependent DFT (TD-DFT) method. The results were found to be in good agreement with the experimental values. Remarkably, the probe, TTB, successfully detected cyanide, hydrazine, and hypochlorite in complex water samples. Moreover, the detection of cyanide was successfully performed in apricot kernels, as well as hypochlorite in fruits and vegetables.

Highly Sensitive Detection of Chymotrypsin Based on Metal Organic Frameworks with Peptides Sensors

In this study, peptides and composite nanomaterials based on copper nanoclusters (CuNCs) were used to detect chymotrypsin. The peptide was a chymotrypsin-specific cleavage peptide. The amino end of the peptide was covalently bound to CuNCs. The sulfhydryl group at the other end of the peptide can covalently combine with the composite nanomaterials. The fluorescence was quenched by fluorescence resonance energy transfer. The specific site of the peptide was cleaved by chymotrypsin. Therefore, the CuNCs were far away from the surface of the composite nanomaterials, and the intensity of fluorescence was restored. The limit of detection (LOD) using Porous Coordination Network (PCN)@graphene oxide (GO) @ gold nanoparticle (AuNP) sensor was lower than that of using PCN@AuNPs. The LOD based on PCN@GO@AuNPs was reduced from 9.57 pg mL^-1 to 3.91 pg mL^-1. This method was also used in a real sample. Therefore, it is a promising method in the biomedical field.

De Novo Design of a Highly Selective Nonpeptide Fluorogenic Probe for Chymotrypsin Activity Sensing in a Living System

Chymotrypsin, an extensively known proteolytic enzyme, plays a substantial role in maintaining physiological functions, including protein digestion, immune response, and tissue repair. To date, intense attention has been focused on the invention of efficient and sensitive chemical tools for chymotrypsin activity measurement. Among them, the "nonpeptide"-based chymotrypsin probe design strategy utilizing the esterase activity of chymotrypsin has been well-developed due to its low cost and high atom-economy feature. However, the ester-bond-based nature of these probes make them possibly vulnerable to esterases and active chemicals. These defects strictly restricted the application of the previously reported probes, especially for imaging in living systems. Therefore, to acquire fluorogenic probes with sufficient stability and specificity for chymotrypsin sensing in a complicated biological environment, a more stable skeleton for nonpeptide-based chymotrypsin probe construction is urgently needed. Herein, a novel nonpeptide-based fluorogenic probe for specific chymotrypsin activity sensing was designed and synthesized by the substitution of an ester-based linker with a heptafluorobutylamide moiety. The acquired probe, named TMBIHF, showed high selectivity toward various enzymes and reactive chemicals, while it retained high sensitivity and catalytic efficiency toward chymotrypsin. Moreover, TMBIHF was successfully applied for monitoring chymotrypsin activity and pancreas development in live zebrafish, specific sensing of exogenous and endogenous chymotrypsin in nude mice, and visualizing chymotrypsin-like activity-dependent cellular apoptosis, thus providing an alternative and reliable way for chymotrypsin-targeted biosensor or prodrug construction.

Development of Small-Molecule Fluorescent Probes Targeting Enzymes

As biological catalysts, enzymes are vital in controlling numerous metabolic reactions. The regulation of enzymes in living cells and the amount present are indicators of the metabolic status of cell, whether in normal condition or disease. The small-molecule fluorescent probes are of interest because of their high sensitivity and selectivity, as well as their potential for automated detection. Fluorescent probes have been useful in targeting particular enzymes of interest such as proteases and caspases. However, it is difficult to develop an ideal fluorescent probe for versatile purposes. In the future, the design and synthesis of enzyme-targeting fluorescent probes will focus more on improving the selectivity, sensitivity, penetration ability and to couple the fluorescent probes with other available imaging molecules/technologies.

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.

Detection of Chymotrypsin Using Peptide Sensor Based on Graphene Oxide Modified with Sulfhydryl Group and Gold Nanoparticles

In this study, GO modified with sulfhydryl group was prepared by thiolation on the surface of GO, which makes a meaningful material. GO with sulfhydryl group combined with gold nanoparticles,...

Activatable endoplasmic reticulum-targeted NIR fluorescent probe with a large Stokes shift for detecting and imaging chymotrypsin

In this work, the first endoplasmic reticulum-targeted near-infrared fluorescent probe, ISO-Chy, with a large Stokes shift is reported by introducing a recognition group of 4-bromobutyl for chymotrypsin detection.

A non-peptide probe for detecting chymotrypsin activity based on protection-deprotection strategy in living systems

Chymotrypsin (CHT) plays a vital role in the metabolism of organisms and affects cell proliferation and apoptosis. Abnormal levels of CHT will lead to a variety of diseases, such as inflammatory arthritis, diabetes, pharyngitis, indigestion, and pancreatic cancer. Therefore, it is significant to design an effective method for the detection of CHT in living systems. Here, we synthesized a specific deep-red non-peptide probe DT by effectively combining isophorone and p-hydroxybenzaldehyde for the detection of CHT using 3-phenylpropionate chloride as the recognition group based on a protection-deprotection strategy. The DT probe exhibited an emission range of 525-700 nm and showed excellent photostability, high sensitivity (LOD = 0.071 U mL^-1), and selectivity for CHT detection. The cellular experiments demonstrated that DT could sensitively recognize CHT activity in three cell lines and the content of CHT was much higher in P815 cells than in MCF-7 and 3T3 cells. Also, DT was successfully used to visualize the endogenous CHT in zebrafish. Notably, the DT probe provided an intuitive way to visualize endogenous CHT in mouse pancreas for the first time, demonstrating the potential for application in the future clinical diagnosis of pancreatic diseases. Therefore, the small-molecule probe DT is expected to be a useful molecular tool for CHT-related disease diagnosis and drug discovery.

Review on the recent progress in the development of fluorescent probes targeting enzymes

Enzymes are very important for biological processes in a living being, performing similar or multiple tasks in and out of cells, tissues and other organisms at a particular location. The abnormal activity of particular enzyme usually caused serious diseases such as Alzheimer's disease, Parkinson's disease, cancers, diabetes, cardiovascular diseases, arthritis etc. Hence, nondestructive and real-time visualization for certain enzyme is very important for understanding the biological issues, as well as the drug administration and drug metabolism. Fluorescent cellular probe-based enzyme detectionin vitroandin vivohas become broad interest for human disease diagnostics and therapeutics. This review highlights the recent findings and designs of highly sensitive and selective fluorescent cellular probes targeting enzymes for quantitative analysis and bioimaging.

Detection of Chymotrypsin by Optical and Acoustic Methods

Chymotrypsin is an important proteolytic enzyme in the human digestive system that cleaves milk proteins through the hydrolysis reaction, making it an interesting subject to study the activity of milk proteases. In this work, we compared detection of chymotrypsin by spectrophotometric dynamic light scattering (DLS) and quartz crystal microbalance (QCM) methods and determined the limit of chymotrypsin detection (LOD), 0.15 ± 0.01 nM for spectrophotometric, 0.67 ± 0.05 nM for DLS and 1.40 ± 0.30 nM for QCM methods, respectively. The sensors are relatively cheap and are able to detect chymotrypsin in 3035 min. While the optical detection methods are simple to implement, the QCM method is more robust for sample preparation, and allows detection of chymotrypsin in non-transparent samples. We give an overview on methods and instruments for detection of chymotrypsin and other milk proteases.

The detection of chymotrypsin using peptides covalent bound to the surface of graphene oxide and gold nanoparticles

In this study, pyrene was used as a fluorescent dye for peptides.

Perspective on chymotrypsin detection

Chymotrypsin is one of the most extensively known proteases participating in the pathogenesis of various diseases, which can be used in drug discovery and clinical diagnosis.