Deeper insight into protease-sensitive "covalent-assembly" fluorescent probes for practical biosensing applications

Proteases, a powerful biochemical tool in the service of medicine, clinical and pharmaceutical

Proteases, enzymes that hydrolyze peptide bonds, have various applications in medicine, clinical applications, and pharmaceutical development. They are used in cancer treatment, wound debridement, contact lens cleaning, prion degradation, biofilm removal, and fibrinolytic agents. Proteases are also crucial in cardiovascular disease treatment, emphasizing the need for safe, affordable, and effective fibrinolytic drugs. Proteolytic enzymes and protease biosensors are increasingly used in diagnostic and therapeutic applications. Advanced technologies, such as nanomaterials-based sensors, are being developed to enhance the sensitivity, specificity, and versatility of protease biosensors. These biosensors are becoming effective tools for disease detection due to their precision and rapidity. They can detect extracellular and intracellular proteases, as well as fluorescence-based methods for real-time and label-free detection of virus-related proteases. The active utilization of proteolytic enzymatic biosensors is expected to expand significantly in biomedical research, in-vitro model systems, and drug development. We focused on journal articles and books published in English between 1982 and 2024 for this study.

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.

Design, synthesis and biological evaluation of novel indole-3-carboxylic acid derivatives with antihypertensive activity

Molecular design, synthesis, in vitro and in vivo studies of novel derivatives of indole-3-carboxylic acid - new series of angiotensin II receptor 1 antagonists is presented. Radioligand binding studies using [¹²⁵I]-angiotensin II displayed that new derivatives of indole-3-carboxylic acid have a high nanomolar affinity for the angiotensin II receptor (AT₁ subtype) on a par with the known pharmaceuticals such as losartan. Biological studies of synthesized compounds in spontaneously hypertensive rats have demonstrated that compounds can lower blood pressure when administered orally. Maximum the decrease in blood pressure was 48 mm Hg with oral administration of 10 mg/kg and antihypertensive effect was observed for 24 hours, which is superior to losartan.

Proteolytic Biosensors with Functional Nanomaterials: Current Approaches and Future Challenges

Proteolytic enzymes are one of the important biomarkers that enable the early diagnosis of several diseases, such as cancers. A specific proteolytic enzyme selectively degrades a certain sequence of a polypeptide. Therefore, a particular proteolytic enzyme can be selectively quantified by changing detectable signals causing degradation of the peptide chain. In addition, by combining polypeptides with various functional nanomaterials, proteolytic enzymes can be measured more sensitively and rapidly. In this paper, proteolytic enzymes that can be measured using a polypeptide degradation method are reviewed and recently studied functional nanomaterials-based proteolytic biosensors are discussed. We anticipate that the proteolytic nanobiosensors addressed in this review will provide valuable information on physiological changes from a cellular level for individual and early diagnosis.

Tracking the concentration of Al3+ in the aqueous system up to nanomolar range using modified biopolymer chitosan based fluorophore

The paper reports the development of biopolymer chitosan based fluorophore for selective detection of Al3+ in aqueous streams. Fluorescence sensing based on the change in the photophysical properties of the...

Small-molecule fluorescent probes based on covalent assembly strategy for chemoselective bioimaging

In this review, we comprehensively summarize the recent progress in the development of small molecular fluorescent probes based on the covalent assembly principle. The challenges and perspective in this field are also presented.

"Covalent-Assembly"-Triggered Striking Far-Red to near-Infrared Emitting Fluorescent Probe for Abrupt Detection of Nerve-Agent Mimic (DCP): Real Time Application in Monitoring the Presence of Trace Amounts in Soil and Live Cells

Detection of chemical warfare agents (CWA) by simple and rapid methods with real-sample applications are quite inevitable in order to ease the threats to living systems caused by uncertain terror attacks and wars. Herein we have developed the first far-red to near infra-red (NIR) probe based on a covalent assembly approach for the detection of trace amounts of nerve agent mimic diethyl chloro phosphate (DCP) in soil and their fluorescent bio imaging in live cells. The probe features abrupt fluorescence turn on sensing of DCP with fluorescence quantum yield Φ = 0.622. It senses DCP selectively over other analytes in excellent sensitivity with a detection limit of 6.9 nM. In real time, the probe treated strips were employed to detect the DCP vapor effectively with eye catching fluorescence response. The presence of trace amounts of these acute warfare agents in the environment were monitored by soil analysis. Further fluorescent bio imaging was carried out to monitor trace level DCP in living cells using the HeLa cell line.

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.

Fluorescent Determination of Butyrylcholinesterase Activity and Its Application in Biological Imaging and Pesticide Residue Detection

Butyrylcholinesterase (BChE) is an essential human cholinesterase relevant to liver conditions and neurodegenerative diseases, which makes it a pivotal biomarker of health. It therefore remains challenging and highly desired to elaborate efficient chemical tools for BChE with simple operations and satisfactory working performance. In this work, a background-free detection strategy was built by virtue of the judicious coupling of a specific BChE-enzymatic reaction and in situ cyclization. High sensitivity with a low limit of detection (LOD) of 0.075 μg/mL could be readily achieved from the blank background and the as-produced emissive indicators, and the specific reaction site contributed to the high selectivity over other bio-species even acetylcholinesterase (AChE). In addition to the multifaceted spectral experiments to verify the sensing mechanism, this work assumed comprehensive studies on the application. The bio-investigation ranged from cells to an organism, declaring a noteworthy prospect in disease diagnosis, especially for Alzheimer's disease (AD), a common neurodegenerative disease with over-expressed BChE. Moreover, its excellent work for inhibition efficacy elucidation was also proved with the accuracy IC₅₀ of tacrine for BChE (8.6 nM), giving rise to an expanded application for trace pesticide determination.

Fluorogenic Enzyme-Triggered Domino Reactions Producing Quinoxalin-2(1H)-one-based Heterocycles

A simple and effective biocompatible domino reaction triggered by a model protease and leading to the formation of strongly fluorescent quinoxalin-2(1H)-one N-heterocycles is described. Some positive attributes including versatility and the ability to provide outstanding fluorescence "OFF-ON" responses were revealed by this work. They open the way for practical applications of this novel type of "covalent-assembly"-based fluorescent probe in the fields of sensing and bioimaging.

Evaluation of a GSH-targeting prodrug via a sulfonamide-induced "integrative" platform for selective cancer therapy

A sulfonamide-appended gemcitabine prodrug was newly produced. The prodrug was shown to efficiently distinguish GSH from cysteine and homocysteine. Upon reaction of this prodrug with GSH, which is relatively abundant in tumor cells, sulfonyl group cleavage occurred as well as active release of the drug GMC and a concomitant increase in the innate fluorescence intensity. As a proof of concept, colocalization experiments were carried out; these experiments demonstrated that the probe LHX resulted in, via receptor-mediated endocytosis, significantly improved therapeutic efficacy and few side effects. Thus, these results indicated the theranostic agent to be a promising "integrative" platform for efficient cancer therapy. The agent can be activated in real time, and not only be selectively monitored and localized by specific tumour cells, but also undergo cascaded cleavage to induce both a fluorogenic response and release of an active cytotoxic drug.

Molecular probe designviathe “covalent-assembly” principle

Fluorescent probes are useful molecular tools. We summarize the recent progress with the “covalent-assembly” design principle, which warrants high-performance fluorescence probes exhibiting a highly sensitive turn-on signal from the dark background.

Chromogenic agents built around a multifunctional double-triazine framework for enzymatically triggered cross-linking under physiological conditions

A molecular architecture designed for bioconjugation and internal absorption ratiometry undergoes enzymatically triggered cleavage of glucosyl groups and subsequent oxidative dimerization in aqueous solution to yield indigoid-containing scaffolds.