Rational design of matrix metalloproteinase-13 activatable probes for enhanced specificity

Fluorescent probes for visualizing ROS-associated proteins in disease

Abnormal expression of proteins, including catalytic and expression dysfunction, is directly related to the development of various diseases in living organisms. Reactive oxygen species (ROS) could regulate protein expression by redox modification or cellular signal pathway and thus influence the development of disease. Determining the expression level and activity of these ROS-associated proteins is of considerable importance in early-stage disease diagnosis and the identification of new drug targets. Fluorescence imaging technology has emerged as a powerful tool for specific in situ imaging of target proteins by virtue of its non-invasiveness, high sensitivity and good spatiotemporal resolution. In this review, we summarize advances made in the past decade for the design of fluorescent probes that have contributed to tracking ROS-associated proteins in disease. We envision that this review will attract significant attention from a wide range of researchers in their utilization of fluorescent probes for in situ investigation of pathological processes synergistically regulated by both ROS and proteins.

Near-Infrared Fluorescent Probes for the Detection of Cancer-Associated Proteases

Proteases are enzymes capable of catalyzing protein breakdown, which is critical across many biological processes. There are several families of proteases, each of which perform key functions through the degradation of specific proteins. As our understanding of cancer improves, it has been demonstrated that several proteases can be overactivated during the progression of cancer and contribute to malignancy. Optical imaging systems that employ near-infrared (NIR) fluorescent probes to detect protease activity offer clinical promise, both for early detection of cancer as well as for the assessment of personalized therapy. In this Review, we review the design of NIR probes and their successful application for the detection of different cancer-associated proteases.

Optical Detection of Distal Lung Enzyme Activity in Human Inflammatory Lung Disease

Objective and Impact Statement. There is a need to develop platforms delineating inflammatory biology of the distal human lung. We describe a platform technology approach to detect in situ enzyme activity and observe drug inhibition in the distal human lung using a combination of matrix metalloproteinase (MMP) optical reporters, fibered confocal fluorescence microscopy (FCFM), and a bespoke delivery device. Introduction. The development of new therapeutic agents is hindered by the lack of in vivo in situ experimental methodologies that can rapidly evaluate the biological activity or drug-target engagement in patients. Methods. We optimised a novel highly quenched optical molecular reporter of enzyme activity (FIB One) and developed a translational pathway for in-human assessment. Results. We demonstrate the specificity for matrix metalloproteases (MMPs) 2, 9, and 13 and probe dequenching within physiological levels of MMPs and feasibility of imaging within whole lung models in preclinical settings. Subsequently, in a first-in-human exploratory experimental medicine study of patients with fibroproliferative lung disease, we demonstrate, through FCFM, the MMP activity in the alveolar space measured through FIB One fluorescence increase (with pharmacological inhibition). Conclusion. This translational in situ approach enables a new methodology to demonstrate active drug target effects of the distal lung and consequently may inform therapeutic drug development pathways.

Biosensors and bioassays for determination of matrix metalloproteinases: state of the art and recent advances

Matrix metalloproteinases (MMPs) are closely associated with various physiological and pathological processes, and have been regarded as potential biomarkers for severe diseases including cancer. Accurate determination of MMPs would advance our understanding of their roles in disease progression, and is of great significance for disease diagnosis, treatment and prognosis. In this review, we present a comprehensive overview of the developed bioassays/biosensors for detection of MMPs, and highlight the recent advancement in nanomaterial-based immunoassays for MMP abundance measurements and nanomaterial-based biosensors for MMP activity determination. Enzyme-linked immunosorbent assay (ELISA)-based immunoassays provide information about total levels of MMPs with high specificity and sensitivity, while target-based biosensors measure the amounts of active MMPs, and allow imaging of MMP activities in vivo. For multiplex and high-throughput analysis of MMPs, microfluidics and microarray-based assays are described. Additionally, we put forward the existing challenges and future prospects from our perspective.

Fluorine-18-Labeled Fluorescent Dyes for Dual-Mode Molecular Imaging

Recent progress realized in the development of optical imaging (OPI) probes and devices has made this technique more and more affordable for imaging studies and fluorescence-guided surgery procedures. However, this imaging modality still suffers from a low depth of penetration, thus limiting its use to shallow tissues or endoscopy-based procedures. In contrast, positron emission tomography (PET) presents a high depth of penetration and the resulting signal is less attenuated, allowing for imaging in-depth tissues. Thus, association of these imaging techniques has the potential to push back the limits of each single modality. Recently, several research groups have been involved in the development of radiolabeled fluorophores with the aim of affording dual-mode PET/OPI probes used in preclinical imaging studies of diverse pathological conditions such as cancer, Alzheimer's disease, or cardiovascular diseases. Among all the available PET-active radionuclides, 18F stands out as the most widely used for clinical imaging thanks to its advantageous characteristics (t1/2 = 109.77 min; 97% β+ emitter). This review focuses on the recent efforts in the synthesis and radiofluorination of fluorescent scaffolds such as 4,4-difluoro-4-bora-diazaindacenes (BODIPYs), cyanines, and xanthene derivatives and their use in preclinical imaging studies using both PET and OPI technologies.

Targeting of an antecedent proteinase by an activatable probe with deep tissue penetration facilitates early visualization and dynamic malignancy evaluation of orthotopic pancreatic ductal adenocarcinoma (PDAC)

Pancreatic ductal adenocarcinoma (PDAC) is highly lethal and most commonly diagnosed at an advanced stage; therefore, early detection with an effective approach is vital. However, due to the anatomical stealthiness and hypovascular features of PDAC, clinically available imaging techniques lack specificity and sensitivity for early detection. As important components of the tumour microenvironment, elevated matrix metalloproteinase (MMP) levels during the early stages of tumour formation lead to tumour invasion and metastases by degrading the extracellular matrix. Thus, in the current study, we hypothesized that MMPs might be promising markers for early visualization and prognosis evaluation of PDAC. An MMP activatable probe, I₇₈₀BP-PEG12, was synthesized utilizing a long wavelength near-infrared (NIR) fluorophore that could map the dynamic development of orthotopic PDAC in vivo with deep tissue penetration. Elevated MMP activity in tumours was detected as early as 4 days after tumour transplantation. At that time, the tumour diameter was approximately 3 mm, which is much smaller than the size visualized by clinical approaches. Furthermore, much higher levels of MMP activity were detected in PDAC under diabetic conditions, which promote the malignant actions of tumours. By noninvasively monitoring MMP alteration, tumour growth, and prognostic evaluation, we found that malignant actions under diabetic conditions were reversed by inhibition of MMPs. Generally, in addition to earlier visualization of PDAC, a probe targeting MMPs can facilitate dynamic monitoring of tumour progression and inhibitory treatment in vivo, which is beneficial for personal therapeutic strategy planning and optimization of PDAC management, especially for diabetic individuals.

Fluorogenic probes for disease-relevant enzymes

Traditional biochemical methods for enzyme detection are mainly based on antibody-based immunoassays, which lack the ability to monitor the spatiotemporal distribution and, in particular, the in situ activity of enzymes in live cells and in vivo. In this review, we comprehensively summarize recent progress that has been made in the development of small-molecule as well as material-based fluorogenic probes for sensitive detection of the activities of enzymes that are related to a number of human diseases. The principles utilized to design these probes as well as their applications are reviewed. Specific attention is given to fluorogenic probes that have been developed for analysis of the activities of enzymes including oxidases and reductases, those that act on biomacromolecules including DNAs, proteins/peptides/amino acids, carbohydrates and lipids, and those that are responsible for translational modifications. We envision that this review will serve as an ideal reference for practitioners as well as beginners in relevant research fields.

Enzymatically activated reduction-caged SERS reporters for versatile bioassays

Here we report a facile strategy for activating reduction caged Raman reporters for surface-enhanced Raman scattering (SERS) with peroxidases. After selecting suitable caged reporters, versatile bioassays were developed. First, the bioassays for bioactive small molecules were developed. Then, the immunoassay was developed for C reactive protein (CRP), a biomarker for cardiovascular diseases.

Highly Selective Red-Emitting Fluorescent Probe for Imaging Cancer Cells in Situ by Targeting Pim-1 Kinase

Based on the fact that enzyme-targeting probes are highly sensitive and selective, a novel red-emitting probe (NB-BF) for Pim-1 kinase including three parts, fluorophore (NB), linker, and inhibitor (BF), has been designed for cancer optical imaging. In its free state, NB-BF is folded and the fluorescence quenched by PET between fluorophore and inhibitor both in PBS buffer and in normal cells. Significantly, it emitted strong red fluorescence in Pim-1 overexpressed cancer cells. The specificity of NB-BF for Pim-1 kinase was directly demonstrated by gene silencing analysis. Furthermore, it is the first time to know where Pim-1 kinase mainly distributes at mitochondria with Pearson's correlation factor (R_r) of 0.965 and to provide a fluorescent tool to verify the function of the Pim-1 kinase. More importantly, NB-BF was applied in tissue imaging and preferentially labeled tumors in vivo.

Recent progresses in small-molecule enzymatic fluorescent probes for cancer imaging

An overview of recent advances in small-molecule enzymatic fluorescent probes for cancer imaging, including design strategies and cancer imaging applications.

Functional ferritin nanoparticles for biomedical applications

Ferritin, a major iron storage protein with a hollow interior cavity, has been reported recently to play many important roles in biomedical and bioengineering applications. Owing to the unique architecture and surface properties, ferritin nanoparticles offer favorable characteristics and can be either genetically or chemically modified to impart functionalities to their surfaces, and therapeutics or probes can be encapsulated in their interiors by controlled and reversible assembly/disassembly. There has been an outburst of interest regarding the employment of functional ferritin nanoparticles in nanomedicine. This review will highlight the recent advances in ferritin nanoparticles for drug delivery, bioassay, and molecular imaging with a particular focus on their biomedical applications.

Role of P38 MAPK on MMP Activity in Photothrombotic Stroke Mice as Measured using an Ultrafast MMP Activatable Probe

Matrix metalloproteinases (MMPs) exert a dual effect in ischemic stroke and thus represent an ideal target for detection and therapy. However, to date, all clinical trials of MMP inhibitors have failed, and alternative drug candidates and therapeutic targets are urgently required. Nonetheless, further investigations are limited by the lack of non-invasive imaging techniques. Here, we report a novel, fast and ultrasensitive MMP activatable optical imaging probe for the dynamic visualization of MMP activity in photothrombotic stroke mice. This probe provides a significant signal enhancement in as little as 15 min, with the highest signal intensity occurring at 1 h post-injection, and shows high sensitivity in measuring MMP activity alterations, which makes it specifically suitable for the real-time visualization of MMP activity and drug discovery in preclinical research. Moreover, using this probe, we successfully demonstrate that the regulation of the p38 mitogen-activated protein kinase (MAPK) signal pathway is capable of modulating MMP activity after stroke, revealing a novel regulatory mechanism of postischemic brain damage and overcoming the limitations of traditional therapeutic strategies associated with MMP inhibitors by using a non-invasive molecular imaging method.

Enzyme-Specific Doxorubicin Drug Beacon as Drug-Resistant Theranostic Molecular Probes

We report here on the use of anticancer drug doxorubicin (Dox) to construct a Förster resonance energy transfer (FRET)-based theranostic molecular probe by covalently linking together through a lysine junction a fluorescent drug, a black hole quencher, and a cell-penetrating peptide. We show that upon cleavage by the target lysosomal protease cathepsin B (CatB) the designed drug beacon could release the fluorescent drug serving as an indicator for CatB. Our cell studies suggest that the drug-beacon design can help to circumvent the Dox drug resistance in NCI/ADR-Res ovarian cancer cells, showing significant improvement in cell cytotoxicity compared to the free drug. We believe our design opens up new opportunities to exploit the new functional and structural features of anticancer drugs in addition to their characteristic cytotoxicity.

Bioresponsive probes for molecular imaging: concepts and in vivo applications

Molecular imaging is a powerful tool to visualize and characterize biological processes at the cellular and molecular level in vivo. In most molecular imaging approaches, probes are used to bind to disease-specific biomarkers highlighting disease target sites. In recent years, a new subset of molecular imaging probes, known as bioresponsive molecular probes, has been developed. These probes generally benefit from signal enhancement at the site of interaction with its target. There are mainly two classes of bioresponsive imaging probes. The first class consists of probes that show direct activation of the imaging label (from "off" to "on" state) and have been applied in optical imaging and magnetic resonance imaging (MRI). The other class consists of probes that show specific retention of the imaging label at the site of target interaction and these probes have found application in all different imaging modalities, including photoacoustic imaging and nuclear imaging. In this review, we present a comprehensive overview of bioresponsive imaging probes in order to discuss the various molecular imaging strategies. The focus of the present article is the rationale behind the design of bioresponsive molecular imaging probes and their potential in vivo application for the detection of endogenous molecular targets in pathologies such as cancer and cardiovascular disease.

A Nile blue based infrared fluorescent probe: imaging tumors that over-express cyclooxygenase-2

The free Niblue-C6-IMC exists in a folded conformation where fluorescence is quenched, and when it binds to COX-2 in the Golgi apparatus of cancer cells, it is forced to adopt the unfolded state, and then fluorescence is turned on. Niblue-C6-IMC was proved to specifically target COX-2 by native polyacrylamide gel electrophoresis analysis.

Activatable hyaluronic acid nanoparticle as a theranostic agent for optical/photoacoustic image-guided photothermal therapy

Photothermal therapy (PTT) is an emerging treatment modality that is under intensive preclinical investigations for the treatment of various medical conditions, including cancer. However, the lack of targeting function of PTT agents hampers its clinical application. An effective and nontoxic delivery vehicle that can carry PTT agents into tumor areas is still needed urgently. In this study, we developed a multifunctional nanocomposite by loading copper sulfide (CuS) into Cy5.5-conjugated hyaluronic acid nanoparticles (HANP), obtaining an activatable Cy5.5-HANP/CuS (HANPC) nanocomposite. In this system, Cy5.5 fluorescent signal is quenched by CuS inside the particle until the whole nanocomposite is degraded by hyaluronidase present in tumor, giving strong fluorescence signals delineating the tumor. Importantly, CuS with strong NIR absorbance appears to be an excellent contrast agent for photoacoustic (PA) imaging and an effective PTT agent. After intravenous administration of HANPC into SCC7 tumor-bearing mice, high fluorescence and PA signals were observed in the tumor area over time, which peaked at the 6 h time point (tumor-to-normal tissue ratio of 3.25±0.25 for optical imaging and 3.8±0.42 for PA imaging). The tumors were then irradiated with a laser, and a good tumor inhibition rate (89.74% on day 5) was observed. Our studies further encourage application of this HA-based multifunctional nanocomposite for image-guided PTT in biomedical applications, especially in cancer theranostics.

Monitoring the biomolecular interactions and the activity of Zn-containing enzymes involved in conformational diseases: experimental methods for therapeutic purposes

Zinc metalloproteases (ZnMPs) participate in diverse biological reactions, encompassing the synthesis and degradation of all the major metabolites in living organisms. In particular, ZnMPs have been recognized to play a very important role in controlling the concentration level of several peptides and/or proteins whose homeostasis has to be finely regulated for the correct physiology of cells. Dyshomeostasis of aggregation-prone proteins causes pathological conditions and the development of several different diseases. For this reason, in recent years, many analytical approaches have been applied for studying the interaction between ZnMPs and their substrates/inhibitors and how environmental factors can affect enzyme activities. In this scenario, nuclear magnetic resonance, X-ray diffraction, mass spectrometric (MS), and optical methods occupy a very important role in elucidating different aspects of the ZnMPs-substrates/inhibitors interaction, ranging from identification of cleavage sites to quantitation of kinetic parameters and inhibition constants. Here, an overview of all the main achievements in the application of different experimental approaches with special attention to MS methods to the investigation of ZnMPs-substrates/inhibitors interaction is given. A general MS experimental protocol which has been proved to be useful to study such interactions is also described.