Imaging Of Enzymatic Activity Research Articles

Recent Advancement in Fluorescent Probes for Sensing and Imaging Tyrosinase Activity in Living Cells

Tyrosinase, a multi-copper oxidase enzyme, is widely distributed in different organisms and plays a vital role in the melanogenesis and enzymatic browning in fruits and vegetables. An abnormal level of tyrosinase in the living system is often associated with different kinds of skin diseases including albinism, vitiligo, skin hyperpigmentation etc. Moreover, overexpressed tyrosinase has become a prognostic biomarker for melanoma. Therefore early detection of tyrosinase activity both in vivo and in vitro has a potential diagnostic and therapeutic application. Small-molecule fluorescent probes have become a powerful device over the traditional biochemical method for the detection and imaging of enzymatic activities in biological systems by virtue of their superior sensitivity, nondestructive fast analysis, spatiotemporal resolution and real-time detection abilities. Moreover, due to their structural tunability, several small-molecule fluorescent probes have been developed to meet various aspects such as enhancing sensitivity, selectivity, cell permeability, real-time monitoring and easy imaging in biological systems. This review article sums up the recent progress of small-molecules fluorescent probes for tyrosinase activity, including their synthesis strategies, mechanistic paths and potential applications based on reports mainly in the past five years. The rapid advancement in this field suggests that fluorescence detection and imaging is a promising technology and widen up new horizons for early diagnosis of melanoma.

Recent advances in stimuli-responsive in situ self-assembly of small molecule probes for in vivo imaging of enzymatic activity.

Stimuli-responsive in situ self-assembly of small molecule probes into nanostructures has been promising for the construction of molecular probes for in vivo imaging. In the past few years, a number of intelligent molecular imaging probes with fluorescence, magnetic resonance imaging (MRI), positron electron tomography (PET) or photoacoustic imaging (PA) modality have been developed based on the in situ self-assembly strategy. In this minireview, we summarize the recent advances in the development of different modality imaging probes through controlling in situ self-assembly for in vivo imaging of enzymatic activity. This review starts from the brief introduction of two different chemical approaches amenable for in situ self-assembly, including (1) stimuli-mediated proteolysis and (2) stimuli-triggered biocompatible reaction. We then discuss their applications in the design of fluorescence, MRI, PET, PA, and bimodality imaging probes for in vivo imaging of different enzymes, such as caspase-3, furin, gelatinase and phosphatase. Finally, we discuss the current and prospective challenges in the stimuli-responsive in situ self-assembly strategy for in vivo imaging.

19F MRI Nanoprobes for the Turn-On Detection of Phospholipase A2 with a Low Background.

The highly sensitive detection and imaging of enzymatic activities in vivo could provide effective information about biological functions for monitoring the process of disease and evaluating the effect of therapy. 19F magnetic resonance imaging (MRI) has attracted wide interest because of its deep tissue imaging capability and negligible endogenous background interference, which are suitable for the visualization of enzymatic activities in vivo, but the fabrication of this probe faces challenges. Here, we report nanoprobes with turn-on 19F MRI for sensing the activity of phospholipase A2 (PLA2). These nanoprobes are composed of Gd3+-exchanged NaYF4:Yb3+/Er3+ upconversion luminescent nanoparticles grafted with perfluoro-15-crown-5-ether (PFCE) as the hydrophobic core with a phospholipid shell in which the 19F MRI signal of PFCE is obviously quenched by adjacent Gd3+. The shielded 19F MRI signal of these nanoprobes is then turned on by the nanoprobe dissolution stemming from phospholipid hydrolysis by PLA2 and increases linearly along with the increment of PLA2 in the range of 5.0-200 U/L. Apart from the in vitro detection of PLA2 by 19F NMR, these nanoprobes show great potential for both the in vivo 19F MRI sensing of PLA2 and activity screening of PLA2 inhibitors with a high signal-to-noise ratio and a high penetration depth.

Light emission enhancement by supramolecular complexation of chemiluminescence probes designed for bioimaging.

Chemiluminescence offers advantages over fluorescence for bioimaging, since an external light source is unnecessary with chemiluminescent agents. This report demonstrates the first encapsulation of chemiluminescence phenoxy-adamantyl-1,2-dioxetane probes with trimethyl β-cyclodextrin. Clear proof for the formation of a 1 : 1 host-guest complex between the adamantyl-1,2-dioxetane probe and trimethyl β-cyclodextrin was provided by mass spectroscopy and NMR experiments. The calculated association constant of this host-guest system, 253 M-1, indicates the formation of a stable inclusion complex. The inclusion complex significantly amplified the light emission intensity relative to the noncomplexed probe under physiological conditions. Complexation of adamantyl-dioxetane with fluorogenic dye-tethered cyclodextrin resulted in light emission through energy transfer to a wavelength that corresponds to the fluorescent emission of the conjugated dye. Remarkably, the light emission intensity of this inclusion complex was approximately 1500-fold higher than that of the non-complexed adamantyl-dioxetane guest. We present the first demonstration of microscopic cell images obtained using a chemiluminescence supramolecular dioxetane probe and demonstrate the utility of these supramolecular complexes by imaging of enzymatic activity and bio-analytes in vitro and in vivo. We anticipate that the described chemiluminescence supramolecular dioxetane probes will find use in various biological applications.

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

Abnormal enzymatic activities are directly related to the development of cancers. Identifying the location and expression levels of these enzymes in live cancer cells have considerable importance in early-stage cancer diagnoses and monitoring the efficacy of therapies. Small-molecule fluorescent probes have become a powerful tool for the detection and imaging of enzymatic activities in biological systems by virtue of their higher sensitivity, nondestructive fast analysis, and real-time detection abilities. Moreover, due to their structural tailorability, numerous small-molecule enzymatic fluorescent probes have been developed to meet various demands involving real-time tracking and visualizing different enzymes in live cancer cells or in vivo. In this review, we provide an overview of recent advances in small-molecule enzymatic fluorescent probes mainly during the past decade, including the design strategies and applications for various enzymes in live cancer cells. We also highlight the challenges and opportunities in this rapidly developing field of small-molecule fluorescent probes for interventional surgical imaging, as well as cancer diagnosis and therapy.

FRET Imaging of Enzymatic Activities Using Smart Probes.

Tumor-related enzymes are extensively involved in the occurrence, development, invasion, and metastasis of tumors, indicating they hold the potential to serve as biomarkers for tumor diagnosis and treatment. Smart probes based on characteristic activities of these enzymes and fluorescence resonance energy transfer (FRET) have been widely developed for fluorescent imaging of enzymatic activities. Here, we describe the detailed chemical strategies for construction of smart probe and its application for FRET imaging of fibroblast activation protein alpha in vitro and in vivo.

Imaging of enzymatic activities in living cells

Imaging of enzymatic activities in living cells