Imaging Tumorous Methylglyoxal by an Activatable Near-Infrared Fluorescent Probe for Monitoring Glyoxalase 1 Activity

Electroacupuncture Facilitates Vascular Normalization by Inhibiting Glyoxalase1 in Endothelial Cells to Attenuate Glycolysis and Angiogenesis in Triple-Negative Breast Cancer

Recent therapeutic strategies for the treatment of triple-negative breast cancer (TNBC) have shifted the focus from vascular growth factors to endothelial cell metabolism. This study highlights the underexplored therapeutic potential of peri-tumoral electroacupuncture, a globally accepted non-pharmacological intervention for TNBC, and molecular mechanisms. Our study showed that peri-tumoral electroacupuncture effectively reduced the density of microvasculature and enhanced vascular functionality in 4T1 breast cancer xenografts, with optimal effects on day 3 post-acupuncture. The timely integration of peri-tumoral electroacupuncture amplified the anti-tumor efficacy of paclitaxel. Multi-omics analysis revealed Glyoxalase 1 (Glo1) and the associated methylglyoxal-glycolytic pathway as key mediators of electroacupuncture-induced vascular normalization. Peri-tumoral electroacupuncture notably reduced Glo1 expression in the endothelial cells of 4T1 xenografts. Using an in vivo matrigel plug angiogenesis assay, we demonstrated that either Glo1 knockdown or electroacupuncture inhibited angiogenesis. In contrast, Glo1 overexpression increased blood vessel formation. In vitro pharmacological inhibition and genetic knockdown of Glo1 in human umbilical vein endothelial cells inhibited proliferation and promoted apoptosis via downregulating the methylglyoxal-glycolytic pathway. The study using the Glo1-silenced zebrafish model further supported the role of Glo1 in vascular development. This study underscores the pivotal role of Glo1 in peri-tumoral electroacupuncture, spotlighting a promising avenue for enhancing vascular normalization and improving TNBC treatment outcomes.

Activatable probes with potential for intraoperative tumor-specific fluorescence-imaging guided surgery

Owing to societal development and aging population, the impact of cancer on human health and quality of life has increased. Early detection and surgical treatment are the most effective approaches for most cancer patients. As the scope of conventional tumor resection is determined by auxiliary examination and surgeon experience, there is often insufficient recognition of tiny tumors. The ability to detect such tumors can be improved by using fluorescent tumor-specific probes for surgical navigation. This review mainly describes the design principles and mechanisms of activatable probes for the fluorescence imaging of tumors. This type of probe is nonfluorescent in normal tissue but exhibits obvious fluorescence emission upon encountering tumor-specific substrates, such as enzymes or bioactive molecules, or changes in the microenvironment, such as a low pH. In some cases, a single-factor response does not guarantee the effective fluorescence labeling of tumors. Therefore, two-factor-activatable fluorescence imaging probes that react with two specific factors in tumor cells have also been developed. Compared with single biomarker testing, the simultaneous monitoring of multiple biomarkers may provide additional insight into the role of these substances in cancer development and aid in improving the accuracy of early cancer diagnosis. Research and progress in this field can provide new methods for precision medicine and targeted therapy. The development of new approaches for early diagnosis and treatment can effectively improve the prognosis of cancer patients and help enhance their quality of life.

Recent progress of oxidative stress associated biomarker detection

Oxidative stress denotes the imbalance between the generation of reactive oxygen species (ROS) and antioxidant defenses in living organisms, participating in various pathophysiological processes and mediating the occurrence of diseases. Typically, the excessive production of ROS under oxidative stress elicits oxidative modification of biomacromolecules, including lipids, proteins and nucleic acids, leading to cell dysfunction and damage. Therefore, the analysis and detection of oxidative stress-associated biomarkers are of considerable importance to accurately reflect and evaluate the oxidative stress status. This review comprehensively elucidates the recent advances and applications of imaging probes for tracking and detecting oxidative stress-related biomarkers such as lipid peroxidation, and protein and DNA oxidation. The existing challenges and future development directions in this field are also discussed.

Rapid sensing and imaging of methylglyoxal in living cells enabled by a near-infrared fluorescent probe

A novel near-infrared fluorescent probe (SWJT-2) has been designed and synthesized for the detection of methylglyoxal (MGO). It showed a low detection limit (0.32 μM), high selectivity and the fastest detection (15 min) over various reactive carbonyl compounds in aqueous solution. SWJT-2 had been successfully applied to bioimaging in HeLa cells to detect exogenous and endogenous MGO.

Mitochondria-targeted fluorescent probe for visualization of exogenous and endogenous methylglyoxal in living cells

An activatable mitochondria-targeted fluorescent probe Hcy-OPD was synthesized for the detection of methylglyoxal (MGO). For the introduction of a preorganized isopropylamino group on the aromatic o-diamine framework to regulate the hindrance effect, Hcy-OPD showed high selectivity and sensitivity (0.22 μM) for monitoring MGO. The probe can be applied successfully in the imaging of exogenous and endogenous MGO in living cells.

A Ratiometric Fluorescence Probe for Selective Detection of ex vivo Methylglyoxal in Diabetic Mice

Accurate monitoring of methylglyoxal (MGO) at cell and living level was crucial to reveal its role in the pathogenesis of diabetes since MGO was closely related to diabetes. Herein, a ratiometric fluorescence strategy was constructed based on the capture probe 2,3-diaminonaphthalene (DAN) for the specific detection of MGO. Compared to the fluorescent probes with a single emission wavelength, the ratiometric mode by monitoring two emissions can effectively avoid the interference from the biological background, and provided additional self-calibration ability, which can realize accurate detection of MGO. The proposed method showed a good linear relationship in the range of 0-75 μm for MGO detection, and the limit of detection was 0.33 μm. DAN responded to MGO with good specificity and was successfully applied for detecting the ex vivo MGO level in plasma of KK-Ay mice as a type II diabetes model. Besides, the prepared DAN test strip can be visualized for rapid semi-quantitative analysis of MGO using the naked eye. Furthermore, human skin fibroblasts and HeLa cells were utilized for exogenous MGO imaging, and ex vivo MGO imaging was performed on tissues of KK-Ay mice. All results indicated that the DAN-based ratiometric fluorescence probe can be used as a potential method to detect the level of MGO, thus enabling indications for the occurrence of diabetes and its complications.

Activity-based fluorescent probes for sensing and imaging of Reactive Carbonyl species (RCSs)

This review explains various strategies for developing fluorescent probes to detect reactive carbonyl species (RCS). There are sevaral number of mono and diacarbonyls among 30 varieties of reactive carbonyl species (RCSs) so far discovered, which play pivotal roles in pathological processes such as cancer, neurodegenerative diseases, cardiovascular disease, renal failure, and diabetes mellitus. These RCSs play essential roles in maintaining ion channels regulation, cellular signaling pathways, and metabolisms. Among RCSs, Carbon moxide (CO) is also utilized for its cardioprotective, anti-inflammatory, and anti-apoptotic effects. Fluorescence-based non-invasive optical tools have come out as one of the promising methods for analyzing the concentrations and co-localizations of these small metabolites. There has been a tremendous eruption in developing fluorescent probes for selective detection of specific RCSs within cellular and aqueous environments due to its high sensitivity, high spatial and temporal resolution of fluorescence imaging. Fluorescence-based sensing mechanisms such as intramolecular charge transfer (ICT), photoinduced electron transfer (PeT), excited-state intramolecular proton transfer (ESIPT), and fluorescence resonance energy transfer (FRET) are described. In particular, probes for dicarbonyls such as methylglyoxal (MGO), malondialdehyde (MDA), along with monocarbonyls that include formaldehyde (FA), carbon monoxide (CO) and phosgene are discussed. One of the most exciting advances in this review is the summary of fluorescent probes of dicarbonyl compounds.

NIR-I fluorescence imaging tumorous methylglyoxal by an activatable nanoprobe based on peptide nanotubes by FRET process

Methylglyoxal (MGO), a glycolysis metabolite with high reactivity, can nonenzymatically modify proteins, lipids and nucleic acids etc., and it is closely related to the development of tumors. The accurate detection and high-performance optical imaging of MGO from deep tumor issues is of great significance for understanding their roles in tumor initiation and progression. Herein, we have presented a nanoprobe D/I-PNTs with emission in the first near infrared (NIR-I) region by employing a fluorescence resonance energy transfer (FRET) process between a far-red emission MGO probe and IR783 based on peptide nanotubes. The nanoplatform extended the emission range of MGO probe through FRET process and avoided complex molecular design and synthesis. The biocompatible peptide nanotubes improved the water solubility of MGO probe. D/I-PNTs was sensitive to MGO with a detection limit of 272 nM and enabled high-resolution NIR-I fluorescence imaging of MGO induced by glyoxalase I (GLO1) inhibitor in tumor with higher penetration depth (∼4 mm) than that in visible (Vis) region (∼3 mm). Most importantly, the FRET process based on the structure characteristics of peptide nanotubes can be a universal approach to realize the extension of emission wavelength and ratio detection of target analytes, which will be a promising strategy for bioimaging in deep tissue with high contrast.

Design of an activatable NIR-II nanoprobe for the in vivo elucidation of Alzheimer's disease-related variations in methylglyoxal concentrations

A biocompatible Fe3O4 nanoparticle integrating methylglyoxal-activatable NIR-II fluorescent probe and brain-targeting peptide was developed for visualizing Alzheimer's disease (AD)-related methylglyoxal variation in vivo.

A photostable reaction-based A-A-A type two-photon fluorescent probe for rapid detection and imaging of sulfur dioxide

In this study, a novel reaction-based A-A-A (acceptor-acceptor-acceptor) type two-photon fluorescent probe, BTC, is prepared using the benzothiadiazole (BTD) scaffold as the two-photon fluorophore and electron-accepting centre. Two β-chlorovinyl aldehyde moieties are symmetrically connected to both ends of the BTD scaffold and act as reaction groups to recognize SO2 and quenching groups to make the dis-activated probe stay at off-state due to their weak electron-withdrawing effect. In the presence of SO2 derivatives, the aldehyde groups are consumed through aldehyde addition, resulting in the activation of intramolecular charge transfer (ICT) processes and therefore recovering the fluorescence of the probe. The designed probe shows excellent two-photon properties including large two-photon absorption cross-sections (TPA) of 91 GM and photostability. Beyond these, the BTC probe exhibits a fast response to SO2 within 30 s, high specificity without foreign interference and a broad detection range from 500 nM to 120 μM with a detection limit of 190 nM. The designed fluorescent probe is further applied to the two-photon imaging of exogenous and endogenous SO2 derivatives under different physiological processes in HeLa cells and zebrafish with satisfactory results. We believe that the proposed design strategy can be extended to fabricate versatile BTD-based two-photon fluorescent probes through molecular engineering for further applications in bioassays and two-photon imaging.

Monodisperse functionalized GO for high-performance sensing and bioimaging of Cu2+ through synergistic enhancement effect

The metal ion fluorescence probes based on chemical reactions triggered by specific metal ions is characterized by high selectivity. However, they are also subject to inherent limitations, such as easy aggregation under water solution, poor optical stability, and long response time. In order to solve these problems, a simple and effective method was studied. The specific design is as follows. Fluorescence probe RACD is assembled onto a single layer graphene oxide (GO) via π-π interaction and hydrogen bonding to prepare RACD functionlized graphene oxide RACD/GO. The experimental results show that the resulting RACD/GO possesses very well monodispersion, hydrophilicity and photostability, particularly reduce the aggregation degree of RACD owing to π-π effect. Simultaneously, it was found that due to the strong synergy between GO and RACD, the response time, selectivity, anti-interference ability, detection sensitivity, detection limit and bioimaging ability of RACD/GO were significantly improved compared with RACD. The resulting RACD/GO not only possesses very well photostability, multiple repeated cycles, but also have been triumphantly put into the monitoring Cu²⁺ of environmental water, sewage, cells and zebrafish specimens in practice. The detection limit is as low as 1.76 nM, and the correlation coefficient is 0.9998.

A red-emissive D-A-D type fluorescent probe for lysosomal pH imaging

Visual detection of pH changes in lysosomes is critical because lysosomes not only play an important role in diverse cellular functions but also are closely related to various physiological and pathological processes. Herein, we disclose a donor-acceptor-donor (D-A-D) type fluorescent probe DBTD for detecting pH fluctuation in lysosomes. DBTD was rationally designed by using benzothiadiazole as the electron acceptor and N,N-diethylamino groups as the electron donor. Owing to its unique D-A-D structure, DBTD displayed a red-emission centered at 614 nm. It showed a sensitive and a linear response to pH from 4.5 to 5.2 with a pKa of 5.0, which is very suitable for lysosomal pH imaging. The response was based on the intramolecular charge transfer (ICT) effect owing to the protonation of the diethylamino group. Furthermore, DBTD could accurately monitor lysosomal pH variations in SGC-7901 cells. More importantly, it was able to image the pH change in lysosomes during the autophagy process successfully, suggesting the great potential of DBTD acting as a powerful tool for monitoring lysosomal pH-related biological processes.