Chromo-fluorogenic probes for β-galactosidase detection

A novel NIR fluorescent probe for enhanced β-galactosidase detection and tumor imaging in ovarian cancer models

The advancement of biological imaging techniques critically depends on the development of novel near-infrared (NIR) fluorescent probes. In this study, we introduce a designed NIR fluorescent probe, NRO-βgal, which exhibits a unique off-on response mechanism to β-galactosidase (β-gal). Emitting a fluorescence peak at a wavelength of 670 nm, NRO-βgal showcases a significant Stokes shift of 85 nm, which is indicative of its efficient energy transfer and minimized background interference. The probe achieves a remarkably low in vitro detection limit of 0.2 U/L and demonstrates a rapid response within 10 min, thereby underscoring its exceptional sensitivity, selectivity, and operational swiftness. Such superior analytical performance broadens the horizon for its application in intricate biological imaging studies. To validate the practical utility of NRO-βgal in bio-imaging, we employed ovarian cancer cell and mouse models, where the probe's efficacy in accurately delineating tumor cells was examined. The results affirm NRO-βgal's capability to provide sharp, high-contrast images of tumor regions, thereby significantly enhancing the precision of surgical tumor resection. Furthermore, the probe's potential for real-time monitoring of enzymatic activity in living tissues underscores its utility as a powerful tool for diagnostics in oncology and beyond.

A novel AIE-based mitochondria-targeting fluorescent probe for monitoring of the fluctuation of endogenous hypochlorous acid in ferroptosis models

Ferroptosis is a way of cell death mainly due to the imbalance between the production and degradation of lipid reactive oxygen species, which is closely associated with various diseases. Endogenous hypochlorous acid (HOCl) mainly produced in mitochondria is regarded as an important signal molecule of ferroptosis. Therefore, monitoring the fluctuation of endogenous HOCl is beneficial to better understand and treat ferroptosis-related diseases. Inspired by the promising aggregation-induced emission (AIE) properties of tetraphenylethene (TPE), herein, we rationally constructed a novel AIE-based fluorescent probe, namely QTrPEP, for HOCl with nice mitochondria-targeting ability and high sensitivity and selectivity. Probe QTrPEP consisted of phenylborate ester and the AIE fluorophore of quinoline-conjugated triphenylethylene (QTrPE). HOCl can brighten the strong fluorescence through a specific HOCl-triggered cleavage of the phenylborate ester bond and release of QTrPE, which has been demonstrated by MS, HPLC, and DLS experiments. In addition, combining QTrPE-doped test strips with a smartphone-based measurement demonstrated the excellent performance of the probe to sense HOCl. The obtained favorable optical properties and negligible cytotoxicity allowed the use of this probe for tracking of HOCl in three different cells. In particular, this work represents the first AIE-based mitochondria-targeting fluorescent probe for monitoring the fluctuation of HOCl in ferroptosis.

Revolutionizing Senescence Detection: Advancements from Traditional Methods to Cutting-Edge Techniques

The accumulation of senescent cells is an important factor in the complex progression of aging, with significant implications for the development of numerous diseases. Thus, understanding the fundamental mechanisms of senescence is paramount for advancing preventive and therapeutic approaches to age-related conditions. Important to this pursuit is the precise identification and examination of senescent cells, contingent upon the recognition of specific biomarkers. Historically, detection methods relied on assessing molecular protein and mRNA levels and various staining techniques. While these conventional approaches have contributed substantially to the field, they possess limitations in capturing the dynamic evolution of cellular aging in real time. The emergence of novel technologies has led to a paradigm shift in senescence research. Gene-edited mouse models and the application of advanced probes have revolutionized our ability to detect senescent cells. These cutting-edge methodologies provide a more detailed and accurate means of dynamically monitoring, characterizing and potentially eliminating senescent cells, thus enhancing our understanding of the complex mechanisms of aging. This review comprehensively explores both traditional and innovative senescent cell detection methods, elucidating their advantages, limitations and implications for future investigations and could serve as a comprehensive guide and catalyst for further advancements in the understanding of aging and associated pathologies.

Cancerous Conditions Accelerate the Aging of Skeletal Muscle via Mitochondrial DNA Damage

Skeletal muscle aging and sarcopenia result in similar changes in the levels of aging markers. However, few studies have examined cancer sarcopenia from the perspective of aging. Therefore, this study investigated aging in cancer sarcopenia and explored its causes in vitro and in vivo. In mouse aging, in vitro cachexia, and mouse cachexia models, skeletal muscles showed similar changes in aging markers including oxidative stress, fibrosis, reduced muscle differentiation potential, and telomere shortening. Furthermore, examination of mitochondrial DNA from skeletal muscle revealed a 5 kb deletion in the major arc; truncation of complexes I, IV, and V in the electron transport chain; and reduced oxidative phosphorylation (OXPHOS). The mouse cachexia model demonstrated high levels of high-mobility group box-1 (HMGB1) and tumor necrosis factor-α (TNFα) in cancer ascites. Continuous administration of neutralizing antibodies against HMGB1 and TNFα in this model reduced oxidative stress and abrogated mitochondrial DNA deletion. These results suggest that in cancer sarcopenia, mitochondrial oxidative stress caused by inflammatory cytokines leads to mitochondrial DNA damage, which in turn leads to decreased OXPHOS and the promotion of aging.

Chemical Strategies for the Detection and Elimination of Senescent Cells

Cellular senescence can be defined as an irreversible stopping of cell proliferation that arises in response to various stress signals. Cellular senescence is involved in diverse physiological and pathological processes in different tissues, exerting effects on processes as differentiated as embryogenesis, tissue repair and remodeling, cancer, aging, and tissue fibrosis. In addition, the development of some pathologies, aging, cancer, and other age-related diseases has been related to senescent cell accumulation. Due to the complexity of the senescence phenotype, targeting senescent cells is not trivial, is challenging, and is especially relevant for in vivo detection in age-related diseases and tissue samples. Despite the elimination of senescent cells (senolysis) using specific drugs (senolytics) that have been shown to be effective in numerous preclinical disease models, the clinical translation is still limited due to the off-target effects of current senolytics and associated toxicities. Therefore, the development of new chemical strategies aimed at detecting and eliminating senescent cells for the prevention and selective treatment of senescence-associated diseases is of great interest. Such strategies not only will contribute to a deeper understanding of this rapidly evolving field but also will delineate and inspire new possibilities for future research.In this Account, we report our recent research in the development of new chemical approaches for the detection and elimination of senescent cells based on new probes, nanoparticles, and prodrugs. The designed systems take advantage of the over-representation in senescent cells of certain biomarkers such as β-galactosidase and lipofuscin. One- and two-photon probes, for higher tissue penetration, have been developed. Moreover, we also present a renal clearable fluorogenic probe for the in vivo detection of the β-galactosidase activity, allowing for correlation with the senescent burden in living animals. Moreover, as an alternative to molecular-based probes, we also developed nanoparticles for senescence detection. Besides, we describe advances in new therapeutic agents to selectively eradicate senescent cells using β-galactosidase activity-sensitive gated nanoparticles loaded with cytotoxic or senolytic agents or new prodrugs aiming to increase the selectivity and reduction of off-target toxicities of current drugs. Moreover, new advances therapies have been applied in vitro and in vivo. Studies with the probes, nanoparticles, and prodrugs have been applied in several in vitro and in vivo models of cancer, fibrosis, aging, and drug-induced cardiotoxicity in which senescence plays an important role. We discuss the benefits of these chemical strategies toward the development of more specific and sophisticated probes, nanoparticles, and prodrugs targeting senescent cells.

Novel PET Imaging Probe for Quantitative Detection of Senescence In Vivo

Real-time detection of cellular senescence remains a clinical challenge. Here, we aimed to develop a positron emission tomography (PET) imaging probe targeting senescence-associated β-galactosidase (SA-β-Gal), the most widely used biomarker of cellular senescence, and investigate its performance for real-time in vivo quantitative detection of cellular senescence. A stable PET imaging agent [68Ga]Ga-BGal was obtained with a high labeling yield (90.0 ± 4.3%) and a radiochemical purity (>95%). [68Ga]Ga-BGal displayed high sensitivity and specificity for β-Gal both in vitro and in vivo. The reaction and uptake of the probe correlated with the β-Gal concentration and reaction time. In PET imaging, high β-Gal-expressing CT26.CL25 tumors and doxorubicin-treated HeLa tumors showed high signals from [68Ga]Ga-BGal, while a low signal was observed in CT26.WT and untreated HeLa tumors. In summary, we showcased successful PET imaging of senescence in preclinical models using probe [68Ga]Ga-BGal. This finding holds the potential for translating senescence imaging into clinical applications.

A renal clearable fluorogenic probe for in vivo β-galactosidase activity detection during aging and senolysis

Accumulation of senescent cells with age leads to tissue dysfunction and related diseases. Their detection in vivo still constitutes a challenge in aging research. We describe the generation of a fluorogenic probe (sulfonic-Cy7Gal) based on a galactose derivative, to serve as substrate for β-galactosidase, conjugated to a Cy7 fluorophore modified with sulfonic groups to enhance its ability to diffuse. When administered to male or female mice, β-galactosidase cleaves the O-glycosidic bond, releasing the fluorophore that is ultimately excreted by the kidneys and can be measured in urine. The intensity of the recovered fluorophore reliably reflects an experimentally controlled load of cellular senescence and correlates with age-associated anxiety during aging and senolytic treatment. Interestingly, our findings with the probe indicate that the effects of senolysis are temporary if the treatment is discontinued. Our strategy may serve as a basis for developing fluorogenic platforms designed for easy longitudinal monitoring of enzymatic activities in biofluids.

Detection and Elimination of Senescent Cells with a Self-Assembled Senescence-Associated β-Galactosidase-Activatable Nanophotosensitizer

Senescent cells have become an important therapeutic target for many age-related dysfunctions and diseases. We report herein a novel nanophotosensitizing system that is responsive to the senescence-associated β-galactosidase (β-gal) for selective detection and elimination of these cells. It involves a dimeric zinc(II) phthalocyanine linked to a β-galactose unit via a self-immolative linker. This compound can self-assemble in aqueous media, forming stable nanoscale particles in which the phthalocyanine units are stacked and self-quenched for fluorescence emission and singlet oxygen production. Upon internalization into senescent HeLa cells, these nanoparticles interact with the overproduced senescence-associated β-gal inside the cells to trigger the disassembly process through enzymatic cleavage of the glycosidic bonds, followed by self-immolation to release the photoactive monomeric phthalocyanine units. These senescent cells can then be lit up with fluorescence and eliminated through the photodynamic action upon light irradiation with a half-maximal inhibitory concentration of 0.06 μM.

Fidelity-oriented fluorescence imaging probes for beta-galactosidase: From accurate diagnosis to precise treatment

Beta-galactosidase (β-gal), a typical glycosidase catalyzing the hydrolysis of glycosidic bonds, is regarded as a vital biomarker for cell senescence and cancer occurrence. Given the advantages of high spatiotemporal resolution, high sensitivity, non-invasiveness, and being free of ionizing radiations, fluorescent imaging technology provides an excellent choice for in vivo imaging of β-gal. In this review, we detail the representative biotech advances of fluorescence imaging probes for β-gal bearing diverse fidelity-oriented improvements to elucidate their future potential in preclinical research and clinical application. Next, we propose the comprehensive design strategies of imaging probes for β-gal with respect of high fidelity. Considering the systematic implementation approaches, a range of high-fidelity imaging-guided theragnostic are adopted for the individual β-gal-associated biological scenarios. Finally, current challenges and future trends are proposed to promote the next development of imaging agents for individual and specific application scenarios.

An Overview of the Public Health Challenges in Diagnosing and Controlling Human Foodborne Pathogens

Pathogens found in food are believed to be the leading cause of foodborne illnesses; and they are considered a serious problem with global ramifications. During the last few decades, a lot of attention has been paid to determining the microorganisms that cause foodborne illnesses and developing new methods to identify them. Foodborne pathogen identification technologies have evolved rapidly over the last few decades, with the newer technologies focusing on immunoassays, genome-wide approaches, biosensors, and mass spectrometry as the primary methods of identification. Bacteriophages (phages), probiotics and prebiotics were known to have the ability to combat bacterial diseases since the turn of the 20th century. A primary focus of phage use was the development of medical therapies; however, its use quickly expanded to other applications in biotechnology and industry. A similar argument can be made with regards to the food safety industry, as diseases directly endanger the health of customers. Recently, a lot of attention has been paid to bacteriophages, probiotics and prebiotics most likely due to the exhaustion of traditional antibiotics. Reviewing a variety of current quick identification techniques is the purpose of this study. Using these techniques, we are able to quickly identify foodborne pathogenic bacteria, which forms the basis for future research advances. A review of recent studies on the use of phages, probiotics and prebiotics as a means of combating significant foodborne diseases is also presented. Furthermore, we discussed the advantages of using phages as well as the challenges they face, especially given their prevalent application in food safety.

Lipofuscin labeling through biorthogonal strain-promoted azide-alkyne cycloaddition for the detection of senescent cells

A new method for senescent cell detection is described, which is based on lipofuscin labeling with a fluorescent reporter through a biorthogonal strain-promoted azide-alkyne cycloaddition. The sensing protocol involves a first step where the interaction of lipofuscin with a Sudan Black B derivative containing an azide moiety (SBB-N₃ ) is carried out. In the final step, the azide moiety reacts with a fluorophore containing a cyclooctene ring (BODIPY). The efficacy of this two-step protocol is assessed in senescent melanoma SK-MEL-103 cells, senescent triple-negative breast cancer MDA-MB-231 cells and senescent WI-38 fibroblasts. In all cases, a clear fluorescence pattern was observed in senescent cells, compared to proliferative cells, only when the SBB-N₃ -BODIPY probe was formed. Our results provide an alternative tool for the detection of senescent cells, based on an in situ bio-orthogonal reaction for lipofuscin labeling.

Dual-Parameter Recognition-Directed Design of the Activatable Fluorescence Probe for Precise Imaging of Cellular Senescence

Specific imaging of cellular senescence emerges as a promising strategy for early diagnosis and treatment of various age-related diseases. The currently available imaging probes are routinely designed by targeting a single senescence-related marker. However, the inherently high heterogeneity of senescence makes them inaccessible to achieve specific and accurate detection of broad-spectrum cellular senescence. Here, we report the design of a dual-parameter recognition fluorescent probe for precise imaging of cellular senescence. This probe remains silent in non-senescent cells, yet produces bright fluorescence after sequential responses to two senescence-associated markers, namely, SA-β-gal and MAO-A. In-depth studies reveal that this probe allows for high-contrast imaging of senescence, independent of the cell source or stress type. More impressively, such dual-parameter recognition design further allows it to distinguish senescence-associated SA-β-gal/MAO-A from cancer-related β-gal/MAO-A, compared to commercial or previous single-marker detection probes. This study offers a valuable molecular tool for imaging cellular senescence, which is expected to significantly expand the basic studies on senescence and facilitate advances of senescence-related disease theranostics.

Dualplex lateral flow assay for simultaneous scopolamine and "cannibal drug" detection based on receptor-gated mesoporous nanoparticles

We report herein the design of a strip-based rapid test utilizing bio-inspired hybrid nanomaterials for the in situ and at site detection of the drug scopolamine (SCP) using a smartphone for readout, allowing SCP identification in diluted saliva down to 40 nM in less than 15 min. For this purpose, we prepared a nanosensor based on mesoporous silica nanoparticles loaded with a fluorescent reporter (rhodamine B) and functionalized with bethanechol, a potent agonist of recombinant human muscarinic acetylcholine receptor M₂ (M₂-AChR). M₂-AChR interaction with the anchored bethanechol derivative leads to capping of the pores. The sensing mechanism relies on binding of SCP to M₂-AChR resulting in pore opening and delivery of the entrapped rhodamine B reporter. Moreover, the material was incorporated into strips for lateral-flow assays coupled to smartphone readout, giving fast response time, good selectivity, and exceptional sensitivity. In an attempt to a mobile analytical test system for law enforcement services, we have also developed a dualplex lateral flow assay for SCP and 3,4-methylenedioxypyrovalerone (MDPV) also known as the so-called "cannibal drug".

Current Scenario of Pathogen Detection Techniques in Agro-Food Sector

Over the past-decade, agricultural products (such as vegetables and fruits) have been reported as the major vehicles for foodborne diseases, which are limiting food resources. The spread of infectious diseases due to foodborne pathogens poses a global threat to human health and the economy. The accurate and timely detection of infectious disease and of causative pathogens is crucial in the prevention and treatment of disease. Negligence in the detection of pathogenic substances can be catastrophic and lead to a pandemic. Despite the revolution in health diagnostics, much attention has been paid to the agro-food sector regarding the detection of food contaminants (such as pathogens). The conventional analytical techniques for pathogen detection are reliable and still in operation. However, laborious procedures and time-consuming detection via these approaches emphasize the need for simple, easy-to-use, and affordable detection techniques. The rapid detection of pathogens from food is essential to avoid the morbidity and mortality originating from the suboptimal nature of empiric pathogen treatment. This review critically discusses both the conventional and emerging bio-molecular approaches for pathogen detection in agro-food.

Developing a far-red fluorogenic beta-galactosidase probe for senescent cell imaging and photoablation

A methylene blue (MB)-based beta-galactosidase (β-gal) activatable molecule, Gal-MB, was developed for senescence imaging and light-triggered senolysis. When in contact with LacZ β-gal or senescence-associated β-gal (SA-β-gal), the photoinsensitive Gal-MB becomes fluorescent. Gal-MB also offered selective phototoxicity toward LacZ β-gal expressing cells and drug-induced senescent cells, which express SA-β-gal, after light illumination at 665 nm.

A methylene blue (MB)-based beta-galactosidase (β-gal) activatable molecule, Gal-MB, was developed for senescence imaging and light-triggered senolysis.

Gene-Directed Enzyme Prodrug Therapy by Dendrimer-Like Mesoporous Silica Nanoparticles against Tumor Cells

We report herein a gene-directed enzyme prodrug therapy (GDEPT) system using gated mesoporous silica nanoparticles (MSNs) in an attempt to combine the reduction of side effects characteristic of GDEPT with improved pharmacokinetics promoted by gated MSNs. The system consists of the transfection of cancer cells with a plasmid controlled by the cytomegalovirus promoter, which promotes β-galactosidase (β-gal) expression from the bacterial gene lacZ (CMV-lacZ). Moreover, dendrimer-like mesoporous silica nanoparticles (DMSNs) are loaded with the prodrug doxorubicin modified with a galactose unit through a self-immolative group (DOXO-Gal) and modified with a disulfide-containing polyethyleneglycol gatekeeper. Once in tumor cells, the reducing environment induces disulfide bond rupture in the gatekeeper with the subsequent DOXO-Gal delivery, which is enzymatically converted by β-gal into the cytotoxic doxorubicin drug, causing cell death. The combined treatment of the pair enzyme/DMSNs-prodrug are more effective in killing cells than the free prodrug DOXO-Gal alone in cells transfected with β-gal.

Exploring the utility of Au@PVP-polyamide-Triton X-114 for SERS tracking of extracellular senescence associated-beta-galactosidase activity

A compound with enrichment and SERS enhancement was successfully developed, which could rapidly adsorb X-gal hydrolysates from a liquid matrix in 5 minutes and further be used for SERS analysis with a detection limit of less than 1 × 10-9 mol L-1. This novel strategy will facilitate the development of an analytical approach for cellular senescence.