High-fidelity fluorescent probes for visualizing the inhibitory behavior of selenium on cadmium uptake in rice

Recent Advances in Fluorescent Probe for Detecting Biorelevant Analytes during Stress in Plants

Plants are constantly exposed to various stressors that can severely hinder their growth and threaten agricultural productivity. Recent advancements in plant imaging using fluorescent probes have opened new avenues for exploring the intricate processes involved in plant stress perception and signaling. This review represents the comprehensive effort to consolidate recent advances in fluorescent probe technologies, encompassing small-molecule probes, nanoprobes, and genetically encoded indicators, as revolutionary tools for deciphering stress-induced physiological dynamics. We present a comprehensive classification of fluorescent probes designed for detecting key biomolecules involved in plant stress responses, including reactive species, phytohormones, enzymes, and other signaling molecules. By critically evaluating their design principles, practical applications, and distinct advantages over conventional analytical methods, we aim to empower plant scientists in unraveling the spatiotemporal regulation of stress signaling networks. Finally, we propose strategic directions to overcome current technical bottlenecks and maximize the potential of fluorescence-based sensing in advancing sustainable agriculture.

In situ images of Cd2+ in rice reveal Cd2+ protective mechanism using DNAzyme fluorescent probe

As a common pollutant, cadmium (Cd) poses a serious threat to the growth and development of plants. Currently, there is no effective method to elucidate the protective mechanism of Cd2+ in plant cells. For the first time, we designed a Cd2+ fluorescent probe to observe the adsorption and sequestration of Cd2+ in rice cell walls and vacuoles. Specifically, Cd2+ is blocked by the Casparian strip and electrostatically attracted to hemicellulose, which is abundantly adsorbed and fixed to the cell walls of the endodermis. For Cd2+ that successfully entered the endodermis, one part entered the cells and was compartmentalised and fixed in the vacuoles, while the other part entered the vascular bundles and precipitated in the cell walls of the sclerenchyma through the ion exchange effect. Furthermore, with prolonged exposure to Cd2+, compartmentalised bodies that were strongly labelled by fluorescence gradually appeared in the vacuoles, which were assumed to be a new heavy metal protective mechanism activated by plants in response to continuous Cd2+ exposure. In conclusion, this study provides an innovative and effective method for the detection of adsorption, transportation, and accumulation of Cd2+ in plant tissues, which can be employed for the rapid identification of crops with low Cd accumulation.

A Ratiometric Fluorescence Probe for Visualized Detection of Heavy Metal Cadmium and Application in Water Samples and Living Cells

Heavy metal cadmium (II) residuals have inflicted severe damage to human health and ecosystems. It has become imperative to devise straightforward and highly selective sensing methods for the detection of Cd2+. In this work, a ratiometric benzothiazole-based fluorescence probe (BQFA) was effortlessly synthesized and characterized using standard optical techniques for the visual detection of Cd2+ with a change in color from blue to green, exhibiting a significant Stokes shift. Moreover, the binding ratio of BQFA to Cd2+ was established as 1:1 by the Job's plot and was further confirmed by FT-IR and 1HNMR titrations. The ratiometric fluorescence response via the ICT mechanism was confirmed by DFT calculations. Furthermore, the limit of detection for detecting Cd2+ was determined to be 68 nM. Furthermore, it is noteworthy that BQFA showed good performance in real water samples, paper strips, smartphone colorimetric identification, and cell imaging.

Near-infrared fluorescent probe to track Cys in plant roots under heavy metal hazards and its application in cells and zebrafish

Heavy metals, including Hg2+, Cr6+ and Cd2+, have always been a major issue in environmental pollution, leading to abnormal changes in the levels of biologically active molecules including Cys in plants, seriously affecting all aspects of the growth and development of plants. This makes it essential to develop a simple and practical method to study the potential impact of heavy metals on plants. In this paper, our research group has developed near-infrared fluorescent probe WRM-S, which has the advantages of fast response, sensitivity to Cys, and successfully applying it to cells and zebrafish. Moreover, it combined the close relationship between heavy metal stress on plants and Cys, using Cys as the detection target, monitoring the internal environment changes of two plants under Hg2+, Cr6+, and Cd2+ stress in the environment, and then conducting 3D imaging. The results indicated that the probe has strong penetration ability in plant tissues, and revealed abnormal changes in plant Cys levels caused by heavy metal stress-induced cellular oxidative stress or cytotoxicity. Thus, the in-situ imaging detection of this probe provides a direction for the physiological dynamics research of plant environmental stress.

A remote-controlled portable workstation for highly sensitive and real-time chemiluminescent detection of cadmium

The prevention of pollution requires real-time monitoring of cadmium (Cd2+) concentration in the food, as it has a dramatic impact on poultry and can pose a threat to human health. Here, we fabricate a portable workstation integrating a microfluidic chip that facilitates real-time monitoring of Cd2+ levels in real samples by utilizing the Luminol-KMnO4 chemiluminescence (CL) system. Interestingly, Cd2+ can significantly enhance the CL signal, resulting in sensitive detection of Cd2+ in the range of 0-0.18 mg/L with the limit of detection (LOD) of 0.207 μg/L. Furthermore, a remote-controlled unit is integrated into the portable workstation to form a remote-controlled portable workstation (RCPW) performing automated point-of-care testing (POCT) of Cd2+. The as-prepared strategy allows remote control of RCPW to avoid long-distance transportation of samples to achieve real-time target monitoring. Consequently, this system furnishes RCPW for monitoring Cd2+ levels in real samples, thereby holding potential for applications in preventing food pollution.

Dual-recognition "turn-off-on" fluorescent Biosensor triphenylamine-based continuous detection of copper ion and glyphosate applicated in environment and living system

Heavy metal Cu2+ emitted in industry and residues of glyphosate pesticides are pervasive in ecosystems, accumulated in water bodies and organisms' overtime, constituting hazard to human and ecological balance. The development of rapid, highly selective, reversibility and sensitive biosensor in vivo detection for Cu2+ and glyphosate was imminent. A novel dual-recognition fluorescence biosensor MPH was successfully synthesized based on triphenylamine, which demonstrated remarkable ratiometric fluorescence quenching toward Cu2+, while MPH-Cu2+ (1:1) ensemble exhibited ratiometric fluorescence restoration for glyphosate, both with observable color changes in daylight and UV lamp. The biosensor exhibited rapid, outstanding selectivity, anti-interference, and multiple cycles reversibility through "turn-off-on" fluorescence towards Cu2+ and glyphosate, respectively. Surprisingly, the clearly binding mechanisms of MPH to Cu2+ and MPH-Cu2+ ensemble to glyphosate were determined, respectively, based on the Job's plot, FT-IR, ESI-HRMS, 1H NMR titration and theoretical calculations of dynamics and thermodynamics. In addition, biosensor MPH demonstrated successful detection of Cu2+ and glyphosate across diverse environmental samples including tap water, extraction solutions of traditional Chinese medicine honeysuckle and soil samples. In the meantime, fluorescence imaging of Cu2+ and glyphosate at both micro and macro scales in various living organisms, such as rice roots, MCF-7 cells, zebrafish, and mice, were successfully achieved. Overall, this work was expected to become a promising and versatile fluorescence biosensor for rapid and reversible detection of Cu2+ and glyphosate both in vitro and vivo.

Imaging gastrointestinal damage due to acute mercury poisoning using a mitochondria-targeted dual near-infrared fluorescent probe

Mercury (Hg) is one of the most widespread pollutants that pose serious threats to public health and the environment. People are inevitably exposed to Hg via different routes, such as respiration, dermal contact, drinking or diet. Hg poisoning could cause gingivitis, inflammation, vomiting and diarrhea, respiratory distress or even death. Especially during the developmental stage, there is considerable harm to the brain development of young children, causing serious symptoms such as intellectual disability and motor impairments, and delayed neural development. Therefore, it's of great significance to develop a specific, quick, practical and labor-saving assay for monitoring Hg2+. Herein, a mitochondria-targeted dual (excitation 700 nm and emission 728 nm) near-infrared (NIR) fluorescent probe JZ-1 was synthesized to detect Hg2+, which is a turn-on fluorescent probe designed based on the rhodamine fluorophore thiolactone, with advantages of swift response, great selectivity, and robust anti-interference capability. Cell fluorescence imaging results showed that JZ-1 could selectively target mitochondria in HeLa cells and monitor exogenous Hg2+. More importantly, JZ-1 has been successfully used to monitor gastrointestinal damage of acute mercury poisoning in a drug-induced mouse model, which provided a great method for sensing Hg species in living subjects, as well as for prenatal diagnosis.

Molecular engineering of a new method for effective removal of cadmium from water

Cadmium (Cd) is a widespread and highly toxic environmental pollutant, seriously threatening animal and plant growth. Therefore, monitoring and employing robust tools to enrich and remove Cd from the environment is a major challenge. In this work, by conjugating a fluorescent indicator (CCP) with a functionalized glass slide, a special composite material (CCPB) was constructed to enrich, remove, and monitor Cd2+ in water rapidly. Then Cd2+ could be effectively eluted by immersing the Cd-enriched CCPB in an ethylenediaminetetraacetic acid (EDTA) solution. With this, the CCPB was continuously reused. Its recovery of Cd2+was above and below 100 % after multiple uses by flame atomic absorption spectrometry (FAAS), which was excellent for practical use in enriching and removing Cd2+ in real aqueous samples. Therefore, CCPB is an ideal material for monitoring, enriching, and removing Cd2+ in wastewater, providing a robust tool for future practical applications of Cd enrichment and removal in the environment.

Dual-channel versatile molecular sensing platform for individual and successive HClO and H2S detection: Applicable in toxic alerts of environmental samples and living organisms

In this study, we have successfully developed a novel dual-response fluorescent probe, NACou, designed for the visual and quantitative detection of HClO/H2S in real water samples and liquid beverages by a thin-film sensing platform. Additionally, NACou demonstrated efficacy for sensing HClO/H2S in HeLa cells, plants and zebrafish through distinct fluorescent channels, yielding satisfactory results. NACou exhibited a multi-modal fluorescence response mechanism for detecting HClO and H2S with remarkable low detection limits of 27.8 nM and 34.4 nM, accompanied by outstanding fluorescent enhancement (209-fold and 148-fold, respectively). These advantages position NACou as a potent molecular tool for HClO and H2S sensing. The specific recognition performance of NACou towards HClO/H2S were confirmed through fluorescence spectroscopy, mass analysis and UV-vis spectroscopy. Importantly, the thin-film sensing platform with the visible fluorescence change can enable rapid assays for water quality and food safety monitoring, showcasing significant practical application value. Impressively, NACou has been employed in warning against liver injury induced by multiple drugs, allowing for the exploration of the pathogenesis and degree of drug-induced injury.

Fluorescence probes evaluated the hydrogen peroxide level in rice roots under cadmium ion stress

Abiotic stress and oxidative stress are closely related to the health status of plants. Plants will produce oxidative stress under abiotic stress, induce mitochondrial dysfunction, cause programmed cell death, and decrease plant survival rate. It is well known that rice is an essential crop for humans, but its cadmium tolerance is poor. Therefore, it is crucial to determine whether cadmium stress causes oxidative stress in rice in order to guide rice cultivation. Hydrogen peroxide (H2O2), a highly reactive oxygen species (ROS), is one of the most critical signals in corps under oxidative stress. In this work, we adopted a near-infrared (NIR) H2O2 fluorescent probe YFE-1 and a cadmium ion (Cd2+) fluorescent probe SCP to observe the fluctuation of H2O2 in rice roots under Cd2+ co-incubation conditions. Due to the advantages of fast response (within 2 min), a large Stokes shift (181 nm), good selectivity, and a low detection limit (LOD:26.4 nM), YFE-1 achieved the visualization of H2O2 produced by Cd2+ stress in rice roots. This study provides a new idea for assessing the risk of oxidative stress of Cd2+ in rice roots. It is expected to guide the control of Cd2+ in the rice planting industry to improve rice yield.