A Hg(II)-specific probe for imaging application in living systems and quantitative analysis in environmental/food samples

A shikimic acid derived carbon dots (SACNDs-FITC) for multi-modal detection and removal of Hg2+: Probe design, sensing performance, and applications in food analysis

The first shikimic acid derived fluorescent carbon dots (SACNDs-FITC) for multi-modal detection and simultaneous removal of Hg2+ is revealed. The fluorescence of SACNDs-FITC centered at 520 nm can be selectively quenched by Hg2+, while the emission centered at 420 nm remains constant which can be used for self-calibration. Naked-eye distinguishable color change from yellow to colourless under daylight and from green to blue under UV light could be observed for SACNDs-FITC in the real-time detection of Hg2+. Novel approaches that combine smartphone automated color hue (RGB and HSV) readout for intelligent Hg2+ analysis was developed. Moreover, SACNDs-FITC could work as an effective absorbent for Hg2+ with an adsorption capacity of 19.24 mg/g. Mechanism studies revealed the success of the post-modification strategy and the crucial role of -NCSN- groups in detecting and adsorbing Hg2+. Most importantly, multi-modal analysis of Hg2+ in celery cabbage and apples was performed using this analytical platform.

Visualization of Hg2+ Stress on Plant Health at the Subcellular Level Revealed by a Highly Sensitive Fluorescent Sensor

The presence of Hg2+ causes substantial stress to plants, adversely affecting growth and health by disrupting cell cycle divisions, photosynthesis, and ionic homeostasis. Accurate visualization of the spatiotemporal distribution of Hg2+ in plant tissues is crucial for the management of Hg pollution; however, the related research is still at its early stage. Herein, a small-molecule amphiphilic fluorescent probe (termed LJTP2) was developed for the specific detection of Hg2+ with a high sensitivity (~16 nM). Fluorescent imaging applications with LJTP2 not only detected the dynamic distribution of Hg2+ within plant cells at the subcellular level but also enabled the understanding of cell membrane health under Hg2+ stress. This study introduces a valuable imaging tool for elucidating the molecular mechanism of Hg2+ stress in plants, demonstrating the potential of the application of small-molecule fluorescent probes in plant science.

Near-infrared fluorescent probe visual detection of Hg2+ and its application in biological system and ecological system

Mercury ion (Hg2+), a heavy metal cation with greater toxicity, is widely present in the ecological environment and has become a serious threat to human health and environmental safety. Currently, developing a solution to simultaneously visualize and monitor Hg2+ in environmental samples, including water, soil, and plants, remains a great challenge. In this work, we created and synthesized a near-infrared fluorescent probe, BBN-Hg, and utilized Hg2+ to trigger the partial cleavage of the carbon sulfate ester in BBN-Hg as a sensing mechanism, and the fluorescence intensity of BBN-Hg was significantly enhanced at 650 nm, thus realizing the visualization of Hg2+ with good selectivity (detection limit, 53 nM). In live cells and zebrafish, the probe BBN-Hg enhances the red fluorescence signal in the presence of Hg2+, and successfully performs 3D imaging on zebrafish, making it a powerful tool for detecting Hg2+ in living systems. More importantly, with BBN-Hg, we are able to detect Hg2+ in actual water samples, soil and plant seedling roots. Furthermore, the probe was prepared as a test strip for on-site determination of Hg2+ with the assistance of a smartphone. Therefore, this study offers an easy-to-use and useful method for tracking Hg2+ levels in living organisms and their surroundings.

Accurate and rapid mercury susceptibility detection in aquatic samples using fluorescent probe integrated rhodamine with pyridyl isothiocyanate

Mercury, one of the various harmful metals, is particularly significant in affecting aquatic organisms, currently gaining more attentions and sparking discussions. In response to the limitations of traditional detections, fluorescent probes have emerged as a promising solution with some advantages, such as weaker background interference, shorter processing time, higher accuracy. Thus, a novel fluorescent probe, FS-Hg-1, has been developed for assessing mercury ion (Hg2+) concentrations in aquatic products. This probe displays specific recognition of mercury ions in fluorescence spectra. Notably, FS-Hg-1 exhibits a distinct color change to pink when combined with Hg2+ (with a 948-fold increase in absorption at 568 nm) and a substantial fluorescence change towards Hg2+ (361-fold increase, excitation at 562 nm, emission at 594 nm) in N, N-dimethylformamide. The probe boasts a detection limit of 0.14 μM and rapid reaction with Hg2+ within 10 s, showing an excellent linear correlation with [Hg2+] in the range of 0 to 10 μM. Through thorough analysis using FS-Hg-1, the results align with those from the standard method (P > 0.05), with spiked recovery rates ranging from 108.4% to 113.2%. With its precise recognition, low detection limit, and remarkable sensitivity, this fluorescent assay proves effective in mercury concentration determination in aquatic samples without interference. The potential of FS-Hg-1 is promising for speedy detection of residual Hg2+ and holds significance in ensuring food safety.

Fluorescent polymers for environmental monitoring: Targeting pathogens and metal contaminants with naphthalimide derivatives

Monitoring Hg2+ levels in aqueous environments is crucial to assess the potential methylmercury contamination via bacterial conversion, however, existing methods often require extensive sample treatment and expensive equipment. To mitigate this issue, this study examines the synthesis and application of three naphthalimide-based compounds, with significant fluorescent and solvatochromic behavior (C1, C2, and C3). Compounds C1 and C2 demonstrated a strong affinity for Hg2+ metal ions, with C2 showing selectivity and a strong antibacterial profile, particularly against S. aureus (MIC50 (C2) = 0.01 µg/mL). Moreover, these compounds were incorporated into three polymeric matrices, namely polyvinyl chloride (PVC), poly (methyl methacrylate-co-methacrylic acid) (PMMMA), and Starch, allowing for the development of solid-support sensors/surfaces with a strong antibacterial profile, highlighting the inherent dual-functionality of the compounds. Interestingly, the C2-doped Starch biopolymer detected low concentrations of Hg2+ ions, such as 23 nM in tap water (value within the WHO standards for drinking water), through a rapid spectroscopic evaluation without sample treatment. This biopolymer was generated via a sustainable, green-chemistry-oriented, temperature-dependent water/Starch synthetic route, without the addition of plasticizers and any associated ecotoxicity. The study used sustainable methods for environmental monitoring and antibacterial applications, advancing material science to offer effective, accessible, and eco-friendly solutions for detecting and mitigating mercury pollution and bacterial contaminations, enhancing environmental and health safety.

A ratiometric fluorescent probe with a large Stokes shift for the detection of Hg2+ and its applications in environmental sample and living system analysis

Toxic mercury ions (Hg2+) can cause serious environmental pollution and accumulate in living organisms via the food chain. Therefore, monitoring Hg2+ is crucial in ensuring the safety of ecosystems and organisms. In this work, a novel ratiometric fluorescent probe CMT (5-(4-(diphenylamino)phenyl)-1-(7-hydroxy-coumarin-3-yl)-4-pentene-1,3-dione) based on coumarin was developed for detecting Hg2+, which displayed obvious fluorescence changes, a low detection limit (2.24 × 10-7 M), good selectivity, and a large Stokes shift (255 nm). The CMT probe could detect Hg2+ in real environmental soil and water samples. Furthermore, the CMT probe enabled the naked-eye detection of Hg2+ using test paper experiments. CMT was also applied for fluorescence imaging in living zebrafish and plants. This work provides a highly efficient tool for monitoring Hg2+ in environmental samples and biological systems.

A coumarin-based fluorescent probe for highly selective detection of hazardous mercury ions in living organisms

In recent years, heavy metal mercury (II) pollutants have caused serious harm to human health and ecosystems. It has become critical to develop simple and highly selective sensing solutions for monitoring mercury (II). In this work, we designed and developed a novel fluorescent probe Coa-SH using the Hg2+-induced chemical reaction as a sensing mechanism. The probe Coa-SH showed high selectivity for the detection of Hg2+ by desulfurization reactions in solution. The test strips prepared with this probe could be applied to detect mercury ions in aqueous solutions. In addition, the probe Coa-SH provided a tool to detect Hg2+ in living systems. In living cells and zebrafish, the probe turned on bright red fluorescent signals in the presence of mercury ions. Importantly, the probe Coa-SH enabled Hg2+ detection in plant onion roots. This work provides an effective method for monitoring mercury ions in the environment and in living organisms.

Recent Progress on Fluorescent Probes in Heavy Metal Determinations for Food Safety: A Review

One of the main challenges faced in food safety is the accumulation of toxic heavy metals from environmental sources, which can sequentially endanger human health when they are consumed. It is invaluable to establish a practical assay for the determination of heavy metals for food safety. Among the current detection methods, technology based on fluorescent probes, with the advantages of sensitivity, convenience, accuracy, cost, and reliability, has recently shown pluralistic applications in the food industry, which is significant to ensure food safety. Hence, this review systematically presents the recent progress on novel fluorescent probes in determining heavy metals for food safety over the past five years, according to fluorophores and newly emerging sensing cores, which could contribute to broadening the prospects of fluorescent materials and establishing more practical assays for heavy metal determinations.

A dicyanoisophorone-based ICT fluorescent probe for the detection of Hg2+ in water/food sample analysis and live cell imaging

Mercury ions are notoriously difficult to biodegradable, and its abnormal bioaccumulation in the human body through the food chain can cause various diseases. Therefore, the quantitative and real-time detection of Hg²⁺ is very extremely important. Herein, we have brilliant designed and synthesized (E)-O-(4-(2-(3-(dicyanomethylene)-5,5-dimethylcyclohex-1-en-1-yl)vinyl)phenyl) O-phenyl carbonothioate (ICM-Hg) as a selective fluorescent probe for Hg²⁺ detection in real samples and intracellular staining. ICM-Hg displayed high specificity toward Hg²⁺ by activating the intramolecular charge transfer (ICT) process, resulting in distinguished color change from colorless to bright yellow along with noticeable switch on yellow fluorescence emission. The fluorescent intensity of ICM-Hg at 585 nm shows a well linear relationship in the range of Hg²⁺ concentration (0-45 μM), and the detection of limit for Hg²⁺ is calculated to be 231 nM. Promisingly, ICM-Hg can efficiently detect Hg²⁺ in real samples including tap water, tea, shrimp, and crab with quantitative recovery as well as the intracellular fluorescence imaging.

A fluorescent probe based on an enhanced ICT effect for Hg2+ detection and cell imaging

The mercury ion (Hg²⁺) has hindered society to some extent due to its high biological toxicity, and a rapid method for Hg²⁺ detection is urgently needed. In the present work, two fluorescent probes, YF-Hg and YF-Cl-Hg, were developed. YF-Cl-Hg was produced by introducing an electron-withdrawing substituent (-Cl) into the structure of YF-Hg. The probe YF-Cl-Hg possesses a larger Stokes shift and a more pronounced UV-vis absorption redshift compared to YF-Hg in a pH = 7.4 environment. The reasons for the superior spectral performance of YF-Cl-Hg over YF-Hg were explored by density functional theory (DFT) calculations and UV-vis absorption spectroscopy. Furthermore, the good biocompatibility suggests that YF-Cl-Hg possesses the potential to be a tool for Hg²⁺ detection in cells.

Molecular probes for fluorescent sensing of metal ions in non-mammalian organisms

While metal ions play an important role in the proper functioning of all life, many questions remain unanswered about exactly how different metals contribute to health and disease. The development of fluorescent probes, which respond to metals, has allowed greater understanding of the cellular location, concentration and speciation of metals in living systems, giving a new appreciation of their function. While the focus of studies using these fluorescent tools has largely been on mammalian organisms, there has been relatively little application of these powerful tools to other organisms. In this review, we highlight recent examples of molecular fluorophores, which have been applied to sensing metals in non-mammalian organisms.

How Does Changing Environment Influence Plant Seed Movements as Populations of Dispersal Vectors Decline?

Plants differ widely in their ability to find tolerable climatic ranges through seed dispersal, depending on their life-history traits and habitat characteristics. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic review on seed dispersal mechanisms was conducted to elucidate plant seed movements amid changing environments. Here, the highest relative count of studies was found in Spain (16.47%), followed by Brazil (14.12%), and the USA (14.12%). The megadiverse, hotspot countries (e.g., Philippines, Vietnam, Myanmar, India, and Indonesia) and Africa (Tanzania, South Africa, Democratic Republic of the Congo) have very low to no data about the reviewed topic. The effects of land use changes, habitat degradation/disturbances, climate, and extreme weather conditions on seed dispersal mechanisms and agents had the highest share of studies across topics and countries. Plant diversity and distribution of anemochorous, endozoochorous, epizoochorous, hydrochorous, myrmecochorous, and ornithochorous species are seriously affected by changing environments due to altered long-distance seed dispersal. The fruit types commonly associated with endozoochory and ornithochory are species with achene, capsule, drupe, fleshy, and nut fruits/seeds, whereas achene, capsule, samara/winged seeds are associated with anemochory. The present review provides a summary of evidence on how plants are affected by climate change as populations of dispersal vectors decline. Finally, recommendations for further study were made based on the identified knowledge gaps.

Molecular Design and Photothermal Application of Thienoisoindigo Dyes with Aggregation-Induced Emission

Organic fluorescent dyes with aggregation-induced emission (AIE) property have an extensive application range, especially in the fields of imaging, labeling, and adjusting microprocesses in aggregated environments. In particular, the thienoisoindigo skeleton, which exhibits an outstanding electron-withdrawing capacity in optoelectronic materials, has been defined as a promising AIE candidate. For instance, by installing AIE blocks or other rotatable groups at two terminal sites, such as various arylamine groups, thienoisoindigo derivatives can be efficiently turned to be functional AIE structures. In this work, a thienoisoindigo derivative with AIE characteristics, namely, TII-TPE, was developed. This AIE system was expanded by linking typical AIE fragments, namely, tetraphenylethene, with the proposed thienoisoindigo derivative, which exhibited typical AIE fluorescence in the 600-850 nm range and maintained high photostability. Then, employing the reported derivative TII-TPA coating thienoisoindigo and triphenylamine as a contrast, aggregated TII-TPE and TII-TPA nanoparticles were prepared and demonstrated photothermal conversion efficiencies of 36.2 and 35.6%, respectively. Moreover, both nanoparticles were evaluated as photothermal therapeutic (PTT) agents in a tumor mouse model, which showed to significantly inhibit tumor growth after four treatment cycles in vivo. This work not only presents an enriched thienoisoindigo system but also provides a pattern for subsequent construction of functional AIE molecules.

A small molecule fluorescent probe for mercury ion analysis in broad low pH range: Spectral, optical mechanism and application studies

Development of new fluorescent probes for mercury ion analysis in environmental or living organism is undergoing quick growth due to its detrimental toxicity to environmental safety, ecological security, and human being. However, in most cases, the industrial waste water is acidic whereas it remains a great challenge to real-time monitor mercury ion directly at low pH using small molecule fluorescence probe. In this study, we have successfully designed and synthesized the Naph (1, 8-Naphthalimide derivative) -based small molecule probe termed as Naph-NSS capable of monitoring mercury ion in a broad range at low pH (from 2.0 to 7.0). The solid spectral studies demonstrated the high sensitivity and selectivity of the probe towards mercury ion among various species. After binding with Hg²⁺, the fluorescence of Naph-NSS greatly enhanced, and the mechanism of which was investigated by DFT studies. The probe was able to be loaded on paper strip for instant and fast detection of mercury ions. In addition, the probe is also suitable for detection of mercury ion in environmental samples, living cells and in vivo.

New analytical methods using carbon-based nanomaterials for detection of Salmonella species as a major food poisoning organism in water and soil resources

Salmonella is one of the most prevalent causing agents of food- and water-borne illnesses, posing an ongoing public health threat. These food-poisoning bacteria contaminate the resources at different stages such as production, aggregation, processing, distribution, as well as marketing. According to the high incidence of salmonellosis, effective strategies for early-stage detection are required at the highest priority. Since traditional culture-dependent methods and polymerase chain reaction are labor-intensive and time-taking, identification of early and accurate detection of Salmonella in food and water samples can prevent significant health economic burden and lessen the costs. The immense potentiality of biosensors in diagnosis, such as simplicity in operation, the ability of multiplex analysis, high sensitivity, and specificity, have driven research in the evolution of nanotechnology, innovating newer biosensors. Carbon nanomaterials enhance the detection sensitivity of biosensors while obtaining low levels of detection limits due to their possibility to immobilize huge amounts of bioreceptor units at insignificant volume. Moreover, conjugation and functionalization of carbon nanomaterials with metallic nanoparticles or organic molecules enables surface functional groups. According to these remarkable properties, carbon nanomaterials are widely exploited in the development of novel biosensors. To be specific, carbon nanomaterials such as carbon nanotubes, graphene and fullerenes function as transducers in the analyte recognition process or surface immobilizers for biomolecules. Herein the potential application of carbon nanomaterials in the development of novel Salmonella biosensors platforms is reviewed comprehensively. In addition, the current problems and critical analyses of the future perspectives of Salmonella biosensors are discussed.

Fluorescence Probes for Reactive Sulfur Species in Agricultural Chemistry

Sulfur is an element that is indispensable throughout the growth of plants. In plant cells, reactive sulfur species (RSS) play a vital role in maintaining cellular redox homeostasis and signal transduction. There is demand accordingly for a simple, highly selective, and sensitive method of RSS detection and imaging for monitoring dynamic changes and clarifying the biological functions of RSS in plant systems. Fluorescent analysis based on organic small-molecule fluorescent probes is an effective and specific approach to tracking plant RSS characteristics. This perspective summarizes the recent progress regarding organic small-molecule fluorescent probes for RSS monitoring, including small-molecule biological thiols, hydrogen sulfide, and sulfane sulfurs, in plants; it also discusses their response mechanism toward RSS and their imaging applications in plants across the agricultural chemistry field.

A simple strategy for the visual detection and discrimination of Hg2+ and CH3Hg+ species using fluorescent nanoaggregates

Fluorescent nanoaggregates (FNAs) based on phenanthroline-based amphiphiles show changes in solution color from colorless to yellow upon addition of both Hg²⁺ (LOD ∼4 ppb) and CH₃Hg⁺ (LOD ∼18 ppb). However, the extent of fluorescence quenching is more prominent with Hg²⁺ (∼12 fold) than with CH₃Hg⁺ (∼4 fold). Also, unlike Hg²⁺, the interaction of CH₃Hg⁺ needs more time, ∼10 min at room temperature. Experimental evidence indicates that both mercury species coordinate with the phenanthroline unit and facilitate the charge transfer interaction while destabilizing the nanoassembly. The lower charge density on CH₃Hg⁺ along with its large size compared to Hg²⁺ may be the reason for such observations. Interestingly, FNAs show a selective response towards CH₃Hg⁺ when pre-treated with EDTA. Further, analysis of heavy metal pollutants in drinking water and biological samples was performed. High recovery values ranging from 96% to 103.0% were estimated along with relatively small standard deviations (<3%). Low-cost, reusable test strips were designed for rapid, on-site detection of mercury species. Further, the in situ formed metal complexes are allowed to interact with thiol-containing amino acids. As expected, CH₃Hg⁺, being less thiophillic, endures less interaction with cysteine. Mechanistic investigations indicate that thiolated amino acids can bind with the metal ion center and form a tertiary complex (cooperative interaction).

Recent progress in fluorescent probes for bacteria

Food fermentation, antibiotics, and pollutant degradation are closely related to bacteria. Bacteria play an irreplaceable role in life. However, some bacteria seriously threaten human health and cause large-scale infectious diseases. Therefore, there is a pressing need to develop strategies to accurately monitor bacteria. Technology based on molecular probes and fluorescence imaging is noninvasive, results in little damage, and has high specificity and sensitivity, so it has been widely applied in the detection of bacteria. In this review, we summarize the recent progress in bacterial detection using fluorescence. In particular, we generalize the mechanisms commonly used to design organic fluorescent probes for detecting and imaging bacteria. Moreover, a perspective regarding fluorescent probes for bacterial detection is discussed.