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Sulfur dioxide (SO 2) is a significant gas signaling molecule in organisms, and viscosity is a crucial parameter of the cellular microenvironment. They are both involved in regulating many physiological processes in the human body. However, abnormalities in SO 2 and viscosity levels are associated with various diseases, such as cardiovascular disease, lung cancer, respiratory diseases, neurological disorders, diabetes and Alzheimer's disease. Hence, it is essential to explore novel and efficient fluorescent probes for simultaneously monitoring SO 2 and viscosity in organisms. We selected quinolinium salt with good stability, high fluorescence intensity, good solubility and low cytotoxicity as the fluorophore and developed a highly sensitive ratiometric probe QQD to identify SO 2 and viscosity changes based on Förster resonance energy transfer/twisted intramolecular charge transfer (FRET/TICT) mechanism. Excitingly, compared with other probes for SO 2 detection, QQD not only identified HSO 3 −/SO 3 2− with a large Stokes shift (218 nm), low detection limit (1.87 μM), good selectivity, high energy transfer efficiency (92 %) and wide recognition range (1.87–200 μM), but also identified viscosity with a 26-fold fluorescence enhancement and good linearity. Crucially, QQD was applied to detect HSO 3 −/SO 3 2− and viscosity in actual water and food samples. In addition, QQD had low toxicity and good photostability for imaging HSO 3 −/SO 3 2− and viscosity in cells. These results confirmed the feasibility and reliability of QQD for HSO 3 −/SO 3 2− and viscosity imaging and environmental detection. We reported a unique ratiometric probe QQD for detecting HSO 3 −/SO 3 2− and viscosity based on the quinolinium skeleton. In addition to detecting HSO 3 −/SO 3 2− and viscosity change in actual water and food samples, QQD could also monitor the variations of HSO 3 −/SO 3 2− and viscosity in cells, which provided an experimental basis for further exploration of the role of SO 2 derivatives and viscosity in biological systems. [Display omitted] • A dual-function fluorescent probe was designed for detecting SO 2 and viscosity. • QQD had large Stokes shift of 218 nm and wide detection rang of 1.87–200 μM. • QQD showed high sensitivity and selectivity. • QQD achieved the dual colorimetric and ratiometric fluorescent strategy. • QQD achieved the application of foods, water samples and living cells. [ABSTRACT FROM AUTHOR]

Detecting and neutralizing Pd2+ ions are a significant challenge due to their cytotoxicity, even at low concentrations. To address this issue, various chemosensors have been designed for advanced detection systems, offering simplicity and the potential to differentiate signals from different analytes. Nonetheless, these chemosensors often suffer from limited emission response and complex synthesis procedures. As a result, the tracking and quantification of residual palladium in biological systems and environments remain challenging tasks, with only a few chemosensing probes available for commercial use. In this paper, a straightforward approach for the selective detection of Pd2+ ions is proposed, which involves the design, synthesis, and utilization of a propargylated naphthalene-derived probe (E)-N'-((2-(prop-2-yn-1-yloxy)naphthalen-1-yl)methylene)benzohydrazide (NHP). The NHP probe exhibits sensitive dual-channel colorimetry and fluorescence Pd2+ detection over other tested metal ions. The detection process is performed through a catalytic depropargylation reaction, followed by an excited state intramolecular proton transfer (ESIPT) process, the detection limit is as low as 11.58 × 10−7 M under mild conditions. Interestingly, the resultant chemodosimeter adduct (E)-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (NHH) was employed for the consecutive detection of CN− ions, exhibiting an impressive detection limit of 31.79 × 10−8 M. Validation of both detection processes was achieved through 1H nuclear magnetic resonance and density functional theory calculations. For real-time applications of the NHP and NHH probes, smartphone-assisted detection, and intracellular detection of Pd2+ and CN− ions within HeLa cells were studied. This research presents a novel naphthalene derivative for visually detecting environmentally toxic Pd2+ and CN− ions. The synthesized probe selectively binds to Pd2+, forming a chemodosimeter. It successfully detects CN− ions through colorimetry and fluorimetry, offering a low detection limit and quick response. Notably, it's the first naphthalene-based small molecule to serve as a dual probe for toxic analytes - palladium and cyanide. Moreover, it effectively detects Pd2+ and CN− intracellularly in cancer cells. [Display omitted] • Probe NHP selectively detects Pd2+ and forms chemodosimeter adduct NHH , showing a specific turn-on response to CN- ions. • The "off-on-off" ESIPT process led to the dual-channel detection of Pd2+ and CN− in an ethanol-H 2 O solution. • Consecutive detection, first of Pd2+ and then of CN-, showed naked-eye visibility, rapid response, and a low detection limit. • The study explored both on-site smartphone-based detection and intracellular detection of Pd2+ and CN- within HeLa cells. [ABSTRACT FROM AUTHOR]

Al exists naturally in the environment and is an important component in acidic soils, which harm almost all plants. Furthermore, Al is widely used in food additives, cosmetics, and medicines, resulting in living organisms ingesting traces of Al orally or dermally every day. Accordingly, Al accumulates in the body, which can cause negative bioeffects and diseases, and this concern is gaining increasing attention. Therefore, to detect and track Al in the environment and in living organisms, the development of novel Al-selective probes that are water-soluble and exhibit fluorescence at long wavelengths is necessary. In this study, an Al3+-selective fluorescent probe PSP based on a novel pyrone molecule was synthesized and characterized to detect and track Al in biological systems. PSP exhibited fluorescence enhancement at 580 nm in the presence of Al3+ in aqueous media. Binding analysis using Job's plot and structural analysis using 1H NMR showed that PSP formed a 1:1 complex with Al3+ at the two carbonyl groups of the dimethyl malonate of the pyrone ring. Upon testing in biological systems, PSP showed good cell membrane permeability, detected intracellular Al3+ in human breast cancer cells (MDA-MB-231), and successfully imaged accumulated Al3+ in Microcystis aeruginosa and the larvae of Rheocricotopus species. The novel Al3+-selective fluorescent probe PSP is highly effective and is expected to aid in elucidating the role of Al3+ in the environment and living organisms. [Display omitted] • Water-soluble fluorescent Al3+ probe PSP developed based on phenylsulfonyl-2-pyrone • PSP exhibited fluorescence enhancement toward Al3+ at 580 nm in aqueous media • PSP successfully detected accumulated Al3+ in breast cells and small aquatic organisms [ABSTRACT FROM AUTHOR]

Heavy metal pollution has become one of the world's most important environmental pollution, especially Hg2+ is enriched, it is easy to enter the human body through the food chain, bind to the sulfhydryl group in the protein, cause mercury poisoning. Traditional methods for detecting Hg2+ have obvious drawbacks, such as poor selectivity and long detection time. Fluorescence detection has attracted attention because of its good sensitivity and specificity detection ability. In previously reported probes for detecting Hg2+, Cu2+ often interferes. Therefore, it is of great practical significance to synthesize a fluorescent probe that can distinguish between Hg2+ and Cu2+. We have successfully synthesized the probe DFS, a fluorescent probe that can differentially detect Hg2+ and Cu2+, and the probe DFS has good selectivity and anti-interference ability for Hg2+ and Cu2+. The fluorescence intensity at 530 nm increased rapidly when Hg2+ was detected; during the Cu2+ detection, the fluorescence intensity at 636 nm gradually decreased, fluorescence quenching occurred, and the detection limits of Hg2+ and Cu2+ were 7.29 × 10−9 M and 2.13 × 10−9 M, respectively. Through biological experiments, it was found that probe DFS can complete the fluorescence imaging of Hg2+ and Cu2+ in Staphylococcus aureus and HUVEC cells, which has certain research value in the field of environmental monitoring and microbiology, and the probe DFS has low cytotoxicity, so it also has broad application prospects in the field of biological imaging. In addition, the probe DFS also has good applicability for Hg2+ and Cu2+ detection in actual samples. This is a fluorescent probe that can distinguish between Hg2+ and Cu2+, the fluorescence emission peak appears at 530 nm when Hg2+ is detected; when detecting Cu2+, fluorescence quenching occurs at 636 nm, the fluorescence emission peak distance between Hg2+ and Cu2+ differs by 106 nm. This reduces mutual interference between Hg2+ and Cu2+ during detection, it provides a new idea for the detection of Hg2+ and Cu2+. [Display omitted] • The probe with low limits of detection. • The probe enables differential detection of Hg2+ and Cu2+. • The probe exhibits good biopenetrability and biocompatibility. • The probe can qualitatively detect Hg2+ and Cu2+ in actual samples. [ABSTRACT FROM AUTHOR]

Cell surface glycans (CSGs) are essential for cell recognition, adhesion, and invasion, and they also serve as disease biomarkers. Traditional CSG recognition using lectins has limitations such as limited specificity, low stability, high cytotoxicity, and multivalent binding. Aptamers, known for their specific binding capacity to target molecules, are increasingly being employed in the biosensing of CSGs. Aptamers offer the advantage of high flexibility, small size, straightforward modification, and monovalent recognition, enabling their integration into the profiling of CSGs on living cells. In this review, we summarize representative examples of aptamer-based CSG biosensing and identify two strategies for harnessing aptamers in CSG detection: direct recognition based on aptamer-CSG binding and indirect recognition through protein localization. These strategies enable the generation of diverse signals including fluorescence, electrochemical, photoacoustic, and electrochemiluminescence signals for CSG detection. The advantages, challenges, and future perspectives of using aptamers for CSG biosensing are also discussed. [Display omitted] • The aptamer-based cell surface glycan biosensing with a potential future to facilitate clinical diagnostics. • The representative examples of aptamer-based cell surface glycan biosensing are summarized. • The design strategies for identifying cell surface glycan by aptamers are introduced. • The challenges and prospects of aptamer-based cell surface glycan biosensing are described. [ABSTRACT FROM AUTHOR]

Tyrosine kinase inhibitors (TKIs) are commonly used in tumor targeting therapy. However, the rapid analysis of TKIs remains a significant challenge, especially in complex biological fluid environments. In this work, we have constructed a supramolecular fluorescence sensor array based on a cucurbituril-dye host-guest complex. The binding affinity between the three complexes and each TKI is different, resulting in different cross-response signals of the complexes to the fluorescence of each TKI. Combined with linear discriminant analysis(LDA), five kinds of TKIs can be well identified. The supramolecular fluorescence sensor array could accurately identify and distinguish the five TKIs in water and could classify mixtures containing different concentrations of TKIs in serum. The concentration and Factor 1 exhibited a good linear relationship and the detection limit (LOD) was as low as 10−7 mol L−1. The method has good reproducibility and stability. In addition, the differentiation of four clinical concentrations of first-generation TKIs further validated the potential application of arrays in drug monitoring. Finally, our proposed array enabled drug imaging in living cells. Our array platform provided the foundation for the rapid and easy monitoring of 4-anilinoquinazoline TKIs. [Display omitted] • A supramolecular fluorescence array sensor was constructed based on the dye-cucurbit [8]uril host-guest complexes. • The sensor array can identify five 4-anilinequinoline TKIs. • Five 4-anilinequinolines TKIs in serum were detected by sensor array. [ABSTRACT FROM AUTHOR]

Human telomerase is a ribonucleoprotein complex that includes proteins and human telomerase RNA (hTR). Emerging evidence suggested that the expression level of hTR was high related with the development of tumor, so it is important to accurately detect the content of hTR. Optical control of DNAzyme activity shows a promising strategy for precise biosensing, biomedical imaging and modulation of biological processes. Although DNAzyme-based sensors can be controlled spatiotemporally by light, its application in the detection of hTR in living cells is still rare. Therefore, designing DNAzyme activity spatiotemporal controllable sensors for hTR detection is highly needed. We developed a UV light-activated DNAzyme-based nanoprobe for spatially accurate imaging of intracellular hTR. The proposed nanoprobe was named MDPH, which composed of an 8–17 DNAzyme (D) inactivated by a protector strand (P), a substrate strand (H), and MnO 2 nanosheets. The MnO 2 nanosheets can enhance the cellular uptake of DNA strands, so that MDPH probe can enter cells autonomously through endocytosis. Under the high concentration of GSH in cancer cells, MnO 2 nanosheets can self-generate cofactors to maintain the catalytic activity of DNAzyme. When exposing UV light and in presence of target hTR , DNAzyme could cleave substrate H, resulting in the recovery of fluorescence of the system. The cells imaging results show that MDPH probe could be spatiotemporally controlled to image endogenous hTR in cancer cells. With this design, telomerase RNA-specific fluorescent imaging was achieved by MDPH probe in both cancer and normal cells. Our probe made a promising new platform for spatiotemporal controllable intracellular hTR monitoring. This current method can be applied to monitor a variety of other biomarkers in living cells and perform medical diagnosis, so it may has broad applications in the field of medicine. We developed a UV light-activated DNAzyme-based nanoprobe for fluorescent imaging of hTR in living cells. This nanoprobe achieved spatiotemporally controlled intracellular hTR detection with high sensitivity and specificity. [Display omitted] • A novel DNAzyme-based nanoprobe was developed for sensing hTR with high sensitivity. • A spatiotemporal controllable hTR detection was achieved in living cells. • The nanocarrier of MnO 2 could self-generate cofactors to maintain the activity of DNAzyme. • This work can be applied to monitor a variety of biomarkers. [ABSTRACT FROM AUTHOR]

As a basic parameter of the intracellular microenvironment, viscosity is closely related to the development of cancer. Thus, it is necessary to utilize a sensitive tool to visualize the viscosity in tumor cells and mice, which is helpful for the diagnosis of cancer. Herein, a novel dual-modal probe (IX-V) that has a near-infrared fluorescence (NIRF) and photoacoustic (PA) response to viscosity is synthesized. In low viscosity media, the probe has no fluorescence. With the increase of viscosity, the fluorescence is produced in the near-infrared region due to the inhibition of the TICT process. At the same time, the probe shows different photoacoustic (PA) signals in different viscosity media. Most notably, the viscosity in tumor cells has been imaged successfully by the application of IX-V, and the probe can effectively distinguish cancer cells from normal cells co-cultured in one dish by the difference of fluorescence intensity. In addition, the probe has been used for dual-modal imaging (NIRF and PA) of viscosity in tumor mice, which provides a tool for exploring the relationship between viscosity and diseases. That is to say, IX-V can achieve complementary imaging effects and has great application prospects in the tumor diagnosis. [Display omitted] • A probe (IX-V) has a NIR fluorescence and photoacoustic response to viscosity. • IX-V shows high sensitivity and selectivity for viscosity over other analytes. • This probe can be used in visualizing viscosity change in various living cells. • IX-V can distinguish cancer cells from normal cells co-cultured in one dish. • IX-V is applied for monitoring the viscosity level in mice by dual-modal imaging. [ABSTRACT FROM AUTHOR]

A sensitive method for the detection of β-glucuronidase was established using functionalized carbon dots (β-CD-SiCDs) as fluorescent probes. The β-CD-SiCDs were found to be obtained through in situ autopolymerization by mixing the solutions of methyldopa, mono-6-ethylenediamine-β-cyclodextrin and N -(β-aminoethyl)-γ-aminopropyltrimethoxysilane at room temperature. The method has the characteristics of low energy consumption, simple and rapid. β-CD-SiCDs exhibited green fluorescence at 515 nm emission with a quantum yield of 7.9 %. 4-nitrophenyl-β-D-glucuronide was introduced as a substrate for β-glucuronidase to generate p -nitrophenol. Subsequently, p -nitrophenol self-assembled with β-CD-SiCDs through host-guest recognition to form a stable inclusion complex, resulting in the fluorescence quenching of β-CD-SiCDs. The linear range of β-CD-SiCDs for detecting β-glucuronidase activity was 0.5–60 U L−1 with a detection limit of 0.14 U L−1. For on-site detection, gel reagents were prepared by a simple method and the images were visualized and quantified by taking advantage of smartphones, avoiding the use of large instrumentation. The constructed fluorescence sensing platform has the benefits of easy operation and time saving, and has been successfully used for the detection of β-glucuronidase activity in serum and cell imaging. [Display omitted] • Amination induced in situ self-polymerization formation of β-CD-SiCDs without external energy. • β-CD-SiCDs can selectively recognize p -nitrophenol through host-guest recognition. • Smartphone-integrated hydrogel sensing platform was used to detect β-glucuronidase on site. • The approach is suitable for detecting β-glucuronidase in serum and bioimaging in cells. [ABSTRACT FROM AUTHOR]

Cellular heterogeneity poses a major challenge for tumor theranostics, requiring high-resolution intercellular bioanalysis strategies. Over the past decades, the advantages of electrochemical analysis, such as high sensitivity, good spatio-temporal resolution, and ease of use, have made it the preferred method to uncover cellular differences. To inspire more creative research, herein, we highlight seminal works in electrochemical techniques for biomolecule analysis and bioimaging. Specifically, micro/nano-electrode-based electrochemical techniques enable real-time quantitative analysis of electroactive substances relevant to life processes in the micro-nanostructure of cells and tissues. Nanopore-based technique plays a vital role in biosensing by utilizing nanoscale pores to achieve high-precision detection and analysis of biomolecules with exceptional sensitivity and single-molecule resolution. Electrochemiluminescence (ECL) technology is utilized for real-time monitoring of the behavior and features of individual cancer cells, enabling observation of their dynamic processes due to its capability of providing high-resolution and highly sensitive bioimaging of cells. Particularly, scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM) which are widely used in real-time observation of cell surface biological processes and three-dimensional imaging of micro-nano structures, such as metabolic activity, ion channel activity, and cell morphology are introduced in this review. Furthermore, the expansion of the scope of cellular electrochemistry research by innovative functionalized electrodes and electrochemical imaging models and strategies to address future challenges and potential applications is also discussed in this review. [Display omitted] • Recent progress of electrochemical science biological research. • Overview of molecular detection techniques ranging from extracellular to intracellular levels. • Overview of electrochemical imaging techniques for monitoring of structural characteristics. [ABSTRACT FROM AUTHOR]