A mitochondria-targeted fluorescent probe based on biocompatible RBH-U for the enhanced response of Fe3+ in living cells and quenching of Cu2+ in vitro

Fluorometric/colorimetric dual-mode sensor based on silicon quantum dots for rapid and on-site detection of tert-butyl hydroquinone

Tert-butyl hydroquinone (TBHQ) is a synthetic phenolic antioxidant commonly found in food. The overuse of TBHQ poses a potential toxicity to human health, which has attracted significant attention in food safety. In this study, we developed a dual-mode test platform strategy centered on silicon quantum dots (SiQDs) for fluorometric/colorimetric TBHQ detection. The SiQDs with Fe (III) as the fluorescence switch and co-enzyme, were synthesized and characterized, facilitating the catalysis of TBHQ to 2-tert-butyl-1,4-benzoquinone (TBBQ). There was a linear correlation with TBHQ concentration in the range of 5-200 μM, with a limit of detection (LOD) of 0.12 μM. Furthermore, with the assistance of 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate, the nanoprobes exhibited good colorimetric detection performance for TBHQ, with an LOD of 7 μM in the 15-500 μM range. Moreover, smartphone-integrated agarose gel strips were successfully developed for simple TBHQ detection with naked-eyes and the quantitative analysis with a LOD of 15 μM. The fabricated sensors successfully monitored TBHQ levels in spiked edible oil samples with recoveries in the range of 89.05-109.61 % and relative standard deviations (RSDs, %) less than 1.75 %, suggesting applicability for the detection of TBHQ in a complex food matrix.

A quinoline colorimetric ionic liquid probe by electrostatic enhancement for visual detection of Fe3+ in food

Excessive or insufficient iron(Ⅲ) will pose burdens of human body, and its content is the key to control the function of iron-fortified food. In this regard, a functionalized quinoline ionic probe, benefiting from the electrostatic attraction, was designed for the colorimetric detection of Fe3+ in food. This probe formed a 2: 1 complex with Fe3+, altering the UV-vis spectra and solution color. The UV-vis detection limit was 0.2 μM, and visually, the color shifted from light-yellow to dark-green as Fe3+ concentrations increased, with a visual detection limit of 3.4 μM, meeting the maximum acceptable level of 5.4 μM. Noteworthy, ionic liquid-based sensing paper was constructed for rapid, semi-quantitative Fe3+ detection. Furthermore, the satisfying recovery (97.4-102.9 %) was obtained in real samples, showcasing the probe's efficiency. This work demonstrated the potential of ionic liquids for the fast, sensitive, and visual detection of Fe3+, offering a promising direction for metal element sensing platforms.

3D-printed colorimetric copper ion detection kit and portable fluorescent sensing device using smartphone based on ratiometric fluorescent probes

Copper ion (Cu2+) is not only a transition metal ion but also a significant environmental pollutant. The imbalance of Cu2+ content will threaten the safety of the environment and even life. The portable detection devices based on ratiometric fluorescent probes have garnered increasing attention and acclaim because of their reliable analysis parameters. Therefore, two Cu2+ ratiometric fluorescent probes (RH-1 and RH-2) were developed, which exhibit pronounced fluorescence changes, high sensitivity, excellent selectivity, and large Stokes shift. Both probes are capable of detecting Cu2+ in water and milk samples. It is worth noting that a 3D-printed fluorescence sensing device was constructed using RH-1, and a new 3D-printed copper ion detection kit was developed based on RH-2, enabling on-the-spot estimation of Cu2+ concentration. These devices significantly facilitate Cu2+ detection in daily life. RH-2 has been successfully employed for imaging Cu2+ in living cells and zebrafish. In conclusion, this work provides, for the first time, the 3D-printed ideal tools for detecting Cu2+. It also provides valuable insights for the establishment of on-site portable detection methods for other important substances.

Xylan derived fluorescence carbon dots composite with cotton cellulose paper as 'turn-off' fluorescence platform for sensitive and selective detection Cu2+ in real samples

The pollution of heavy metals such as Cu2+ is still serious and the discharge of sewage of Cu2+ will cause damage to soil environment and human health. Herein, a biomass-based solid-state fluorescence detection platform (CPU-CDs) was developed as fluorescent sensor for detection Cu2+ via fluorescence and colorimetric dual-model methods in real time. CPU-CDs was composed of xylan-derived CDs (U-CDs) and cotton cellulose paper, which exhibiting good reusability, non-toxicity, excellent fluorescence characteristics and high biocompatibility. Further, CPU-CDs displayed high effectiveness and sensitivity for Cu2+ with the detection limit as low as 0.14 μM, which was well below U.S. EPA safety levels (20 μM). Practical application indicated that CPU-CDs could achieve precision response of Cu2+ change in real environment water samples with good recovery range of 90 %-119 %. This strategy demonstrated a promising biomass solid-state fluorescence sensor for Cu2+ detection for water treatment research, which is of great significance in dealing with water pollution caused by heavy metal ions.

Biomass-based indole derived fluorescence sensor composited with cellulose paper: Detection of picric acid in food and environment samples

Picric acid (PA) is highly water-soluble, the fact makes it stand out as the most hazardous environment pollutant. Therefore, accurate determination of PA is of great significance for human health and environmental protection. Herein, a novel indole-based fluorescent sensor (H1) with good water solubility and fluorescence stability was reported. H1 exhibited 'turn-off' fluorescence response for PA with fast reaction rate (<30 s), unique specificity and excellent selectivity and high sensitivity (limit of detection = 34 nM). Further, H1 was successfully applied to detect PA in real samples (tap water, Yangtze River, Xuanwu Lake, soil, food, fish and shrimp) with satisfactory recoveries at three spiking levels ranging from 98.0 to 112.0 %. In addition, H1 displayed high biocompatibility in mung beans and fresh blood. Moreover, aiming to attain portable analysis, H1 was composited with biomass cellulose paper (H1-FP) and integrated with smartphone for construction as a solid-state fluorescence platform to achieve fast and visual detection of PA in suit with significant stability, high sensitively and selectivity. The establishment of this sensing approach is expected to offer new insight into rapid, selective, and sensitive detection of major pollutants for food and environmental safety.

Enhancing or Quenching of a Mitochondria-Targeted AIEgens-Floxuridine Sensor by the Regulation of pH-Dependent Self-assembly, Efficient Recognition of Hg2+, and Stimulated Response of GSH

Biocompatible fluorescent probes have emerged as essential tools in life sciences for visualizing subcellular structures and detecting specific analytes. Herein, we report the synthesis and characterization of a novel fluorescent probe (TPE-FdU), incorporated with hydrophilic 2'-fluoro-substituted deoxyuridine and hydrophobic ethynyl tetraphenylethene moieties, which possessed typical aggregation-induced emission (AIE) behavior. In comparison to the TPE-FdU (pKa 7.68) treated in neutral conditions, it performed well at pH 4, exhibiting an enhanced 450 nm emission signal of approximately four times stronger. As the pH value was increased to 10, the fluorescence intensity was completely quenched. The TEM images of TPE-FdU in an acidic environment (nanospherical morphology, AIE enhance, pH = 4) and in a basic environment (microrods, fluorescence quenching, pH = 9) revealed that it was a pH-dependent self-assembled probe, which was also illustrated by the interpretation of the NMR spectrum. Furthermore, the TPE-FdU probe exhibited a specific response to trace Hg2+ ions. Interestingly, the quenched fluorescence of the TPE-FdU probe caused by Hg2+ can be recovered by the addition of GSH due to the formation of the Hg-S bond being released away. MTT assay and CLSM images demonstrated that TPE-FdU was nontoxic and selectively visualized in the intracellular mitochondria. These results contributed to the development of advanced fluorescent probes with diverse applications in cell imaging, environment protection, and biomedical research.

Fluorescence switch based on NIR-emitting carbon dots revealing high selectivity in the rapid response and bioimaging of oxytetracycline

The abuse of antibiotics has led to serious environmental pollution and the emergence of drug-resistant bacteria surpassing the replacement rate of antibiotics. Herein, near-infrared fluorescent carbon dots (NIR-CDs) were developed to meet the requirements for oxytetracycline (OTC) detection in food and water samples (milk, honey, and lake water) with a detection limit of 0.112 μM. These NIR-CDs, possessing excellent water-solubility, deep tissue penetration ability, and tunable optical properties, exhibit maximum emission at 790 nm (NIR-I window). Unlike traditional CDs, this novel NIR-CDs nanoprobe provides a dual response in the presence of OTC (quenching and bathochromic shifting), without obvious interference from other existing biomolecules and metal ions. Additionally, these NIR-CDs exhibit excellent photostability and multi-resistance under UV irradiation, exceptional pH stability (pH 6-12), reliable long-time exposure, and durability in ionic (NaCl) environments. Moreover, NIR-CDs and NIR-CDs@OTC are nontoxic and were successfully utilized for cell-imaging applications in normal (NIH3T3) and cancer cells (HeLa).

Multifunctional nucleoside-AIEgens bearing quaternary ammonium cationic for reversible response, bioimaging, and antibacterial

A multifunctional nucleoside-based AIEgens sensor (TPEPy-dU) was constructed for visual screening of Hg2+, determine to the reversible response of Fe3+ and biothiols, and applied for cell imaging, and drug-free bacterial killing. The TPEPy-dU displayed 10-folds fluorescence enhancement at 540 nm of emission in response to trace Hg2+ ions with 10 nM of LOD, which can be immediately quenched by adding Fe3+ or GSH/Cys-containing sulfhydryl groups. Moreover, their bacterial staining efficiency closely correlates with their antibacterial efficacy as they demonstrated comparatively higher antibacterial activity against Gram-positive bacteria than Gram-negative bacteria. The drug-free antibacterial results involved the stating prominent surface damages at the sites of interactions between bacterial cells and TPEPy-dU that were further verified by CLSM and SEM images. It can be applied as a potential fluorescent agent to explore the related antibacterial mechanisms for treating and monitoring bacterial infections in vivo due to their nontoxic nature. Compared with conventional sensors and antibacterial therapies, these findings elevated the synthetic strategies of fluorescent probes and represented an advanced antibacterial agent wearing quaternary ammonium cationic with low resistance in clinical diagnosis.

Multimorphological Remoldable Silver Nanomaterials from Multimode and Multianalyte Colorimetric Sensing to Molecular Information Technology

Inspired by life's interaction networks, ongoing efforts are to increase complexity and responsiveness of multicomponent interactions in the system for sensing, programmable control, or information processing. Although exquisite preparation of single uniform-morphology nanomaterials has been extremely explored, the potential value of facile and one-pot preparation of multimorphology nanomaterials has been seriously ignored. Here, multimorphological silver nanomaterials (M-AgN) prepared by one pot can form interaction networks with various analytes, which can be successfully realized from multimode and multianalyte colorimetric sensing to molecular information technology (logic computing and security). The interaction of M-AgN with multianalytes not only induces multisignal responses (including color, absorbance, and wavelength shift) for sensing metal ions (Cr3+, Hg2+, and Ni2+) but also can controllably reshape its four morphologies (nanodots, nanoparticles, nanorods, and nanotriangles). By abstracting binary relationships between analytes and response signals, multicoding parallel logic operations (including simple logic gates and cascaded circuits) can be performed. In addition, taking advantage of natural concealment and molecular response characteristics of M-AgN nanosystems can also realize molecular information encoding, encryption, and hiding. This research not only promotes the construction and application of multinano interaction systems based on multimorphology and multicomponent nanoset but also provides a new imagination for the integration of sensing, logic, and informatization.