Selective monitoring ATP using a fluorogenic Al(III)-probe complex in aqueous medium

A naked-eye visible aluminium (III)-based complex fluorescence sensor for sensitive detection of mesotrione

Mesotrione, which is a kind of herbicide to control broad-leaved weeds, has been increasingly used due to its excellent selectivity, rapid process and low toxicity. However, the excessive application of mesotrione have led to widespread contamination. Herein, a turn-on competitive coordination-based fluorescent probe, 2-hydroxy-1-(9-purin)-methylidenehydrazinenaphthalene (HPM), has been successfully synthesized. HPM could effectively detect Al3+ in CH3OH/HEPES (1/9, v/v) with low limit of detection (LOD) being 0.2 µM via coordination. HPM also exhibited excellent imaging capabilities for Al3+ in living cells with low cytotoxicity. On the basis of the competitive coordination of HPM with Al3+, the [HPM-Al3+] complex could also serve as a potential fluorescence sensor for detecting mesotrione with the LOD of 0.2 µM. Furthermore, [HPM-Al3+] complex was applied for the detection of mesotrione in real samples and test paper. Finally, the mechanism of [HPM-Al3+] for sensing mesotrione was investigated deeply as well. This work designed a new convenient method for on-site detection of mesotrione without the large-scale equipment or complicated pre-treatment.

A novel pyrene-based fluorescent probe for Al3+ detection

Based on the classical Schiff base reaction, fluorescent probe dimethyl 5-((pyren-1-ylmethylene)amino)isophthalate (PAI) is designed and synthesized through introducing Schiff base structure to pyrene unit for structural modification. The structure of the synthesized probe PAI is determined and characterized by FT-IR, ¹H NMR, ¹³C NMR and HRMS. PAI is a type of "turn-on" probe which can specifically recognize Al³⁺ ion with high selectivity. The limit of detection is calculated to be 3.07 × 10^-8 M, which proves the probe's high sensitivity and is lower than that of many efficient reported probes. The probe PAI is intrinsically non-fluorescent due to the photoinduced electron transfer (PET) process. However, the addition of Al³⁺ ion leads to the breakage of the carbon-nitrogen double bond of Schiff base in PAI resulting in the product without PET property, which shows a typical localized state with enhanced fluorescence and blue color. In addition, PAI can recognize Al³⁺ ion through test papers, which is in favor of the future research regarding to Al³⁺ ion sensing.

A novel hydrazone-based fluorescent "off-on-off" probe for relay sensing of Ga3+ and PPi ions

A novel hydrazone-based fluorescent probe (E)-3-((2-(benzo[d]thiazol-2-yl)hydrazono)methyl)-4H-chromen-4-one (BTC) has been rationally designed and synthesized. BTC can subsequently detect Ga³⁺ and PPi ions through the absorption and emission off-on-off response with high specificity. Importantly, fluorescent probe BTC can well discriminate Ga³⁺ from Al³⁺ and In³⁺. The association constant (K) was calculated as 2.06 × 10⁴M^-1, and the limit of detection (LOD) was calculated as 4.88 × 10^-2μM. Competitive binding studies also illustrated good results of the probe BTC towards Ga³⁺. Job's plot and HRMS results substantiated the 1:1 stoichiometry between BTC and Ga³⁺ ion. The interaction binding mode of BTC with Ga³⁺ was proposed by HRMS, ¹H NMR spectral titration, UV-vis absorption and fluorescence spectral measurements. The combination of the restraint of the photo-induced electron transfer (PET) process and the chelation enhanced fluorescence (CHEF) process is responsible for the fluorescence enhancement of this probe. The in situ chelated BTC-Ga³⁺ could further monitor pyrophosphate ion (PPi) by demetallization process with quenching fluorescence emission. Additionally, the BTC and BTC-Ga³⁺ showed good cell permeability and could detect Ga³⁺ and PPi ions in onioninner epidermal cells, respectively.

Near-Infrared Fluorescence MOF Nanoprobe for Adenosine Triphosphate-Guided Imaging in Colitis

Adenosine triphosphate (ATP) is mainly produced in mitochondria and plays an important role in lots of pathological processes such as colitis. Unfortunately, to date, few suitable fluorescence probes have been developed for monitoring the ATP level in colitis. Herein, a fluorescence nanoprobe named NIR@ZIF-90 is proposed and prepared by encapsulating a rhodamine-based near-infrared (NIR) dye into zeolitic imidazolate frameworks (ZIF-90). The nanoprobe is nonfluorescent because the emission of NIR is suppressed by the encapsulation, while in the presence of ATP, the framework of ZIF-90 is dissembled to release NIR and thus NIR fluorescence at 750 nm is observed. The nanoprobe shows high sensitivity to ATP with a 72-fold increase and excellent selectivity to ATP over other nucleotides. Moreover, with low cytotoxicity and good mitochondria-targeted ability, NIR@ZIF-90 is used to image ATP in colorectal cancer cells (HCT116). In addition, due to the NIR emission, the nanoprobe is further employed to successfully monitor the ATP level in a colitis mouse model. To the best of our knowledge, the nanoprobe is the first example to study colitis in vivo with the guidance of ATP, which will provide an efficient tool for understanding colitis.

Thiazolidine based fluorescent chemosensors for aluminum ions and their applications in biological imaging

Utilization of fluorescent techniques in detection of various metal ions actively pursued allow ultrasensitive and selective detections of metal ions and prevent the adverse effect of cations such as aluminum (III) ions. In this study, two novel fluorescent chemosensors containing thiazole derivatives, ((E)-2-(4-hydroxy-3-(((2-hydroxyphenyl)imino)methyl)phenyl)-3-phenyl thiazolidin-4-one) AM1 and (2,3-bis(4-hydroxy-3-((E)-((2-hydroxyphenyl)imino) methyl) phenyl) thiazolidin-4-one) AM2, have been fabricated. The probes AM1 and AM2 were prepared using the condensation reaction between 2-hydroxy-5-(4-oxo-3-phenyl thiazolidin-2-yl) benzaldehyde and 2-aminophenol for the probe AM1 and 5,5'-(4-oxothiazolidine-2,3-diyl)bis(2-hydroxy benzaldehyde) and 2-aminophenol for the probe AM2. Afterwards, they were analyzed by various types of NMR and FT-IR spectroscopy, ESI-MS spectra, and elemental anayzer. As a second step, each fabricated chemosensor was able to use turn on fluorescence sensing for detecting of Al³⁺ ions in ACN/H₂O (v/v = 50/50, 10.0 μM, pH = 7.0) solution. Clear complexes formed between the probe AM1 and Al³⁺ ions and also the probe AM2 and Al³⁺ ions was determined by not only ¹H NMR titration study but also calculated by using the Job's plot. The limit of detection (LOD) value was found to be 0.11 μM (AM1) and 4.4 μM (AM2) for Al³⁺ ions. Likewise, cell imaging and in vitro cytotoxicity experiments of Al³⁺ ions in Human epithelium Lovo cells exhibited that prepared chemosensors had low cytotoxicity and blue fluorescence when they treated with of Al³⁺ ions in the cellular system.