Adenosine triphosphate (ATP) and zinc(II) ions responsive pyrene based turn-on fluorescent probe and its application in live cell imaging

Solvent-regulated fluorescence off-on signaling of Ni(II) and Zn(II) with the formation of two mononuclear complexes with an ATP detection ability by Zn(II) assembly

The current study shows that Schiff base HL, (Z)-2,4-dibromo-6-(((piperidin-2-ylmethyl)imino)methyl)phenol, can be used successfully as a selective chemosensor for Zn(II) and Ni(II) among several competing cations in purely aqueous and semi-aqueous media. Under UV light in methanol-water (9 : 1) HEPES buffer, the receptor gives its response by changing its color to cyan color in the presence of Zn(II) and to bluish cyan color in the presence of Ni(II). Surprisingly, the chemosensor can only reliably identify Zn(II) in a hundred percent aqueous medium by changing its color to light yellow. UV and fluorescence studies in both aqueous and semi-aqueous media are used to further investigate this Zn(II) and Ni(II) recognition phenomenon. The high values of the host-guest binding constants, obtained by electronic and fluorescence titration, ensure that a strong bond exists between HL and Ni(II)/Zn(II). As anticipated, two highly luminescent mononuclear, crystalline compounds, complexes 1 and 2, have been developed by a separate reaction of HL and Zn(II)/Ni(II), and the high luminous properties are due to the occurrence of Chelation Enhanced Fluorescence (CHEF). According to the single crystal structure, the asymmetric units of both complexes consist of two deprotonated chemosensor units and one Zn(II)/Ni(II), leading to the formation of an octahedral complex. For Ni(II) and Zn(II) sensing, the predicted LOD is in the nanomolar range. Both complexes 1 and 2 are fluorescence active and studies to check their ATP detection ability, but intriguingly, only complex 2 is capable of detecting ATP in a fully aqueous solution. Finally, the live cell imaging study validates the two sensors' biosensing functionality.

Colorimetric Detection of ATP by a Chlorophosphonazo III -based Mg2+ Complex in Aqueous Solution via Indicator Displacement Approach

A simple and effective colorimetric detection of adenosine 5-triphosphate (ATP) in 100% aqueous media was developed based on an indicator displacement approach (IDA). A commercially available dye, Chlorophosphonazo III (CPA), was utilized as the indicator and the ATP detection was achieved using the complex of CPA with Mg²⁺ in a 2:1 stoichiometric ratio (CPA₂-Mg²⁺) through the regeneration of CPA by the binding of ATP to Mg²⁺. Upon addition of a series of anions to the CPA₂-Mg²⁺ complex, only the appearance of the solution of the complex with ATP exhibited a color change from blue to purple which can be detected by the naked eye. Moreover, the ATP recognition was not hampered by the presence of other anions. Hence, CPA₂-Mg²⁺ is efficient in ATP highly selective and sensitive colorimetric detection in 100% aqueous media.

Efficient fluorescent recognition of ATP/GTP by a water-soluble bisquinolinium pyridine-2,6-dicarboxamide compound. Crystal structures, spectroscopic studies and interaction mode with DNA

The new dicationic pyridine-2,6-dicarboxamide-based compound 1 bearing two N-alkylquinolinium units was synthesized, structurally determined by single-crystal X-ray diffraction, and studied in-depth as a fluorescent receptor for nucleotides and inorganic phosphorylated anions in pure water. The addition of nucleotides to 1 at pH = 7.0 quenches its blue emission with a selective affinity towards adenosine 5'-triphosphate (ATP) and guanosine 5'-tripohosphate (GTP) over other nucleotides such CTP, UTP, ADP, AMP, dicarboxylates and inorganic anions. On the basis of the spectroscopic tools (1H, 31P NMR, UV-vis, fluorescence), MS measurements and DFT calculations, receptor 1 binds ATP with high affinity (log K = 5.04) through the simultaneous formation of strong hydrogen bonds and π-π interactions between the adenosine fragment and quinolinium ring with binding energy calculated in 8.7 kcal mol-1. High affinity for ATP/GTP is attributed to the high acidity of amides and preorganized rigid structure of 1. Receptor 1 is an order of magnitude more selective for ATP than GTP. An efficient photoinduced electron transfer quenching mechanism with simultaneous receptor-ATP complexation in both the excited and ground states is proposed. Additionally, multiple spectroscopic studies and molecular dynamics simulations showed that 1 can intercalate into DNA base pairs.

Application of a novel hydroxyl functionalized fluorescent covalent organic framework for turn-off ultrasensitive Zn2+ ion detection

In this research, a novel hydroxyl functionalized covalent organic framework (COF) with fluorescence properties was rationally designed based on the reaction between 2,5-dihydroxy-terephthalic-dihydrazide (DHTPz) and 1,3,5-benzenetricarboxaldehyde (Bt) for Zn²⁺ detection. The prepared DHTPz-Bt exhibited strong fluorescence, while the apparent quenching of fluorescence was observed after the introduction of Zn²⁺. Meanwhile, DHTPz-Bt exhibited high sensitivity and promising selectivity during the detection of Zn²⁺. Additionally, the recognition process was revealed to be attributed to the coordination between the hydroxyl groups on the phenyls of DHTPz-Bt and Zn²⁺ ions, as verified by using Fourier-transform infrared spectra and X-ray photoelectron spectra. This work demonstrates the great potential of fluorescent probes by rationally introducing metal ligands, which will lead to a suite of new COF materials for metal ion sensing in a practical manner.

Mitochondria targeting drugs for neurodegenerative diseases—design, mechanism and application

Neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD) are a heterogeneous group of disorders characterized by progressive degeneration of neurons. NDDs threaten the lives of millions of people worldwide and regretfully remain incurable. It is well accepted that dysfunction of mitochondria underlies the pathogenesis of NDDs. Dysfunction of mitochondria results in energy depletion, oxidative stress, calcium overloading, caspases activation, which dominates the neuronal death of NDDs. Therefore, mitochondria are the preferred target for intervention of NDDs. So far various mitochondria-targeting drugs have been developed and delightfully some of them demonstrate promising outcome, though there are still some obstacles such as targeting specificity, delivery capacity hindering the drugs development. In present review, we will elaborately address 1) the strategy to design mitochondria targeting drugs, 2) the rescue mechanism of respective mitochondria targeting drugs, 3) how to evaluate the therapeutic effect. Hopefully this review will provide comprehensive knowledge for understanding how to develop more effective drugs for the treatment of NDDs.

Simultaneous preconcentration and fluorescence detection of ATP by a hybrid nanocomposite of magnetic nanoparticles incorporated in mixed metal hydroxide

A new approach for increasing the sensitivity of adenosine triphosphate (ATP) detection was demonstrated. The assay was based on the synergetic function of a hybrid nanocomposite (MNPs@MMH) composed of magnetic nanoparticles (MNPs) incorporated in a mixed metal hydroxide (MMH). MNPs@MMH can be utilized as an efficient green extractant and peroxidase catalyst. The trace level of ATP in the sample solution was first extracted by the MNPs@MMH hybrid nanocomposite through the ion exchange properties of MMH and adsorbed on the surface of the MNPs@MMH. The concentration of ATP was related to the fluorescence intensity of 2,3-diaminophenazine (DAP) generated from peroxidase-like activity of the MNPs in the presence of H₂O₂ and o-phenylenediamine (OPD). In the presence of ATP, the active surface of the MNPs was diminished, and the amount of DAP generated was reduced. Thus, the concentration of ATP was related to the degree of fluorescence decrease compared to the fluorescence intensity of the system without ATP. Based on the proposed strategy, a highly sensitive assay for ATP was achieved. This assay exhibited good selectivity for detection of ATP over derivatives and other common anions. The proposed assay allowed the detection of ATP in a concentration range of 2.5-20 μM with a detection limit of 0.41 μM.