A Pyrene Derivative for Hg2+-Selective Fluorescent Sensing and Its Application in In Vivo Imaging

Elucidating sensing mechanisms of a pyrene excimer-based calix[4]arene for ratiometric detection of Hg(ii) and Ag(i) and chemosensor behaviour as INHIBITION or IMPLICATION logic gates

This article reports the synthesis and characterisation of two lower rim calix[4]arene derivatives with thiourea as spacer and pyrene or methylene-pyrene as fluorophore. Both derivatives exhibit a fluorimetric response towards Hg²⁺, Ag⁺ and Cu²⁺. Only methylene-pyrenyl derivative 2 allows for selective detection of Hg²⁺ and Ag⁺ by enhancement or decrease of excimer emission, respectively. The limits of detection of 2 are 8.11 nM (Hg²⁺) and 2.09 nM (Ag⁺). DFT and TD-DFT computational studies were carried out and used to identify possible binding modes that explain the observed response during fluorescence titrations. Calculations revealed the presence of different binding sites depending on the conformation of 2, which suggest a reasonable explanation for non-linear changes in fluorescence depending on the physical nature of the interaction between metal centre and conformer. INHIBITION and IMPLICATION logic gates have also been generated monitoring signal outputs at pyrene monomer (395 nm) and excimer (472 nm) emission, respectively. Thus 2 is a potential primary sensor towards Ag⁺ and Hg²⁺ able to configure two different logic gate operations.

Firefly Luciferin-Inspired Biocompatible Chemistry for Protein Labeling and In Vivo Imaging

Biocompatible reactions have emerged as versatile tools to build various molecular imaging probes that hold great promise for the detection of biological processes in vitro and/or in vivo. In this Minireview, we describe the recent advances in the development of a firefly luciferin-inspired biocompatible reaction between cyanobenzothiazole (CBT) and cysteine (Cys), and highlight its versatility to label proteins and build multimodality molecular imaging probes. The review starts from the general introduction of biocompatible reactions, which is followed by briefly describing the development of the firefly luciferin-inspired biocompatible chemistry. We then discuss its applications for the specific protein labeling and for the development of multimodality imaging probes (fluorescence, bioluminescence, MRI, PET, photoacoustic, etc.) that enable high sensitivity and spatial resolution imaging of redox environment, furin and caspase-3/7 activity in living cells and mice. Finally, we offer the conclusions and our perspective on the various and potential applications of this reaction. We hope that this review will contribute to the research of biocompatible reactions for their versatile applications in protein labeling and molecular imaging.

Our Expedition in Linear Neutral Platinum-Acetylide Complexes: The Preparation of Micro/nanostructure Materials, Complicated Topologies, and Dye-Sensitized Solar Cells

During the past few decades, the construction of various kinds of platinum-acetylide complexes has attracted considerable attention, because of their wide applications in photovoltaic cells, non-linear optics, and bio-imaging materials. Among these platinum-acetylide complexes, the linear neutral platinum-acetylide complexes, due to their attractive properties, such as well-defined linear geometry, synthetic accessibility, and intriguing photoproperties, have emerged as a rising star in this field. In this personal account, we will discuss how we entered the field of linear neutral platinum-acetylide chemistry and what we found in this field. The preparation of various types of linear neutral platinum-acetylide complexes and their applications in the areas of micro/nanostructure materials, complicated topologies, and dye-sensitized solar cells will be summarized in this account.

N-(3-Imidazolyl)propyl dansylamide as a selective Hg(2+) sensor in aqueous media through electron transfer

N-Imidazolylpropyl dansylamide 1 was synthesized for the sensing of metal ions and found to be selective and sensitive toward Hg(2+) ions in a PBS-EtOH (1:4, pH=7.4) solution. The sensing ability of probe 1 was examined by UV-Vis, fluorescence, and (1)H NMR spectroscopy. The sensing of Hg(2+) exhibited a quenching of emission band at λmax=515 nm of probe 1, which was associated with quenching of green fluorescence emission under 365 nm illumination. Probe 1 showed a good association constant with Hg(2+) (Ka=6.48×10(4) M(-1)) with a stoichiometry of 1:1 in PBS-EtOH (1:4, pH=7.4) having the lowest detection limit of 1 μM for Hg(2+); on the other hand, probe 2, which has no imidazole moiety, was not able to detect any metal ion. In the case of probe 1, electrons on the imidazole nitrogen are available for electron transfer (ET), which was responsible for its green emission band that was quenched on addition of Hg(2+); this clearly indicates that these electrons were used for the formation of a coordinate bond with Hg(2+) and that ET was switched off.

Iron(III)-Selective Chelation-Enhanced Fluorescence Sensing for In Vivo Imaging Applications

A "turn-on" pattern Fe(3+) -selective fluorescent sensor was synthesized and characterized that showed high fluorescence discrimination of Fe(3+) over Fe(2+) and other tested ions. With a 62-fold fluorescence enhancement towards Fe(3+) , the probe was employed to detect Fe(3+) in vivo in HeLa cells and Caenorhabditis elegans, and it was also successfully used to elucidate Fe(3+) enrichment and exchange infected by innexin3 (Inx3) in hemichannel-closed Sf9 cells.

1,8-Naphthyridine-based molecular clips for off–on fluorescence sensing of Zn2+ in living cells

New 1,8-naphthyridine-based clip-like receptor as “off–on” fluorescent probe was designed and synthesised for selectively sensing Zn²⁺ in living cells.

A near-infrared chemodosimeter with Pi-selective colorimetric and fluorescent sensing and its application in vivo imaging

A near-infrared colorimetric and fluorescent chemosensor for detecting phosphate ion (Pi) has been developed. The practical utility of this chemosensor was demonstrated by employing it to detect Pi in Paramecium and C. elegans.

Switching of the triplet excited state of styryl 2,6-diiodo-bodipy and its application in acid-activatable singlet oxygen photosensitizing

IodoBodipy-styrylBodipy dyads triplet photosensitizers were prepared (B-1 and B-2) which contain acid-responsive moiety. Both compounds show broadband visible light absorption, due to the resonance energy transfer (RET) between the two different visible light-harvesting Bodipy units. The photophysical properties of the dyads were studied with steady-state and nanosecond time-resolved transient absorption spectroscopy. The production of triplet excited state is switched ON or OFF by protonation/deprotonation of the amino group in the dyads. In the neutral form, the excited state is short-lived (<10 ns) and no singlet oxygen ((1)O2) photosensitizing was observed. Upon protonation, a long-lived triplet excited state was observed (τT = 3.1 μs) and the (1)O2 quantum yield (ΦΔ) is up to 73.8%. The energy levels of the components of the dyads were changed upon protonation and this energy level tuning exerts significant influence on the triplet state property of the dyad. Acid-activated shuffling of the localization of the triplet excited state between two components of a dyad was observed. Furthermore, we observed a rare example that a chromophore giving shorter absorption wavelength is acting as the singlet energy acceptor in RET. The experimental results were rationalized by density functional theory (DFT) and time-dependent DFT (TDDFT) calculations.