Conjugating a groove-binding motif to an Ir(iii) complex for the enhancement of G-quadruplex probe behavior

Ni-Based metal–organic framework derived Ni@C nanosheets on a Ni foam substrate as a supersensitive non-enzymatic glucose sensor

Uniform and compact porous Ni@C nanosheet membranes on Ni foam showing remarkable electrocatalytic activity for non-enzymatic glucose sensing.

Selective recognition of c-myc promoter G-quadruplex and down-regulation of oncogene c-myc transcription in human cancer cells by 3,8a-disubstituted indolizinone

Indolizinone could selectively recognize c-myc promoter G-quadruplex.

Anionic cyclometallated Pt(ii) square-planar complexes: new sets of highly luminescent compounds

Novel anionic Pt(ii) complexes were synthesized, displaying an outstanding enhancement of the emission efficiency in the solid state.

Half-sandwich iridium N-heterocyclic carbene anticancer complexes

Half-sandwich iridium N-heterocyclic carbene complexes display potent anticancer activities and are attractive for development as new anticancer agents.

Enhanced cancer therapy by the marriage of metabolic alteration and mitochondrial-targeted photodynamic therapy using cyclometalated Ir(iii) complexes

A series of DCA-Ir(iii) co-drug complexes were demonstrated to act in synergy by sensitizing cancer cell for PDT to achieve cancer-specifically enhanced two-photon PDT in the hypoxic muticellular tumor spheroids.

Fluorescence detection of endogenous bisulfite in liver cancer cells using an effective ESIPT enhanced FRET platform

Probe L-HF1, which featured large (pseudo) Stokes shifts and high FRET efficiency, was designed on a new ESIPT enhanced FRET platform for the detection of HSO₃⁻/SO₃²⁻.

Preparation of metalated azine complexes of iridium(iii)

The preparation of half-sandwich κ¹-aldazine and κ¹-ketazine complexes of iridium and their metalation reaction affording chelate κ²-azine derivatives are described. The photoluminescence properties of the chelate complexes are also described.

The Thiophene "Sigma-Hole" as a Concept for Preorganized, Specific Recognition of G⋅C Base Pairs in the DNA Minor Groove

In spite of its importance in cell function, targeting DNA is under-represented in the design of small molecules. A barrier to progress in this area is the lack of a variety of modules that recognize G⋅C base pairs (bp) in DNA sequences. To overcome this barrier, an entirely new design concept for modules that can bind to mixed G⋅C and A⋅T sequences of DNA is reported herein. Because of their successes in biological applications, minor-groove-binding heterocyclic cations were selected as the platform for design. Binding to A⋅T sequences requires hydrogen-bond donors whereas recognition of the G-NH2 requires an acceptor. The concept that we report herein uses pre-organized N-methylbenzimidazole (N-MeBI) thiophene modules for selective binding with mixed bp DNA sequences. The interaction between the thiophene sigma hole (positive electrostatic potential) and the electron-donor nitrogen of N-MeBI preorganizes the conformation for accepting an hydrogen bond from G-NH2 . The compound-DNA interactions were evaluated with a powerful array of biophysical methods and the results show that N-MeBI-thiophene monomer compounds can strongly and selectively recognize single G⋅C bp sequences. Replacing the thiophene with other moieties significantly reduces binding affinity and specificity, as predicted by the design concept. These results show that the use of molecular features, such as sigma-holes, can lead to new approaches for small molecules in biomolecular interactions.

A G-quadruplex-selective luminescent iridium(III) complex and its application by long lifetime

BACKGROUND

The G-quadruplex motif has been widely used for the construction of analytical detection platforms due to its rich structural polymorphism and flexibility. Luminescent assays are often limited due to the interference from endogenous fluorophores in biological samples.

METHODS

To address this challenge, a novel long lifetime iridium(III) complex 1 was synthesized and used to construct a G-quadruplex-based assay for detecting prostate specific antigen (PSA) in aqueous solution. PSA is a common biomarker in serum and used as a model for demonstration in this work.

RESULTS

The PSA assay has achieved a detection limit of 40.8pg·mL^-1, and shows high selectivity towards PSA over other proteins. Additionally, the assay could function in diluted human serum by using time-resolved luminescent spectroscopy, with good linearity from 1 to 10ng·mL^-1 of PSA, which is adequate to detect the PSA levels for physiological (<4ng·mL^-1) and clinical (4-10ng·mL^-1) applications.

CONCLUSIONS

The assay was successfully constructed. As revealed from time-resolved method, the long lifetime property of iridium(III) complex 1 plays an important role in distinguishing phosphorescence signals from short-life auto-fluorescence of human serum.

GENERAL SIGNIFICANCE

Luminescent transition metal complexes offer several advantages over other widely used organic fluorophores, such as long phosphorescence lifetime, large Stokes shift and modular syntheses. In addition, the assay could work effectively in diluted human serum using time-resolved luminescent spectroscopy, it therefore could be potentially developed to monitor PSA in biological samples. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.

An enzyme-free and resettable platform for the construction of advanced molecular logic devices based on magnetic beads and DNA

A series of multiple logic circuits based on magnetic beads and DNA are constructed to perform resettable nonarithmetic functions, including a digital comparator, 4-to-2 encoder and 2-to-3 decoder, 2-to-1 encoder and 1-to-2 decoder. The signal reporter is composed of a G-quadruplex/NMM complex and a AuNP-surface immobilized molecular beacon. It is the first time that the designed DNA-based nonarithmetic nanodevices can share the same DNA platform with a reset function, which has great potential application in information processing at the molecular level. Another novel feature of the designed system is that the developed nanodevices are operated on a simple DNA/magnetic bead platform and share a constant threshold setpoint without the assistance of any negative logic conversion. The reset function is realized by heating the output system and the magnetic separation of the computing modules. Due to the biocompatibility and design flexibility of DNA, these investigations may provide a new route towards the development of resettable advanced logic circuits in biological and biomedical fields.

Novel One-Tube-One-Step Real-Time Methodology for Rapid Transcriptomic Biomarker Detection: Signal Amplification by Ternary Initiation Complexes

We have developed a novel RNA detection method, termed signal amplification by ternary initiation complexes (SATIC), in which an analyte sample is simply mixed with the relevant reagents and allowed to stand for a short time under isothermal conditions (37 °C). The advantage of the technique is that there is no requirement for (i) heat annealing, (ii) thermal cycling during the reaction, (iii) a reverse transcription step, or (iv) enzymatic or mechanical fragmentation of the target RNA. SATIC involves the formation of a ternary initiation complex between the target RNA, a circular DNA template, and a DNA primer, followed by rolling circle amplification (RCA) to generate multiple copies of G-quadruplex (G4) on a long DNA strand like beads on a string. The G4s can be specifically fluorescence-stained with N(3)-hydroxyethyl thioflavin T (ThT-HE), which emits weakly with single- and double-stranded RNA/DNA but strongly with parallel G4s. An improved dual SATIC system, which involves the formation of two different ternary initiation complexes in the RCA process, exhibited a wide quantitative detection range of 1-5000 pM. Furthermore, this enabled visual observation-based RNA detection, which is more rapid and convenient than conventional isothermal methods, such as reverse transcription-loop-mediated isothermal amplification, signal mediated amplification of RNA technology, and RNA-primed rolling circle amplification. Thus, SATIC methodology may serve as an on-site and real-time measurement technique for transcriptomic biomarkers for various diseases.

A double responsive smart upconversion fluorescence sensing material for glycoprotein

A novel strategy was developed to prepare double responsive smart upconversion fluorescence material for highly specific enrichment and sensing of glycoprotein. The novel double responsive smart sensing material was synthesized by choosing Horse radish peroxidase (HRP) as modal protein, the grapheme oxide (GO) as support material, upconversion nanoparticles (UCNPs) as fluorescence signal reporter, N-isopropyl acrylamide (NIPAAM) and 4-vinylphenylboronic acid (VPBA) as functional monomers. The structure and component of smart sensing material was investigated by transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared (FTIR), respectively. These results illustrated the smart sensing material was prepared successfully. The recognition characterizations of smart sensing material were evaluated, and results showed that the fluorescence intensity of smart sensing material was reduced gradually, as the concentration of protein increased, and the smart sensing material showed selective recognition for HRP among other proteins. Furthermore, the recognition ability of the smart sensing material for glycoprotein was regulated by controlling the pH value and temperature. Therefore, this strategy opens up new way to construct smart material for detection of glycoprotein.

Application of iridium(III) complex in label-free and non-enzymatic electrochemical detection of hydrogen peroxide based on a novel "on-off-on" switch platform

We herein report a label-free and non-enzymatic electrochemical sensor for the highly sensitive detection of hydrogen peroxide (H2O2) based on a novel "on-off-on" switch system. In our design, MB was used as an electron mediator to accelerate the electron transfer while AuNPs was used to amplify the electrochemical signal due to its excellent biocompatibility and good conductivity. The "switch-off" state was achieved by introducing the guanine-rich capture probe (CP) and an iridium complex onto the electrode surface to form a hydrophobic layer, which then hinders electron transfer. Upon addition of H2O2, fenton reaction occurs and produces OH• in the presence of Fe(2+). The OH• cleaves the CP into DNA fragments, thus resulting in the release of CP and iridium complex from the sensing interface, recovering the electrochemical signal to generate a "switch-on" state. Based on this novel switch system, a detection limit as low as 3.2 pM can be achieved for H2O2 detection. Moreover, satisfactory results were obtained by using this method for the detection of H2O2 in sterilized milk. To the best of our knowledge, this is the first G-quadruplex-based electrochemical sensor using an iridium(III) complex.

A novel dinuclear iridium(III) complex as a G-quadruplex-selective probe for the luminescent switch-on detection of transcription factor HIF-1α

A novel dinuclear Ir(III) complex 5 was discovered to be specific to G-quadruplex DNA, and was utilized in a label-free G-quadruplex-based detection platform for transcription factor activity. The principle of this assay was demonstrated by using HIF-1α as a model protein. Moreover, this HIF-1α detection assay exhibited potential use for biological sample analysis.

Novel aminoalkyl tris-cyclometalated iridium complexes as cellular stains

Novel tris-cyclometalated luminescent iridium complexes capable of staining cells and showing in cellulo lifetimes in the microsecond regime are reported.

I-motif-stapled and spacer-dependent multiple DNA nanostructures

The DNA spacers between duplexes and i-motif structures are critical for the morphology of assembled pH-responsive DNA nanostructures, which is very instructive for fabrication of distinct-scale molecular devices in the future.

Iridium(iii) complexes with 1,10-phenanthroline-based N^N ligands as highly selective luminescent G-quadruplex probes and application for switch-on ribonuclease H detection

A study was performed to investigate the relationship between molecular structure and G4 sensing ability for a series of iridium(iii) complexes. The complex7was used to construct a G4-based assay for RNase H.

The development of a light-up red-emitting fluorescent probe based on a G-quadruplex specific cyanine dye

Cyanine dye-dimethylindole red containing an anionic propylsulfonate substituent and an extending polymethine chain was found to behave as a highly specific red-emitting G-quadruplex probe, especially for parallel G-quadruplex c-myc.