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

DNA G-quadruplex-stabilizing metal complexes as anticancer drugs

Guanine quadruplexes (G4s) are important targets for cancer treatments as their stabilization has been associated with a reduction of telomere ends or a lower oncogene expression. Although less abundant than purely organic ligands, metal complexes have shown remarkable abilities to stabilize G4s, and a wide variety of techniques have been used to characterize the interaction between ligands and G4s. However, improper alignment between the large variety of experimental techniques and biological activities can lead to improper identification of top candidates, which hampers progress of this important class of G4 stabilizers. To address this, we first review the different techniques for their strengths and weaknesses to determine the interaction of the complexes with G4s, and provide a checklist to guide future developments towards comparable data. Then, we surveyed 74 metal-based ligands for G4s that have been characterized to the in vitro level. Of these complexes, we assessed which methods were used to characterize their G4-stabilizing capacity, their selectivity for G4s over double-stranded DNA (dsDNA), and how this correlated to bioactivity data. For the biological activity data, we compared activities of the G4-stabilizing metal complexes with that of cisplatin. Lastly, we formulated guidelines for future studies on G4-stabilizing metal complexes to further enable maturation of this field.

Chiral RuII -PtII Complexes Inducing Telomere Dysfunction against Cisplatin-Resistant Cancer Cells

The application of G-quadruplex stabilizers presents a promising anticancer strategy. However, the molecular crowding conditions within cells diminish the potency of current G-quadruplex stabilizers. Herein, chiral Ru^II -Pt^II dinuclear complexes were developed as highly potent G-quadruplex stabilizers even under challenging molecular crowding conditions. The compounds were encapsulated with biotin-functionalized DNA cages to enhance sub-cellular localization and provide cancer selectivity. The nanoparticles were able to efficiently inhibit the endogenous activities of telomerase in cisplatin-resistant cancer cells and cause cell death by apoptosis. The nanomaterials demonstrated high antitumor activity towards cisplatin-resistant tumor cells as well as tumor-bearing mice. To the best of our knowledge, this study presents the first example of a Ru^II -Pt^II dinuclear complex as a G-quadruplex stabilizer with an anti-cancer effect towards drug-resistant tumors inside an animal model.

Thiazole Containing PNA Mimic Regulates c-MYC Gene Expression through DNA G-Quadruplex

Peptide nucleic acids (PNAs), besides hybridizing to complementary DNA and RNAs, bind and stabilize DNA secondary structures. Herein, we illustrate the design and synthesis of PNA-like scaffolds by incorporating five-membered thiazole rings as modified bases instead of nucleobases and their subsequent effects on gene regulation by biophysical and in vitro assays. A thiazole-modified PNA trimer selectively recognizes c-MYC G-quadruplex (G4) DNA over other G4s and duplex DNA. It displays a high stabilization potential for the c-MYC G4 DNA and shows remarkable fluorescence enhancement with the c-MYC G4. It is flexible enough to bind at 5' and 3' ends as well as in the groove region of c-MYC G4. Furthermore, the PNA trimer easily permeates the cellular membrane and suppresses c-MYC mRNA expression in HeLa cells by targeting the promoter G4. This study illuminates modified PNAs as flexible molecular tools for selective targeting of noncanonical nucleic acids and modulating gene function.

Ruthenium(II) Polypyridyl Complexes and Their Use as Probes and Photoreactive Agents for G-quadruplexes Labelling

Due to their optical and electrochemical properties, ruthenium(II) polypyridyl complexes have been used in a wide array of applications. Since the discovery of the light-switch ON effect of [Ru(bpy)2dppz]2+ when interacting with DNA, the design of new Ru(II) complexes as light-up probes for specific regions of DNA has been intensively explored. Amongst them, G-quadruplexes (G4s) are of particular interest. These structures formed by guanine-rich parts of DNA and RNA may be associated with a wide range of biological events. However, locating them and understanding their implications in biological pathways has proven challenging. Elegant approaches to tackle this challenge relies on the use of photoprobes capable of marking, reversibly or irreversibly, these G4s. Indeed, Ru(II) complexes containing ancillary π-deficient TAP ligands can create a covalently linked adduct with G4s after a photoinduced electron transfer from a guanine residue to the excited complex. Through careful design of the ligands, high selectivity of interaction with G4 structures can be achieved. This allows the creation of specific Ru(II) light-up probes and photoreactive agents for G4 labelling, which is at the core of this review composed of an introduction dedicated to a brief description of G-quadruplex structures and two main sections. The first one will provide a general picture of ligands and metal complexes interacting with G4s. The second one will focus on an exhaustive and comprehensive overview of the interactions and (photo)reactions of Ru(II) complexes with G4s.

An organic molecular compound for in situ identification of mitochondrial G-quadruplexes in live cells

Emerging studies have shown that mitochondrial G-quadruplex plays a critical role in regulating mitochondrial gene replication and transcription, which makes it a promising target for the diagnosis and treatment of cancer or other major diseases. Molecular compounds that can highly target the mitochondrial G-quadruplexes in live cells are essential for further revealing the function and mechanism of these G-quadruplexes. Here, we have developed an organic molecular compound that can highly target the mitochondria of living cells by virtue of the membrane potential mechanism. Then it shows high selectivity to the G-quadruplex structure in the mitochondria, and its fluorescence overlaps well with that of the BG4 antibody. Moreover, the compound has extremely low cytotoxicity and does not interfere with the natural state of G-quadruplex structure. With these good properties, this compound will have great potential in mitochondrial G-quadruplex tracking research or targeted drug screening.

Kinetics and mechanism of formation of nickel(II)porphyrin and its interaction with DNA in aqueous medium

Kinetics between 5,10,15,20-tetrakis(N-methylpyridium-4-yl)porphyrin and Ni²⁺ species were investigated in aqueous solution at 25 ±1 °C in I = 0.10 M (NaNO₃). Speciation of Ni²⁺ was done in I = 0.10 M (NaNO₃) for knowing distribution of Ni²⁺ species with solution pH. Experimental data were compared with speciation diagram constructed from the values of hydrolysis constants of Ni²⁺ ion. Speciation data showed that hexaaquanickel(II) ions took place in hydrolysis reactions through formation of [Ni(OH₂)_6-n(OH)_n]^2-n species with solution pH. According to speciation of Ni²⁺ and pH dependent rate constants, rate expression can be written as: d[Ni(TMPyP)⁴⁺]/dt = (k₁[Ni²⁺_(aq)] + k₂[Ni(OH)⁺_(aq)] + k₃[Ni(OH)₂^o_(aq)] + k₄[Ni(OH)₃^-_(aq)])[H₂TMPyP⁴⁺], where k₁, k₂, k₃ and k₄ were found to be k₁ = (0.62 ± 0.22) × 10^-2; k₂ = (3.60 ± 0.40) × 10^-2; k₃ = (2.09 ± 0.52) × 10^-2, k₄ = (0.53 ± 0.04) × 10^-2 M^-1s^-1 at 25 ±1 °C, respectively. Formation of hydrogen bonding between [Ni(H₂O)₅(OH)]⁺ and [H₂TMPyP]⁴⁺ causes enhanced reactivity. Rate of formation of [Ni(II)TMPyP]⁴⁺ complex was to be 3.99 × 10^-2 M^-1s^-1 in I = 0.10 M, NaNO₃ (25 ± 1 °C). UV-Vis and fluorescence data suggested that [Ni(II)TMPyP]⁴⁺ and [H₂(TMPyP)]⁴⁺ interact with DNA via outside binding with self-stacking and intercalation, respectively.

SYNOPSIS

Spectroscopic and molecular docking studies for the binding and interaction aspects of curcumin-cysteine conjugate and rosmarinic acid with human telomeric G-quadruplex DNA

The binding and interaction aspects of potential anticancer ligands like: curcumin-cysteine (CC) and rosmarinic acid (RA) with human telomeric G-quadruplex DNA, a novel anticancer target, have been probed by spectroscopic and molecular docking approach. The circular dichroism study unravels the conformational switching from mixed hybrid to parallel structure for the short sequence of human telomeric G-quadruplex structure in the presence of both the ligands. Further a good correlation for binding affinity has been established from the emission and absorption binding spectrum analysis. Further our spectroscopic and molecular docking studies have suggested that the CC having better binding capability than RA to human telomeric G-quadruplex. The presence of L-cysteine moiety in CC ligand is responsible factor for its binding via both minor as well as major groove of human telomeric G-quadruplex DNA where-as RA binds only via minor groove of telomeric G-DNA.

In-vitro and In-vivo Photocatalytic Cancer Therapy with Biocompatible Iridium(III) Photocatalysts

Photocatalytic anticancer profile of a Ir^III photocatalyst (Ir3) with strong light absorption, high turnover frequency, and excellent biocompatibility is reported. Ir3 showed selective photo-cytotoxicity against cisplatin- and sorafenib-resistant cell lines while remaining dormant to normal cell lines in the dark. Ir3 exhibited excellent photo-catalytic oxidation of cellular co-enzyme, the reduced nicotinamide adenine dinucleotide phosphate (NADPH), and amino acids via a single electron transfer mechanism. The photo-induced intracellular redox imbalance and change in mitochondrial membrane potential resulted in necrosis and apoptosis of cancer cells. Importantly, Ir3 exhibited high biocompatibility and photo-catalytic anticancer efficiency as evident from in vivo zebrafish and mouse cancer models. To the best of our knowledge, Ir3 is the first Ir^III based photocatalyst with such a high biocompatibility and photocatalytic anticancer therapeutic effect.

Fingerprint Analysis of Vitex Negundo by HPLC Coupled with Multi-components Analysis

Background:

Vitex negundo (Nagod) is a very useful medicinal plant growing throughout India. The leaves of Nagod are aromatic, tonic and vermifuge. They are useful in the treatment of many ailments.

Introduction:

Both seasonal and geographical variations have been observed in the active constituents in Vitex negundo. A comprehensive and reproducible HPLC method based on HPLC fingerprint analysis was developed for assessing the quality of Vitex negundo.

Methods:

Sixteen samples of Nagod collected from different locations and seasons of India were analysed by HPLC and chromatograms were recorded for each of them using PDA detector and 10 peaks were considered for further data analysis. The data were then treated for PCA and cluster analysis using Minitab software.

Results:

PCA and HCA analysis were used in determining the variability in the leaves of Nagod collected from different places and seasons.

Conclusion:

The method was useful for discriminating the location of plant within or outside Gujarat but was unable to display any effective seasonal variation in collected samples.

ATP-responsive mitochondrial probes for monitoring metabolic processes of glioma stem cells in a 3D model

The metastatic cascade of cancer stem cells (CSCs) is always accompanied by elevated levels of adenosine triphosphate (ATP) as well as the alterntion of energy metabolism to support their differentiation and migration. Here we propose a 3D microfluidic tumor model coupled with an ATP-responsive mitochondrial probe (AMP) for investigation of metabolic processes of glioma stem cells (GSCs). The 3D tumor model has a middle matrix gel microchannel mimicking the extracellular matrix (ECM), which is sandwiched between a GSC culture chamber and a stimulation chamber. The AMPs consist of structure-switching ATP aptamers and triphenylphosphonium (TPP)-conjugated peptide nucleic acids (PNAs). Under TGF-β stimulation, invasive migration of GSCs accompanied by a high ATP level and spindle mesenchymal morphologies is observed due to the epithelial-to-mesenchymal transition (EMT). Moreover, acidic stress can keep GSCs in a low-energy state, while long-term low pH stimulation screens out more malignant glioma cells. This AMP-assisted 3D microfluidic tumor model provides a tremendous opportunity for studying the biological properties of CSCs.

Fluorogenic Pt complexes distinguish the quantity and folding behavior of RNA G-quadruplexes between live cancerous and healthy cells

Fluorogenic Pt complexes were developed to track and compare the intracellular un/folding behaviors of RNA G-quadruplexes among different cell lines.

Development and Validation of a Specific RP-HPLC Method for Simultaneous Estimation of Anti-retroviral Drugs: Application to Nanoparticulate Formulation System

Objective:

A simple, accurate and economical reverse phase- high performance liquid chromatographic method has been developed for the simultaneous quantitative estimation of two anti-retro viral drugs, Etravirine and Elvitegravir in nanoparticulate formulations for the first time. This method is a novel analytical technique for the detection of the both the drugs concurrently, as there is no method available for their simultaneous quantification, to the best of our knowledge.

Methods:

Optimization and validation of the chromatographic conditions were completed according to the standard ICH guidelines. The separation was done on a C18 column (250 mm x 4.6mm, 5μm) using methanol and phosphate buffer of pH (5.6) as the mobile phase in the ratio 78:22 v/v at a flow rate of 1ml/min for a short run time of 13 min. The detection wavelength was 285nm and the column temperature was maintained at 32oC.

Results:

The developed method was linear over 10 to 160 μg/ml with a regression coefficient of 0.999 for each. The LOD values were 4.83 and 9.25 µg/ml while LOQ values were 14.63 and 28.01 µg/ml for etravirine and elvitegravir respectively. The recovery values obtained by etravirine and elvitegravir were between 97.6% and 100.8%.

Conclusion:

The method was specific, precise, fast and accurate with good inter and intra day precision. The method was also effectively employed for the characterization and simultaneous quantification of both drugs in nanoparticulate formulation.

Characterization of clinically used oral antiseptics as quadruplex-binding ligands

Approaches to characterize the nucleic acid-binding properties of drugs and druglike small molecules are crucial to understanding the behavior of these compounds in cellular systems. Here, we use a Small Molecule Microarray (SMM) profiling approach to identify the preferential interaction between chlorhexidine, a widely used oral antiseptic, and the G-quadruplex (G4) structure in the KRAS oncogene promoter. The interaction of chlorhexidine and related drugs to the KRAS G4 is evaluated using multiple biophysical methods, including thermal melt, fluorescence titration and surface plasmon resonance (SPR) assays. Chlorhexidine has a specific low micromolar binding interaction with the G4, while related drugs have weaker and/or less specific interactions. Through NMR experiments and docking studies, we propose a plausible binding mode driven by both aromatic stacking and groove binding interactions. Additionally, cancer cell lines harbouring oncogenic mutations in the KRAS gene exhibit increased sensitivity to chlorhexidine. Treatment of breast cancer cells with chlorhexidine decreases KRAS protein levels, while a KRAS gene transiently expressed by a promoter lacking a G4 is not affected. This work confirms that known ligands bind broadly to G4 structures, while other drugs and druglike compounds can have more selective interactions that may be biologically relevant.

Cell penetrating thiazole peptides inhibit c-MYC expression via site-specific targeting of c-MYC G-quadruplex

The structural differences among different G-quadruplexes provide an opportunity for site-specific targeting of a particular G-quadruplex structure. However, majority of G-quadruplex ligands described thus far show little selectivity among different G-quadruplexes. In this work, we delineate the design and synthesis of a crescent-shaped thiazole peptide that preferentially stabilizes c-MYC quadruplex over other promoter G-quadruplexes and inhibits c-MYC oncogene expression. Biophysical analysis such as Förster resonance energy transfer (FRET) melting and fluorescence spectroscopy show that the thiazole peptide TH3 can selectively interact with the c-MYC G-quadruplex over other investigated G-quadruplexes and duplex DNA. NMR spectroscopy reveals that peptide TH3 binds to the terminal G-quartets and capping regions present in the 5′- and 3′-ends of c-MYC G-quadruplex with a 2:1 stoichiometry; whereas structurally related distamycin A is reported to interact with quadruplex structures via groove binding and end stacking modes with 4:1 stoichiometry. Importantly, qRT-PCR, western blot and dual luciferase reporter assay show that TH3 downregulates c-MYC expression by stabilizing the c-MYC G-quadruplex in cancer cells. Moreover, TH3 localizes within the nucleus of cancer cells and exhibits antiproliferative activities by inducing S phase cell cycle arrest and apoptosis.

Non-Invasive Extraction of Gabapentin for Therapeutic Drug Monitoring by Reverse Iontophoresis: Effect of pH, Ionic Strength, and Polyethylene Glycol 400 in the Receiving Medium

Background:

Monitoring of plasma concentrations is a necessity for narrow therapeutic index potent drugs. Development of non-invasive methods can save the patients from the trauma of needles and hence is considered as a research priority.

Introduction:

Gabapentin, an anti-epileptic drug requires therapeutic monitoring because of its narrow therapeutic index. The objective of the study was to develop a suitable method for the non-invasive extraction of gabapentin for the same.

Methods:

Transdermal reverse iontophoresis was performed using pig ear skin as a barrier membrane. Three compartment iontophoretic cells were used for the extraction study. Extractions were carried out under low intensity electric field (current intensity- 0.5 mA/cm2, electrical field approximately 5 V). The donor compartment was charged with aqueous gabapentin (10 µg/ml in phosphate buffer of pH 7.4). For studying the effect of receiving vehicle (pH, ionic strength, and enhancer) on the extraction efficiency of gabapentin, the two receiver chambers were charged with media having varying concentration of these factors. Drug content was determined by HPLC.

Results:

Compared to other pHs, cumulative extraction of gabapentin at pH 5 was significantly higher at both anode and cathode (p<0.001). At low ionic strength, extraction of gabapentin increased linearly with the increase in concentration of ions up to a certain value but at very high ionic strength the pattern reversed. Similar results were obtained with enhancer (polyethylene glycol 400). Extraction increased with increase in polyethylene glycol 400 up to 3% and then decreased.

Conclusion:

Extraction flux can be optimized by manipulation of the receiver media.

Curcumin attenuates hypoxia/reoxygenation‑induced cardiomyocyte injury by downregulating Notch signaling

Recovery of the blood supply is the most effective treatment against ischemic heart disease; however, it is also a major cause of myocardial ischemia/reperfusion injury in clinical therapy. Curcumin has been reported to possess beneficial effects against hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury by regulating cell proliferation, apoptosis and antioxidant enzyme activity. The aim of the present study was to investigate the molecular mechanisms underlying the effects of curcumin on H/R-injured cardiomyocytes. H9C2 cardiomyocytes were pretreated with curcumin, and then cultured under H/R conditions. The viability of H9C2 cells was measured using a Cell Counting kit-8 assay, and the levels of intracellular lactate dehydrogenase (LDH), malondialdehyde (MDA) and superoxide dismutase (SOD) were measured to assess cell injury. Levels of reactive oxygen species (ROS) and apoptosis were evaluated by flow cytometry. The expression levels of Notch intracellular domain (NICD) and numerous downstream genes were analyzed via reverse transcription-quantitative polymerase chain reaction and western blotting. The results revealed that curcumin protected H9C2 cells against H/R-induced injury, reversing the H/R-induced increases in LDH and MDA levels, and decreases in SOD levels. ROS levels in H/R-induced cells were also significantly downregulated by curcumin treatment (P<0.01), and the apoptotic rate was significantly decreased from 15.13% in the H/R group to 7.7% in the H/R + curcumin group (P<0.01). The expression levels of NICD, hairy and enhancer of split (Hes)-1, Hes-5 and hairy/enhancer-of-split related with YRPW motif protein 1 (Hey-1) were significantly decreased in H/R-treated cells following curcumin treatment. Treatment with Jagged1 attenuated the effects of curcumin on cell viability, ROS levels and apoptosis; the Notch pathway was also reactivated. The present study indicated that there was a role for the Notch pathway in the protective effects of curcumin against H/R-induced cardiomyocyte injury, suggesting that downregulation of the Notch pathway may alleviate H/R-induced injury in H9C2 cells.

Benzothiazole-based cyanines as fluorescent "light-up" probes for duplex and quadruplex DNA

Analogs of benzothiazole orange (BO) with one, two or three methylbenzothiazolylmethylidene substituents in the 1-methylpyridinium ring were obtained from the respective picolinium, lutidinium or collidinium salts. Fluorescence parameters of the known and new dyes in complexes with various DNA structures, including G-quadruplexes (G4s) and i-motifs (IMs), were analyzed. All dyes efficiently distinguished G4s and ss-DNA. The bi- and tri-substituted derivatives had basically similar distributions of relative fluorescence intensities. The mono-substituted derivatives exhibited enhanced sensitivity to parallel G4s. All dyes were particularly sensitive to a G4 structure with an additional duplex module (the thrombin-binding aptamer TBA31), presumably due to a distinctive binding mode (interaction with the junction between the two modules). In particular, BO showed a strong (160-fold) enhancement in fluorescence quantum yield in complex with TBA31 compared to the free dye. The fluorescence quantum yields of the 2,4-bisubstituted derivative in complex with well-characterized G4s from oncogene promoters were in the range of 0.04-0.28, i.e. comparable to those of ThT. The mono/bi-substituted derivatives should be considered as possible light-up probes for G4 formation.

Cationic porphyrins with large side arm substituents as resonance light scattering ratiometric probes for specific recognition of nucleic acid G-quadruplexes

Specific G-quadruplex-probing is crucial for both biological sciences and biosensing applications. Most reported probes are focused on fluorescent or colorimetric recognition of G-quadruplexes. Herein, for the first time, we reported a new specific G-quadruplex-probing technique-resonance light scattering (RLS)-based ratiometric recognition. To achieve the RLS probing of G-quadruplexes in the important physiological pH range of 7.4-6.0, four water soluble cationic porphyrin derivatives, including an unreported octa-cationic porphyrin, with large side arm substituents were synthesized and developed as RLS probes. These RLS probes were demonstrated to work well for ratiometric recognition of G-quadruplexes with high specificity against single- and double-stranded DNAs, including long double-stranded ones. The working mechanism was speculated to be based on the RLS signal changes caused by porphyrin protonation that was promoted by the end-stacking of porphyrins on G-quadruplexes. This work adds an important member in G-quadruplex probe family, thus providing a useful tool for studies on G-quadruplex-related events concerning G-quadruplex formation, destruction and changes in size, shape and aggregation. As a proof-of-concept example of applications, the RLS probes were demonstrated to work well for label-free and sequence-specific sensing of microRNA. This work also provides a simple and useful way for the preparation of cationic porphyrins with high charges.

Hydrophilic, Red-Emitting, and Thermally Activated Delayed Fluorescence Emitter for Time-Resolved Luminescence Imaging by Mitochondrion-Induced Aggregation in Living Cells

Thermally activated delayed fluorescence (TADF) materials have provided new strategies for time-resolved luminescence imaging (TRLI); however, the development of hydrophilic TADF luminophores for specific imaging in cells remains a substantial challenge. In this study, a mitochondria-induced aggregation strategy for TRLI is proposed with the design and utilization of the hydrophilic TADF luminophore ((10-(1,3-dioxo-2-phenyl-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)-9,9-dimethyl-9,10-dihydroacridin-2-yl)methyl)triphenylphosphonium bromide (NID-TPP). Using a nonconjugated linker to introduce a triphenylphosphonium (TPP+) group into the 6-(9,9-dimethylacridin-10(9H)-yl)-2-phenyl-1H-benzo[de]isoquinoline-1,3(2H)-dione (NID) TADF luminophore preserves the TADF emission of NID-TPP. NID-TPP shows clear aggregation-induced delayed fluorescence enhancement behavior, which provides a practical strategy for long-lived delayed fluorescence emission in an oxygen-containing environment. Finally, the designed mitochondrion-targeting TPP+ group in NID-TPP induces the adequate accumulation of NID-TPP and results in the first reported TADF-based time-resolved luminescence imaging and two-photon imaging of mitochondria in living cells.

Fluorescing Isofunctional Ribonucleosides: Assessing Adenosine Deaminase Activity and Inhibition

The enzymatic conversion of isothiazolo[4,3-d]pyrimidine-based adenosine (^tz A) and 2-aminoadenosine (^tz 2-AA) analogues to the corresponding isothiazolo[4,3-d]pyrimidine-based inosine (^tz I) and guanosine (^tz G) derivatives is evaluated and compared to the conversion of native adenosine to inosine. Henri-Michaelis-Menten analyses provides the foundation for a high-throughput screening assay, and the efficacy of the assay is showcased by fluorescence-based analysis of ^tz A conversion to ^tz I in the presence of known and newly synthesized inhibitors.

A Label-free and Universal Platform for the Construction of Various Logic Circuits Based on Graphene Oxide and G-Quadruplex Structure

Due to structual polymorphism, excellent binding activity and functional significances in biological regulation, G-quadruplex has become the focus of research as an innovated module for analytical chemistry and biomedicine. Meanwhile, in the biosensor fields, new nanomaterial graphene oxide (GO) has also received extensive attention due to its brilliant physical and chemical properties. Herein, we propose a non-label and enzyme-free logic operation platform based on G-quadruplex structure and GO instead of any expensive modification. Taking advantage of the quenching ability of GO to AgNCs and the fluorescence enhancement of NMM (N-methylmesoporphyrin IX) mediated by the split G-quadruplex, a series of binary logic gates (AND, OR, INHIBIT, XOR) have been constructed and verified by biological experiments. Subsequently, two combinatorial logic gates were successfully realized conceptually on the basis of the same BGG platform, including half adder and half subtractor. Taken together, such a universal platform has great potential in applications, such as biocomputing, bio-imaging and disease diagnosis, which cultivate a new view for future biological research.

Dynamic split G-quadruplex programmed reversible nanodevice

We propose a dynamic nanodevice based on a split G-quadruplex (G4). By splitting it apart, we can successfully decouple the G-tetrad formation from external stimuli, greatly expanding the stimulus for G4 based devices. Taking advantage of the rigid force from a DNA duplex, the nanodevice can be switched reversibly through the conformational transformation.

Rapid Quantitative Fluorescence Detection of Copper Ions with Disposable Microcapsule Arrays Utilizing Functional Nucleic Acid Strategy

In this work, an economical and easy-to-use microcapsule array fabricated by ice printing technique has been realized for ultrasensitive fluorescence quantification of copper ions employing functional nucleic acid strategy. With ice printing, the detection reagents are sealed by polystyrene (PS) film isolation and photopolymer, which guarantees a stable and contamination-free environment for functional nucleic acid reaction. Our microcapsule arrays have shown long-term stability (20 days) under -20 °C storage in frozen form before use. During the Cu²⁺ on-site detection, 1 μL sample is simply injected into the thawy microcapsule by a microliter syringe under room temperature, and after 20 minutes the fluorescence result can be obtained by an LED transilluminator. This method can realize the detection limit to 100 nM (100 fmol/μL) with high specificity.

A supersensitive biosensor based on MoS2 nanosheet arrays for the real-time detection of H2O2 secreted from living cells

A self-supported MoS₂ nanosheet biosensor for highly sensitive detection of H₂O₂ secreted from live cells.

Selective parallel G-quadruplex recognition by a NIR-to-NIR two-photon squaraine

Fluorescence imaging probes for specific G-quadruplex (G4) conformations are of considerable interest in biomedical research. Herein, we present the synthesis and the binding properties of a new water-soluble near-infrared (NIR) amphiphilic squaraine dye (CAS-C1) which is capable of selective detection of parallel over non-parallel and non G4 topologies. The striking changes in its linear optical response upon binding to parallel G4s give rise to high fluorescence quantum yields (Φ f ≈ 0.7) and one-photon molecular brightness in the far-red-NIR region. The outstanding recognition process of CAS-C1 for parallel G4s via end-stacking provides binding constants in the nanomolar regime (K b = 107 to 108 M-1) awarding it as one of the most potent parallel G4 binders currently available. Moreover, the CAS-C1-parallel G4 system exhibits large two-photon absorption (TPA) cross-sections and molecular brightness in the second NIR biological transparency window (λ ≈ 1275 nm), making it an ideal candidate for NIR-to-NIR ultrasensitive two-photon procedures.

Rapid Detection of AGs using Microchip Capillary Electrophoresis Contactless Conductivity Detection

Background:

In order to realize current aminoglycosides supervision in food and environment, our team improved the sensitivity and separation efficiency of the portable ITO detector, based on the technology of microchip capillary electrophoresis and contactless conductivity detection.

Experiment:

Parameters (the separation voltage, buffer concentration, electrodes gap, elicitation frequency, elicitation voltage) were optimized for the detection of three aminoglycosides, gentamicin, kanamycin and streptomycin and the separation of their mixture in background electrolyte consists of 2-(N-Morpholino) ethanesulfonic acid (MES) and L-Histidine (His). The enhanced method was also applied to other types of aminoglycosides.

Results:

Under optimal conditions, the monitoring of three types of aminoglycosides obtained such a sensitive response that the limits of detection of gentamicin sulfate, kanamycin sulfate and streptomycin sulfate were calculated as 3.1 µg/ml, 0.89 µg/ml and 0.96 µg/ml, at signal-to-noise ratio 3, respectively. In addition they got separated completely from each other only in 40 s. The results of other varieties of aminoglycosides including tobramycin sulfate and amikacin sulfate also met the standard.

Conclusion:

We successfully proposed here an unprecedentedly portable, miniaturized and rapid microchip capillary electrophoresis contactless conductivity detection system to realize current aminoglycosides supervision in food and environment.

Label-free molecular probe based on G-quadruplex and strand displacement for sensitive and selective detection and naked eye discrimination of exon 2 deletion of AIMP2

Exon 2 deletion of aminoacyl tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2) is a genetic deletion related to various cancers, for instance ovarian and lung cancers. It can be worked as an indicator of cancer for diagnosis of diseases. Here, we developed a label-free method based on the formation of split G-quadruplex in the presence of target DNA combined with strand displacement to detect exon 2 deletion of AIMP2 (DE2) sensitively and selectively. This method is easy-operating and cost-saving. Moreover, it has observed discrimination of gene deletion from wild-types by naked eyes. The results demonstrate that this strategy can be further used for the detection of different gene deletions to achieve early diagnosis of diseases and allow better prognosis.

Thiazole Orange-Modified Carbon Dots for Ratiometric Fluorescence Detection of G-Quadruplex and Double-Stranded DNA

A new carbon dot (CD)-based nanoprobe for the ratiometric fluorescence detection of DNA was constructed in this work. Thiazole orange (TO), a specific organic small molecular probe toward DNA, is covalently linked to the surface of CDs, acting as the recognition element and the fluorescence response unit. In the absence of DNA, the nanoprobe only emitted the blue fluorescence of CDs, whereas TO was almost nonfluorescent. Upon addition of DNA, a turn-on emission at 530 nm appeared and gradually enhanced along with the increasing of the target DNA, whereas the fluorescence of CDs was unchanged, which realized the ratiometric detection of the target DNA. The CD-TO nanoprobe showed good selectivity to parallel G-quadruplex (G4) and double-stranded (ds) DNA over antiparallel G4 and single-stranded DNA. Moreover, the ratiometric fluorescence nanoprobe exhibited high sensitivity for ssab (a dsDNA) and c-myc (a parallel G4) with a low detection limit of 0.90 and 3.31 nM, respectively. Additionally, the G4/hemin peroxidase activity inhibition experiment demonstrated that CD-TO bound to the G4s through the end-stacking mode.

Supramolecular Analytical Chemistry in Cancer Research

Supramolecular interactions, such as those observed between antibodies and antigens, have been employed in developing analytical methods for several decades. One major area of interest concerns cancer research, where intricate supramolecular designs have emerged to tackle difficult analytes in complex tumor systems. Our increasing knowledge toward supramolecular systems have elicited profound interest in creating more efficient analytical approaches, evidenced by the ever-growing body of literature in the field. Some of the novel tools have indeed facilitated our understanding of cancer biology, through providing previously inaccessible information. In this review, we describe common strategies of developing supramolecular analytical methods and their implementations in cancer research. We provide an overview for each of the approaches and discuss representative examples in recent literature.