Real-time monitoring of cellular superoxide anion release in THP-1 cells using a catalytically amplified superoxide dismutase-based microbiosensor.

Reactive oxygen species (ROS) including the superoxide anion (O2•-) are typically studied in cell cultures using fluorescent dyes, which provide only discrete single-point measurements. These methods lack the capabilities for assessing O2•- kinetics and release in a quantitative manner over long monitoring times. Herein, we present the fabrication and application of an electrochemical biosensor that enables real-time continuous monitoring of O2•- release in cell cultures for extended periods (> 8 h) using an O2•- specific microelectrode. To achieve the sensitivity and selectivity requirements for cellular sensing, we developed a biohybrid system consisting of superoxide dismutase (SOD) and Ti3C2Tx MXenes, deposited on a gold microwire electrode (AuME) as O2•- specific materials with catalytic amplification through the synergistic action of the enzyme and the biomimetic MXenes-based structure. The biosensor demonstrated a sensitivity of 18.35 nA/µM with a linear range from 147 to 930 nM in a cell culture medium. To demonstrate its robustness and practicality, we applied the biosensor to monitor O2•- levels in human leukemia monocytic THP-1 cells upon stimulation with lipopolysaccharide (LPS). Using this strategy, we successfully monitored LPS-induced O2•- in THP-1 cells, as well as the quenching effect induced by the ROS scavenger N-acetyl-L-cysteine (NAC). The biosensor is generally useful for exploring the role of oxidative stress and longitudinally monitoring O2•- release in cell cultures, enabling studies of biochemical processes and associated oxidative stress mechanisms in cellular and other biological environments.

Salt-Induced High-Density Vacancy-Rich 2D MoS2 for Efficient Hydrogen Evolution.

Emerging non-noble metal 2D catalysts, such as molybdenum disulfide (MoS2 ), hold great promise in hydrogen evolution reactions. The sulfur vacancy is recognized as a key defect type that can activate the inert basal plane to improve the catalytic performance. Unfortunately, the method of introducing sulfur vacancies is limited and requires costly post-treatment processes. Here, a novel salt-assisted chemical vapor deposition (CVD) method is demonstrated for synthesizing ultrahigh-density vacancy-rich 2H-MoS2 , with a controllable sulfur vacancy density of up to 3.35 × 1014  cm-2 . This approach involves a pre-sprayed potassium chloridepromoter on the growth substrate. The generation of such defects is closely related to ion adsorption in the growth process, the unstable MoS2 -K-H2 O triggers the formation of sulfur vacancies during the subsequent transfer process, and it is more controllable and nondestructive when compared to traditional post-treatment methods. The vacancy-rich monolayer MoS2 exhibits exceptional catalytic activity based on the microcell measurements, with an overpotential of ≈158.8 mV (100 mA cm-2 ) and a Tafel slope of 54.3 mV dec-1 in 0.5 m H2 SO4 electrolyte. These results indicate a promising opportunity for modulating sulfur vacancy defects in MoS2 using salt-assisted CVD growth. This approach represents a significant leap toward achieving better control over the catalytic performances of 2D materials.

The smart-home study: A feasibility study to pilot the use of smartphone technology to identify environmental falls risk factors in the home.

Introduction: While occupational therapy home assessments are effective to identify environmental falls risk factors, patients may not receive these services due to workforce distribution and geographical distances. Technology may offer a new way for occupational therapists to conduct home assessments to identify environmental fall risks. Objectives: To (i) explore the feasability of identifying environmental risk factors using smartphone technology, (ii) develop and pilot a suite of procedures for taking smartphone images and (iii) examine the inter-rater reliability and content validity between occupational therapists when assessing smartphone images using a standardised assessment tool. Method: Following ethical approval a procedure was developed and participants recruited to submit smartphone images of their bedroom, bathroom and toilet. Two independent occupational therapists then assessed these images using a home safety checklist. Findings were analysed using inferential and descriptive statistics. Results: Of 100 volunteers screened, 20 individuals participated. A guideline for instructing patients to take home images was developed and tested. Participants averaged 9.00 minutes (SD 4.401) to complete the task, whilst occupational therapists took approximately 8 minutes to review the images. The inter-rater reliability between the two therapists was 0.740 (95% CI: 0.452-0.888). Conclusion: The study found that use of smartphones was to a large extent feasible and conclude that the use of smartphone technologies is a potential complimentary service to traditional home visits. The effective prescription of equipment in this trial was identified as a challenge. The impact on costs and potential falls incidents remains uncertain and more research is warranted in representative populations.

Controlled Adhesion of Ice-Toward Ultraclean 2D Materials.

The scalable 2D device fabrication and integration demand either the large-area synthesis or the post-synthesis transfer of 2D layers. While the direct synthesis of 2D materials on most targeted surfaces remains challenging, the transfer approach from the growth substrate onto the targeted surfaces offers an alternative pathway for applications and integrations. However, the current transfer techniques for 2D materials predominantly involve polymers and organic solvents, which are liable to contaminate or deform the ultrasensitive atomic layers. Here, novel ice-aided transfer and ice-stamp transfer methods are developed, in which water (ice) is the only medium in the entire process. In practice, the adhesion between various 2D materials and ice can be well controlled by temperature. Through such controlled adhesion of ice, it is shown that the new transfer methods can yield ultrahigh quality and exceptional cleanliness in transferred 2D flakes and continuous 2D films, and are applicable for a wide range of substrates. Furthermore, beyond transfer, ice can also be used for cleaning the surfaces of 2D materials at higher temperatures. These novel techniques can enable unprecedented ultraclean 2D materials surfaces and performances, and will contribute to the upcoming technological revolutions associated with 2D materials.

Proton-activated chloride channel PAC regulates endosomal acidification and transferrin receptor-mediated endocytosis.

During vesicular acidification, chloride (Cl-), as the counterion, provides the electrical shunt for proton pumping by the vacuolar H+ ATPase. Intracellular CLC transporters mediate Cl- influx to the endolysosomes through their 2Cl-/H+ exchange activity. However, whole-endolysosomal patch-clamp recording also revealed a mysterious conductance releasing Cl- from the lumen. It remains unknown whether CLCs or other Cl- channels are responsible for this activity. Here, we show that the newly identified proton-activated Cl- (PAC) channel traffics from the plasma membrane to endosomes via the classical YxxL motif. PAC deletion abolishes the endosomal Cl- conductance, raises luminal Cl- level, lowers luminal pH, and increases transferrin receptor-mediated endocytosis. PAC overexpression generates a large endosomal Cl- current with properties similar to those of endogenous conductance, hypo-acidifies endosomal pH, and reduces transferrin uptake. We propose that the endosomal Cl- PAC channel functions as a low pH sensor and prevents hyper-acidification by releasing Cl- from the lumen.

Determination of cell metabolite VEGF165 and dynamic analysis of protein-DNA interactions by combination of microfluidic technique and luminescent switch-on probe.

In this paper, we rationally design a novel G-quadruplex-selective luminescent iridium (III) complex for rapid detection of oligonucleotide and VEGF165 in microfluidics. This new probe is applied as a convenient biosensor for label-free quantitative analysis of VEGF165 protein from cell metabolism, as well as for studying the kinetics of the aptamer-protein interaction combination with a microfluidic platform. As a result, we have successfully established a quantitative analysis of VEGF165 from cell metabolism. Furthermore, based on the principles of hydrodynamic focusing and diffusive mixing, different transient states during kinetics process were monitored and recorded. Thus, the combination of microfluidic technique and G-quadruplex luminescent probe will be potentially applied in the studies of intramolecular interactions and molecule recognition in the future.

Development of an Aptamer-Based Sensing Platform for Metal Ions, Proteins, and Small Molecules through Terminal Deoxynucleotidyl Transferase Induced G-Quadruplex Formation.

We report a label-free, structure-independent luminescent-sensing platform for metal ions, proteins, and small molecules utilizing an Ir(III) complex, terminal deoxynucleotidyl transferase (TdT), and a structure-folding aptamer. A novel G-quadruplex-selective Ir(III) complex was identified to detect the nascent G-quadruplex motifs with an enhanced luminescence response. Unlike most label-free DNA-based assays reported in the literature, this sensing platform does not require a specific secondary structure of aptamer, thus greatly simplifying DNA design. The detection platform was demonstrated by the detection of K(+) ions, thrombin, and cocaine as representative examples of metal ions, proteins, and small molecules.

An iridium(iii)-based irreversible protein-protein interaction inhibitor of BRD4 as a potent anticancer agent.

Bromodomain-containing protein 4 (BRD4) has recently emerged as an attractive epigenetic target for anticancer therapy. In this study, an iridium(iii) complex is reported as the first metal-based, irreversible inhibitor of BRD4. Complex 1a is able to antagonize the BRD4-acetylated histone protein-protein interaction (PPI) in vitro, and to bind BRD4 and down-regulate c-myc oncogenic expression in cellulo. Chromatin immunoprecipitation (ChIP) analysis revealed that 1a could modulate the interaction between BRD4 and chromatin in melanoma cells, particular at the MYC promoter. Finally, the complex showed potent activity against melanoma xenografts in an in vivo mouse model. To our knowledge, this is the first report of a Group 9 metal complex inhibiting the PPI of a member of the bromodomain and extraterminal domain (BET) family. We envision that complex 1a may serve as a useful scaffold for the development of more potent epigenetic agents against cancers such as melanoma.

Label-free luminescence switch-on detection of hepatitis C virus NS3 helicase activity using a G-quadruplex-selective probe.

A series of luminescent Ir(iii) complexes were synthesised and evaluated for their ability to act as luminescent G-quadruplex-selective probes. The Ir(iii) complex 9, [Ir(phq)2(phen)]PF6 (where phq = 2-phenylquinoline; phen = 1,10-phenanthroline), exhibited high luminescence in the presence of G-quadruplex DNA compared to dsDNA and ssDNA, and was employed to construct a label-free G-quadruplex-based assay for hepatitis C virus NS3 helicase activity in aqueous solution. Moreover, the application of the assay for screening potential helicase inhibitors was demonstrated. To our knowledge, this is the first G-quadruplex-based assay for helicase activity.

Discovery of a small-molecule inhibitor of STAT3 by ligand-based pharmacophore screening.

STAT3 modulates the transcription of a wide variety of regulatory genes involved in cell proliferation, differentiation, migration, apoptosis, and other critical cellular functions. Constitutive activation of STAT3 has been detected in a wide spectrum of human malignancies. A pharmacophore model constructed from a training set of STAT3 inhibitors binding to the SH2 domain was used to screen an in-house database of compounds, from which azepine 1 emerged as a top candidate. Compound 1 inhibited STAT3 DNA-binding activity in vitro and attenuated STAT3-directed transcription in cellulo with comparable potency to the well-known STAT3 inhibitor S3I-201. A fluorescence polarization assay revealed that compound 1 targeted the SH2 domain of STAT3. Furthermore, compound 1 inhibited STAT3 phosphorylation in cells without affecting the total expression of STAT3. This study also validates the use of pharmacophore modeling to identify inhibitors of protein-protein interactions.

Discovery of deoxyvasicinone derivatives as inhibitors of NEDD8-activating enzyme.

NEDD8-activating enzyme (NAE) controls the specific degradation of proteins regulated by cullin-RING ubiquitin E3 ligases, and has been considered as an attractive molecular target for the development of drugs against cancer. A pharmacophore model constructed from a training set of deoxyvasicinone derivatives was used to screen 376 compounds from an analogue database. From the initial screening, the valine-linked deoxyvasicinone derivative 9 and the N-isopropyl-linked deoxyvasicinone derivative 10 emerged as the top scoring candidates. Compounds 9 and 10 showed micromolar potencies in both cell-free and cell-based systems, with selectivity for NAE over the related enzymes SAE and UAE. Molecular modelling analysis suggested that 9 and 10 may inhibit NAE by blocking the ATP-binding domain. Thus, these deoxyvasicinone derivatives could be considered as promising lead molecules for the development of more potent inhibitors of NAE.

Pharmacophore modeling for the identification of small-molecule inhibitors of TACE.

Tumor necrosis factor α-converting enzyme (TACE) plays a critical role in diverse physiological processes such as inflammation, hematopoiesis, and development. In this study, a pharmacophore model constructed from a training set of TACE inhibitors was used to screen an in-house database of organic compounds, from which compound 1 emerged as a top candidate. In a cell-free assay, compound 1 inhibited TACE enzymatic activity in a dose-dependent manner. Moreover, compound 1 inhibited the production of soluble TNF-α in human acute monocytic leukemia THP-1 cells without impacting nitric oxide production, and exhibited anti-proliferative activity against THP-1 cells. We envisage that compound 1 may be employed as a useful scaffold for the development of more potent TACE inhibitors. This study also validates the use of pharmacophore modeling to identify enzyme inhibitors.

A colorimetric chemosensor for Cu²âº ion detection based on an iridium(III) complex.

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1-3 bearing a rhodamine-linked NˆN ligand for the detection of Cu(2+) ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu(2+) ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu(2+) ions in tap water or natural river water samples was demonstrated.

Antagonizing STAT3 dimerization with a rhodium(III) complex.

Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity.

An oligonucleotide-based label-free luminescent switch-on probe for RNA detection utilizing a G-quadruplex-selective iridium(III) complex.

We report herein the synthesis and application of a novel G-quadruplex-selective luminescent iridium(iii) complex for the construction of an oligonucleotide-based, label-free, rapid and convenient luminescent RNA detection platform.

Label-free luminescence switch-on detection of T4 polynucleotide kinase activity using a G-quadruplex-selective probe.

A label-free, oligonucleotide-based, switch-on luminescence detection method for T4 polynucleotide kinase activity has been developed using a novel G-quadruplex-selective luminescent Ir(iii) complex probe. The application of the assay for screening potential T4 PNK inhibitors is also demonstrated. To our knowledge, this is the first metal-based assay for PNK activity.

A G-quadruplex-based, label-free, switch-on luminescent detection assay for Ag+ ions based on the exonuclease III-mediated digestion of C-Ag+-C DNA.

We report herein the ability of exonuclease III to cleave C-Ag+-C mismatched DNA, which was utilised for the construction of an exonuclease III-assisted, label-free, switch-on luminescent platform for Ag+ ions using a novel G-quadruplex-selective iridium(iii) complex.

Antagonism of mTOR Activity by a Kinetically Inert Rhodium(III) Complex.

Kinetically inert Group 9 metal complexes have found emerging use as inhibitors of protein kinases or as modulators of protein-protein interactions. A series of cyclometalated rhodium(III) and iridium(III) complexes was investigated as inhibitors of mammalian target of rapamycin (mTOR) activity. Cell-free and cell-based experiments revealed rhodium(III) complex 1 to be a potent mTOR inhibitor (IC50 =0.01 µM in the cell-free system), with potency comparable to that of rapamycin. The inhibition by complex 1 was found to be dependent on FK506-binding protein 12 (FKBP12), which suggests that complex 1 may behave as a modulator of the mTOR-FKBP12 interaction. Preliminary structure-activity relationships indicated that the donor ligand and the nature of the metal center are important determinants for mTOR inhibitory activity. Rhodium(III) complex 1 represents the first metal-based inhibitor of mTOR activity, and demonstrates the potential of kinetically inert Group 9 complexes as protein-protein interaction modulators.

Label-free luminescent switch-on detection of endonuclease IV activity using a G-quadruplex-selective iridium(III) complex.

We report herein the synthesis and application of a novel G-quadruplex-selective luminescent iridium(III) complex [Ir(ppy)2(bcp)](+) (where ppy = 2-phenylpyridine and bcp = 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) for the sensitive detection of apurinic/apyrimidinic (AP) endonuclease activity. Using endonuclease IV (Endo IV) as a model enzyme, a duplex DNA substrate containing a G-quadruplex-forming sequence is cleaved by Endo IV at the abasic site. This releases the G-quadruplex sequence, which folds into a G-quadruplex and is recognised by the G-quadruplex-selective iridium(III) complex with an enhanced luminescence response. The assay achieved high sensitivity and selectivity for Endo IV over other tested enzymes.

A label-free luminescent switch-on assay for ATP using a G-quadruplex-selective iridium(III) complex.

We report herein the G-quadruplex-selective property of a luminescent cyclometallated iridium(III) complex for the detection of adenosine-5'-triphosphate (ATP) in aqueous solution. The ATP-binding aptamer was employed as the ATP recognition unit, while the iridium(III) complex was used to monitor the formation of the G-quadruplex structure induced by ATP. The sensitivity and fold enhancement of the assay were higher than those of the previously reported assay using the organic dye crystal violet as a fluorescent probe. This label-free luminescent switch-on assay exhibits high sensitivity and selectivity towards ATP with a limit of detection of 2.5 µM.