Amidoxime-grafted cotton fibers with anti-microbial sludge for efficient uranium recovery.

Uranium as a nuclear fuel, its source and aftertreatment has been a hot topic of debate for developers. In this paper, amidoxime and guanidino-modified cotton fibers (DC-AO-PHMG) were synthesized by the two-step functionalization approach, which exhibited remarkable antimicrobial and high uranium recovery property. Adsorption tests revealed that DC-AO-PHMG had excellent selectivity and anti-interference properties, the maximum adsorption capacity of 609.75 mg/g. More than 85 % adsorption capacity could still be kept after 10 adsorption-desorption cycles, and it conformed to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model as a spontaneous heat-absorbing chemical monolayer process. FT-IR, EDS and XPS analyses speculated that the amidoxime and amino synergistically increased the uranium uptake. The inhibitory activities of DC-AO-PHMG against three aquatic bacteria, BEY, BEL (from Yellow River water and lake bottom silt, respectively) and B. subtilis were significantly stronger, and the uranium adsorption was not impacted by the high bacteria content. Most importantly, DC-AO-PHMG removed up to 94 % of uranium in simulated seawater and extracted up to 4.65 mg/g of uranium from Salt Lake water, which demonstrated its great potential in the field of uranium resource recovery.

3D flower-like bimetallic Ni-Co metal-organic framework as an electrocatalyst for the oxygen evolution reaction.

The rational design and facile preparation of a catalyst with high activity, strong durability and low consumption for the oxygen evolution reaction (OER) is an ongoing challenge in water splitting to generate clean and renewable H2 fuel. Herein, bimetallic metal-organic frameworks (MOFs) with a uniform morphology, controlled metal ratio and low crystallinity were constructed using a simple and reliable one-step solvothermal method. The three-dimensional (3D) flower-like MOF (F-Ni1Co4-BTC) with a Ni to Co molar ratio of 1 : 4 coordinated with 1,3,5-benzenetricarboxylic acid exhibited excellent OER catalytic activity compared with its corresponding counterparts, which can be attributed to the establishment of the exquisite morphology, the proportion of the dual-metal center, and the formation of active intermediates. Furthermore, when F-Ni1Co4-BTC was directly grown on carbon cloth (F-Ni1Co4-BTC/CC), it achieved an obvious improvement in electrochemical performance, affording a low overpotential of 292 mV at a current density of 10 mA cm-2, a small Tafel slope (48 mV dec-1), and excellent mechanical durability in an alkaline electrolyte, which is due to the integrated electrode attained richer active sites and faster electron transfer rate with the introduction of highly conductive carbon cloth. Our work offers a promising strategy to tailor the properties of bimetallic MOFs and the possibility of highly efficient earth-abundant catalysts for practical applications.

Metal-organic frame material encapsulated Rhodamine 6G: A highly sensitive fluorescence sensing platform for the detection of picric acid contaminants in water.

As a water pollutant with excellent solubility, 2,4,6-trinitrophenol (also known as picric acid, PA) poses a potential threat to the natural environment and human health, so it is crucial important to detect PA in water. In this study, a novel composite material (MIL-53(Al)@R6G) was successfully synthesized by encapsulating Rhodamine 6G into a metal-organic frame material, which was used for fluorescence detection of picric acid (PA) in water. The composite exhibits bright yellow fluorescence emission with a fluorescence quantum yield of 58.23 %. In the process of PA detection, the composite has excellent selectivity and anti-interference performance, and PA can significantly quench the fluorescence intensity of MIL-53(Al)@R6G. MIL-53(Al)@R6G has the advantages of fast detection time (20 s), wide linear range (1-100 µM) and low detection limit (4.8 nM). In addition, MIL-53(Al)@R6G has demonstrated its potential for the detection of PA in environmental water samples with satisfactory results.

Synthesis Strategies, Preparation Methods, and Applications of Chiral Metal-Organic Frameworks.

Chiral Metal-Organic Frameworks (CMOFs) is a kind of material with great application value in recent years. Formed by the coordination of metal ions or metal clusters with organic ligands. It has ordered and adjustable pores, multi-dimensional network structure, large specific surface area and excellent adsorption properties. This material structure combines the properties of metal-organic frameworks (MOFs) with the chiral properties of chiral molecules. It has great advantages in catalysis, adsorption, separation and other fields. Therefore, it has a wide range of applications in chemistry, biology, medicine and materials science. In this paper, various synthesis strategies and preparation methods of chiral metal-organic frameworks are reviewed from different perspectives, and the advantages of each method are analyzed. In addition, the applications of chiral metal-organic framework materials in enantiomer recognition and separation, circular polarization luminescence and asymmetric catalysis are systematically summarized, and the corresponding mechanisms are discussed. Finally, the challenges and prospects of the development of chiral metal-organic frame materials are analyzed in detail.

Zirconium-based metal-organic framework encapsulated dye molecules: An excellent sensing platform for sensitive detection of Cu2+ in aqueous environments.

Residual heavy metal ions in water pose a major hazard to ecology as well as human health, and Cu2+, as the most common heavy metal ion in water bodies, can cause a variety of diseases in human beings with prolonged exposure, therefore, a rational sensing platform is needed for the specific detection of Cu2+. In this work, based on the solvothermal method, we successfully prepared the composite UIO-66@FS by encapsulating the dye fluorescein sodium molecule (FS) with a metal-organic framework material (UIO-66). The composite material has bright fluorescence emission properties with a fluorescence quantum yield of 62.03 %, and the composite material has been used to construct a fluorescence sensing platform for detecting the heavy metal Cu2+ in the aqueous environment. The fluorescence of UIO-66@FS can be greatly quenched by Cu2+, which is visible to the naked eye under UV lamp. The sensing platform is able to withstand environmental interference and has the advantages of high selectivity, excellent sensitivity, fast response, wide linear range (2.5 µM-500 µM), and low detection limit (0.246 µM) in the fluorescence quenching detection of Cu2+. In addition, the sensor has been used to detect Cu2+ in real water samples with satisfactory recoveries. Therefore, this sensing probe can be an excellent candidate for Cu2+ detection and has wonderful potential for real water sample detection.

Acupuncture vs Massage for Pain in Patients Living With Advanced Cancer: The IMPACT Randomized Clinical Trial.

Importance: Pain is challenging for patients with advanced cancer. While recent guidelines recommend acupuncture and massage for cancer pain, their comparative effectiveness is unknown. Objective: To compare the effects of acupuncture and massage on musculoskeletal pain among patients with advanced cancer. Design, Setting, and Participants: A multicenter pragmatic randomized clinical trial was conducted at US cancer care centers consisting of a northeastern comprehensive cancer center and a southeastern cancer institute from September 19, 2019, through February 23, 2022. The principal investigator and study statisticians were blinded to treatment assignments. The duration of follow-up was 26 weeks. Intention-to-treat analyses were performed (linear mixed models). Participants included patients with advanced cancer with moderate to severe pain and clinician-estimated life expectancy of 6 months or more. Patient recruitment strategy was multipronged (eg, patient database queries, mailings, referrals, community outreach). Eligible patients had English or Spanish as their first language, were older than 18 years, and had a Karnofsky score greater than or equal to 60 (range, 0-100; higher scores indicating less functional impairment). Interventions: Weekly acupuncture or massage for 10 weeks with monthly booster sessions up to 26 weeks. Main Outcomes and Measures: The primary end point was the change in worst pain intensity score from baseline to 26 weeks. The secondary outcomes included fatigue, insomnia, and quality of life. The Brief Pain Inventory (range, 0-10; higher numbers indicate worse pain intensity or interference) was used to measure the primary outcome. The secondary outcomes included fatigue, insomnia, and quality of life. Results: A total of 298 participants were enrolled (mean [SD] age, 58.7 [14.1] years, 200 [67.1%] were women, 33 [11.1%] Black, 220 [74.1%] White, 46 [15.4%] Hispanic, and 78.5% with solid tumors). The mean (SD) baseline worst pain score was 6.9 (1.5). During 26 weeks, acupuncture reduced the worst pain score, with a mean change of -2.53 (95% CI, -2.92 to -2.15) points, and massage reduced the Brief Pain Inventory worst pain score, with a mean change of -3.01 (95% CI, -3.38 to -2.63) points; the between-group difference was not significant (-0.48; 95% CI, -0.98 to 0.03; P = .07). Both treatments also improved fatigue, insomnia, and quality of life without significant between-group differences. Adverse events were mild and included bruising (6.5% of patients receiving acupuncture) and transient soreness (15.1% patients receiving massage). Conclusions and Relevance: In this randomized clinical trial among patients with advanced cancer, both acupuncture and massage were associated with pain reduction and improved fatigue, insomnia, and quality of life over 26 weeks; however, there was no significant different between the treatments. More research is needed to evaluate how best to integrate these approaches into pain treatment to optimize symptom management for the growing population of people living with advanced cancer. Trial Registration: ClinicalTrials.gov Identifier: NCT04095234.

Chiral Carbon Dots and Chiral Carbon Dots with Circularly Polarized Luminescence: Synthesis, Mechanistic Investigation and Applications.

Chiral carbon dots (CCDs) can be widely used in various fields such as chiral recognition, chiral catalysis and biomedicine because of their unique optical properties, low toxicity and good biocompatibility. In addition, CCDs with circularly polarized luminescence (CPL) can be synthesized, thus broadening the prospects of CCDs applications. Since the research on CCDs is still in its infancy, this paper reviews the chiral origin, formation mechanism, chiral evolution, synthesis and emerging applications of CCDs, with a special focus on CCDs with CPL activity. It is hoped that it will provide some reference to solve the current problems faced by CCDs. Finally, the opportunities and challenges of the current research on CCDs are described, and their future development trends have also been prospected.

Enantioseparation Membranes: Research Status, Challenges, and Trends.

The purity of enantiomers plays a critical role in human health and safety. Enantioseparation is an effective way and necessary process to obtain pure chiral compounds. Enantiomer membrane separation is a new chiral resolution technique, which has the potential for industrialization. This paper mainly summarizes the research status of enantioseparation membranes including membrane materials, preparation methods, factors affecting membrane properties, and separation mechanisms. In addition, the key problems and challenges to be solved in the research of enantioseparation membranes are analyzed. Last but not least, the future development trend of the chiral membrane is expected.

An electrochemical chiral sensor based on the synergy of chiral ionic liquid and 3D-NGMWCNT for tryptophan enantioselective recognition.

A facile chiral composite (3D-NGMWCNT@(S,S)-CIL) was prepared by integrating three-dimensional N-doped graphene oxide multi-walled carbon nanotubes (3D-NGMWCNT) and chiral ionic liquid ((S,S)-CIL) via electrodeposition. SEM, XRD, XPS, and electrochemical methods were used to characterize this composite and it revealed that the integrated 3D-NGMWCNT@(S,S)-CIL composite showed excellent electrochemical performance. Therefore, a 3D-NGMWCNT@(S,S)-CIL/GCE electrochemical sensor was constructed for enantioselective recognition of Trp enantiomers. The coefficient (IL/ID) of the 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor was 2.26 by differential pulse voltammograms (DPV), revealing that the synthesized 3D-NGMWCNT@(S,S)-CIL had a higher affinity for L-Trp than D-Trp. Moreover, UV-V is spectroscopy and a water contact angle test also proved this result. The 3D-NGMWCNT@(S,S)-CIL/GCE sensor had a detection limit of 0.024 µM and 0.055 µM, and sensitivity of 62.35 µA·mM-1·cm-2 and 30.40 µA·mM-1·cm-2 for L-Trp and D-Trp, respectively, with a linear response range of 0.01 to 5 mM. In addition, the 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor showed excellent stability, and good reproducibility and was applied to detect L-Trp or D-Trp in real samples. The novel 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor provides an efficient and convenient strategy for chiral enantioselective recognition. Schematic construction of the 3D-NGMWCNT@(S,S)-CIL/GCE chiral electrochemical sensors.

Highly sensitive fluorescence sensor for mercury(II) based on boron- and nitrogen-co-doped graphene quantum dots.

In this work, we invented a new method to synthesize boron- and nitrogen-co-doped graphene quantum dots (B, N-GQDs). This synthesis method was more reliable, simple, and environmentally friendly than the bottom-up methods reported in the current literature that use citric acid or other organic materials as the carbon source. Instead, B, N-GQDs were synthesized from graphene oxide (GO) by a top-down method. The obtained B, N-GQDs showed a bright blue luminescence under a UV lamp at 365 nm, and the absolute photoluminescence quantum yield (PLQY) was 5.13%. Because mercury(II) ions (Hg2+) are highly toxic and can seriously affect the ecological environment and human health, the detection of low-concentration Hg2+ and the establishment of rapid, accurate and sensitive methods for detecting Hg2+ are of great significance to the activities of life, including those of humans. Therefore, using the good luminescence properties of B, N-GQDs, we invented a new type of fluorescence sensor that can detect Hg2+. The sensor was very sensitive to Hg2+, had a good linear relationship in the concentration range of 0.2-1 µM, and exhibited a minimum limit of detection of 6.4 nM. Furthermore, this approach was successfully applied to the detection of Hg2+ in real environmental water samples.

Fabrication of an electrochemical chiral sensor via an integrated polysaccharides/3D nitrogen-doped graphene-CNT frame.

We report a novel chiral interface based on polysaccharides that was integrated via an amidation reaction between the COOH of sodium alginate and the NH2 of chitosan to form a chiral selector (SA-CS) with three dimensional N-doped graphene-CNT (NGC) as the substrate material. This interface was used for chiral discrimination of tryptophan (Trp) enantiomers via electrochemical measurements. The FT-IR, SEM, TEM and XPS characterization showed that the chiral selector and substrate materials were prepared successfully. Compared with individual SA-CS and NGC, the integrated polysaccharides/3D NGC showed higher enantioselectivity for L-Trp than D-Trp due to the smaller steric hindrance for D-Trp during the formation of three-point interactions between the two diastereoisomeric enantiomer-selector complexes, which allowed L-Trp to more easily detach from the electrode modification layer and approach the electrode surface, facilitating its approach and confirming that SA-CS had a higher constant for L-Trp when applied to real samples.

Electrochemical chiral sensing of tryptophan enantiomers by using 3D nitrogen-doped reduced graphene oxide and self-assembled polysaccharides.

A chiral sensor is described for the enantioselective recognition of L- and D-tryptophan (Trp). The sensor is based on the use of (a) Cu(II) ions coordinated with ß-cyclodextrin (Cu-ß-CD) that was self-assembled with carboxymethyl cellulose (CD-Cu-CMC) as a chiral selector, (b) of N-doped reduced graphene oxide (N-rGO) as substrate materials, and (c) of differential pulse voltammetry that was used for enantiorecognition. The 3D N-rGO was prepared by using reduced graphene oxide and pyrrole as the starting materials. Electrostatic interaction occurs between the carboxy groups of CMC and Cu(II) ions in Cu-ß-CD. The FT-IR, SEM, XRD and XPS techniques showed that 3D N-rGO and the CD-Cu-CMC composite were successfully synthesized. The 3D N-rGO enabled the immobilization of the chiral selector (CD-Cu-CMC) and improves the active areas. A glassy carbon electrode was modified with N-rGO/CD-Cu-CMC and then showed a stronger electrochemical signal for L-Trp than for D-Trp, typically at a working potential of around 0.78 V (vs. SCE). UV-vis spectroscopy proved that CD-Cu-CMC has a higher affinity for D-Trp. The enantioselectivity for D-Trp over L-Trp is 4.72. The modified electrode had a limit of detection of 0.063 µM and 0.0035 µM for L-Trp and D-Trp, respectively, with a linear response range of 0.01 mM to 5 mM. The sensor was used to detect Trp (D- or L-Trp) in spiked real human urine and human serum protein samples. Graphical abstract Schematic representation of an electrochemical chirality sensor based on the merits of N-rGO and CD-Cu-CMC. It involves the preparation of a chiral selector and a substrate material. N-Doped graphene oxide (N-rGO) was prepared by using graphene oxide (GO) and pyrrole as precursor. The combination of carboxymethyl cellulose (CMC) with Cu-ß-CD leads to a novel self-assembly framework.

Perylene-functionalized graphene sheets modified with ß-cyclodextrin for the voltammetric discrimination of phenylalanine enantiomers.

A facile approach was reported to synthesize ß-cyclodextrin functionalized graphene that is bridged by 3,4,9,10-perylene tetracarboxylic acid (rGO-PTCA-CD) via a chemical route that involves the functionalization of rGO with PTCA followed by covalently cross-linking NH2-ß-CD. The as-prepared rGO-PTCA-CD was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. The working electrodes were thoroughly studied for the cyclic voltammetry by using [Fe(CN)6]4-/3- as redox probe and using ferrocene as an internal standard. Furthermore, rGO-PTCA-CD was successfully applied to the recognition of phenylalanine enantiomers. The host-guest inclusion interaction between rGO-PTCA-CD and the phenylalanine enantiomers was investigated by differential pulse voltammetry with Fc used as a competitor. The recognition result showed that the rGO-PTCA-CD-modified glassy carbon electrode exhibited higher chiral recognition capability for L-Phe than for D-Phe with an enantioselectivity coefficient of 2.07. The proposed modified electrode had a limit of detection of 0.08 nM and 0.2 nM (S/N = 3) for L-Phe and D-Phe, respectively, with a linear response range of 0.01 mM to 5 mM, which was ascribed to the synergy of the rGO-PTCA (e.g., its excellent electrochemical performance) and ß-CD (e.g., the hydrophobic inner cavity with good molecular recognition and enrichment abilities).

Perylene-functionalized graphene sheets modified with chitosan for voltammetric discrimination of tryptophan enantiomers.

A composite was prepared from graphene functionalized with 3,4,9,10-perylene tetracarboxylic acid and chitosan (rGO-PTCA-chitosan) by a chemical method. It involves non-covalent functionalization of rGO with PTCA followed by amidation reaction with chitosan. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electrochemical methods were used to characterize the composites. By combining the chiral features of chitosan and the excellent electrochemical behaviors of rGO-PTCA, a graphene-based material with enantioselectivity was constructed for electrochemical chiral recognition of tryptophan (Trp) enantiomers. A glassy carbon electrode (GCE) modified with rGO-PTCA-chitosan had a higher recognition capability for L-Trp than for D-Trp. Best operated at a working voltage near 0.78 V (vs. SCE), the enantioselectivity coefficient is 3.0. The sensor has a linear response in the 1 mM to 10 mM Trp concentration range and a 1.2 µM detection limit (at S/N = 3) for L-Trp, and of 3.0 µM to D-Trp. The sensor was successfully used to detect Trp enantiomers in real samples, and a recognition mechanism is presented. Graphical abstract Schematic presentation of a composoie prepared by graphene functionalized with 3,4,9,10-perylene tetracarboxylic acid and chitosan (rGO-PTCA-chitosan) via a chemical method. It involves non-covalent functionalization of rGO with PTCA followed by amidation reaction with chitosan and voltammetric determination of tryptophan enantiomers.

Graphene-ferrocene functionalized cyclodextrin composite with high electrochemical recognition capability for phenylalanine enantiomers.

Graphene oxide (GO) modified with ferrocene (Fc) was successfully assembled via the π-π interaction (GO-Fc) and had the features of large surface area and high loading. Then, a novel composite was synthesized via ß-cyclodextrin (ß-CD) functionalized GO-Fc by combining the advantages of GO-Fc and ß-CD. An efficient chiral electrochemical sensing interface was constructed by using the rGO-Fc-CD composite as the electrode modification for the recognition of phenylalanine (Phe) enantiomers. The successful synthesis of the composites was confirmed by FTIR, XRD, TGA, SEM, and XPS results. The host-guest inclusion interaction was detected by ultraviolet spectroscopy and DPV. The recognition results demonstrated that the rGO-Fc-CD/GCE showed a higher chiral recognition capability for L-Phe than for D-Phe. The enantioselectivity coefficient (ID/IL) of the proposed sensor was 2.47. The LOD values of 27 nM and 52 nM (S/N = 3) for L-Phenylalanine and D-Phenylalanine were obtained for this electrochemical sensor. The as-synthesized material was successfully exploited for the recognition of Phe enantiomers, indicating that the developed sensor has wide application prospects.

Advances in the use of functional composites of ß-cyclodextrin in electrochemical sensors.

ß-Cyclodextrin (ß-CD) possess a hydrophobic inner cavity and a hydrophilic exterior surface. They exhibit excellent inclusion properties with the guest molecules that match cavity size, and ß-CD-based materials drew widespread attention in electrochemical sensors. The hydroxy groups at the edge of the cavity can form hydrogen bonds and undergo electrostatic and dipole-dipole interactions with other molecules. This review (with 109 refs.) reveals ß-CD-based detection mechanisms from the viewpoint of the size/shape-fit concept, and summarizes the current state of multiple electrochemical sensors based on the use of ß-CD and functionalized ß-CD such as carboxymethyl-ß-CD, mono-(6-ethanediamine-6-deoxy)-ß-CD, hydroxypropyl-ß-CD, thio-ß-cyclodextrin, and others. Graphical abstract Schematic diagram of cyclodextrin inclusion complex formation in aqueous solution, represents water molecules, represents guest molecule.

Superparamagnetic functional C@Fe3O4 nanoflowers: development and application in acetaminophen delivery.

Fe3O4 nanoflowers (NFs) were synthesized via an aqueous solution method and coated with carbon through an in situ carbonization process. The synthesized C@Fe3O4 composites were further modified with strong oxidizing agents, forming functional C@Fe3O4 (FCF) flower-like composites with porous superstructure. Finally, the stable composites were used in the drug delivery test under ambient conditions; the amount of acetaminophen adsorption on the composite can weigh up to 25.07% in 3 h. The FCF composites show excellent porosity (165.23 m2 g-1) and magnetic properties (24.33 emu g-1). The -COOH, C[double bond, length as m-dash]O and -OH groups in the composites could be used for interaction with biomolecules that contain -OH, C[double bond, length as m-dash]O and -NH2 groups. Therefore, the composite exhibits a sustained release model, with release rates of 51% in the first 6 h and 73% in 12 h. This special character gives the composites potential to be used in magnetic bio-separation and drug/gene delivery. The findings in this study are useful for the engineering design of porous iron oxide coated with functional carbon that is used for medical delivery applications and other biomedical devices.

Discovery of ((1S,3R)-1-isopropyl-3-((3S,4S)-3-methoxy-tetrahydro-2H-pyran-4-ylamino)cyclopentyl)(4-(5-(trifluoromethyl)pyridazin-3-yl)piperazin-1-yl)methanone, PF-4254196, a CCR2 antagonist with an improved cardiovascular profile.

We describe the systematic optimization, focused on the improvement of CV-TI, of a series of CCR2 antagonists. This work resulted in the identification of 10 (((1S,3R)-1-isopropyl-3-((3S,4S)-3-methoxy-tetrahydro-2H-pyran-4-ylamino)cyclopentyl)(4-(5-(trifluoromethyl)pyridazin-3-yl)piperazin-1-yl)methanone) which possessed a low projected human dose 35-45mg BID and a CV-TI=3800-fold.

Effect of compound plate composition on measurement of hERG current IC(50) using PatchXpress.

Inhibition of the human ether-a-go-go-related gene (hERG) potassium channel by pharmaceutical agents can lead to acquired long QT syndrome and the generation of potentially lethal arrhythmias. Higher throughput automated patch clamp systems, such as PatchXpress, can greatly increase the speed and capacity of evaluation of pharmaceutical compounds for hERG blocking activity. A factor that may affect the IC(50) value of a compound measured in this system is the composition of the multi-well compound plate. Hydrophobic compounds may adsorb to the surfaces of multi-well plates resulting in a reduction in the effective concentration of the compound delivered to the cell and altered IC(50) values. In the present study, we investigated the effects of four different compound plates--glass vials, non-binding polystyrene, hydrophilic polystyrene, and polystyrene--on determination of IC(50)s for four compounds--sotalol, dofetilide, cisapride, and bepridil--which ranged in hydrophobicity. In addition, we investigated the effects of incubation time in the compound plate on determination of IC(50)s. hERG currents were measured using the PatchXpress 7000A Automated Parallel Patch Clamp System (Molecular Devices Corporation; Sunnyvale, CA) and hERG channels stably expressed in HEK293 cells. The results suggest that more hydrophobic compounds may adsorb to non-binding polystyrene, hydrophilic, and polystyrene compound plates versus glass plates, especially with increasing time on the plates, resulting in altered IC(50) values.

Evaluation of the rubidium efflux assay for preclinical identification of HERG blockade.

Inhibition of the delayed-rectifier potassium channel current, human ether-a-go-go (hERG), by pharmaceutical agents can lead to acquired long QT syndrome and the generation of potentially lethal arrhythmias and sudden death. There remains an unmet need for higher-throughput assays to screen compounds in preclinical development for the potential to block hERG and cause QT prolongation. We evaluated the rubidium efflux assay for its ability to determine block of the hERG potassium channel. hERG-transfected human embryonic kidney-293 cells were cultured on 96-well assay plates and loaded with rubidium ion by incubating in media in which potassium was replaced by 5.4 mM Rb+. Cells were exposed to test compounds and then depolarized with a K+ channel opening buffer containing 50 mM K+. The supernatant was removed, and cells were lysed using 0.1% Triton X-100. Concentration-response curves were generated for test agents by determining the Rb+ efflux using a flame atomic absorption spectrometer. Multiple trials with cisapride yielded 50% inhibitory concentration values between 308.1 +/- 11 nM to 456.3 +/- 24 nM for inhibition of Rb+ efflux and a Z factor of 0.80 +/- 0.07 (n = 5 plates, 12 wells per plate). The values for inhibition of the hERG channel exhibited a rightward shift in potency as compared to those measured using electrophysiological techniques. In addition, we evaluated 19 blinded compounds at 10 microM in the Rb+ efflux assay, and compared results to those using patch clamp electrophysiology and the dofetilide displacement binding assay. The dofetilide displacement binding assay yielded a good correlation with electrophysiological measurements of hERG block. The rubidium efflux assay lacked sensitivity to consistently identify significant channel blockade. In conclusion, the rubidium efflux assay provides a higher-throughput means to identify potent hERG channel blocking agents, but lacks the sensitivity required to accurately determine the potency of blockade.