Palladium-Mediated Synthesis of a Near-Infrared Fluorescent K+ Sensor

6-(2′-(4″-Oxabutyloxy)phenyl)-1,6,11-triaza-3,9,14,17,22,25-hexaoxa-2(1,2)(4-methylbenzena)-10(1,2)(5-methylbenzena)bicyclo(9.8.8)heptacosaphane Sodium Bromide Dichloromethane

Potassium ion sensors are important for the study of concentration profiles in tissues. The synthesis of a cryptand suited for potassium ions and the crystal structure of it with a chelated sodium ion are presented.

Tricolor dual sensor for ratiometrically analyzing potassium ions and dissolved oxygen

A potassium ion‑oxygen (K⁺-O₂) dual fluorescent sensing film was developed. The film contains three probes, which are K⁺ probe (KS), O₂ probe (OS), and reference probe (RP) in a polymer film composed of poly(ethylene glycol) methyl ether methacrylate (PEGMA), poly(ethylene glycol) dimethacrylate (PEGDMA) and methacrylic acid (MAA). The RP showed blue emission, the KS exhibited green emission, and the OS showed red emission. The emission peaks of three probes do not interfere with each other, which enable the sensing film to be used for ratiometrically and quantitatively detecting the concentrations of K⁺ and dissolved oxygen (DO). The sensing films showed high sensitivity and selectivity to potassium ions over other metal ions and also good sensitivity for DO from deoxygenated to oxygenated conditions. The sensing film was demonstrated to be capable of analyzing K⁺ and DO concentrations with experimental errors smaller than ±8.5% in aqueous solutions, showing the potential applications of the sensing films.

A mitochondria-targeting NIR fluorescent potassium ion sensor: real-time investigation of the mitochondrial K+ regulation of apoptosis in situ

TAC-Rh, as the first mitochondria-targeting NIR K⁺ sensor, was applied to explore mutual regulation between mitochondrial K⁺ and apoptosis.

Graphene Quantum Dots Integrated in Ionophore-Based Fluorescent Nanosensors for Na+ and K

To enrich the recipes of ion-selective nanosensors, graphene quantum dots (GQDs) were integrated into ionophore-based fluorescent nanosensors with exquisite selectivity and high sensitivity for Na⁺ and K⁺. The unique property of GQDs gave the nanosensors ultrasmall size (ca. 10 nm), high brightness, good biocompatibility, and potential pH sensing possibility. At pH 7.4, the sensors exhibited a detection range from 0.1 mM to 1 M for Na⁺ and from 3 μM to 1 mM for K⁺. The nanosensors were successfully applied to blood serum and urine samples. Chemically induced intracellular sodium concentration change in HeLa cells was also qualitatively monitored.

A Ratiometric Fluorescent Probe for K+ in Water Based on a Phenylaza-18-Crown-6 Lariat Ether

This work presents two molecular fluorescent probes 1 and 2 for the selective determination of physiologically relevant K⁺ levels in water based on a highly K⁺ /Na⁺ selective building block, the o-(2-methoxyethoxy)phenylaza-18-crown-6 lariat ether unit. Fluorescent probe 1 showed a high K⁺ -induced fluorescence enhancement (FE) by a factor of 7.7 of the anthracenic emission and a dissociation constant (K_d ) value of 38 mm in water. Further, for 2+K⁺ , we observed a dual emission behavior at 405 and 505 nm. K⁺ increases the fluorescence intensity of 2 at 405 nm by a factor of approximately 4.6 and K⁺ decreases the fluorescence intensity at 505 nm by a factor of about 4.8. Fluorescent probe 2+K⁺ exhibited a K_d value of approximately 8 mm in Na⁺ -free solutions and in combined K⁺ /Na⁺ solution a similar K_d value of about 9 mm was found, reflecting the high K⁺ /Na⁺ selectivity of 2 in water. Therefore, 2 is a promising fluorescent tool to measure ratiometrically and selectively physiologically relevant K⁺ levels.

Making, Testing, and Using Potassium Ion Selective Microelectrodes in Tissue Slices of Adult Brain

Potassium ions significantly contribute to the resting membrane potential of cells and, therefore, extracellular K⁺ concentration is a crucial regulator of cell excitability. Altered concentrations of extracellular K⁺ affect the resting membrane potential and cellular excitability by shifting the equilibria between closed, open and inactivated states for voltage-dependent ion channels that underlie action potential initiation and conduction. Hence, it is valuable to directly measure extracellular K⁺ dynamics in health and diseased states. Here, we describe how to make, calibrate and use monopolar K⁺-selective microelectrodes. We deployed them in adult hippocampal brain slices to measure electrically evoked K⁺ concentration dynamics. The judicious use of such electrodes is an important part of the tool-kit needed to evaluate cellular and biophysical mechanisms that control extracellular K⁺ concentrations in the nervous system.

Highlights for the 6th International Ion Channel Conference: ion channel structure, function, disease and therapeutics

To foster communication and interactions amongst international scholars and scientists in the field of ion channel research, the 6th International Ion Channel Conference (IICC-2017) was held between June 23–27, 2017 in the eastern coastal city of Qingdao, China. The meeting consisted of 450 attendees and 130 speakers and poster presenters. The program consisted of research progress, new findings and ongoing studies that were focused on (1) Ion channel structure and function; (2) Ion channel physiology and human diseases; (3) Ion channels as targets for drug discovery; (4) Technological advances in ion channel research. An insightful overview was presented on the structure and function of the mechanotransduction channel Drosophila NOMPC (No mechanoreceptor potential C), a member of the transient receptor potential (TRP) channel family. Recent studies on Transmembrane protein 16 or Anoctamin-1 (TMEM16A, a member of the calcium-activated chloride channel [CaCC] family) were summarized as well. In addition, topics for ion channel regulation, homeostatic feedback and brain disorders were thoroughly discussed. The presentations at the IICC-2017 offer new insights into our understanding of ion channel structures and functions, and ion channels as targets for drug discovery.