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1.
Analyst ; 145(11): 3846-3850, 2020 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-32293619

RESUMO

Ionophores have been integrated into various electrochemical and optical sensing platforms for the selective detection of ions. Previous ionophore-based optical sensors rely on a H+ chromoionophore as the signal transducer and consequently, suffered from a pH cross-response. pH independent methods were proposed very recently by utilizing the solvatochromic dyes or the exhaustive mode. Here, we report a pH independent sensing principle based on nanospheres containing ionophores. As the ion-exchange occurs, the signal transducer undergoes aggregation-induced emission (AIE) or aggregation-caused quenching (ACQ), leading to a dramatic change in fluorescence intensity. The principle was evaluated on different ionophores including those selective for K+, Na+, Ca2+, and Pb2+. The nanospheres were also introduced into microfluidic chips and successfully applied for the determination of sodium and potassium ion concentrations in diluted blood serum and urine samples.

2.
ACS Sens ; 5(2): 313-318, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-32050757

RESUMO

Potentiometric probes used in direct potentiometry are attractive sensing tools. They give information on ion activities, which is often uniquely useful. If, instead, concentrations are desired as sensor output, the ionic strength of the sample must be precisely known, which is often not possible. Here, for the first time, direct potentiometry can be made to report concentrations, rather than activities. It is demonstrated for the detection of monovalent anionic species by using a self-referencing Ag/AgI pulstrode as the reference element instead of a traditional reference electrode. This reference pulstrode releases a discrete quantity of iodide ions from the electrode and the resulting reference potential varies with the activity coefficient of iodide. The effects of activity coefficient on the indicator and reference electrode are therefore compensated and the observed cell potential may now be described in a Nernstian manner against anion concentration, rather than activity. Theoretical simulations and experimental results support the validity of this approach. For most monovalent anions of practical relevance, the potential difference between this approach and from a traditional activity coefficient calculation is less than 0.5 mV. The concept is validated with an all-solid-state nitrate sensor as well as a commercial fluoride-selective electrode, giving Nernstian responses in different ionic strength backgrounds against concentration without the need for correcting activity coefficients or liquid junction potentials.

3.
Angew Chem Int Ed Engl ; 59(6): 2294-2298, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31714666

RESUMO

The design of solid-state reference electrodes without a liquid junction is important to allow miniature and cost-effective electrochemical sensors. To address this, a pulse control is proposed using an Ag/AgI element as reliable solid-state reference electrode. It involves the local release of iodide by a cathodic current that is immediately followed by an electromotive force (EMF) measurement that serves as the reference potential. The recapture of iodide ions is achieved by potentiostatic control. This results in intermittent potential values that are reproducible to less than one millivolt (SD=0.27 mV, n=50). The ionic strength is shown to influence the activity coefficient of released iodide in accordance with the extended Debye-Hückel equation, resulting in a predictable change of the potential reading. The principle is applied to potentiometric potassium detection with a valinomycin-based ion-selective electrode (ISE), demonstrating a completely solid-state sensor configuration.

4.
Analyst ; 144(18): 5617-5623, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31432884

RESUMO

Smart hydrogels incorporating various functional nanomaterials are becoming popular tools for chemical sensing. Here, ion-exchange nanospheres composed of the block copolymer Pluronic F-127 played the role of a scavenger for a signal transducer dye (Rhodamine 800) in a three-phase based optical detection system for potassium ions. Rhodamine 800, a positively charged dye, was incorporated into a hydrogel together with the potassium ionophore valinomycin and an ion-exchanger (Na+R-). The concentration of Rhodamine 800 in the aqueous sample was kept low by the nanospheres containing Na+R-. Consequently, the detection limit (0.3 µM) of the three-phase based system was shifted 2 orders of magnitude lower compared with those of previously reported two-phase based sensing systems. The concept of controlling the dye transfer among the three phases provided a new train of thought for the design of ionophore-based chemical sensors.

5.
Anal Chem ; 91(16): 10390-10394, 2019 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-31339689

RESUMO

Demand for rapid quantitation of polyions such as heparin and protamine are ever growing. Previous paper-based and polymeric optical and electrochemical sensing devices required more than several hours for signal stabilization. Therefore, signals were acquired with fixed sample exposure time modes, which was time-consuming and technically demanding. We present here for the first time the optical detection of protamine and heparin in equilibrium mode with emulsified nanospheres. The method significantly shortens the response time from hours to typically less than 10 s and offers tunable, sensitive, and colorimetric detection within the clinically relevant range (10 to 100 mg/L) for heparin. The improved characteristics are attributable to the small size of the nanospheres (ca. 50 nm in diameter) as well as the reversible recognition at the nanoscale liquid-liquid interface. Detection of the anticoagulant heparin was also successfully demonstrated in human blood serum background.

6.
Anal Chem ; 91(13): 8638-8643, 2019 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-31247723

RESUMO

We report here an ionophore-based chemiluminescent platform for the selective detection of ions. This method functions on the basis of the ion-exchange between the target ion and the divalent organic cation lucigenin, which luminesces after reacting with hydrogen peroxide in alkaline conditions. Using the K+ ionophore valinomycin, chemiluminescent detection of K+ (from 10 nM to 1 M) was performed on both dichloromethane solutions and polymeric films. While the ionophores ensured excellent selectivity, the detection range could be adjusted with the ratio between the aqueous and the organic phases, and the divalent lucigenin ions also made the sensitivity for divalent target ions higher than conventional ionophore-based ion-selective optodes. The generalizability of the method was shown by changing the K+ ionophore into a Pb2+ ionophore, which successfully realized the highly selective detection of Pb2+ from 0.1 nM to 0.1 mM. Preliminary application of the method was demonstrated with the determination of K+ in diluted human blood serum (five samples), and the results agreed well with those obtained from potentiometric ion-selective electrodes.

7.
Anal Chem ; 91(14): 8973-8978, 2019 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-31190528

RESUMO

It has recently been reported that polystyrene microbeads may be modified to realize plasticizer-free ion-selective optical sensors (optodes) on the basis of solvatochromic dye transducers. We show here that the functionalized microbeads, individually isolated by flow cytometry, exhibit unexpectedly poor fluorescent properties and that the sensor response is instead attributed to the supernatant. A more thorough study reveals that such optical microemulsion sensors can be made operationally functional and chemically selective, seemingly in the absence of any solvent matrix or added surfactant. Instead, it is shown that residual THF used in the fabrication of the emulsified sensors may solubilize the sensing components and give a functional optode response. To evaluate this further, the number of sensing components was stepwise simplified to assess their need. Variation of residual THF levels has no effect on the ion optode response when plasticizer is present, in support of established results. Lipophilic solvatochromic dye transducers are also shown not to require an added surfactant as their nature already endows the emulsified sensors with a stabilizing ionic surface charge. The ionophores are shown to exhibit much larger stability constants in the surfactant-free formulations than surfactant-based ones (valionomycin, log ß > 9.2 compared to 6.1; Na+-ionophore X, 6.7 vs 4.7), which is attributed to a less polar solvent environment for the ionophore. Potassium-, sodium-, and calcium-selective sensors were used as model systems in this study.

8.
ACS Sens ; 4(4): 1017-1022, 2019 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-30895782

RESUMO

We present here an innovative platform for the determination of pH buffer capacity based on FITC-dextran loaded hydrogels. Optical signals from the pH-sensitive hydrogels were analyzed by simple parameters including distance and color change. The methodology was validated on five different buffer systems and exhibited wide linearity (0.1 to 100 mM), good batch-to-batch reproducibility, high versatility, and resistance to background ionic strength changes. Experimental results also fit well with a theoretical model based on numerical simulation. Preliminary application in carbonate alkalinity determination of seawater proved very successful. This hydrogel buffer concentration sensor is fundamentally different from conventional acid-base titrations, brings minimum perturbation to samples, and shows great potential in real applications.


Assuntos
Ácidos não Carboxílicos/análise , Álcalis/análise , Dextranos/química , Fluoresceína-5-Isotiocianato/análogos & derivados , Hidrogéis/química , Sefarose/química , Trometamina/análise , Tampões (Química) , Cor , Fluoresceína-5-Isotiocianato/química , Concentração de Íons de Hidrogênio , Água do Mar/análise , Espectrofotometria Ultravioleta/métodos
9.
Anal Chem ; 91(7): 4889-4895, 2019 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-30835441

RESUMO

We introduce here a general strategy to read out chronopotentiometric sensors by electrogenerated chemiluminescence (ECL). The potentials generated in chronopotentiometry in a sample compartment are used to control the ECL in a separate detection compartment. A three-electrode cell is used to monitor the concentration changes of the analyte, while the luminol-H2O2 system is responsible for ECL. The principle was shown to be feasible by theoretical simulations, indicating that the sampled times at a chosen potential, rather than traditional transition times, similarly give linear behavior between concentration and the square root of sampled time. With the help of a voltage adapter, the experimental combination between chronopotentiometry and ECL was successfully implemented. As an initial proof of concept, the ferro/ferricyanide redox couple was investigated. The square root of time giving maximum light output changed linearly with ferrocyanide concentration in the range from 0.70 to 4.81 mM. The method was successfully applied to the visual detection of carbonate alkalinity from 0.06 to 0.62 mM using chronopotentiometry at an ionophore-based hydrogen ion-selective membrane electrode. The measurements of carbonate in real samples including river water and commercial mineral water were successfully demonstrated.

10.
J Am Chem Soc ; 141(10): 4468-4473, 2019 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-30785740

RESUMO

We report a quite flexible naphthol-based cage (so-called "naphthocage") which adopts a self-inclusion conformation in its free state and is able to bind singly charged organic cations extremely strongly ( Ka > 107 M-1). Ion-selective electrodes prepared with this naphthocage show a super-Nernstian response to acetylcholine. In addition, the highly stable complex (1010 M-1) between ferrocenium and the naphthocage can be switched electrochemically, which lays a basis for its application in stimuli-responsive materials.

11.
Chem Commun (Camb) ; 55(12): 1774-1777, 2019 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-30666333

RESUMO

We report here a rapid and versatile metal ion analytical platform based on the dye release from hydrogels entrapping ion-selective microdroplets. Using Ca2+, Pb2+, and Na+ as model ions, the ion-selective hydrogels were developed in combination with four positively charged dyes, making the hydrogels highly promising for point-of-care diagnostics as well as environmental monitoring.

12.
ACS Sens ; 3(11): 2408-2414, 2018 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-30387340

RESUMO

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.


Assuntos
Corantes Fluorescentes/química , Grafite/química , Ionóforos/química , Potássio/análise , Pontos Quânticos/química , Sódio/análise , Células HeLa , Humanos , Microscopia Confocal/métodos , Microscopia de Fluorescência/métodos , Tamanho da Partícula , Potássio/sangue , Potássio/urina , Sódio/sangue , Sódio/urina , Valinomicina/química
13.
Anal Chem ; 90(21): 12791-12795, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30264992

RESUMO

Optical ion sensors normally have a relative narrow sensitive detection window. Here, based on multicolor light-emitting diodes (LEDs), we report on an electrochemical-to-optical signal transduction scheme under chronoamperometry control to convert the potentiometric response of ion-selective electrodes (ISEs) to optical output with tunable sensitivity and much wider response range. The sensing principle was demonstrated on K+, Ca2+, and Pb2+. LED light intensity was found to depend linearly on the concentration of monovalent ions. Optical signals could be captured with photomultiplier tubes or digital cameras, and a visual alarming system to monitor abnormal ion concentration was also developed from super-Nernstian electrodes.

14.
Anal Chem ; 90(9): 5818-5824, 2018 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-29649866

RESUMO

Nanoscale ionophore-based ion-selective optodes (nano-ISOs) are effective sensing tools for in situ and real time measurements of ion concentrations in biological and environmental samples. While searching for novel sensing materials, nano-ISOs free of plasticizers are particularly important for biological and environmental applications. This work described plasticizer-free nano-ISOs based on Si-containing particles including PEGylated organosilica nanoparticles, PDMS nanospheres, and SiO2 microspheres, with diameters around 50 nm, 100 nm, and 5 µm, respectively. The platform enabled the use of highly selective ionophores, where the nanomatrices played important roles in tuning the ion-carrier complex formation constants and led to better selectivity for the PEGylated organosilica nano-ISOs than those based on PDMS. With use of the versatile silica chemistry, pH and ion dual sensing was achieved on SiO2 microspheres. In addition, increasing the cross-linking degree of the PDMS nano-ISOs extended the linear response range, and cellular uptake experiments showed that the nano-ISOs could readily enter HeLa cells with very low cytotoxicity.


Assuntos
Ionóforos/química , Silício/química , Sobrevivência Celular/efeitos dos fármacos , Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/farmacologia , Células HeLa , Humanos , Concentração de Íons de Hidrogênio , Eletrodos Íon-Seletivos , Ionóforos/farmacologia , Microscopia Confocal , Estrutura Molecular , Nanopartículas/química , Imagem Óptica , Fenômenos Ópticos , Compostos de Organossilício/química , Compostos de Organossilício/farmacologia , Tamanho da Partícula , Plastificantes , Silício/farmacologia , Propriedades de Superfície
15.
Chemistry ; 24(31): 7921-7925, 2018 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-29575391

RESUMO

Ion-selective optical microsensors based on surface-modified polystyrene (PS) beads with positively charged lipophilic solvatochromic dye (SD) on the surface were studied with K+ as model ion. Water-soluble SDs are expelled into the aqueous phase by ion exchange with the cationic analyte of interest, resulting in a detectable color change. In contrast, lipophilic SDs are more attractive, as they appear to remain anchored to the surface after expulsion from the sensing phase. This transfers just the ionic chromophore functionality into the aqueous phase and allows the system to act as a reversible, truly self-contained sensor. In this work this mechanism was evaluated with ζ-potential measurements on microsensor suspensions. It indeed provides experimental evidence for the mechanism of SD transfer, as a reversal of the ζ-potential of the PS microsensors was observed for higher potassium concentrations with valinomycin-doped microspheres. For a discriminated ion such as sodium, the ζ-potential change occurs at much higher electrolyte concentrations, in agreement with sensor selectivity. Undoped microspheres showed no apparent dependence of ζ-potential on electrolyte concentration. The study also shows that the effective range of microsensor surface charge is tunable and depends on the concentration of the SD on the coating phase.

16.
ACS Omega ; 3(10): 12476-12481, 2018 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31457978

RESUMO

Design strategies for small molecular probes lay the foundation of numerous synthetic chemosensors. A water-soluble colorimetric calcium molecular probe inspired by the ionophore-based ion-selective optode is presented here with a tunable detection range (around micromolar at pH 7). The binding of Ca2+ resulted in the deprotonation of the probe and thus a significant spectral change, mimicking the ion-exchange process in ion-selective optodes. The 1:1 exchange between Ca2+ and H+ was confirmed with Job's plot. Computational studies revealed possible monomer and dimer forms of the probe-Ca2+ complexes.

17.
Talanta ; 177: 191-196, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29108575

RESUMO

A heterogeneous pH buffer based on a colloidal emulsion containing ion-exchanger and lipophilic base is described that can be integrated into hydrogels without affecting their ion-exchange properties. Each sphere works on the basis of reversible ion-exchange of hydrogen ions with solution cations, acting as a pH buffer while staying removed from solution in the nonpolar core of the spheres. The ion-exchange mechanism is supported by titration experiments in aqueous emulsion, showing that the nature and concentration of the exchanging solution cations influences the buffer action, with increasing lipophilicity moving the equilibrium to lower pH values. Agarose gels with entrapped pH buffer emulsions and mounted in a transport cell are shown by zero current potentiometry to exhibit negligible permselective properties above an ionic strength of 1mM, a behavior no different from unmodified agarose, with an observed ion-exchanger concentration of 7mM in dry agarose. This suggests that such pH buffers do not give rise to substantial ion-exchange properties of the gel material. In a first attempt to control the pH in the vicinity of an electrode surface by this approach, the emulsion was entrapped in an agarose gel in direct contact with a pH electrode, demonstrating the ability to buffer such gel films.

18.
Nat Commun ; 8(1): 2173, 2017 12 14.
Artigo em Inglês | MEDLINE | ID: mdl-29242600

RESUMO

The Peer Review File associated with this Article was updated shortly after publication to redact from the authors' point-by-point response a description of unpublished work describing how Speed OPIOM may in future be used to facilitate discrimination between FRET and direct excitation.

19.
Nat Commun ; 8(1): 969, 2017 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-29042541

RESUMO

We present speed out-of-phase imaging after optical modulation (OPIOM), which exploits reversible photoswitchable fluorophores as fluorescent labels and combines optimized periodic illumination with phase-sensitive detection to specifically retrieve the label signal. Speed OPIOM can extract the fluorescence emission from a targeted label in the presence of spectrally interfering fluorophores and autofluorescence. Up to four fluorescent proteins exhibiting a similar green fluorescence have been distinguished in cells either sequentially or in parallel. Speed OPIOM is compatible with imaging biological processes in real time in live cells. Finally speed OPIOM is not limited to microscopy but is relevant for remote imaging as well, in particular, under ambient light. Thus, speed OPIOM has proved to enable fast and quantitative live microscopic and remote-multiplexed fluorescence imaging of biological samples while filtering out noise, interfering fluorophores, as well as ambient light.Generally, fluorescence imaging needs to be done in a dark environment using molecules with spectrally separated emissions. Here, Quérard et al. develop a protocol for high-speed imaging and remote sensing of spectrally overlapping reversible photoswitchable fluorophores in ambient light.


Assuntos
Microscopia de Fluorescência/métodos , Imagem Óptica/métodos , Brassicaceae/genética , Desenho de Equipamento , Corantes Fluorescentes/análise , Análise de Fourier , Proteínas de Fluorescência Verde/análise , Células HeLa , Humanos , Processamento de Imagem Assistida por Computador , Dispositivos Lab-On-A-Chip , Imagem Óptica/instrumentação , Plantas Geneticamente Modificadas , Proteínas Recombinantes/análise , Proteínas Recombinantes/genética
20.
ACS Sens ; 2(10): 1410-1414, 2017 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-28949507

RESUMO

Blood electrolyte measurements play important roles in clinical diagnostics. Optical ion sensors as simple and elegant as a mercury thermometer are in high demand. We present here an analytical method to quantify potassium ions in undiluted human blood and plasma by measuring the distance or the rate of the color propagation. The sensor was composed of K+-selective nanospheres embedded in an agarose hydrogel where mass transport was diffusion controlled. The sensor's color-changing rate and the distance of color propagation depended linearly on the logarithm of K+ activity. A theoretical model was established and fully supported the experimental findings. This work lays the foundation of a new family of optical ion sensors for direct determination of common blood electrolytes.


Assuntos
Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Eletrodos Íon-Seletivos , Potássio/sangue , Difusão , Humanos , Concentração de Íons de Hidrogênio
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