Fluorescent Indicators for Intracellular pH

Han, Junyan; Burgess, Kevin

doi:10.1021/cr900249z

Cited by 1,477 publications

(1,148 citation statements)

References 153 publications

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“…S3), and the pH measurement is sensitive and reliable in the range between 6.2 and 7.8 ( Fig. 1D) (30). We determine the change in pH with time (corresponding to the position on the chip) inside the aqueous droplets (with a radius R ∼ 80 μm) for the different concentrations of surfactants used (Fig.…”

Section: Resultsmentioning

confidence: 99%

Surfactant adsorption kinetics in microfluidics

Riechers

Maes

Akoury

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning-here through ion exchange-unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore-surfactant interactions.droplet | interfaces | surfactant | emulsion | microfluidics S urface active compounds are ubiquitous in our daily life, be it in living systems or in industrial and technological products (1-3). The compounds are used widely for the stabilization of foams and emulsions for food and cosmetic products, painting materials, and industrial coatings (3). Emulsions are nowadays also used in combination with microfluidic systems for applications in biotechnology (3-11). An emulsion is a dispersion of one liquid phase into another, stabilized by surfactants in a metastable state. The kinetic stabilization of emulsions occurs through several mechanisms, involving electrostatic or steric repulsion and the buildup of Marangoni stresses to improve the lifetime of emulsions against coalescence (12, 13). On the other hand, surfactants are involved in transport processes such as Ostwald ripening or solute transport, which mediates the chemical equilibration of the system (14-17): in general, all processes affecting the lifetime of emulsions (coalescence, rupture, exchange, and loss of molecules) are directly related to the physics and dynamics of the surfactant molecules at interfaces (3,4,6,10,11,15,16). The first analysis of surfactant layers dates back to the 18th century with Franklin's experiments (1) and the first comprehensive studies on adsorption kinetics by Ward and Tordai (18) and Langmuir (19). From this point, a wide variety of models describe the adsorption dynamics, accounting for all kinds of molecular effects at interfaces (20-26). We expect two limiting cases: (i) the adsorption is limited by the bulk transport toward the interface, leading to a local equilibrium between the surfactant interfacial concen...

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Section: Resultsmentioning

confidence: 99%

Surfactant adsorption kinetics in microfluidics

Riechers

Maes

Akoury

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The methyl ester moiety makes both dyes membrane-permeant but is cleaved by intracellular esterases, which trap the dyes within cells (Han & Burgess, 2010). The dual-excitation/single-emission dye BCECF has a pH-sensitive excitation at 490 nm (Em 535 nm).…”

Section: Ph-sensitive Ratiometric Dyesmentioning

confidence: 99%

“…23.2). For additional information, several excellent reviews describe the use of genetically encoded fluorescent pH sensors (Ashby, Ibaraki, & Henley, 2004;Benčina, 2013;Han & Burgess, 2010;Pinton, Rimessi, Romagnoli, Prandini, & Rizzuto, 2007).…”

Section: Genetically Encoded Ph Sensorsmentioning

confidence: 99%

“…The development of genetically encoded pH-sensitive fluorescent proteins targeted to the mitochondrial matrix and inner membrane space allows determining mitochondrial pH gradients (Boron & De Weer, 1976;De Michele, Carimi, & Frommer, 2014;Pinton et al, 2007); the pH of the mitochondrial matrix is $7.78 while the intermembrane space is $6.88 (Porcelli et al, 2005;Thomas et al, 1979). Further, spontaneous, transient increases in pHi in the mitochondrial matrix, termed "flashes," have been recently observed and likely reflect changes in proton pump activity and the transmembrane H + gradient (Han & Burgess, 2010;Schwarzländer, Logan, Fricker, & Sweetlove, 2011;Schwarzländer et al, 2012).…”

Section: Subcellular Ph Measurementsmentioning

confidence: 99%

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Ratiometric Imaging of pH Probes

Grillo-Hill

Webb

Barber

2014

Methods in Cell Biology

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“…At present, lots of pH fluorescent probes have been developed and used, the protonation and deprotonation of phenol group were used in cyanine, [24,25] BODIPY, [26,27] and other fluorophores. [28,29] The structure of rosamine is different from rhodamine with the absence of carboxyl group, [30] which can form the five-member ring in detection, [31] and rosamine is used for a kind of red emission fluorophore. [32] Its related probes, such as commercial mitochondrial markers (MitoTracker® Red CMXRos), RhSN-mito, rhodamine 123 [33,34] and so on, were known as mitochondria biomarkers, [35] and a red-emitting lysosome-specific probe based on rosamine was once reported with the protonation of dialkylamino group; [36] some other related compounds can be applied in selectively staining pluripotent stem cells.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence Responses of the Protonation and Deprotonation Processes between Phenolate and Phenol within Rosamine

et al. 2017

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Two rosamine-based pH probes 1a and 1b with pyronine-phenol skeleton were designed and synthesized by a simple one-step reaction. pH titration experiments showed that probes 1a and 1b exhibit near OFF-ON fluorescence responses around 550-750 nm towards the hydrogen ions. The pK a of the probe 1a is 8.29, while that of the probe 1b increases to 12.1 because of the hydrogen bond inside it. Selective and competitive experiments indicated that both common ions and amino acids did not interfere their emission with hydrogen ions. Moreover, confocal fluorescent imaging showed that the probe 1a could be served as mitochondria biomarker in HeLa and Ges-1 cells.

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Fluorescent Indicators for Intracellular pH

Cited by 1,477 publications

References 153 publications

Surfactant adsorption kinetics in microfluidics

Surfactant adsorption kinetics in microfluidics

Ratiometric Imaging of pH Probes

Fluorescence Responses of the Protonation and Deprotonation Processes between Phenolate and Phenol within Rosamine

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