Exclusion-zone formation from discontinuous nafion surfaces

Figueroa, Xavier A.; Pollack, Gerald H.

doi:10.2495/dne-v6-n4-286-296

Cited by 16 publications

(16 citation statements)

References 15 publications

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“…Moreover, one of the hydrophilic surfaces used prominently in Pollack’s studies of EZs comprised sheets of the sulfonate-rich fluoropolymer Nafion R [ 55 , 56 , 71 ]. Recent studies of Pollack and coworkers with potential high relevance to water behavior in blood vessels include observations on water flow through submerged Nafion R tubes [ 72 ] and elegant work on EZ formation near discontinuous Nafion R surfaces [ 73 ]. Figure 1 depicts the capillary glycocalyx and shows how the Nafion R -based tubes can model its behavior.…”

Section: Resultsmentioning

confidence: 99%

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A novel hypothesis for atherosclerosis as a cholesterol sulfate deficiency syndrome

Seneff¹,

Davidson

Lauritzen

et al. 2015

Theor Biol Med Model

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BackgroundDespite a vast literature, atherosclerosis and the associated ischemia/reperfusion injuries remain today in many ways a mystery. Why do atheromatous plaques make and store a supply of cholesterol and sulfate within the major arteries supplying the heart? Why are treatment programs aimed to suppress certain myocardial infarction risk factors, such as elevated serum homocysteine and inflammation, generally counterproductive?MethodsOur methods are based on an extensive search of the literature in atherosclerotic cardiovascular disease as well as in the area of the unique properties of water, the role of biosulfates in the vascular wall, and the role of electromagnetic fields in vascular flow. Our investigation reveals a novel pathology linked to atherosclerosis that better explains the observed facts than the currently held popular view.ResultsWe propose a novel theory that atherosclerosis can best be explained as being due to cholesterol sulfate deficiency. Furthermore, atheromatous plaques replenish the supply of cholesterol and sulfate to the microvasculature, by exploiting the inflammatory agent superoxide to derive sulfate from homocysteine and other sulfur sources. We argue that the sulfate anions attached to the glycosaminoglycans in the glycocalyx are essential in maintaining the structured water that is crucial for vascular endothelial health and erythrocyte mobility through capillaries. Sulfate depletion leads to cholesterol accumulation in atheromas, because its transport through water-based media depends on sulfurylation. We show that streaming potential induces nitric oxide (NO) release, and NO derivatives break down the extracellular matrix, redistributing sulfate to the microvasculature. We argue that low (less negative) zeta potential due to insufficient sulfate anions leads to hypertension and thrombosis, because these responses can increase streaming potential and induce nitric-oxide mediated vascular relaxation, promoting oxygen delivery. Our hypothesis is a parsimonious explanation of multiple features of atherosclerotic cardiovascular disease.ConclusionsIf our interpretation is correct, then it would have a significant impact on how atherosclerosis is treated. We recommend a high intake of sulfur-containing foods as well as an avoidance of exposure to toxicants that may impair sulfate synthesis.

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Section: Resultsmentioning

confidence: 99%

“…Diagram on the far right indicates the viewing height (arrow) on which the objective was focused. (Reproduced from Figueroa and Pollack (2011) [ 73 ] with permission from WIT Press) …”

Section: Resultsmentioning

confidence: 99%

A novel hypothesis for atherosclerosis as a cholesterol sulfate deficiency syndrome

Seneff¹,

Davidson

Lauritzen

et al. 2015

Theor Biol Med Model

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“…Nafion has become, in the recent past, a popular polymeric material in the investigation of EZ properties [7,15,16,18]. In order to minimize flow artifacts and to precisely monitor EZ formation, microfluidic devices were constructed that allow the simultaneous, precise control of fluid exchange and time-lapse microscopy ( Figure 1).…”

Section: Resultsmentioning

confidence: 99%

“…This theory has been debated [5] and needs experimental testing. Although the EZ has been characterized by numerous experimental approaches [1,[6][7][8][9][10][11][12][13][14][15][16][17][18], key features related to its thermodynamics and kinetics still need to be investigated. In the present work we measured the short-and long-time-scale kinetics of EZ formation in specially designed microfluidic devices that reduce unwanted local perturbation effects, estimated the magnitude of the exclusion force, and tested key predictions of the most plausible microscopic mechanisms of EZ formation.…”

Section: Introductionmentioning

confidence: 99%

Exclusion-Zone Dynamics Explored with Microfluidics and Optical Tweezers

Huszár

Mártonfalvi

Laki

et al. 2014

Entropy

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Abstract:The exclusion zone (EZ) is a boundary region devoid of macromolecules and microscopic particles formed spontaneously in the vicinity of hydrophilic surfaces. The exact mechanisms behind this remarkable phenomenon are still not fully understood and are debated. We measured the short-and long-time-scale kinetics of EZ formation around a Nafion gel embedded in specially designed microfluidic devices. The time-dependent kinetics of EZ formation follow a power law with an exponent of 0.6 that is strikingly close to the value of 0.5 expected for a diffusion-driven process. By using optical tweezers we show that exclusion forces, which are estimated to fall in the sub-pN regime, persist within the fully-developed EZ, suggesting that EZ formation is not a quasi-static but rather an irreversible process. Accordingly, the EZ-forming capacity of the Nafion gel could be exhausted with time, on a scale of hours in the presence of 1 mM Na 2 HPO 4 . EZ formation may thus be a non-equilibrium thermodynamic cross-effect coupled to a diffusion-driven transport process. Such phenomena might be particularly important in the living cell by providing mechanical cues within the complex cytoplasmic environment. OPEN ACCESSEntropy 2014, 16 4323

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“…A few researchers have proposed that the EZ is due to a change in water’s structure [ 12 , 39 , 40 , 41 , 42 , 43 , 44 ]. One problem with this is there are no obvious thermodynamic forces in the system to drive such a phase change or long range ordering, and such effects are not observed in conventional molecular dynamics simulations.…”

Section: The Structure Change Theorymentioning

confidence: 99%

Exclusion Zone Phenomena in Water—A Critical Review of Experimental Findings and Theories

Elton

Spencer

Riches³

et al. 2020

IJMS

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The existence of the exclusion zone (EZ), a layer of water in which plastic microspheres are repelled from hydrophilic surfaces, has now been independently demonstrated by several groups. A better understanding of the mechanisms which generate EZs would help with understanding the possible importance of EZs in biology and in engineering applications such as filtration and microfluidics. Here we review the experimental evidence for EZ phenomena in water and the major theories that have been proposed. We review experimental results from birefringence, neutron radiography, nuclear magnetic resonance, and other studies. Pollack theorizes that water in the EZ exists has a different structure than bulk water, and that this accounts for the EZ. We present several alternative explanations for EZs and argue that Schurr’s theory based on diffusiophoresis presents a compelling alternative explanation for the core EZ phenomenon. Among other things, Schurr’s theory makes predictions about the growth of the EZ with time which have been confirmed by Florea et al. and others. We also touch on several possible confounding factors that make experimentation on EZs difficult, such as charged surface groups, dissolved solutes, and adsorbed nanobubbles.

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Exclusion-zone formation from discontinuous nafion surfaces

Cited by 16 publications

References 15 publications

A novel hypothesis for atherosclerosis as a cholesterol sulfate deficiency syndrome

A novel hypothesis for atherosclerosis as a cholesterol sulfate deficiency syndrome

Exclusion-Zone Dynamics Explored with Microfluidics and Optical Tweezers

Exclusion Zone Phenomena in Water—A Critical Review of Experimental Findings and Theories

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