Influence of Salt on the Aqueous Lubrication Properties of End-Grafted, Ethylene Glycol-Based Self-Assembled Monolayers

Heeb, R.; Lee, Sang M.; Venkataraman, Nagaiyanallur V.; Spencer, Nicholas D.

doi:10.1021/am900062h

Cited by 48 publications

(48 citation statements)

References 51 publications

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“…It is more likely that PEG, which is known to coordinate cations (31)(32)(33)(34)(35), behaves like a polycation in a high ionic strength solution. This explains the observed increase in the PEG blockade frequency with increasing (negative) electric field (23).…”

Section: Resultsmentioning

confidence: 99%

Theory for polymer analysis using nanopore-based single-molecule mass spectrometry

Reiner

Kasianowicz

Nablo

et al. 2010

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

202

372

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Nanometer-scale pores have demonstrated potential for the electrical detection, quantification, and characterization of molecules for biomedical applications and the chemical analysis of polymers. Despite extensive research in the nanopore sensing field, there is a paucity of theoretical models that incorporate the interactions between chemicals (i.e., solute, solvent, analyte, and nanopore). Here, we develop a model that simultaneously describes both the current blockade depth and residence times caused by individual poly(ethylene glycol) (PEG) molecules in a single α-hemolysin ion channel. Modeling polymer-cation binding leads to a description of two significant effects: a reduction in the mobile cation concentration inside the pore and an increase in the affinity between the polymer and the pore. The model was used to estimate the free energy of formation for K þ -PEG inside the nanopore (≈ − 49.7 meV) and the free energy of PEG partitioning into the nanopore (≈0.76 meV per ethylene glycol monomer). The results suggest that rational, physical models for the analysis of analyte-nanopore interactions will develop the full potential of nanopore-based sensing for chemical and biological applications.alpha-hemolysin | nanopore-based sensing | polymer confinement | polymer analysis P olymers play a fundamental role in life (1) and are central to many emerging technologies (2). Many of these applications require a detailed understanding of the structure, morphology, and chemical interactions of polymers under confinement in either 2-dimensional films (3) or narrow tubes (4). The ability to isolate and study single molecules has shown promise in overcoming the limitations of measurements with ensemble averages and permits probing the inter-and intra-molecular forces, structural changes, and dynamics of polymers (for a detailed review of single-molecule polymer analysis see refs. 5 and 6).Molecules partition into a nanopore and alter the flow of ions resulting in distinct current blockades that can be used to detect, characterize, and quantify a wide range of polymer types (7). These include single-stranded RNA and DNA (8-10), proteins (11-14), biowarfare agents (15), therapeutic agents against anthrax toxins (15, 16), and chemically synthesized molecules (14,(17)(18)(19)(20). More recently, single nanopores were used to determine the size distribution of polymers in a manner akin to mass spectrometry (19).To fully realize the potential of nanopore-based sensors, it is important to develop a detailed understanding of the physical and chemical interactions of polymers with the nanopore, solvent, electrolyte, and other components. In this work, the interaction between poly(ethylene glycol) (PEG) and the α-hemolysin (αHL) channel in a high ionic strength electrolyte was used to develop a unique model of polymers confined within single nanopores.Previous attempts to describe the magnitude of PEG-induced nanopore current blockades focused on volume exclusion (21) and/or microviscosity (22), which required adjustable ad hoc...

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Section: Resultsmentioning

confidence: 99%

Theory for polymer analysis using nanopore-based single-molecule mass spectrometry

Reiner

Kasianowicz

Nablo

et al. 2010

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

202

372

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“…We here developed an alternative strategy by substituting the glycans with PEG polymer chains ( Figure 3 A). PEG was chosen for its known biocompatibility and the well-characterized hydration [ 34,35 ] and lubrication [36][37][38][39] capacity. Deglycosylation can decrease the molecular weight of mucins by up to 80%, [ 40,41 ] thus relatively large 40 kDa PEG chains were chosen to compensate for that loss.…”

Section: Peg Can Be Sequestered To Mucins By Conjugation To a Lectinmentioning

confidence: 99%

Modulating Mucin Hydration and Lubrication by Deglycosylation and Polyethylene Glycol Binding

Crouzier

Boettcher

Geonnotti

et al. 2015

Adv Materials Inter

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glycoproteins, a family of high molecular weight and densely glycosylated biopolymers. Those mucins can act as an infection shield by trapping various viruses in the biopolymer matrix [ 1 ] and they reduce bacterial adhesion to surfaces. [ 2,3 ] Mucins also form highly hydrated and lubricative layers that protect the underlying epithelium from dehydration and shear stress that emerge during eye blinking or when swallowing food. Water typically accounts for up to 95% of the total mass in the mucus gel. [ 4,5 ] Shifts in the mucus water content correlate with substantial changes of the mucus barrier function [6][7][8] and result in important pathological disorders such as dry mouth [ 9 ] and dry eye. [ 10 ] Mucin-associated glycans contribute up to 80% of the molecular weight of mucins [ 11 ] and contain highly hydrated hydroxyl groups. Differences in the amount and composition of glycans from mucins extracted from pig stomachs and mucins from bovine submaxillary glands correlate with their capacity to adsorb water. [ 12 ] However, other properties such as protein composition also differ between these two mucin species, precluding the establishment of a defi nitive link between the presence of mucin glycans and hydration.Mucins, and other well-hydrated molecules such as zwitterionic polymers, polysaccharides, and polyelectrolytes are generally good boundary lubricants when adsorbed [ 13,14 ] or assembled in brush structures [15][16][17][18] on surfaces. Hence, mucin-associated glycans could also be essential for the lubricative function of mucus. In a related system, the mucin-like macromolecule lubricin showed a signifi cant decrease in lubricity when its associated glycans were removed. [ 19 ] Moreover, the lubricity of salivary fi lms, which contain mucins, has also been correlated with the total amount of glycosylation present in the fi lm. However, also here, the complexity of saliva composition precluded the identifi cation of the specifi c role of mucin glycosylation. [ 20 ] Hence, there is a need for a more defi ned experimental system to determine if mucin glycosylation is essential to the hydration and lubrication properties of mucins.This study explores the role of glycosylation in mucin hydration and lubricity, using mucin coatings as a simplifi ed model system. Such mucin coatings can reconstitute levels of surface hydration [ 21,22 ] and lubrication [23][24][25] similar to those found in native mucus. Our data show that the removal of mucin-bound glycans results in a signifi cant reduction in hydration and lubricity of the mucin-coated surface. We show that the hydration and lubricity of deglycosylated mucins can be partially A key property of mucin glycoproteins is their exceptional capacity to hydrate and lubricate surfaces. In vivo, mucins assemble into mucus hydrogels that cover the epithelium and protect it from dehydration and shear stress. A better understanding of the origin of these properties could lead to new treatment strategies for patients with poor mucus coverage, defective mucus produ...

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“…The frictional response of the grafted polymers depends on the interaction of the polymers with the surrounding medium [22,32,33]. In order to verify the role of the solvent during the friction tests, the same surfaces were studied under ethanol-a liquid in which the free poly(alkyl methacrylates) under investigation were found to be insoluble.…”

Section: Nanoscale Friction Measurementsmentioning

confidence: 99%

Lubrication with Oil-Compatible Polymer Brushes

et al. 2012

Self Cite

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A polymer-brush-based, surface-modification strategy for friction and wear reduction in hard contact under boundary-lubrication conditions is proposed, specifically for a non-aqueous environment. Surface-initiated atom-transfer radical polymerization was employed for the synthesis of three different oil-compatible, hydrophobic polymer brushes based on alkyl methacrylates. This study presents polymerization kinetics, chemical characterization by means of Fourier-transform infrared spectroscopy and surface morphologies observed in atomic force microscopy. The lubrication properties of the anchored polymers were evaluated macroscopically by means of ball-on-disk methods and on the nanonewton scale by lateral force microscopy and showed significant reduction in friction up to contact pressures as high as 460 MPa. The frictional response of surface-grafted polymers is shown to depend strongly on the compatibility of the polymer with the chosen lubricating fluid.

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Influence of Salt on the Aqueous Lubrication Properties of End-Grafted, Ethylene Glycol-Based Self-Assembled Monolayers

Cited by 48 publications

References 51 publications

Theory for polymer analysis using nanopore-based single-molecule mass spectrometry

Theory for polymer analysis using nanopore-based single-molecule mass spectrometry

Modulating Mucin Hydration and Lubrication by Deglycosylation and Polyethylene Glycol Binding

Lubrication with Oil-Compatible Polymer Brushes

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