Hydrophobic and ultrahydrophobic multilayer thin films from perfluorinated polyelectrolytes.
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Journal Article↗
Biomedical subjects
Joseph B Schlenoff
Publications and source records attributed to Joseph B Schlenoff.
Optically active polyelectrolyte multilayers as membranes for chiral separations.
Ultrathin films of chiral polyelectrolyte complex, prepared by the multilayering process, exhibit selectivity in the membrane separations of optically active compounds, such as l- and d-ascorbic acid. The flux through these polyelectrolyte multilayers, PEMUs, is exceptionally high and may be controlled by the concentration of salt present in the permeating solutions. Both in-situ ATR-FTIR and chiral capillary electrochromatography indicate that flux selectivity is mainly kinetically controlled, stemming from a difference in diffusion rates of various enantiomers through PEMUs, rather than a difference in partitioning.
Ascorbic Acid↗
Doping-controlled ion diffusion in polyelectrolyte multilayers: mass transport in reluctant exchangers.
A new paradigm for nonlinear doping-controlled ion transport in soft condensed matter is presented, where the mobility of a minority "probe" ion is controlled by majority "salt" ion. The class of materials to which this paradigm applies is represented by ultrathin films of polyelectrolyte complexes, or multilayers. Intersite hopping of probe ions of charge nu occurs only when the charge of the destination site, produced by clustering of monovalent salt ions, is at least -nu, conserving electroneutrality. Salt ions are reversibly "doped" into the multilayer under the influence of external salt concentration. In situ ATR-FTIR reveals that the doping level, y, is proportional to salt concentration. Because hopping requires coincidence, or clustering, of salt, a strongly nonlinear dependence of flux, J, on salt concentration is observed: J approximately [NaCl](nu) approximately y(nu). This scaling was reproduced both by Monte Carlo simulations of ion hopping and by continuum probability expressions. The theory also predicts the observed scaling, though it underestimates the magnitude, of the strong selectivity of multilayers for ions of different charge.
Journal Article↗
Analytical separations using molecular micelles in open-tubular capillary electrochromatography.
Open-tubular capillary electrochromatography (OT-CEC) is an alternative approach to conventional CEC. The primary advantage of OT-CEC is the elimination of problems associated with frits and silica particles in conventional CEC. This report is an investigation of the utility of using a polymeric surfactant (molecular micelle) for OT-CEC. In this approach, fused-silica capillaries coated with thin films of physically adsorbed charged polymers are developed by use of a polyelectrolyte multilayer (PEM) coating procedure. The PEM coating is constructed in situ by alternating rinses with positively and negatively charged polymers, where the negatively charged polymer is a molecular micelle. This can offer a number of advantages for separation of hydrophobic analytes. In this study, poly(diallyldimethylammonium chloride) was used as the cationic polymer and poly(sodium N-undecanoyl-L-glycinate) was used as the anionic polymer for PEM coating. The performance of the modified capillaries as a separation medium is evaluated by use of seven benzodiazepines as analytes. The run-to-run, day-to-day, week-to-week, and capillary-to-capillary reproducibilities of electroosmotic flow are very good with relative standard deviation values of less than 1% in all cases. In addition, the chromatographic performance of the monomeric form of the molecular micelle is compared for the separation of these analytes. The PEM-coated capillary was remarkably robust with more than 200 runs accomplished in this study. Strong stability against extreme pH values was also observed. The general utility of this approach is discussed in detail.
Benzodiazepines↗
Protein adsorption modalities on polyelectrolyte multilayers.
Protein adsorption on polyelectrolyte multilayers (PEMUs) was evaluated using a combination of synthetic polyelectrolytes and proteins, including serum albumin, fibrinogen, and lysozyme. Variables such as surface and protein charge, polymer hydrophobicity, and hydrophilic repulsion were introduced to probe interaction mechanisms. Quantitative analysis with reflectance Fourier transform infrared spectroscopy, optical waveguiding, and UV-vis absorption, together with qualitative information from atomic force microscopy, provided a coordinated picture for what drives protein adsorption and how the molecules are disposed on the multilayer surface. It was found that multilayers bearing a particular surface charge sorbed biomolecules if they were of opposite charge, yielding significant loadings within the bulk PEMU. Adsorption of like-charged proteins, as surface aggregates, occurred to a much lower extent, driven by nonelectrostatic forces. A diblock copolymer comprising a hydrophilic poly(ethylene oxide) block was capable of further minimizing protein adsorption as a result of hydrophilic repulsion, although none of the surfaces tested defeated protein adsorption completely. However, poly(acrylic acid) homopolymer was quite effective in this respect. A composition gradient, formed during multilayer buildup, induced a gradient in hydrophilicity through the PEMU, which is an efficient and economical method of creating a protein-resistant surface.
Adsorption↗
Vascular smooth muscle cells on polyelectrolyte multilayers: hydrophobicity-directed adhesion and growth.
Polyelectrolyte multilayer films were employed to support attachment of cultured rat aortic smooth muscle A7r5 cells. Like smooth muscle cells in vivo, cultured A7r5 cells are capable of converting between a nonmotile "contractile" phenotype and a motile "synthetic" phenotype. Polyelectrolyte films were designed to examine the effect of surface charge and hydrophobicity on cell adhesion, morphology, and motility. The hydrophobic nature and surface charge of different polyelectrolyte films significantly affected A7r5 cell attachment and spreading. In general, hydrophobic polyelectrolyte film surfaces, regardless of formal charge, were found to be more cytophilic than hydrophilic surfaces. On the most hydrophobic surfaces, the A7r5 cells adhered, spread, and exhibited little indication of motility, whereas on the most hydrophilic surfaces, the cells adhered poorly if at all and when present on the surface displayed characteristics of being highly motile. The two surfaces that minimized cell adhesion consisted of two varieties of a diblock copolymer containing hydrophilic poly(ethylene oxide) and a copolymer bearing a zwitterionic group AEDAPS, (3-[2-(acrylamido)-ethyldimethyl ammonio] propane sulfonate). Increasing the proportion of AEDAPS in the copolymer decreased the adhesion of cells to the surface. Cells presented with micropatterns of cytophilic and cytophobic surfaces generated by polymer-on-polymer stamping displayed a surface-dependent cytoskeletal organization and a dramatic preference for adhesion to, and spreading on, the cytophilic surface, demonstrating the utility of polyelectrolyte films in manipulating smooth muscle cell adhesion and behavior.
Animals↗