Hydrophobic Polymer Surfaces Research Articles

Water-Induced Surface Rearrangements of Poly(dimethylsiloxane−urea−urethane) Segmented Block Copolymers

An investigation of the surfaces of linear, segmented block copolymers of poly(dimethylsiloxane−urea−urethanes) by dynamic contact angle analysis is reported. The polymer films are immersed in water, the time-dependent advancing and receding contact angles are observed, and the contact angle hysteresis is reported. The initially hydrophobic polymer surfaces are observed to become more hydrophilic with long-term exposure to water. The advancing contact angles are relatively constant with immersion time; the receding contact angles decrease to some equilibrium value after a few days' exposure to water. It is proposed that the surfaces reorganize by a mechanism in which the hard block urethane−urea domains migrate through the soft block silicone to the polymer−water interface. The surface reorganization kinetics are discussed in terms of the effects of annealing as well as the average molecular weight of the soft block.

Hydrocoating: a new method for coupling biomolecules to solid phases

Solid-phase immunoassays such as enzyme-linked immunosorbent assays require one of the assay components to be immobilized. Most frequently this is achieved by passive adsorption of the antigen or antibody to a hydrophobic polymer surface composed of, e.g., polystyrene. Alternatively the biomolecule can be bound indirectly via passively adsorbed carrier proteins or directly via functional groups on the solid phase using cross-linking agents. Here we describe a new technique — hydrocoating — for covalent immobilization of biomolecules, such as peptides, in highly hydrophilic surroundings. Peptides were immobilized on microtiter plates via covalent bonds to an activated hydrophilic polymer. Soluble dextran was activated using 2,2,2-triflouroethanesulphonyl chloride (tresyl chloride) leading to activation of hydroxyl groups on the dextran polymer. This activated dextran molecule was immobilized on a surface containing amino groups leaving a sufficient number of active groups for secondary binding of other biomolecules. Peptides, that were either undetectable or poorly recognized when adsorbed on polystyrene, were readily recognized when immobilized by the hydrocoating technique. Furthermore, peptides immobilized by this method were recognized 5–10-fold better compared to the same peptides immobilized covalently on a surface containing secondary amino groups. The technique appears to provide an alternative to passive adsorption of biomolecules on solid phases and may be useful in the future development of immunoassays.

Use of psoralens for covalent immobilization of biomolecules in solid phase assays.

The ability of compounds to adsorb passively to hydrophobic polymer surfaces composed of, e.g., polystyrene generally is restricted to limited types of molecules such as proteins. Some proteins, many peptides, polysaccharides, oligonucleotides, and small molecules as well as pro- and eucaryotic cells cannot adsorb directly to such surfaces. Also, solid phase adsorbed antigens, antibodies, or gene probes may not be recognized by its corresponding ligand due to denaturation or steric hindrance of the molecular tertiary structure. Covalent binding, on the other hand, orientates all immobilized compounds in a defined way on the solid phase, thereby exposing the interacting sites on the enzymes, antibodies, gene probes, etc. Here we describe a method for modifying a polymer surface by contacting the polymer with derivatives of psoralen under irradiation with long-wavelength UV light. The psoralen derivatives were immobilized covalently on the polymer surface by this process. The psoralen molecules was conjugated to appropriate chemical linkers, incubated in aqueous solutions, and irradiated with UV light. This resulted in solid phase introduction of functional groups such as, e.g., amino groups on the polystyrene surface. The functional groups could subsequently be used for immobilization of biomolecules using conventional cross-linker technology. The method only involved premodification of the psoralens to be immobilized whereas no pretreatment of the polymer was required. Psoralen modified microtiter plates seems to have future application for the development of solid phase hybridization and immunoassays.

Temperature-dependent adsorption/desorption behavior of lower critical solution temperature (LCST) polymers on various substrates

We have been studying adsorption and retention (resistance to desorption) behavior of temperature sensitive LCST polymers on different substrates as a function of temperature. According to our studies with Poly 64 (a copolymer of 60% (mol) NIPAAm and 40% (mol) NnBAAm, LCST = 8.5 degrees C in water), the copolymer retention depends on the rinse temperature. When the rinse temperature is above the LCST, the polymer adheres well to most surfaces. On the contrary, at rinse temperatures below the LCST, most of the adsorbed polymer is easily rinsed off. These studies are relevant to our work on the thermally reversible adsorption of LCST polymers conjugated to peptides and proteins, such as affinity ligands, for uses in immunoassays and affinity separations. The interaction between the LCST polymer and most hydrophobic polymer surfaces is mainly due to hydrophobic interactions, and the critical surface tension (gamma c) and the solubility parameter (delta) of the solid polymer substrate are the most important factors which influence the LCST polymer adsorption and retention. The critical surface tension appears to correlate best with the LCST polymer adsorption levels on different substrates, while the solubility parameter correlates best with the retention of the adsorbed polymer. According to our preliminary study, n-butyl groups probably interact more strongly with the substrates than isopropyl groups because of the greater hydrophobic surface area of the former groups.

New immobilization method of filamentous cells with thin paper carrier surfaces modified by radiation

A new immobilization method of filamentous cells such as Trichoderman reesei with thin paper carrier surfaces modified by electron beam irradiation has been developed, in which the immobilization was carried out by adhesion of the cells to hydrophobic polymer surfaces. The cells adhered firmly and grew on the surface of the carrier producing the enzyme cellulase. The productivity of the enzyme in immobilized growing cells was higher than that in free cells. The diffusional barrier for substrate, nutrients and products (enzymes) in the immobilized carrier was improved. The effect of the condition of carrier preparation and immunobilization on enzyme productivity was studied to get the optimum condition of immobilization.

Ferrocene-mediated needle-type glucose sensor covered with newly designed biocompatible membrane

A ferrocene-mediated needle-type glucose sensor covered with a newly designed biocompatible membrane of 2-methacryloyloxyethyl phosphorylcholine (MPC) has been developed and its characteristics examined in vitro and in vivo. Application of ferrocene derivatives to the glucose sensor could solve the oxygen-limitation problems, and also compensate the sensor decay due to an insufficient microconvection and diffusion of oxygen resulting from protein fixation on the sensor surface during continuous subcutaneous tissue glucose monitoring. The MPC membrane, a hydrophobic polymer surface covered with a grafted hydrophilic phosphorylcholine chain, has the potential for supressing adsorption of biochemical molecules due to the mobility of the grafted polymer chain. With this glucose sensor covered with an MPC membrane, subcutaneous tissue glucose concentrations can be monitored for up to seven days without any in situ calibrations, followed by 14 days with one-point in situ calibrations. Therefore, we conclude that a ferrocene-mediated needle-type glucose sensor covered with an MPC membrane is stable and reliable, as compared to any other glucose sensors already developed, and can thus be applied for continuous glucose monitoring and for glycaemic control with a wearable artificial endocrine pancreas.

Calculation of solvation interaction energies for protein adsorption on polymer surfaces

Of the interactions that govern protein adsorption on polymer surfaces, solvation interactions (repulsive hydration and attractive hydrophobic interactions) are thought to be among the most important. The solvation interactions in protein adsorption, however, have not been dealt with in theoretical calculation of the adsorption energy owing to the difficulties in modelling such interactions. We have evaluated the solvation interaction energies using the fragment constant method of calculating the partition coefficients of amino acids. The fundamental assumption of this approach is that the partition coefficients of amino acids between water and organic solvent phases are related to the free energies of transfer from bulk water to the polymer surface. The X-ray crystallographic protein structures of lysozyme, trypsin, immunoglobulin Fab, and hemoglobin from the Brookhaven Protein Data Bank were used. The model polymer surfaces were polystyrene, polypropylene, polyethylene, poly(hydroxyethyl methacrylate) [poly(HEMA)], and poly(vinyl alcohol). All possible adsorption orientations of the proteins were simulated to study the effect of protein orientation on the solvation interactions. Protein adsorption on either hydrophobic or hydrophilic polymer surfaces was examined by considering the sum of solvation and other interaction energies. The results showed that the contribution of the solvation interaction to the total protein adsorption energy was significant. The average solvation interaction energy ranged from -259.1 to -74.1 kJ/mol for the four proteins on the hydrophobic polymer surfaces, such as polystyrene, polypropylene, and polyethylene. On the other hand, the average solvation interaction energies on hydrophilic surfaces such as poly(HEMA) and poly(vinyl alcohol) were larger than zero. This indicates that repulsive hydration interactions are in effect for protein adsorption on hydrophilic polymer surfaces. The total interaction energies of the proteins with hydrophobic surfaces were always lower than those with more hydrophilic surfaces. This trend is in agreement with the experimental observations in the literature. This study suggests that consideration of the solvation interaction energies is necessary for accurate calculation of the protein adsorption energies.

Kinetics of adsorption of proteins on the surface of hydrophobic polymers

Using a diffusion-kinetic model of adsorption of proteins on a hydrophobic polymer surface a method was proposed for determmining parameters of the adsoprtion process experimentally. The method is based on the egg-albumen-PE system. Experimental results agree with data of numerical simulation and give basis for forecasting the behaviour of polymer-protein adsorption systems.

Structural and Kinetic Aspects of Blood Plasma Protein Adsorption on the Surface of Hydrophobic Polymers

Abstract Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood.

Adsorption of blood plasma proteins on a hydrophobic polymer surface dependent on hydrodynamic conditions

A study was made of the effect of hydrodynamic conditions on the formation of an irreversible blood plasma protein layer on a hydrophobi polymer surface. Criteria were found for the relative predominance of processes of adsorption, denaturation and diffusion, according to the rate constant of these processes and flow parameters. Using these criteria formulae were derived to describe kinetics of formation of an irreversible adsorption layer. Results of the theoretical investigation show satisfactory agreement with experimental data published in the literature.

HYDROPHOBIC POLYMER SURFACES AND THEIR INTERACTIONS WITH BLOOD*

Annals of the New York Academy of SciencesVolume 283, Issue 1 p. 356-371 HYDROPHOBIC POLYMER SURFACES AND THEIR INTERACTIONS WITH BLOOD* J. L. Brash, J. L. Brash Departments of Chemical Engineering and Pathology McMaster University Hamilton, Ontario, Canada L8S 4L7Search for more papers by this author J. L. Brash, J. L. Brash Departments of Chemical Engineering and Pathology McMaster University Hamilton, Ontario, Canada L8S 4L7Search for more papers by this author First published: February 1977 https://doi.org/10.1111/j.1749-6632.1977.tb41781.xCitations: 73 * Supported by the Medical Research Council of Canada and the Ontario Heart Foundation. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume283, Issue1The Behavior of Blood and its Components at InterfacesFebruary 1977Pages 356-371 RelatedInformation

Adsorption of proteins onto hydrophobic polymer surfaces: adsorption isotherms and kinetics.

AbstractAdsorption of albumin, γ‐globulin, and fibrinogen from solution, under both static and flow conditions, onto several hydrophobic polymers was studied using internal reflection infrared spectroscopy. Isotherm curves experimentally found were consistant with Langmuir type adsorption. The rate and amount of protein adsorbed was found to be dependent upon both the nature of the polymer substrate and on the flow rate of the solution.

Surface transformations of polymers

Abstract

An Investigation of the Effect of Electrode Geometry and Frequency of Power Supply in the Homogeneity of Dielectric Barrier Discharge in Air

An experimental investigation of dielectric barrier discharge (DBD) produced in air isreported in the present paper. The discharge was produced by applying 0?20 kV AC source atfrequency 10?30 kHz. The main objective of the study was to investigate the dependence ofthe discharge homogeneity on the frequency of applied source and the geometry of theelectrodes. For this propose, three different types of electrodes were used. The discharge wassystematically investigated on an extended range of electrical parameters using highfrequency digital oscilloscope. Non-thermal nature of the discharge was tested by thetreatment of hydrophobic polymer surface by measuring the change in contact angle withwater drops.Key words: DBD; electrode geometry; contact angle measurement; surface treatmentDOI: 10.3126/kuset.v6i1.3316 Kathmandu University Journal of Science, Engineering and Technology Vol.6(1) 2010, pp96-101

Adsorption of plasma proteins in solution to uncharged, hydrophobic polymer surfaces.

AbstractInfraref internal reflection spectroscopy has been used to study the adsorption of certain plasma proteins on a variety of hydrophobic polymer surfaces. The behavior of the systems studied was almost identical. Under Static conditions the proteins appear to be rapidly adsorbed as monomolecular layers from solutions varying in concentration between a few mg‐% and normal plasma levels. These monolayers are deduced to be closely packed arrays in which the protein molecules appear to retain their native globular form. The bearing of these results on the mechanism of surface‐induced coagulation is significant.