201
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Jayaraman A, Schweizer KS. Effect of the number and placement of polymer tethers on the structure of concentrated solutions and melts of hybrid nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:11119-11130. [PMID: 18729491 DOI: 10.1021/la801432b] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have generalized and applied the microscopic polymer reference interaction site model theory to study intermolecular pair correlation functions and collective structure factors of concentrated solutions and melts of spherical nanoparticles carrying one, two, or four tethered polymer chains. A complex interplay of entropy (translational, conformational, and packing) and enthalpy (particle-particle attraction) leads to different structural arrangements with distinctive small- and wide-angle scattering signatures. Strong concentration fluctuations indicative of aggregate formation and/or a tendency for microphase separation occur as the total packing fraction and/or particle-particle attraction strength increase. In analogy with block copolymers, the microphase spinodal curve is estimated by extrapolation of the inverse of the amplitude of the small-angle scattering peak. As the number of tethered chains on nanoparticles increases, the microphase separation boundary spinodal occurs at higher particle-particle attraction strength or lower temperature. For nanoparticles with two tethers, increasing the angle between the attached chains shifts the microphase spinodal to lower temperatures. For nanoparticles with four tethers, the structural correlations are insensitive to various symmetric placements. The tendency for microphase transition is enhanced upon asymmetrically placing all four tethers on one side of the particle due to the high anisotropy of steric hindrance.
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Affiliation(s)
- Arthi Jayaraman
- Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801, USA
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202
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Hiotelis I, Koutsioubas AG, Spiliopoulos N, Anastassopoulos DL, Vradis AA, Toprakcioglu C, Menelle A, Sakellariou G, Hadjichristidis N. Neutron Reflectivity and Computer Simulation Studies of Self-Assembled Brushes Formed by Centrally Adsorbed Star Polymers. Macromolecules 2008. [DOI: 10.1021/ma702749z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ioannis Hiotelis
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Alexandros G. Koutsioubas
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Nikolaos Spiliopoulos
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Dimitris L. Anastassopoulos
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Alexandros A. Vradis
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Chris Toprakcioglu
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Alain Menelle
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - George Sakellariou
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Nikos Hadjichristidis
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
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203
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McGinty KM, Brittain WJ. Hydrophilic surface modification of poly(vinyl chloride) film and tubing using physisorbed free radical grafting technique. POLYMER 2008. [DOI: 10.1016/j.polymer.2008.07.063] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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204
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Hofs B, Brzozowska A, de Keizer A, Norde W, Cohen Stuart M. Reduction of protein adsorption to a solid surface by a coating composed of polymeric micelles with a glass-like core. J Colloid Interface Sci 2008; 325:309-15. [DOI: 10.1016/j.jcis.2008.06.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 06/04/2008] [Accepted: 06/04/2008] [Indexed: 10/22/2022]
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205
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Fundeanu I, van der Mei HC, Schouten AJ, Busscher HJ. Polyacrylamide brush coatings preventing microbial adhesion to silicone rubber. Colloids Surf B Biointerfaces 2008; 64:297-301. [DOI: 10.1016/j.colsurfb.2008.02.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Revised: 02/04/2008] [Accepted: 02/08/2008] [Indexed: 11/16/2022]
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206
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Frischknecht AL. Forces between nanorods with end-adsorbed chains in a homopolymer melt. J Chem Phys 2008; 128:224902. [DOI: 10.1063/1.2929831] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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207
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de Vos WM, Biesheuvel PM, de Keizer A, Kleijn JM, Cohen Stuart MA. Adsorption of the protein bovine serum albumin in a planar poly(acrylic acid) brush layer as measured by optical reflectometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:6575-84. [PMID: 18507422 DOI: 10.1021/la8006469] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The adsorption of bovine serum albumin (BSA) in a planar poly(acrylic acid) (PAA) brush layer has been studied by fixed-angle optical reflectometry. The influence of polymer length, grafting density, and salt concentration is studied as a function of pH. The results are compared with predictions of an analytical polyelectrolyte brush model, which incorporates charge regulation and excluded volume interactions. A maximum in adsorption is found near the point of zero charge (pzc) of the protein. At the maximum, BSA accumulates in a PAA brush to at least 30 vol %. Substantial adsorption continues above the pzc, that is, in the pH range where a net negatively charged protein adsorbs into a negatively charged brush layer, up to a critical pH value. This critical pH value decreases with increasing ionic strength. The adsorbed amount increases strongly with both increasing PAA chain length and increasing grafting density. Experimental data compare well with the analytical model without having to include a nonhomogeneous charge distribution on the protein surface. Instead, charge regulation, which implies that the protein adjusts its charge due to the negative electrostatic potential in the brush, plays an important role in the interpretation of the adsorbed amounts. Together with nonelectrostatic interactions, it explains the significant protein adsorption above the pzc.
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Affiliation(s)
- Wiebe M de Vos
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
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208
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Voets IK, de Vos WM, Hofs B, de Keizer A, Conhen Stuart MA, Steitz R, Lott D. Internal structure of a thin film of mixed polymeric micelles on a solid/liquid interface. J Phys Chem B 2008; 112:6937-45. [PMID: 18489139 DOI: 10.1021/jp709758p] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The adsorption of mixed micelles of poly(4-(2-amino hydrochloride-ethylthio)-butylene)- block-poly(ethylene oxide), PAETB 49- b-PEO 212 and poly(4-(2-sodium carboxylate-ethylthio)-butylene)- block-poly(ethylene oxide), PCETB 47- b-PEO 212 on solid/liquid interfaces has been studied with light, X-ray, and neutron reflectometry. The structure of the adsorbed layer can be described with a two-layer model consisting of an inner layer formed by the coacervate of the polyelectrolyte blocks PAETB 49 and PCETB 47 ( approximately 1 nm) and an outer layer of PEO 212 blocks ( approximately 6 nm). The micelles unfold upon adsorption forming a rather homogeneous flat layer that exposes its polyethylene oxide chains into the solution, thus rendering the surface antifouling after modification with the micelles.
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Affiliation(s)
- Ilja K Voets
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, Wageningen, The Netherlands.
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209
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Dutta N, Green D. Nanoparticle stability in semidilute and concentrated polymer solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:5260-5269. [PMID: 18419144 DOI: 10.1021/la7027516] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The wetting of PDMS-grafted silica spheres (PDMS- g-silica) is connected to their depletion restabilization in semidilute and concentrated PDMS/cyohexane polymer solutions. Specifically, we found that a wetting diagram of chemically identical graft and free homopolymers predicts stability of hard, semisoft, and soft spheres as a function of the bulk free polymer volume fraction, graft density, and the graft and free polymer chain lengths. The transition between stable and aggregated regions is determined optically and with dynamic light scattering. The point of demarcation between the regions occurs when the graft and free polymer chains are equal in length. When graft chains are longer than free chains, the particles are stable; in contrast, the particles are unstable when the opposite is true. The regions of particle stability and instability are corroborated with theoretical self-consistent mean-field calculations, which not only show that the grafted brush is responsible for particle dispersion in the complete wetting region but also aggregation in the incomplete wetting region. Ultimately, our results indicate that depletion restabilization depends on the interfacial properties of the nanoparticles in semidilute and concentrated polymer solutions.
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Affiliation(s)
- Nupur Dutta
- Department of Chemical Engineering, University of Virginia, 102 Engineers Way, Charlottesville, Virginia 22904, USA
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210
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Toomey R, Tirrell M. Functional Polymer Brushes in Aqueous Media from Self-Assembled and Surface-Initiated Polymers. Annu Rev Phys Chem 2008; 59:493-517. [DOI: 10.1146/annurev.physchem.59.032607.093623] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ryan Toomey
- Department of Chemical Engineering, University of South Florida, Tampa, Florida 33620;
| | - Matthew Tirrell
- Department of Chemical Engineering and the Materials Research Laboratory, University of California, Santa Barbara, California 93106;
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211
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de Samaniego MSS, Miller AF. Two-dimensional polymerization of a polydiacetylene functionalized amphiphilic peptide at the air–water interface. Colloids Surf A Physicochem Eng Asp 2008. [DOI: 10.1016/j.colsurfa.2008.02.030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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212
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Jayaraman A, Schweizer KS. Structure and assembly of dense solutions and melts of single tethered nanoparticles. J Chem Phys 2008; 128:164904. [DOI: 10.1063/1.2907717] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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213
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Tugulu S, Klok HA. Stability and Nonfouling Properties of Poly(poly(ethylene glycol) methacrylate) Brushes under Cell Culture Conditions. Biomacromolecules 2008; 9:906-12. [DOI: 10.1021/bm701293g] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stefano Tugulu
- École Polytechnique Fédérale de Lausanne (EPFL), Institut des Matériaux, Laboratoire des Polymères, Bâtiment MXD, Station 12, CH-1015 Lausanne, Switzerland
| | - Harm-Anton Klok
- École Polytechnique Fédérale de Lausanne (EPFL), Institut des Matériaux, Laboratoire des Polymères, Bâtiment MXD, Station 12, CH-1015 Lausanne, Switzerland
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214
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Wang J, Butt HJ. Forces between thiolate-modified gold surfaces in a melt of end-functionalized polymers. J Phys Chem B 2008; 112:2001-7. [PMID: 18229910 DOI: 10.1021/jp0760612] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To better understand surface forces across polymer melts, we measured the force between two chemically well-defined solid surfaces in a melt of polymer chains with a functional end group. As for surfaces, we used self-assembed monolayers (SAMs) of alkyl thiols with different end groups (methyl, amino, and hydroxyl) on gold. The polymer was a hydroxyl-terminated polyisoprene. To measure the force, an atomic force microscope was used. Between methyl-terminated SAMs, a weak and short-range repulsion was detected. Between hydroxyl or amino-terminated SAMs, a strong and long-range repulsion was observed up to distances of 16 nm. This indicates that the hydroxyl group of the polymer binds to the hydroxyl or amino groups of the SAMs. It forms a brush-like structure, which leads to steric repulsion. On amino-terminated SAMs, force-versus-distance curves on approach and retraction were monotonically repulsive and reversible. With hydroxyl-terminated SAMs, a jump was observed on approach when the load exceeded a certain threshold. On retraction, an adhesion had to be overcome. We interpret the jump as a rupture of the polymer layer. It indicates that the kinetics of bond and brush formation is faster on OH-SAMs than on NH2-SAMs.
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Affiliation(s)
- Jijun Wang
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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215
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Norde W. My voyage of discovery to proteins in flatland …and beyond. Colloids Surf B Biointerfaces 2008; 61:1-9. [DOI: 10.1016/j.colsurfb.2007.09.029] [Citation(s) in RCA: 219] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 09/25/2007] [Accepted: 09/25/2007] [Indexed: 10/22/2022]
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216
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Guo DJ, Han HM, Jing-Wang, Xiao SJ, Dai ZD. Surface-hydrophilic and protein-resistant silicone elastomers prepared by hydrosilylation of vinyl poly(ethylene glycol) on hydrosilanes-poly(dimethylsiloxane) surfaces. Colloids Surf A Physicochem Eng Asp 2007. [DOI: 10.1016/j.colsurfa.2007.05.080] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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217
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Saldarriaga Fernández IC, van der Mei HC, Lochhead MJ, Grainger DW, Busscher HJ. The inhibition of the adhesion of clinically isolated bacterial strains on multi-component cross-linked poly(ethylene glycol)-based polymer coatings. Biomaterials 2007; 28:4105-12. [PMID: 17573108 DOI: 10.1016/j.biomaterials.2007.05.023] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Accepted: 05/25/2007] [Indexed: 11/24/2022]
Abstract
This study examined bacterial adhesion to a new multi-component cross-linked poly(ethylene glycol)-based polymer coating that can be applied by spin-coating or spraying onto diverse biomaterials. Adhesion of five clinically isolated bacterial strains involved in biomaterial-centered infections were studied in a parallel-plate flow chamber at different shear rates and after exposure of the coating to different physiological fluids. The new chemistry inhibits non-specific biomolecular and cell binding interactions. Relative to glass, the coating reduced adhesion of all strains used in this study by more than 80%, with the exception of Escherichia coli O2K2. Reductions in adhesion of Staphylococcus epidermidis 3,399 persisted beyond 168h exposure of the coatings to phosphate buffered saline or urine, but not after exposure to protein-rich fluids as saliva and blood plasma, despite evidence from X-ray photoelectron spectroscopy that the coating integrity was not affected by exposure to these fluids. We conclude that this new coating chemistry provides beneficial properties to prevent or hinder bacterial adhesion and colonization in applications where low protein-conditions prevail.
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Affiliation(s)
- Isabel C Saldarriaga Fernández
- Department of BioMedical Engineering, University Medical Center Groningen, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
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218
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Bosker WTE, Patzsch K, Stuart MAC, Norde W. Sweet brushes and dirty proteins. SOFT MATTER 2007; 3:754-762. [PMID: 32900139 DOI: 10.1039/b618259c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We studied the protein repellency of dextran brushes. Dextran was grafted to a polystyrene surface in a broad range of grafting densities using polystyrene-dextran block copolymers and the Langmuir-Blodgett deposition technique. Ellipsometry measurements confirmed a successful transfer of the dextran brush from the air-water interface to the polystyrene surface. Water contact-angle measurements validated the presence of the dextran layer at the surface. At grafting densities <0.20 nm, a heterogeneous dextran coating is detected with tapping mode AFM, consisting of aggregates of polystyrene-dextran and relatively large interstitial areas without dextran chains. This is probably due to surface micellization of the block copolymer in the Langmuir-Blodgett procedure. At grafting densities ≥0.20 nm, a homogeneous dextran brush is observed. Adsorption studies of BSA and trypsin, using optical reflectometry, showed that adsorbed amounts at the heterogeneous coating (<0.20 nm) is only slightly lower, if at all, than at the bare polystyrene surface. Beyond 0.20 nm, a drastic decrease in adsorbed amount was observed, due to excluded volume interactions between the protein and the homogeneous dextran brush. Almost complete protein repellency could be reached at high grafting densities. Comparison with adsorption studies of PEO brushes indicated that dextran brushes do not outperform PEO brushes in suppressing protein adsorption.
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Affiliation(s)
- Wouter T E Bosker
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB, Wageningen, The Netherlands
| | - Katja Patzsch
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB, Wageningen, The Netherlands and Downstream Processing, Institute for Bioengineering, Martin-Luther-University Halle-Wittenberg, Weinbergweg 22, 06120, Halle, Germany
| | - Martien A Cohen Stuart
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB, Wageningen, The Netherlands
| | - Willem Norde
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB, Wageningen, The Netherlands and Department of Biomedical Engineering, University Medical Center Groningen, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands
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219
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Tsao CW, Hromada L, Liu J, Kumar P, DeVoe DL. Low temperature bonding of PMMA and COC microfluidic substrates using UV/ozone surface treatment. LAB ON A CHIP 2007; 7:499-505. [PMID: 17389967 DOI: 10.1039/b618901f] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The use of UV/ozone surface treatments for achieving low temperature bonds between PMMA and COC microfluidic substrates is evaluated. Low temperature bond strengths, approaching those of native polymer substrates bonded above their glass transition temperatures, are demonstrated for both thermoplastics. To evaluate the effects of the UV/O(3) surface treatment on the operation of bonded microfluidic devices, the relationship between UV/O(3) exposure and polymer hydrophilicity and surface chemistry are measured. Post-treatment surface chemistry is evaluated by XPS (X-ray photoelectron spectroscopy) analysis, and the stability of the treated surfaces following solvent exposure is reported. Electroosmotic flow within fabricated microchannels with modified wall surfaces is also characterized. Overall, UV/O(3) treatment is found to enable strong low temperature bonds between thermoplastic microfluidic substrates using a simple, low cost, and high throughput fabrication technology.
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Affiliation(s)
- C W Tsao
- Department of Mechanical Engineering, University of Maryland, College Park, MD, USA
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220
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Yoshikawa C, Goto A, Ishizuka N, Nakanishi K, Kishida A, Tsujii Y, Fukuda T. Size-Exclusion Effect and Protein Repellency of Concentrated Polymer Brushes Prepared by Surface-Initiated Living Radical Polymerization. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/masy.200750220] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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221
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Popelka S, Machová L, Rypácek F. Adsorption of poly(ethylene oxide)-block-polylactide copolymers on polylactide as studied by ATR-FTIR spectroscopy. J Colloid Interface Sci 2007; 308:291-9. [PMID: 17266980 DOI: 10.1016/j.jcis.2006.12.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Revised: 12/06/2006] [Accepted: 12/06/2006] [Indexed: 11/29/2022]
Abstract
In this study, the adsorption of amphiphilic poly(ethylene oxide)-block-polylactide (mPEO-PLA) copolymers from a selective solvent onto a polylactide surface was studied as a method of polylactide surface modification and its effect on nonspecific protein adsorption was evaluated. A series of well defined mPEO-PLA copolymers was prepared to investigate the effect of copolymer composition on the resulting PEO chain density and on the surface resistance to protein adsorption. The copolymers contained PEO blocks with molecular weights ranging between 5600 and 23,800 and with 16-47 wt% of PLA. The adsorption of both the copolymers and bovine serum albumin was quantified by attenuated total reflection FTIR spectroscopy (ATR-FTIR). In addition to the adsorbed copolymer amount, its actual composition was determined. The PEO chain density on the surface was found to decrease with the molecular weight of the PEO block and to increase with the molecular weight of the PLA block. The adsorbed copolymers displayed the ability to reduce protein adsorption. The maximum reduction within the tested series (by 80%) was achieved with the copolymer containing PEO of MW 5600 and a PLA block of the same MW.
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Affiliation(s)
- Stepán Popelka
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovský Sq. 2, 16206 Prague 6, Czech Republic.
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222
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Dukhin SS, Zimmermann R, Werner C. Surface Conductivity Reveals Counterion Condensation within Grafted Polyelectrolyte Layers. J Phys Chem B 2007; 111:979-81. [PMID: 17266251 DOI: 10.1021/jp065585j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Surface conductivity (SC) has been demonstrated to be a valuable parameter for the characterization of surface-bound polyelectrolyte layers (PLs). The measurement of the SC in dependence of the pH and solution concentration yields information about the Donnan potential, PsiD, the intrinsic charge, the potential of the PL electrolyte interface, Psi0, the pK of the ionizable groups within the PLs, and the concentration of segments, n. We discuss herein that SC measurements may additionally provide information about counterion condensation. The mobility of the counterions within grafted poly(acrylic acid) (PAA) layers was estimated from the density of COOH groups and SC data to be only 14% of that of free ions (Zimmermann, et al. Langmuir 2005, 21, 5108). In view of this large deviation and the limited sterical constraints within the brushes, we conclude that the number of freely moving counterions is decreased due to counterion condensation. This interpretation agrees well with the measurement of the osmotic pressure for PAA solution (Boisvert, et al. Polymer 2002, 43, 141), which can be exclusively attributed to the remaining mobile counterions of the polyelectrolyte.
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223
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Teraoka I, Hayes C. Stability of Nonaqueous Ink Jet Inks as Studied by Single Particle Optical Sensing. J Imaging Sci Technol 2006. [DOI: 10.2352/j.imagingsci.technol.(2006)50:6(544)] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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224
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Hlady V, Jogikalmath G. Albumin binding and insertion into PS-b-PEO monolayers at air-water interface. Colloids Surf B Biointerfaces 2006; 54:179-87. [PMID: 17141488 PMCID: PMC1832108 DOI: 10.1016/j.colsurfb.2006.10.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Revised: 10/07/2006] [Accepted: 10/10/2006] [Indexed: 11/30/2022]
Abstract
Interaction of human serum albumin with poly(styrene)-b-poly(ethylene oxide) (PS-b-PEO) monolayer at air/solution interface was studied by measuring surface pressure. The density of PEO chains in the monolayer was controlled using Langmuir trough barriers. The thickness of PS-b-PEO monolayer prior to and after albumin adsorption was computed from in situ surface plasmon resonance (SPR) measurements. Depending on the initial PEO surface density the surface pressure kinetics of albumin insertion displayed two different regimes: below the PEO "pancake-brush" transition albumin binding was initially very rapid and itself induced the "pancake-brush" transition in the monolayer, and above the "pancake-brush" transition where some albumin penetration into the free PS-b-PEO monolayer still occurred into the PEO "brush". In the case of SPR-immobilized monolayer, more than 0.1 PEO chain/nm(2) was required to inhibit albumin or ferritin adsorption. A half-reduction of albumin adsorption required approx. three-fold higher PEO surface density than the half-reduction of ferritin adsorption.
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Affiliation(s)
- Vladimir Hlady
- Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA.
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225
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Atom transfer radical polymerization (ATRP) initiated by aryl diazonium salts: a new route for surface modification of multiwalled carbon nanotubes by tethered polymer chains. Colloids Surf A Physicochem Eng Asp 2006. [DOI: 10.1016/j.colsurfa.2006.05.028] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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226
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Mei Y, Elliott JT, Smith JR, Langenbach KJ, Wu T, Xu C, Beers KL, Amis EJ, Henderson L. Gradient substrate assembly for quantifying cellular response to biomaterials. J Biomed Mater Res A 2006; 79:974-88. [PMID: 16948143 DOI: 10.1002/jbm.a.30883] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Using quantitative fluorescence microscopy in conjunction with a method of gradient substrate assembly established in their group, the authors were able to introduce and measure reproducible changes in cellular morphology and cell density by manipulating polymer grafting density. The mechanism behind this change in cellular behavior was explained by a semiempirical, geometric model that describes the effect of the spatial distribution of the polymer on protein attachment. A 10-fold increase in graft density of poly(2-hydroxyethyl methacrylate) [PHEMA] along the surface of a gradient sample, preexposed to bovine fibronectin, caused a change in the size of fibroblasts on the surface (i.e., cell spreading) from (1238 +/- 704) to (377 +/- 216) microm(2). The results were in quantitative agreement with those obtained on three separate gradient samples. Both cellular response and fibronectin adsorption (as measured via ellipsometry) were found to vary sigmoidally with graft density of PHEMA, demonstrating the high degree of correlation between the two phenomena. A simple, rigid-disk model accounting for the surface coverage of PHEMA was able to predict the amount of adsorbed fibronectin with a correlation coefficient of 0.97. Maximal cell adhesion and cell spreading were found to occur at fibronectin surface densities of 50 and 100 ng/cm(2), respectively. The results demonstrate the role of gradient substrate assembly as a method for quantifying the relationship between protein and cellular response to technologically relevant polymeric materials.
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Affiliation(s)
- Ying Mei
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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227
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Zweistra HJA, Besseling NAM. Adsorption and desorption of reversible supramolecular polymers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:021806. [PMID: 17025465 DOI: 10.1103/physreve.74.021806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Indexed: 05/12/2023]
Abstract
We report numerical mean-field results on the quasichemical level of approximation that describe adsorption of reversible supramolecular polymers at a flat interface. Emphasis is laid on the regime of strong adsorption from a dilute solution. There are two differences with respect to macromolecular polymer adsorption: (i) adsorption sets in at relatively high monomer concentrations of the surrounding solution, and (ii) the surface is filled within a much narrower concentration range. Contrary to macromolecular polymers, supramolecular polymers can therefore be desorbed by dilution of the equilibrium solution by solvent within an experimentally accessible concentration window. Based on simple thermodynamic arguments, we provide a quantitative explanation why supramolecular polymers adsorb at relatively high concentrations. Moreover, we discuss the (by comparison) narrow concentration window wherein filling of the surface occurs. This is attributed to the cooperative nature of supramolecular polymer adsorption. The degree of cooperativity is quantified by means of the Hill parameter n.
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Affiliation(s)
- Henk J A Zweistra
- Laboratory of Physical Chemistry and Colloid Science, Dreijenplein 6, NL-6703 HB Wageningen, the Netherlands.
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228
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Jung J, Kim KW, Na K, Kaholek M, Zauscher S, Hyun J. Fabrication of Micropatterned Gold Nanoparticle Arrays as a Template for Surface-Initiated Polymerization of Stimuli-Responsive Polymers. Macromol Rapid Commun 2006. [DOI: 10.1002/marc.200600069] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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229
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Tscheliessnig R, Billes W, Fischer J, Sokołowski S, Pizio O. The role of fluid wall association on adsorption of chain molecules at functionalized surfaces: A density functional approach. J Chem Phys 2006; 124:164703. [PMID: 16674153 DOI: 10.1063/1.2187010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a density functional theory to describe adsorption in systems where selected segments of chain molecules of fluids can bond (or associate) with functional groups attached to the surfaces. Association of active segments with the surface is modeled within the framework of the first-order thermodynamic perturbation theory. We discuss the influence of several parameters such as the density of surface active sites, the energy of association, the chain length, and the number of the active segment in the chain molecule on the structure of the fluid adjacent to the wall. The proposed model can be considered as a first step towards developing a density functional theory of molecular brushes chemically bonded to solid surfaces.
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Affiliation(s)
- R Tscheliessnig
- Institute for Chemical and Energy Engineering, BOKU University of Natural Resources and Applied Life Sciences, Muthgasse 107, A-1190 Vienna, Austria
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230
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Ivanov AE, Ekeroth J, Nilsson L, Mattiasson B, Bergenståhl B, Galaev IY. Variations of wettability and protein adsorption on solid siliceous carriers grafted with poly(N-isopropylacrylamide). J Colloid Interface Sci 2006; 296:538-44. [PMID: 16243347 DOI: 10.1016/j.jcis.2005.09.064] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Revised: 09/28/2005] [Accepted: 09/28/2005] [Indexed: 11/30/2022]
Abstract
Poly(N-isopropylacrylamide), a thermally responsive polymer, was end-grafted to mercaptopropyl derivatives of silica gel, plane glass sheets and glass capillary tubing by free radical polymerization of the monomer in 1,4-dioxane at 100 degrees C. The polymer monolayer attached to the glass carriers provided them with thermally controlled wettability registered by two independent methods: direct measurements of the water contact angle and capillary rise. The water contact angle changed from 54+/-3 degrees to 68+/-3 degrees in the temperature range from 20 to 50 degrees C. The polymer grafting to silica gel (pore diameter 100 A, particle size 5 microm) resulted in 15-30-fold reduction in protein adsorption on the carrier at 35 degrees C. Adsorption isotherms of myoglobin indicate completely different characters of the protein adsorption to silica gel and its polyNIPAM-grafted derivative. Cooling of the grafted carrier containing adsorbed myoglobin to 9 degrees C led to a partial release of the protein to the contacting solution, whereas heating of the system to 35 degrees C resulted in reversible binding of the protein. Adsorption of myoglobin on polyNIPAM-coated silica was ca. 2-fold higher at 35 than at 9 degrees C, most probably due to steric repulsion displayed by the swollen copolymer at the lower temperature.
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Affiliation(s)
- Alexander E Ivanov
- Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
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231
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Yoshikawa C, Goto A, Tsujii Y, Fukuda T, Kimura T, Yamamoto K, Kishida A. Protein Repellency of Well-Defined, Concentrated Poly(2-hydroxyethyl methacrylate) Brushes by the Size-Exclusion Effect. Macromolecules 2006. [DOI: 10.1021/ma0520242] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chiaki Yoshikawa
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; Department of Nanostructured and Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, 1-21140 Korimoto, Kagoshima 890-0065, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan
| | - Atsushi Goto
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; Department of Nanostructured and Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, 1-21140 Korimoto, Kagoshima 890-0065, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan
| | - Yoshinobu Tsujii
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; Department of Nanostructured and Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, 1-21140 Korimoto, Kagoshima 890-0065, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan
| | - Takeshi Fukuda
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; Department of Nanostructured and Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, 1-21140 Korimoto, Kagoshima 890-0065, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan
| | - Tsuyoshi Kimura
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; Department of Nanostructured and Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, 1-21140 Korimoto, Kagoshima 890-0065, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan
| | - Kazuya Yamamoto
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; Department of Nanostructured and Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, 1-21140 Korimoto, Kagoshima 890-0065, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan
| | - Akio Kishida
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; Department of Nanostructured and Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, 1-21140 Korimoto, Kagoshima 890-0065, Japan; and Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan
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232
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Ren CL, Ma YQ. Phase Behavior in Thin Films of Confined Colloid−Polymer Mixtures. J Am Chem Soc 2006; 128:2733-7. [PMID: 16492061 DOI: 10.1021/ja057569q] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using self-consistent-field and density-functional theories, we first investigate colloidal self-assembly of colloid-polymer films confined between two soft surfaces grafted by polymers. With increasing colloidal concentrations, the film undergoes a series of transitions from disordered liquid --> sparse square --> hexagonal (or mixed square-hexagonal) --> dense square --> cylindrical structures in a plane, which results from the competition between the entropic elasticity of polymer brushes and the steric packing effect of colloidal particles. A phase diagram displays the stable regions of different in-layer ordering structures as the colloidal concentration is varied and layering transitions as the polymer-grafted density is decreased. Our results show a new control mechanism to stabilize the ordering of structures within the films.
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Affiliation(s)
- Chun-lai Ren
- National Laboratory of Solid State Microstructures, Nanjing University, China
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233
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Tsujii Y, Ohno K, Yamamoto S, Goto A, Fukuda T. Structure and Properties of High-Density Polymer Brushes Prepared by Surface-Initiated Living Radical Polymerization. SURFACE-INITIATED POLYMERIZATION I 2006. [DOI: 10.1007/12_063] [Citation(s) in RCA: 520] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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234
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Patra M, Linse P. Simulation of grafted polymers on nanopatterned surfaces. NANO LETTERS 2006; 6:133-7. [PMID: 16402801 DOI: 10.1021/nl051611y] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Structural properties of polymer brushes on nanopatterned surfaces in good solvent have been determined by computer simulations. Scaling relations for the brush height and brush width are proposed. The properties of the central part of the patterned brush remain constant as long as the pattern is wider than a few times the brush height. The results agree qualitatively with recent AFM experiments, but some quantitative differences call for a reassessment of experimental procedures.
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Affiliation(s)
- Michael Patra
- Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, Sweden.
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235
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Savina IN, Mattiasson B, Galaev IY. Graft polymerization of acrylic acid onto macroporous polyacrylamide gel (cryogel) initiated by potassium diperiodatocuprate. POLYMER 2005. [DOI: 10.1016/j.polymer.2005.07.091] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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236
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Roosjen A, de Vries J, van der Mei HC, Norde W, Busscher HJ. Stability and effectiveness against bacterial adhesion of poly(ethylene oxide) coatings in biological fluids. J Biomed Mater Res B Appl Biomater 2005; 73:347-54. [PMID: 15736286 DOI: 10.1002/jbm.b.30227] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Poly(ethylene oxide) (PEO) coatings have been shown to reduce the adhesion of different microbial strains and species and thus are promising as coatings to prevent biomaterial-centered infection of medical implants. Clinically, however, PEO coatings are not yet applied, as little is known about their stability and effectiveness in biological fluids. In this study, PEO coatings coupled to a glass substratum through silyl ether bonds were exposed for different time intervals to saliva, urine, or phosphate-buffered saline (PBS) as a reference at 37 degrees C. After exposure, the effectiveness of the coatings against bacterial adhesion was assessed in a parallel plate flow chamber. The coatings appeared effective against Staphylococcus epidermidis adhesion for 24, 48, and 0.5 h in PBS, urine, and saliva, respectively. Using XPS and contact-angle measurements, the variations in effectiveness could be attributed to conditioning film formation. The overall short stability results from hydrolysis of the coupling of the PEO chains to the substratum.
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Affiliation(s)
- Astrid Roosjen
- Department of Biomedical Engineering, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
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237
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Chen K, Ma YQ. Interactions between Colloidal Particles Induced by Polymer Brushes Grafted onto the Substrate. J Phys Chem B 2005; 109:17617-22. [PMID: 16853254 DOI: 10.1021/jp051403u] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigate the interaction energy between two colloidal particles on or immersed in nonadsorbing polymer brushes grafted onto the substrate as a function of the separation of the particles by the use of a self-consistent-field theory calculation. Depending on the colloidal size and the penetration depth, we demonstrate the existence of a repulsive energy barrier of several kBT, which can be interpreted by separating the interaction energy into three parts: colloid-polymer interfacial energy, entropic contribution due to "depletion zone" overlap of colloidal particles, and entropic elastic energy of grafted chains by the compression of particles. The existence of a repulsive barrier which is of entirely entropic origin can lead to kinetic stabilization of the mixture rather than depletion flocculation or phase separation. Therefore, the present result may suggest an approach for controlling the self-assembling behavior of colloids for the formation of target structures, by tuning the colloidal interaction on the grafting substrate under appropriate selection of colloidal size, effective gravity (influencing the penetration depth), and brush coverage density.
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Affiliation(s)
- Kang Chen
- National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
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238
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Hu S, Brittain WJ. Surface Grafting on Polymer Surface Using Physisorbed Free Radical Initiators. Macromolecules 2005. [DOI: 10.1021/ma0479060] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shuwen Hu
- Department of Polymer Science, University of Akron, Ohio 44325
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239
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Bosker WTE, Iakovlev PA, Norde W, Cohen Stuart MA. BSA adsorption on bimodal PEO brushes. J Colloid Interface Sci 2005; 286:496-503. [PMID: 15897063 DOI: 10.1016/j.jcis.2005.01.091] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2004] [Accepted: 01/24/2005] [Indexed: 11/26/2022]
Abstract
BSA adsorption onto bimodal PEO brushes at a solid surface was measured using optical reflectometry. Bimodal brushes consist of long (N=770) and short (N=48) PEO chains and were prepared on PS surfaces, applying mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) block copolymers and using the Langmuir-Blodgett technique. Pi-A isotherms of (mixtures of) the block copolymers were measured to establish the brush regime. The isotherms of PS(29)-PEO(48) show hysteresis between compression and expansion cycles, indicating aggregation of the PS(29)-PEO(48) upon compression. Mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) demonstrate a similar hysteresis effect, which eventually vanishes when the ratio of PS(37)-PEO(770) to PS(29)-PEO(48) is increased. The adsorption of BSA was determined at brushes for which the grafting density of the long PEO chains was varied, while the total grafting density was kept constant. BSA adsorption onto monomodal PEO(48) and PEO(770) brushes was determined for comparison. The BSA adsorption behavior of the bimodal brushes is similar to the adsorption of BSA at PEO(770) monomodal brushes. The maximum of BSA adsorption at low grafting density of PEO(770) can be explained by ternary adsorption, implying an attraction between BSA and PEO. The contribution of primary adsorption to the total adsorbed amount is negligible.
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Affiliation(s)
- W T E Bosker
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
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240
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Zimmermann R, Norde W, Cohen Stuart MA, Werner C. Electrokinetic characterization of poly(acrylic acid) and poly(ethylene oxide) brushes in aqueous electrolyte solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:5108-14. [PMID: 15896058 DOI: 10.1021/la050191p] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Surfaces carrying hydrophilic polymer brushes were prepared from poly(styrene)-poly(acrylic acid) and poly(styrene)-poly(ethylene oxide) diblock copolymers, respectively, using a Langmuir-Blodgett technique and employing poly(styrene)-coated planar glass as substrates. The electrical properties of these surfaces in aqueous electrolyte were analyzed as a function of pH and KCl concentration using streaming potential/streaming current measurements. From these data, both the zeta potential and the surface conductivity could be obtained. The poly(acrylic acid) brushes are charged due to the dissociation of carboxylic acid groups and give theoretical surface potentials of -160 mV at full dissociation in 10(-)(3) M solutions. The surface conductivity of these brushes is enormous under these conditions, accounting for more than 93% of the total measured surface conductivity. However, the mobility of the ions within the brush was estimated from the density of the carboxylic acid groups and the surface conductivity data to be only about 14% of that of free ions. The poly(ethylene oxide) (PEO) brushes effectively screen the charge of the underlying substrate, giving a very low zeta potential except when the ionic strength is very low. From the data, a hydrodynamic layer thickness of the PEO brushes could be estimated which is in good agreement with independent experiments (neutron reflectivity) and theoretical estimates. The surface conductivity in this system was slightly lower than that of the polystyren substrate. This also indicates that no significant amount of preferentially, i.e., nonelectrostatically attracted, ions taken up in the brush.
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Affiliation(s)
- Ralf Zimmermann
- Department Biocompatible Materials, Leibniz Institute of Polymer Research Dresden and The Max Bergmann Center of Biomaterials Dresden, Hohe Strasse 6, 01069 Dresden, Germany.
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241
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Abstract
Two-dimensional mean-field lattice theory is used to model immobilization and stabilization of an enzyme on a hydrophobic surface using grafted polymers. Although the enzyme affords biofunctionality, the grafted polymers stabilize the enzyme and impart biocompatibility. The protein is modeled as a compact hydrophobic-polar polymer, designed to have a specific bulk conformation reproducing the catalytic cleft of natural enzymes. Three scenarios are modeled that have medical or industrial importance: 1), It is shown that short hydrophilic grafted polymers, such as polyethylene glycol, which are often used to provide biocompatibility, can also serve to protect a surface-immobilized enzyme from adsorption and denaturation on a hydrophobic surface. 2), Screening of the enzyme from the surface and nonspecific interactions with biomaterial in bulk solution requires a grafted layer composed of short hydrophilic polymers and long triblock copolymers. 3), Hydrophilic polymers grafted on a hydrophobic surface in contact with an organic solvent form a dense hydrophilic nanoenvironment near the surface that effectively shields and stabilizes the enzyme against both surface and solvent.
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Affiliation(s)
- Yevgeny Moskovitz
- Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
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242
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Austine J, Juvekar VA. Prediction of Energy of Interaction among Tethered Polymer Chains Confined between Two Parallel Plates. Macromolecules 2005. [DOI: 10.1021/ma048319h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Juedu Austine
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
| | - Vinay A. Juvekar
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
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243
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Biesheuvel PM. Ionizable polyelectrolyte brushes: brush height and electrosteric interaction. J Colloid Interface Sci 2005; 275:97-106. [PMID: 15158386 DOI: 10.1016/j.jcis.2004.02.024] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Accepted: 02/06/2004] [Indexed: 11/21/2022]
Abstract
Semi-analytical scaling theory is used to describe quenched and annealed (weakly charged, ionizable, charge-regulating) polyelectrolyte brushes in electrolyte solutions of arbitrary salt concentration. An Alexander-De Gennes box model with homogeneous distribution of polymer segments and the free ends located at the edge of the brush is assumed, as is local electroneutrality in the brush. For annealed polyelectrolyte and in the low-salt regime, the theory predicts that for sufficiently dense brushes, the salt concentration has a small influence on brush height, while the brush expands with increasing grafting density, in agreement with experiment. Expressions are presented for the interaction free energy of compressed ionizable and quenched polyelectrolyte brushes (proportional to the force between particles or curved surfaces). In all cases, the required prefactors are explicitly stated. The theory is compared directly with published experiments on the influence of salt concentration, pH, and grafting density on the thickness and interaction force of polystyrene sulfonate (quenched) and poly(meth)acrylic acid (annealed) brushes. In general, trends are well reproduced but significant deviations remain.
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Affiliation(s)
- P Maarten Biesheuvel
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
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244
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Bhat RR, Tomlinson MR, Genzer J. Orthogonal surface-grafted polymer gradients: A versatile combinatorial platform. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/polb.20640] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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245
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Dunlop IE, Briscoe WH, Titmuss S, Sakellariou G, Hadjichristidis N, Klein J. Interactions Between Polymer Brushes: Varying the Number of End-Attaching Groups. MACROMOL CHEM PHYS 2004. [DOI: 10.1002/macp.200400236] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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246
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247
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Huang AY, Berg JC. Aggregate restructuring by polymer solvency effects. J Colloid Interface Sci 2004; 279:440-6. [PMID: 15464809 DOI: 10.1016/j.jcis.2004.06.088] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2003] [Accepted: 06/27/2004] [Indexed: 11/16/2022]
Abstract
This study investigates the aggregation in cyclohexane of silica particles initially stabilized by grafted polystyrene and destabilized by temperature reduction. It complements an earlier study by Zhu and Napper (P.W. Zhu, D.H. Napper, Phys. Rev. E 50 (1994) 1360) in which the aggregation of polystyrene latex particles with tethered poly(N-isopropyl acrylamide) (PNIPAM) in water was investigated. Their dynamic light scattering results showed that both the rate of aggregation and the aggregate fractal dimension increased with a sufficient decrease in the PNIPAM adlayer solvency, achieved by means of either salt (NaNO3) addition or temperature rise. This result stands in contrast to those obtained when an electrostatically stabilized colloid is destabilized, i.e., that the more rapidly aggregates are formed, the lower the resulting fractal dimension. The authors explained their results in terms of the effects of both salt effects and increased temperature on the extent of the hydrophobic interactions between the adlayer-covered surfaces in the water. The present study examines a sterically-stabilized colloid in a nonaqueous solvent, where neither salt effects nor hydrophobic effects play a role. Temperature is decreased to bring the system from better-than-theta-conditions to worse-than-theta-conditions. Power-law aggregation kinetics are observed at 15.7 degrees C by dynamic light scattering. The particles first undergo reduced rate aggregation, producing low-fractal-dimension aggregates, which after some time, restructure into more compact aged clusters. The fractal dimension of these aged clusters increases with increasing initial aggregation rate, consistent with results seen by Zhu and Napper, but without the presence of hydrophobic effects. The ability of the polymer-grafted particles to rearrange suggests aggregation into a secondary minimum, with the ability to slide over one another to achieve a more energetically favorable, denser configuration. The reversible nature of the aggregation is verified by additional experiments gradually bringing the system from worse-than-theta-conditions back to better-than-theta-conditions, with an attendant decrease in aggregate fractal dimension, and ultimately full redispersion.
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Affiliation(s)
- Alvin Y Huang
- Department of Chemical Engineering, University of Washington, Box 351750, Seattle, WA 98195-1750, USA
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248
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Picard M, Duval-Terrié C, Dé E, Champeil P. Stabilization of membranes upon interaction of amphipathic polymers with membrane proteins. Protein Sci 2004; 13:3056-8. [PMID: 15459343 PMCID: PMC2286580 DOI: 10.1110/ps.04962104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Amphipathic polymers derived from polysaccharides, namely hydrophobically modified pullulans, were previously suggested to be useful as polymeric substitutes of ordinary surfactants for efficient and structure-conserving solubilization of membrane proteins, and one such polymer, 18C(10), was optimized for solubilization of proteins derived from bacterial outer membranes (Duval-Terrie et al. 2003). We asked whether a similar ability to solubilize proteins could also be demonstrated in eukaryotic membranes, namely sarcoplasmic reticulum (SR) fragments, the major protein of which is SERCA1a, an integral membrane protein with Ca(2+)-dependent ATPase and Ca(2+)-pumping activity. We found that 18C(10)-mediated solubilization of these SR membranes did not occur. Simultaneously, however, we found that low amounts of this hydrophobically modified pullulan were very efficient at preventing long-term aggregation of these SR membranes. This presumably occurred because the negatively charged polymer coated the membranous vesicles with a hydrophilic corona (a property shared by many other amphipathic polymers), and thus minimized their flocculation. Reminiscent of the old Arabic gum, which stabilizes Indian ink by coating charcoal particles, the newly designed amphipathic polymers might therefore unintentionally prove useful also for stabilization of membrane suspensions.
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Affiliation(s)
- Martin Picard
- Unité de Recherche Associée 2096, CEA/INRA, & Section de Biophysique des Fonctions Membranaires, Département de Biologie Joliot-Curie, CEA Saclay, 91191 Gif-Sur-Yvette cedex, France.
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Mouri E, Furuya Y, Matsumoto K, Matsuoka H. Hydrophilic chain length dependence of the ionic amphiphilic polymer monolayer structure at the air/water interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:8062-8067. [PMID: 15350073 DOI: 10.1021/la049256z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Detailed analysis of an interesting poly(methacrylic acid) (PMAA) brush structure in water of a diblock copolymer [(Et(2)SB(m)-b-(MMA)(n), where Et(2)SB is diethylsilacyclobutane] monolayer reported previously was performed by X-ray and neutron reflectometry and indicated that the hydrophilic layer formed with a relatively long PMAA chain is not a simple layer but is divided into two layers, that is, a "carpet"-like dense PMAA layer near the hydrophobic layer and a polyelectrolyte brush layer. The hydrophilic chain length dependence of the diblock copolymer monolayer was analyzed using m:n = 30:x polymer samples, especially of the PMAA double layer structure. With the increase in PMAA chain length in polymer samples, a carpet layer is mainly formed up to n approximately 50. With further increase in the PMAA chain length beyond n approximately 50, a well-defined brush layer appears. On the other hand, the variation in hydrophobic layer thickness with methacrylic acid unit is minimum at the critical PMAA length, that is, n approximately 50 under a constant surface pressure condition. It is strongly suggested that the two discrete layers contribute differently to surface pressure. Furthermore, from the comprehensive viewpoint, the major factor for brush formation was clarified not to be the absolute length of the PMAA chain, but the ratio of PEt(2)SB and PMAA chain length is an important factor.
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Affiliation(s)
- Emiko Mouri
- Department of Polymer Chemistry, Kyoto University, Kyoto 615-8510, Japan
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Jönsson M, Johansson HO. Effect of surface grafted polymers on the adsorption of different model proteins. Colloids Surf B Biointerfaces 2004; 37:71-81. [PMID: 15342016 DOI: 10.1016/j.colsurfb.2004.06.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Accepted: 06/29/2004] [Indexed: 11/20/2022]
Abstract
Adsorption of a model protein to a surface with end-grafted polymers was studied by Monte Carlo simulations. In the model the effect on protein adsorption in the presence of end-grafted polymers was evaluated by calculating the change in free energy between an end-grafted surface and a surface without polymers. The change in free energy was calculated using statistical mechanical perturbation theory. Apart from ordinary athermal polymer-polymer and protein-polymer interactions we also study a broad selection of systems by varying the interaction between proteins and polymers and effective polymer-solvent interactions. The interactions between the molecules span an interval from -0.5 to +0.5 kT. Consequently, general features of protein adsorption to end-grafted surfaces is investigated by systematically changing properties like hydrophilicity/hydrophobicity of the polymer, protein and surface as well as grafting density, degree of polymerization and protein size. Increasing grafting density as well as degree of polymerization decreases the adsorption of protein except in systems with attractive polymer-protein interactions, where adsorption increases with increasing chain length and higher grafting density. At a critical polymer-protein interaction neither chain length nor grafting density affects the free energy of adsorption. Hydrophilic polymers were found to prevent adsorption better than hydrophobic polymers. Very small particles with radii comparable to the size of a polymer segment were, however, better excluded from the surface when using hydrophobic than hydrophilic polymers. For systems with attractive polymer-protein interaction not only the volume of the protein was shown to be of importance but also the size of the exposed surface.
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Affiliation(s)
- Malin Jönsson
- Department of Biochemistry, Lund University, Sweden.
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