Synthetic Polymer Surfaces Research Articles

Immobilizing natural macromolecule on PLGA electrospun nanofiber with surface entrapment and entrapment-graft techniques

Surface entrapment is a convenient method to immobilize the natural macromolecules on the surface of synthetic polymers. In this study, the gelatin modified and sodium alginate/gelatin modified PLGA nanofibrous membranes were fabricated via surface entrapment and entrapment-graft techniques. The surface morphology of the each single modified PLGA nanofiber was as smooth as that of untreated PLGA nanofibers. The results of water angle contact measurements and tensile tests showed that the surface entrapment cannot only improve the hydrophilicity but also enhance mechanical properties of the modified nanofibrous membranes. In addition, the sodium alginate/gelatin modified electrospun PLGA nanofibrous membrane exhibited higher hydrophilicity and better biocompatibility than the simply gelatin modified PLGA nanofibrous membrane, which suggested the surface entrapment is a facile and efficient approach to surface modification for electrospun nanofibours membranes.

Chemical approaches to synthetic polymer surface biofunctionalization for targeted cell adhesion using small binding motifs

In the present review the principal strategies to chemically modify the surface of synthetic polymeric materials with small molecules for targeted cell adhesion are collated and critically discussed. The focus is purposely oriented on the chemistry involved in these modifications and neither the physical characterizations nor the activity evaluations resulting from these modifications are addressed in depth, although most reviewed examples demonstrate cell adhesion. Particularly, the introduction of a chemical anchor onto the polymeric substrate, the spacing via a linker between the polymer surface and the cell-binding motif, as well as the linkage generated on this cell-binding motif are discussed. Particular cases where variable substrate geometries or spatial patterning are achieved are additionally highlighted. © 2012 The Royal Society of Chemistry.

Effect of Glow-Discharge Air Plasma Treatment on Wettability of Synthetic Polymers

Main aim of this study was focused on characterization of the effect of microwave air plasma treatment on wettability of synthetic polymer surfaces. Wettability of solid polymer surfaces polyethylene, polypropylene, polystyrene (PE, PP, PS) was followed as a function of plasma treatment time. For evaluation the equilibrium contact angles of wetting as well as dynamic contact angles of wetting were determined by means of sessile drop and Wilhelmy plate methods. Free surface energy (SFE) of studied samples were calculated from the experimentally determined contact angles using Fowkes and van Oss, Chaudhury and Good (vOCG) approaches. It was found that with prolonged treatment time the total surface free energy of PE was two times increased from 23 mJ/m2 to 45 mJ/m2 after 360 s plasma treatment time (calculated for W and EG as wetting liquids). Similar effect was found for all studied polymers. With respect to the dispersive and polar components of the total surface free energy the vigorous effect was found for polar component, for which it was increased from 7 mJ/m2 to 20 mJ/m2.

One-Step Photochemical Synthesis of Permanent, Nonleaching, Ultrathin Antimicrobial Coatings for Textiles and Plastics

Antimicrobial copolymers of hydrophobic N-alkyl and benzophenone containing polyethylenimines were synthesized from commercially available linear poly(2-ethyl-2-oxazoline), and covalently attached to surfaces of synthetic polymers, cotton, and modified silicon oxide using mild photo-cross-linking. Specifically, these polymers were applied to polypropylene, poly(vinyl chloride), polyethylene, cotton, and alkyl-coated oxide surfaces using solution casting or spray coating and then covalently cross-linked rendering permanent, nonleaching antimicrobial surfaces. The photochemical grafting of pendant benzophenones allows immobilization to any surface that contains a C-H bond. Incubating the modified materials with either Staphylococcus aureus or Escherichia coli demonstrated that the modified surfaces had substantial antimicrobial capacity against both Gram-positive and Gram-negative bacteria (>98% microbial death).

Long-term human pluripotent stem cell self-renewal on synthetic polymer surfaces

Realization of the full potential of human pluripotent stem cells (hPSCs) in regenerative medicine requires the development of well-defined culture conditions for their long-term growth and directed differentiation. Current practices for maintaining hPSCs generally utilize empirically determined combinations of feeder cells and other animal-based products, which are expensive, difficult to isolate, subject to batch-to-batch variations, and unsuitable for cell-based therapies. Using a high-throughput screening approach, we identified several polymers that can support self-renewal of hPSCs. While most of these polymers provide support for only a short period of time, we identified a synthetic polymer poly(methyl vinyl ether-alt-maleic anhydride) (PMVE-alt-MA) that supported the long-term attachment, proliferation and self-renewal of HUES1, HUES9, and iPSCs. The hPSCs cultured on PMVE-alt-MA maintained their characteristic morphology, expressed high levels of markers of pluripotency, and retained a normal karyotype. Such cost-effective, polymer-based matrices that support long-term self-renewal and proliferation of hPSCs will not only help to accelerate the translational perspectives of hPSCs, but also provide a platform to elucidate the underlying molecular mechanisms that regulate stem cell proliferation and differentiation.

Catechol-Grafted Poly(ethylene glycol) for PEGylation on Versatile Substrates

We report on catechol-grafted poly(ethylene) glycol (PEG-g-catechol) for the preparation of nonfouling surfaces on versatile substrates including adhesion-resistant PTFE. PEG-g-catechol was prepared by the step-growth polymerization of PEO to which dopamine, a mussel-derived adhesive molecule, was conjugated. The immersion of substrates into an aqueous solution of PEG-g-catechol resulted in robust PEGylation on versatile surfaces of noble metals, oxides, and synthetic polymers. Surface PEGylation was unambiguously confirmed by various surface analytical tools such as ellipsometry, goniometry, infrared spectroscopy, and X-ray photoelectron spectroscopy. Contrary to existing PEG derivatives that are difficult-to-modify synthetic polymer surfaces, PEG-g-catechol can be considered to be a new class of PEGs for the facile surface PEGylation of various types of surfaces.

Norepinephrine: material-independent, multifunctional surface modification reagent.

A facile approach for material-independent surface modification using norepinephrine was investigated. pH-induced oxidative polymerization of norepinephrine forms adherent films on vastly different types of material surfaces of noble metals, metal oxides, semiconductors, ceramics, shape-memory alloys, and synthetic polymers. Secondary biochemical functionalizations such as immobilization of proteins and growth of biodegradable polyester on the poly(norepinephrine) films were demonstrated.

Formation of superhydrophobic poly(dimethysiloxane) by ultrafast laser-induced surface modification

The formation of hemispherical nanostructures and microscaled papilla by ultrafast laser irradiation was found to be a potential method to generate superhydrophbic surface of synthetic polymers. Irradiation of femtosecond laser creates roughened poly(dimethylsiloxane) (PDMS) surface in nano- and microscales, of which topography fairly well imitate a Lotus leaf in nature. The modified surface showed superhydrophobicity with a contact angle higher than 170 degrees as well as sliding angle less than 3 degrees. We further demonstrated that negative replica of the processed PDMS surface exhibit large contact angle hysteresis with a sliding angle of 90 degrees while the positive replica maintains superhydrophobicity.

Functional group analysis on oxidized surfaces of synthetic textile polymers

A comprehensive collection of wet-chemical analyses of functional groups on oxidatively treated surfaces of hydrophobic polymers like poly(ethylene terephthalate) or polyolefine is presented. New methods are introduced. Textiles and foils have been subjected to advanced oxidation processes and the different oxygen functions have been quantified. Analysis of surface functional groups includes radical site determination with radical scavengers like diphenylpicrylhydrazyl, reduction of peroxides determined iodometrically, cationic dyestuff adsorption, carbonyl binding to Girard reagent P and surface hydroxyl group determination by surface nitrosation and subsequent azo-dye formation photometrically determinable. Use of potential surface swelling agents has been excluded except for addition of wetting agent. Wet-chemical analyses on textile surfaces bear the benefit of integrating over (relatively) large sample areas, a point which is interesting when regarding inhomogenities of textile or other surface constructions. In addition examples for visualisation for the existence of surface groups are described.

BIOMINERALIZED SCAFFOLDS INHIBIT OSTEOGENESIS IN THE PRESENCE OF SOLUBLE OSTEOGENIC SIGNALS.

Strategies to engineer bone have focused on the use of natural or synthetic biodegradable materials to support cell transplantation or as substrates to guide bone regeneration. The deposition of a biomineral on the surface of synthetic polymers has resulted in the formation of hybrid biomaterials with desired biodegradability and enhanced osteoconductivity. It is widely accepted that osteoconductive materials provide a superior environment to promote osteogenesis in vivo. However, the impact of the osteoconductive substrate coupled with soluble signals on progenitor cell differentiation within the three-dimensional substrates is not well known. In this study, we investigated the influence of carbonate apatite on the osteogenic differentiation of human mesenchymal stem cells (hMSCs) seeded in biodegradable poly(lactide-co-glycolide) scaffolds. Two schemes for depositing carbonate apatite were examined: a postmineralized process involved surface hydrolysis of the scaffold followed by incubation in a modified simulated body fluid (mSBF) and a premineralized process entailed microparticle hydrolysis, subsequent incubation in mSBF and then scaffold formation. Under scanning electron microscopy, we observed phenotypic differences in structure between each scaffold. We cultured hMSCs on the scaffolds for 28 days in osteogenic media supplemented with 100 ng/mL BMP-2. Compared with nonmineralized scaffolds, hMSCs cultured on biomineralized substrates exhibited increased cellular proliferation, along with reduced levels of osteogenic differentiation markers as determined by intracellular alkaline phosphatase, osteocalcin, and osteopontin secretion. No significant differences in osteogenic differentiation were observed between the two biomineralized substrates. However, we detected significantly higher levels of scaffold-associated calcium in premineralized scaffolds versus postmineralized and nonmineralized substrates. These results suggest that in the presence of soluble signals, mineralization may prove counterproductive to promoting the osteogenic differentiation of hMSCs. In light of these observations, multiple signaling strategies may be necessary to achieve optimal bone regeneration.

Generic Bioaffinity Silicone Surfaces

Synthetic polymer surfaces require surface modification to improve biocompatibility. A generic route to biocompatible silicone elastomers is described involving high yield surface functionalization of standard silicones with hydrosilanes, hydrosilylation using asymmetric, allyl-, NSC-terminated PEO of narrow molecular weight, and covalent modification in one step with amine-containing biological molecules including oligopeptides (YIGSR, RGDS), proteins (EGF, albumin, fibrinogen, mucin), and glycosaminoglycans (heparin). Efficient, high-density binding (e.g., 0.2 EGF molecules/nm2) was demonstrated using radiolabeling studies. The resulting surfaces were demonstrated to be biocompatible by further reaction with biomolecules, for example, thrombosis suppression on surfaces modified by heparin + ATIII, and the formation of confluent corneal epithelial cell layers on EGF, RGDS, or YIGSR surfaces.

Rapid colorimetric detection of antibody-epitope recognition at a biomimetic membrane interface.

Biomolecular recognition of antigens and epitopes by antibodies is a fundamental event in the initiation of immune response and plays a central role in a variety of biochemical processes. Peptide binding requires, in many cases, presentation of the peptides at interfaces, such as protein surfaces, cellular membranes, and synthetic polymer surfaces. We describe a novel molecular system in which interactions between antibodies and peptide epitopes displayed at a biomimetic membrane interface can be detected through induction of visible, rapid color transitions. The colorimetric assembly consists of a phospholipid/polydiacetylene matrix anchoring a hydrophobic peptide displaying the epitope at its N-terminus. The colorimetric transitions observed in the assembly, corresponding to perturbation of the polydiacetylene framework, are induced only upon recognition of the displayed epitope by its specific antibody present in the aqueous solution. Significantly, the color changes occur after a single mixing step, without further chemical reactions or enzymatic processing. The new molecular system could be utilized for studying antigen-antibody interactions and peptide-protein recognition, epitope mapping, and rapid screening of biological and chemical libraries.

Retinal pigment epithelial cell adhesion on novel micropatterned surfaces fabricated from synthetic biodegradable polymers

Novel synthetic biodegradable polymer substrates with specific chemical micropatterns were fabricated from poly( dl-lactic- co-glycolic acid) (PLGA) and diblock copolymers of poly(ethylene glycol) and poly( dl-lactic acid) (PEG/PLA). Thin films of PLGA and PEG/PLA supported and inhibited, respectively, retinal pigment epithelial (RPE) cell proliferation, with a corresponding cell density of 352 900 and 850 cells/cm 2 after 7 days (from an initial seeding density of 15 000 cells/cm 2). A microcontact printing technique was used to define arrays of circular (diameter of 50 μm) PLGA domains surrounded and separated by regions (width of 50 μm) of PEG/PLA. Reversed patterns composed of PEG/PLA circular domains surrounded by PLGA regions were also fabricated. Both micropatterned surfaces were shown to affect initial RPE cell attachment, limit cell spreading, and promote the characteristic cuboidal cell morphology during the 8-h period of the experiments. In contrast, RPE cells on plain PLGA (control films) were elongated and appeared fibroblast-like. The reversed patterns had continuous PLGA regions that allowed cell–cell interactions and thus higher cell adhesion. These results demonstrate the feasibility of fabricating micropatterned synthetic biodegradable polymer surfaces to control RPE cell morphology.

Interaction between charged soft microcapsules and red blood cells: effects of PEGylation of microcapsule membranes upon their surface properties

Four types of hydrophilic gel microcapsules containing water have been prepared by an interfacial polymerization method. Each type of microcapsules has a membrane of different composition. Using three kinds of monomers, N,N-dimethylacrylamide (DMAAm), 4-(aminomethyl)styrene (AmSt), and N,N-dimethylaminopropylacrylamide (DMAPAA), one type of aqueous copolymer having primary and tertiary amino groups was obtained. By the polymerization of three kinds of monomers, DMAAm, AmSt, and 2-[(methacryloyloxy)ethyl] trimethylammoniumchloride (METAC), another type of aqueous copolymer having primary and quaternary ammonium groups was also obtained. Two more types of copolymers were synthesized by copolymerization of α-acryloxy-ω-methoxy-poly(ethylene glycol) (a-PEG) with the above two kinds of monomer mixture. These copolymers were polymerized with terephthaloyldichloride at the water/oil interface to prepare four types of microcapsules containing water, i.e., poly(DMAAm- co-DMAPAA- co-AmSt- alt-terephthalic acid) microcapsules, poly(DMAAm- co-DMAPAA- co-AmSt- co-PEG- alt-terephthalic acid) microcapsules, poly (DMAAm- co-METAC- co-AmSt- alt-terephthalic acid) microcapsules, and poly (DMAAm- co-METAC- co-AmSt- co-PEG- alt-terephthalic acid) microcapsules, which will be abbreviated to MC 1, MC 2, MC 3, and MC 4, respectively. It has been predicted that the microcapsule membranes are hydrophilic and soft and have two-sublayer structures from electrophoretic mobility measurements and from the analysis of the data with Ohshima’s electrokinetic theory for soft particles. The outer sublayers of MC 1 and MC 2 are negatively charged and those of MC 3 and 4 are slightly positively charged. Also, the surfaces of MC 1 and MC 2 are harder than those of MC 3 and 4. By PEGylation, the surface charge density in the membranes decreases and the surface becomes softer. It has been found that the membrane of red blood cells (RBC) is also soft and is composed of two-sublayers, the outer sublayer of which is negatively charged and the inner one is positively charged. The interaction of four types of microcapsules with RBC has been studied. It was found that microcapsules with soft surfaces (MC 3 and MC 4) do not interact with RBC, even though the microcapsule surfaces are positively charged and the surface of RBC is negatively charged. On the other hand, microcapsules with negatively charged but harder surfaces (MC 1) interact with RBC to introduce hemolysis. The membrane surface of MC 2, which is obtained by PEGylation of MC 1, becomes softer than that of MC 1 so that the interaction with RBC was weakly suppressed. From these, it was concluded that the dominant factor to control the interaction between synthetic polymer surfaces and biological cell surfaces is not the surface charges carried by the polymer surfaces but the softness of the polymer surfaces.

XPS and SIMS studies of surfaces important in biofilm formation. Three case studies.

Although the importance of cell adhesion to synthetic surfaces is well established, a detailed description of the molecular interactions important in adhesion still eludes researchers. In order to fully understand the adhesion events that lead to biofilm formation on synthetic materials it is necessary to have an accurate understanding of the synthetic material surface, to understand the composition and orientation of biopolymers that adsorb to the material, and to understand the surface chemistry of cells that ultimately adhere. The simplest of these three surfaces, the synthetic material, commonly presents a profound level of complexity and presents a wide variety of chemical functional groups in many orientations at the surface. The conditioning film surface and cell surface show yet greater levels of complexity. The three case studies presented here demonstrate that XPS and SIMS are valuable techniques for studying all three of these surfaces. They are not only capable of providing an accurate analysis of the synthetic polymer surface but they are also sensitive to the composition and orientation of biomolecules. The potential for rapid characterization of cell surfaces with SIMS demonstrated in the final case study suggests that intelligent application of these techniques may ultimately aid in answering the elusive question of how cells adhere to synthetic surfaces.

The adsorption of proteins on a polydimethylsiloxane elastomer (PEP) and their antigenic behavior.

One focus of our research during the last two decades has been the immunochemistry of solid-phase immunoassay (Butler, 1991a). Contemporary solid-phase immunoassay involves the interaction of bio-molecules with, on or near, the surface of synthetic polymers composed of polystyrene, polyvinyl, nylon, methylmethacrylate, nitrocellulose, PVDF and their numerous “functionalized” variants. The native form of these polymers is intrinsically hydrophobic and readily adsorbs proteins, viruses, many peptides and nucleic acids. The practical application of biomolecular adsorption to immunoassay dates to Catt and Tregear (1967) who pioneered passive immobilization of receptors2 as a mean of simplifying the separation of bound and free ligand; this application revolutionized immunoassay. However, modern users of the technology were slow to recognize that proteins adsorbed to hydrophobic polymers do not remain in a totally native configuration although this had been shown >30 years ago (Bull, 1956; Kochwa et al., 1967; Oreskes and Singer, 1961). More recently, we have shown that only circa 20% of polyclonal and >10% of monoclonal antibodies passively adsorbed to polystyrene, remain functional (Butler et al., 1993). The subject of adsorption-induced conformational change on polymer surfaces has been reviewed elsewhere (Butler, 1991b; 1992; Butler, 1995).

合成高分子表面へのタンパク質の吸着

In this article I have reviewed (blood) proteins adsorption onto synthetic polymer surfaces, i. e., onto polymeric microspheres. First, the surface characteristics of polymeric microspheres (polymer latices) were examined. As a result, hydrogel polymer layers, e. g., poly (acrylamide) (poly-AAm) and poly (2-hydroxyethyl methacrylate) (poly-HEMA) layers were found to exist on the microsphere surfaces of styrene (St) /AAm and St/HEMA copolymers (P (St/AAm) and P (St/HEMA)), respectively. Subsequently, singular and competitive protein adsorption onto polymeric microspheres was investigated as a function of pH and ionic strength, surface characteristics of microspheres, coexistent electrolyte ions. Each protein showed the maximum adsorption near its isoelectric point. The amounts adsorbed onto hydrophilic P (St/AAm) and P (St/HEMA) microspheres were much smaller than that onto hydrophobic polystyrene (PS) microsphere, particularly in the neutral and alkaline pH regions. Fibrinogen adsorbed preferentially from the protein mixture of albumin, γ-globulin, and fibrinogen. Further, the adsorbability of heat-denatured albumin was studied. Compared with the native component of the protein, the denatured components adsorbed preferentially onto microspheres.

Fibroblast and hepatocyte behavior on synthetic polymer surfaces

Biodegradable poly(phosphoesters) with varying side group chemistry and copolymers of styrene and methyl vinyl ketone (MVK) with varying degrees of hydrophobicity were used to study the growth and behavior of surface-attached fibroblasts and hepatocytes. Mouse 3T3 fibroblasts and chicken embryo fibroblasts attached and proliferated on all of the polymers tested. Fewer cells attached to copolymers of styrene and MVK than to glass or tissue culture polystyrene controls; cell attachment to several poly(phosphoester) surfaces was indistinguishable from controls. The mean speed of fibroblast migration was faster on surfaces where fewer cells attached (59 to 84 microns/h on low attachment surfaces compared with 40 to 46 microns/h on high attachment surfaces). When surface-attached cells were stained with fluorescently labeled phalloidin, only a fraction of the cells on low attachment surfaces were shown to have prominent arrays of actin filament bundles. Chicken hepatocytes also attached to the polymer surfaces. When a suspension containing a large number of cells was placed over the polymer surfaces, approximately 50% of the hepatocytes attached during the first 9 h. Surprisingly, hepatocyte attachment and viability in culture were relatively insensitive to the chemistry of the synthetic polymer substrates. Cell number increased by about a factor of 2 over the first 48 h of culture, then decreased back to approximately 50% of initial cell number over the next several days. Cell morphology did depend on the chemical structure of the substrates.

Decay of electrical charges on organic synthetic polymer surfaces

Surface-charge decay of low-density polyethylene films is studied after corona charging of the polymer. Cross-over and other phenomena related to charge injection processes are not observed. The decay behavior may originate from an induced dielectric polarization in which the carriers are self-trapped or localized by the polarizing influence of their own charge. The equilibrium value of surface charge density can be established at long times by the classical laws of diffusion and field-independent drift processes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modification of polyetherurethane for endothelial cell seeding

AbstractUntil now no synthetic polymer surface was available suitable for cardiovascular implantation which effectively prevents microthrombosis for a long time. The presented concept of our work is to develop a polymer surface to promote the growth of a durable endothelial cell monolayer which would be formed on the prothesis prior to implantation. A microporous polyetherurethane foil is being used as carrier polymer for the cell monolayer. Suitable functional groups are grafted on the polymer surface by plasma polymerization. The success of the first modification steps is followed by ESCA‐analysis and scanning electron microscopy. The modified carrier polymer is the starting material for covalent binding of biopolymers which react as adhesion supporter between the synthetic polymer surface and the endothelial cells.