Fibrinolytic Poly(dimethyl siloxane) Surfaces (original) (raw)
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Blood compatibility of surfaces with superlow protein adsorption
Biomaterials, 2008
In this work, five self-assembled monolayers (SAMs) and three polymeric brushes with very low fibrinogen adsorption were prepared. The five SAMs are oligo(ethylene glycol) (OEG), phosphorylcholine (PC), oligo(phosphorylcholine) (OPC), and two mixed positively and negatively charged SAMs of SO 3 À / N þ (CH 3 ) 3 (SA/TMA) and COO À /N þ (CH 3 ) 3 (CA/TMA). Three polymer brushes were prepared on gold surfaces via surface-initiated atom transfer radical polymerization (ATRP) using three monomers, sulfobetaine methacrylate (SBMA), carboxybetaine methacrylate (CBMA), and oligo(ethylene glycol) methyl ether methacrylate (OEGMA). Surface plasmon resonance (SPR) measurements show that although all of these surfaces are ''nonfouling'' to fibrinogen adsorption from buffer solution, their protein adsorption from undiluted human blood plasma varies widely. Polymer brushes exhibit much lower protein adsorption from plasma than any of the five SAMs tested. However, platelet adhesion measurements on plasma-preadsorbed surfaces show that all of these surfaces have very low platelet adhesion. Clotting time measurements using recalcified platelet poor plasma (PPP) incubation with the eight types of surfaces show that they do not shorten clotting times. Linear polymers of polySBMA and polyCBMA with similar molecular weights were also synthesized and characterized. In the presence of polyCBMA linear polymers, the clotting time of PPP was prolonged and increased with the concentration of the polymer, while no anticoagulant activity was observed for the polySBMA or PEG polymers. The unique anticoagulant activity of polyCBMA, as well as its high plasma protein adsorption resistance, makes polyCBMA a candidate for blood-contacting applications.
Langmuir, 2001
Poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) is a member of a family of polycationic PEG-grafted copolymers that have been shown to chemisorb on anionic surfaces, including various metal oxide surfaces, providing a high degree of resistance to protein adsorption. PLL-g-PEG-modified surfaces are attractive for a variety of applications including sensor chips for bioaffinity assays and blood-contacting biomedical devices. The analytical and structural properties of PLL-g-PEG adlayers on niobium oxide (Nb2O5), tantalum oxide (Ta2O5), and titanium oxide (TiO2) surfaces were investigated using reflection-absorption infrared spectroscopy (RAIRS), angle-dependent X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The combined analytical information provides clear evidence for an architecture with the cationic poly(L-lysine) attached electrostatically to the oxide surfaces (charged negatively at physiological pH) and the poly(ethylene oxide) side chains extending out from the surface. The relative intensities of the vibrational modes in the RAIRS spectra and the angle-dependent XPS data point to the PLL backbone being located directly at and parallel to the oxide/polymer interface, whereas the PEG chains are preferentially oriented in the direction perpendicular to the surface. Both positive and negative ToF-SIMS spectra are dominated by PEG-related secondary ion fragments with strongly reduced metal (oxide) intensities pointing to an (almost) complete coverage by the densely packed PEG comblike grafts. The three different transition metal oxide surfaces with isoelectric points well below 7 were found to behave very similarly, both in respect to the kinetics of the polymer adlayer adsorption and properties as well as in terms of protein resistance of the PLL-g-PEG-modified surface. Adsorption of serum and fibrinogen was evaluated using the OWLS optical planar waveguide technique. The amount of human serum adsorbed on the modified surfaces was consistently below the detection limit of the optical sensor technique used (<1-2 ng cm -2 ), and fibrinogen adsorption was reduced by 96-98% in comparison to the nonmodified (bare) oxide surfaces. Fine, E.; Voros, J.; Makohliso, S. A.; Leonard, D.; Johnston, D. S.; Textor, M.; Mathieu, H. J. J. Biomater. Sci., Polym. Ed. 1999, 10, 931-955. (6) Mori, Y.; Nagaoka, S.; Takinchi, H.; Kikuchi, T.; Noguchi, N.; Tanzawa, H.; Noishiki, Y. Trans. Am.
Fibrinogen adsorption and host tissue responses to plasma functionalized surfaces
Journal of Biomedical Materials Research, 1998
The physical and chemical characteristics of material surfaces are thought to play important roles in biomaterial-mediated tissue responses. To understand the importance of discrete biomaterial chemical characteristics in modifying host tissue responses, we constructed surfaces bearing different functional groups using radio frequency glow discharge plasma polymerization. Surfaces evaluated included those having high concentrations of −OH, −NH 2 , −CF 3 , and siloxyl groups. These surfaces and polyethylene terephthalate controls were used to assess the importance of particular physicochemical characteristics in surface:protein:cell interactions both in vitro and in vivo. The results obtained show that surface functionalities do significantly affect both the adsorption and ''denaturation'' of adsorbed fibrinogen (which is an important mediator of inflammatory responses to biomaterial implants). In addition, these sur-faces provoke different degrees of acute inflammatory responses. Interestingly, the amounts of ''denatured'' fibrinogen that spontaneously accumulate on the individual surfaces correlate closely with the extent of biomaterialmediated inflammation. These results suggest that surfaces that tend to ''irreversibly'' bind fibrinogen prompt greater acute inflammatory responses. Unexpectedly, all test surfaces except those bearing a siloxyl group engender relatively similar biomaterial-mediated fibrotic responses. Thus surface functionalities alone may not be sufficient to affect subsequent fibrotic responses.
Langmuir, 2006
Interaction forces between surfaces designed to be protein resistant and fibrinogen (Fg) were investigated in phosphatebuffered saline with colloid probe atomic force microscopy. The surfaces of the silica probes were coated with a layer of fibrinogen molecules by adsorption from the buffer. The technique of low-power, pulsed AC plasma polymerization was used to make poly(ethylene glycol) (PEG)-like coatings on poly(ethylene teraphthalate) by using diethylene glycol vinyl ether as the monomer gas. The degree of PEG-like nature of the films was controlled by use of a different effective plasma power in the chamber for each coating, ranging from 0.6 to 3.6 W. This produced a series of thin films with a different number of ether carbons, as assessed by X-ray photoelectron spectroscopy. The interaction force measurements are discussed in relation to trends observed in the reduction of fibrinogen adsorption, as determined quantitatively by 125 I radio-labeling. The plasma polymer coatings with the greatest protein-repelling properties were the most PEG-like in nature and showed the strongest repulsion in interaction force measurements with the fibrinogen-coated probe. Once forced into contact, all the surfaces showed increased adhesion with the protein layer on the probe, and the strength and extension length of adhesion was dependent on both the applied load and the plasma polymer surface chemistry. When the medium was changed from buffer to water, the adhesion after contact was eliminated and only appeared at much higher loads. This indicates that the structure of the fibrinogen molecules on the probe is changed from an extended conformation in buffer to a flat conformation in water, with the former state allowing for stronger interaction with the polymer chains on the surface. These experiments underline the utility of aqueous surface force measurements toward understanding protein-surface interactions, and developing nonfouling surfaces that confer a steric barrier against protein adsorption.
Langmuir : the ACS journal of surfaces and colloids, 2007
The hemocompatibility of polymeric vascular implants is in part dependent on the propensity of fibrinogen to adsorb to the implant surface. Fibrinogen surface adsorption was measured in real time using a quartz crystal microbalance with dissipation monitoring (QCM-D). Six new, biodegradable tyrosine-derived polycarbonates were used as test surfaces. Stainless steel, poly(L-lactic acid), poly(D,L-lactide-co-glycolide), and poly(ethylene terephthalate) surfaces served as controls and provided a comparison of the test surfaces with those of commonly used biomaterials. Our study addressed the question regarding to which extent systematic variations in polymer structure can be used to optimize X-ray visibility and provide tunable degradation rates while generating protein-repellant surface properties that minimize fibrinogen adsorption. QCM-D revealed surface-dependent changes in fibrinogen layer thickness (2 to 37 nm), adsorbed wet mass (0.2 to 4.3 microg/cm2), and viscosity (0.001 to 0...
Biomaterials, 2005
The aim of this study was to investigate whole blood coagulation on low blood plasma protein adsorbing surfaces. For this purpose, the polycationic graft copolymer poly(l-lysine)-g-poly(ethylene glycol) (PLL-g-PEG), PLL-g-PEG grafted with a cell adhesive peptide containing the amino acid sequence -Arg-Gly-Asp-(RGD), and PLL-g-PEG with a control peptide -Arg-Asp-Gly-(RDG) were adsorbed onto titanium (oxide), forming stable monomolecular adlayers through electrostatic attraction. Free oscillation rheometry and complementary techniques were used to measure the coagulation time (CT) and other interactions of the surfaces with native whole blood, recalcified platelet-rich plasma (PRP), and recalcified citrated platelet-free plasma (PFP). The results show that the uncoated titanium surfaces (reference) activated platelets and quickly triggered the coagulation cascade via the intrinsic pathway, whereas the PLL-g-PEG surfaces displayed a prolonged CT, approximately 2-3 times longer compared to uncoated titanium. We hypothesise that blood coagulates outside the vascular system independent of low protein adsorption to or activation by surfaces, due to the absence of an active down-regulation of procoagulative processes by the vascular endothelium. r
Surface structural conformations of fibrinogen polypeptides for improved biocompatibility
Biomaterials, 2010
This work reports on how incorporation of silica nanocages into poly(urethane) copolymers (PU) affects conformational orientations of adsorbed fibrinogen and how different surfaces subsequently influenced HeLa cell attachment and proliferation. Incorporation of 2 wt% silica nanocages into poly(urethane) (PU4) substantially altered the surface topography of the films and some 50% of the surface was covered with the nanocages due to their preferential exposure. AFM studies revealed the deposition of a dense protein network on the soft polymeric domains of PU4 and much reduced fibrinogen adsorption on the hard nanocage domains. As on the bare SiO 2 control surface, fibrinogen molecules adsorbed on top of the hard nanocages mainly took the dominant trinodular structures in monomeric and dimeric forms. In addition, net positively charged long a chains were prone to being hidden beneath the D domains whilst g chains predominantly remained exposed. Dynamic interfacial adsorption as probed by spectroscopic ellipsometry revealed fast changes in interfacial conformation induced by electrostatic interactions between different segments of fibrinogen and the surface, consistent with the AFM imaging. On the PU surfaces without nanocage incorporation (PUA), however, adsorbed fibrinogen molecules formed beads-like chain networks, consistent with the structure featured on the soft PU4 domains, showing very different effects of surface chemical nature. Monoclonal antibodies specific to the a and g chains showed reduced a but increased g chain binding at the silicon oxide control and PU4 surfaces, whilst on the PUA, C18 and amine surfaces (organic surface controls) the opposite binding trend was detected with a chain binding dominant, showing different fibrinogen conformations. Cell attachment studies revealed differences in cell attachment and proliferation, consistent with the different polypeptide conformations on the two types of surfaces, showing a strong preference to the extent of exposure of g chains.