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PubMed2006

[Plasma-deposited carbon coating on urological indwelling catheters: Preventing formation of encrustations and consecutive complications].

BACKGROUND: Any material placed in the urinary tract is susceptible to the formation of encrustations of crystalline bacterial biofilms. These biofilms cause severe complications in some cases. The strategies used so far for reduction of these complications by surface modifications of the implant material failed to show the expected results. PATIENTS AND METHODS: In this study, we investigated amorphous carbon coatings (a-C:H) for their ability to effectively reduce or to repress the progressive formation of infection-enhancing crystalline biofilms as new functional surface coatings. In nine patients suffering for several years from stenting, a-C:H-coated ureteral stents were tested in treatment attempts. The current replacement intervals amounted to a mean of 77 days; the principle cause for early replacement was massive stent encrustations associated with symptomatic urinary tract infections. RESULTS: In total, 20 coated ureteral stents were tested spanning indwelling times between 3 and 4 months. No stent-related complications occurred. In all cases extraordinarily facile handling, less pain during replacement, and markedly increased tolerance were observed. Symptomatic urinary tract infections were reduced by more than 50%. The stents remained virtually free of encrustations. CONCLUSION: a-C:H coatings are a novel strategy leading to an enhancement of long-term applicability of ureteral stents and catheters and to improved patient comfort.

Adult↗

PubMed2006

The method of surface PEGylation influences leukocyte adhesion and activation.

The influence of different surface modifications with poly(ethyleneglycol) (PEG) layers on the adsorption of fibrinogen and the adhesion and activation of macrophage-like human leukocytes was investigated. Poly(ethylene terephthalate) (PET) was modified using pulsed AC plasma polymerization with two types of starting monomers to generate: 1) a reactive acid surface using maleic anhydride (MAH) as monomer, and 2) a PEG-like surface using diethyleneglycol methyl vinyl ether (DEGVE) as monomer. The MAH surface was used as a reactive platform to graft linear chains of non-fouling mPEG via an intermediate layer of poly(ethyleneimine) (PEI) under lower critical solution temperature (LCST) conditions of the mPEG. The DEGVE monomer is used to create PEG-like layers by use of low power plasma conditions. The ability of the surfaces to resist protein adsorption was investigated quantitatively using (125)I-radiolabeled human fibrinogen, and the conformation of the adsorbed protein was tested using an anti-fibrinogen monoclonal antibody in an enzyme-linked immunosorbent assay. The results showed that PEGylated surfaces adsorbed significantly less (up to 90% less) fibrinogen, and that unfolding of adsorbed fibrinogen was more pronounced on the linear mPEG layers than on the PEG-like plasma polymer surfaces. Adhesion of in-vitro differentiated macrophage-like U937 cells was reduced on both the PEG-like plasma polymer surfaces and the linear mPEG layers compared to the unmodified PET surface, but cells adhering to the PEG-like plasma polymer surfaces secreted less tumor necrosis factor-alpha (TNF-alpha) than cells adhering to the linear mPEG layers. In conclusion, the method for preparing non-fouling surfaces for long-term implanted devices influence surface-induced cellular responses of the host.

Absorption↗

PubMed2005

Protein binding properties of surface-modified porous polyethylene membranes.

In this study, we quantified the adsorption of immunoglobulin G (IgG) protein onto several polyelectrolyte-modified sintered porous polyethylene (PPE) membranes. The polymer surfaces had both cationic and anionic charges obtained via the adsorption of polyethylenimine (PEI) and polyacrylic acid (PAA), respectively, onto plasma-activated PPE. The amount of IgG adsorption was determined by measuring the gamma radiation emitted by [125I]-IgG radio labeled protein. By studying the impact of pH and ionic strength on IgG adsorption, we attempted to characterize the role and nature of the electrostatic interactions involved in the adsorption process to better understand how these interactions were influenced by the charge and structure of immobilized polyelectrolyte complexes at modified membrane surfaces. We were able to show that surface modification of PPE membranes with adsorbed PEI monolayers and PEI-PAA bilayers can greatly improve the IgG binding ability of the membrane under optimized conditions. We also showed that the observed improvement in the IgG binding is derived from electrostatic interactions between IgG and the polyelectrolyte surface. In addition, we found that the greatest IgG adsorption occurred when the IgG and the surface possessed predominantly opposite charges, rather than when the surface possessed the greatest electrostatic charge. Finally, we have found that the molecular weight of the terminating polyelectrolyte has a noticeable effect upon the electrostatic interactions between IgG and the PEI-PAA bilayer-modified PPE surfaces.

Acrylic Resins↗

PubMed2002

Activated polyurethane modified with latent thiol groups.

A novel type of modified polyurethane with pendant acetylthio groups (as a latent form of thiol groups) has been proposed for the use in surface modifications with various biomolecules. The polymer was prepared via a modified variant of low-temperature bromoalkylation of urethane hard segments followed by the reaction of pendant bromoalkyl groups with thiolacetic acid in mild conditions. The extent of modification with acetylthio groups can be made as high as 0.45 mmol/g. After deprotection of acetylthio groups and reaction of the resulting thiol groups with an excess of Ellman's reagent, 0.1 nmol/cm(2) of thiol-reactive 3-carboxy-4-nitrophenyldithio groups were detected on the surface of films cast from the modified polymer. A sensitive fluorescent probe--dansyl-L-cysteine was used for the quantification of thiol-reactive groups bound to the surface. The acetylthio-modified polyurethane is sufficiently stable to withstand conditions typical for the high-temperature processing (molding, extrusion) of polyurethanes.

Cysteine↗

PubMedDate not supplied

Increase in cell adhesiveness on a poly(ethylene terephthalate) fabric by sintered hydroxyapatite nanocrystal coating in the development of an artificial blood vessel.

Nano-scaled sintered hydroxyapatite (HAp) crystals were covalently linked onto a poly(ethylene terephthalate) (PET) fabric substrate chemically modified by graft polymerization with gamma-methacryloxypropyl triethoxysilane (MPTS) for development of an artificial blood vessel. The weight gain of graft polymerization with poly(MPTS) on PET in benzyl alcohol containing H2O2 as an initiator increased as increasing the reaction time and finally reached a plateau value of about 3.5 wt%. The surface characterization of surface modification with poly(MPTS)-grafting was conducted by x-ray photoelectron spectroscopy. HAp nanocrystals of approximately 50 nm in diameter, monodispersed in pure ethanol, were coupled with alkoxysilyl groups of the poly(MPTS)-grafted PET substrate. The HAp nanocrystals were uniformly and strongly coated on the surface of the PET fabrics, although HAp particles adsorbed physically on the original PET without poly(MPTS) grafting were almost removed by ultrasonic wave treatment. More human umbilical vein endothelial cells adhered to the HAp/PET composite fabric compared with original PET after only 4 hours of initial incubation, and the same was observed on the collagen-coated PET. The coating of sintered HAp nanocrystals imparted bioactivity to the polyester substrate, which is a widely used biomedical polymer, without a coating of adhesion proteins derived from animals, such as collagen or gelatin. A prototype of an artificial blood vessel was finally fabricated by use of HAp/PET composite.

Adhesiveness↗

PubMed2000

Creating long-lived superhydrophobic polymer surfaces through mechanically assembled monolayers.

We show that elastomeric surfaces can be tailored using "mechanically assembled monolayers" (MAMs), structures that are fabricated by combining self-assembly of surface grafting molecules with mechanical manipulation of the grafting points in the underlying elastic surface. The versatility of this surface modification method is demonstrated by fabricating MAMs with semifluorinated (SF) molecules. These SF-MAMs have superior nonwetting and barrier properties in that they are "superhydrophobic" and nonpermeable. We also establish that these material characteristics do not deteriorate even after prolonged exposure to water, which usually causes surface reconstruction in conventionally prepared SF self-assembled monolayers.

Journal Article↗

PubMed1988

The use of silicone/polyurethane graft polymers as a means of eliminating surface cracking of polyurethane prostheses.

The long-term biodegradation of various polyurethanes with and without surface modifications was evaluated by implanting small porous filamentous patches of these materials subcutaneously in the backs of dogs for one month. Data were compared to those obtained with spun polyurethane vascular grafts of similar materials implanted in the aorto-iliac position in dogs. The extremely high surface area of approximately 7 m2/cm3 of these porous filamentous patches provided numerous sites for surface cracking and the very fine filaments (10 microns in diameter) provided an easily identifiable structure to study the cracking phenomenon. Results from numerous one month implants clearly demonstrated that the subcutaneous implant model effectively reproduced the biodegradation behavior observed in vascular graft implants. The degradation was most pronounced in the softer Shore 80A polyurethanes and less pronounced in the harder 55D and 75D polyurethanes. The degradation could not simply be stopped by stress annealing the polyurethane and the degradation did not require the presence of metallic ions. Antioxidants, surface adsorbed albumin, poly(2-hydroxyethyl-methacrylate) grafting, silicone copolymerization, tetrafluoroethylene plasma discharge and the addition of urea linkages to the polymer were also shown to be ineffective in stopping the biodegradation process. In contrast, covalent bonding or grafting of silicone polymer to the surface of the urethane successfully inhibited the biodegradation process.

Animals↗

PubMed1991

Covalent immobilization of proteins on to the surface of poly(vinyl alcohol) hydrogel.

Covalent immobilization of cell-adhesive proteins such as collagen and fibronectin on to the surface of poly(vinyl alcohol) hydrogel was investigated by using diisocyanates, polyisocyanates, and cyanogen bromide. It was found that 0.5 and 12 micrograms/cm2 of collagen were immobilized on to the surface by using hexamethylene diisocyanate and cyanogen bromide, respectively. The big difference in the graft amount between the two methods was ascribed to the different reaction media employed for the surface modifications; toluene for the reaction with hexamethylene diisocyanate and water for the reaction with cyanogen bromide.

Collagen↗

PubMed2003

Constructing thromboresistant surface on biomedical stainless steel via layer-by-layer deposition anticoagulant.

Multilayer films consisting of polyethylenimine (PEI) and heparin were successfully prepared on biomedical 316L stainless steel surface via electrostatic self-assembly (ESA) of the PEI and heparin. The process of ESA of PEI/heparin was monitored by static contact angle, electrochemical impedance spectroscopy (EIS), reflection adsorption spectroscopy and X-ray photoelectron spectroscopy data. The contact angle and EIS data revealed that the multilayer coating was stable in Tris-HCl (pH 7.35) buffer solution for 21 days. The static platelet adhesion and static clotting time experiments indicated that the PEI/heparin-deposited stainless steel could resist the platelet adhesion and prolong the static clotting time effectively. Such an easy processing and shape-independent method may have good potential for surface modification of cardiovascular devices.

Anticoagulants↗

PubMed2005

Control of localized nanorod formation and patterns of semiconducting CuTCNQ phase I crystals by scanning electrochemical microscopy.

Use of the technique of scanning electrochemical microscopy (SECM) enables the surface of single crystals of 7,7',8,8'-tetracyanoquinodimethane (TCNQ) to be modified in a controlled manner to produce highly dense and micrometer sized regions of semiconducting phase I CuTCNQ nanorod crystals by a nucleation and growth mechanism. This method involves the localized reduction of solid TCNQ to TCNQ- by aqueous phase V(aq)2+ reductant generated at a SECM ultramicroelectrode tip by reduction of V(aq)3+, coupled with the incorporation and reduction of Cu(aq)2+ ions also present in the aqueous electrolyte. SECM parameters can be systematically varied to control the extent of surface modification and the packing density of the CuTCNQ crystals. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images provide evidence that the TCNQ to CuTCNQ solid-solid transformation is accompanied by a drastic localized crystal volume and morphology change achieved by fragmentation of the TCNQ crystal surface. Patterns of semiconducting CuTCNQ (phase I) nanorod shaped crystals have been characterized by SEM, AFM, and infrared (IR) techniques. A reaction scheme has been proposed for the interaction between the electrogenerated mediator V(aq)2+, Cu(aq)2+, and the TCNQ crystal in the nucleation and growth stages of phase I CuTCNQ formation.

Copper↗

PubMed2004

Effect of calcium and phosphorus ion implantation on the corrosion resistance and biocompatibility of titanium.

This paper is concerned with the corrosion resistance and biocompatibility of titanium after surface modification by the ion implantation of calcium or phosphorus or calcium + phosphorus. Calcium and phosphorus ions were implanted in a dose of 10(17) ions/cm(2). The ion beam energy was 25 keV. The microstructure of the implanted layers was examined by TEM. The chemical composition of the surface layers was determined by XPS and SIMS. The corrosion resistance was examined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C. The biocompatibility was evaluated in vitro. As shown by TEM results, the surface layers formed during calcium, phosphorus and calcium + phosphorus implantation were amorphous. The results of the electrochemical examinations (Stern's method) indicate that the calcium, phosphorus and calcium + phosphorus implantation into the surface of titanium increases its corrosion resistance in stationary conditions after short- and long-term exposures in SBF. Potentiodynamic tests show that the calcium-implanted samples undergo pitting corrosion during anodic polarisation. The breakdown potentials measured are high (2.5 to 3 V). The good biocompatibility of all the investigated materials was confirmed under the specific conditions of the applied examination, although, in the case of calcium implanted titanium it was not as good as that of non-implanted titanium.

Calcium↗

PubMed2005

Fungal degradation of calcium-, lead- and silicon-bearing minerals.

The aim of this study was to examine nutritional influence on the ability of selected filamentous fungi to mediate biogenic weathering of the minerals, apatite, galena and obsidian in order to provide further understanding of the roles of fungi as biogeochemical agents, particularly in relation to the cycling of metals and associated elements found in minerals. The impact of three organic acid producing fungi (Aspergillus niger, Serpula himantioides and Trametes versicolor) on apatite, galena and obsidian was examined in the absence and presence of a carbon and energy source (glucose). Manifestation of fungal weathering included corrosion of mineral surfaces, modification of the mineral substrate through transformation into secondary minerals (i.e. crystal formation) and hyphal penetration of the mineral substrate. Physicochemical interactions of fungal metabolites, e.g. H+ and organic acids, with the minerals are thought to be the primary driving forces responsible. All experimental fungi were capable of mineral surface colonization in the absence and presence of glucose but corrosion of the mineral surface and secondary mineral formation were affected by glucose availability. Only S. himantioides and T. versicolor were able to corrode apatite in the absence of glucose but none of the fungi were capable of doing so with the other minerals. In addition, crystal formation with galena was entirely dependent on the availability of glucose. Penetration of the mineral substrates by fungal hyphae occurred but this did not follow any particular pattern. Although the presence of glucose in the media appeared to influence positively the mineral penetrating abilities of the fungi, the results obtained also showed that some geochemical change(s) might occur under nutrient-limited conditions. It was, however, unclear whether the hyphae actively penetrated the minerals or were growing into pre-existing pores or cracks.

Aspergillus niger↗

PubMed1985

Hydrophilic albumin microspheres.

A method has been developed for preparing unique hydrophilic HSA/MS. Important aspects of this synthesis include addition of the cross-linking agent (glutaraldehyde) in the organic phase and use of concentrated polymer solutions as dispersion media. The polymer solutions afford excellent steric stabilization of aqueous albumin microdispersions for microsphere synthesis. Steric stabilization of dispersions by polymer solutions was shown to be a function of polymer concentration and molecular weight. The HSA/MS prepared by this method are hydrophilic and easily dispersed in a variety of aqueous media without surfactants. Chemical modifications are easily accomplished using available reactive aldehyde groups remaining after cross-linking. Although hydrophilicity of the microspheres is advantageous for many drug delivery applications, in some instances (such as the use of MS in adjuvant immunotherapy or vaccine preparations) some hydrophobicity may be desirable. For this purpose, surface modifications to produce controlled hydrophobicity is easily achieved by covalent coupling with appropriate reagents (e.g., fatty amines). Adriamycin was bound to HSA/MS by both physical association (to 18 wt%) and covalent binding (also to 18 wt%). In vitro release of drug was measured for the MS using a dynamic flow method. Two distinct release mechanisms could be achieved depending on the type of drug bonding used: slow by hydrolytic degradation of covalent bonds and fast by release of physically adsorbed drug. This new and versatile synthesis of hydrophilic HSA/MS opens up many new opportunities for producing chemically modified MS containing high concentrations of therapeutic agents. Use for immunodiagnostic and adjuvant compositions is also suggested.(ABSTRACT TRUNCATED AT 250 WORDS)

Capsules↗

PubMed2000

Surface reactions of a plasma-sprayed CaO-P2O5-SiO2-based glass with albumin, fibroblasts and granulocytes studied by XPS, fluorescence and chemiluminescence.

X-ray photoelectron spectroscopy (XPS) was used to define the chemical composition of the outermost surface layer and the surface modification of a plasma-coated phospho-silicate glass (identified as BVA) when immersed in K-phosphate buffer or in phosphate buffered human albumin solution. Its behavior was compared with that of a soda-lime-based glass (identified as BVH) treated in the same way. The surface % composition of plasma-sprayed glass was consistent with bulk composition. After incubation with buffer, a Ca-P-rich layer developed only on the surface of BVA glass. Human serum albumin was bound reversibly to both glasses maintaining its native state. However, the protein completely covered the BVA glass surface within 24 h, with the formation of a mixed albumin-Ca-P layer, while 4 days incubation was necessary for complete coverage of BVH glass surface. Murine fibroblasts seeded on plasma-coated BVA glass showed a proliferation pattern similar to that of control cells grown on Petri dish, while cells seeded on BVH had more restricted growth. A limited response was induced in polymorphonuclear granulocytes by both bulk glasses powder. In conclusion, the glass identified as BVA has the suitable characteristics of its surface layers to be considered biologically active from both a chemical and a cellular point of view.

3T3 Cells↗

PubMed2004

Multiple imaging techniques demonstrate the manipulation of surfaces to reduce bacterial contamination and corrosion.

Surface imaging techniques were combined to determine appropriate manipulation of technologically important surfaces for commercial applications. The complementarity of the microscopy methods, scanning electron microscopy, electron probe microanalysis and atomic force microscopy assessed and correlated form and function of the surface modifications. Stainless steel disks (1 cm in diameter) were laser-cut from the same sheets of stainless steel and treated by electropolishing or left untreated for controls. Each treatment was analysed separately using each technique. First, the disks were examined by visual inspection and electron probe microanalysis for surface characteristics and elemental composition, respectively. Aliquots of bacterial suspensions (saline rinses of poultry carcasses from a commercial broiler processing plant) were then diluted in broth and monitored for growth by spectrophotometry. Stainless steel disks (1 cm in diameter) were added and the cultures were grown to sufficient density to allow attachment of bacterial cells to test surfaces. Relative differences in the surface morphology shown by atomic force microscopy, including Z ranges, roughness and other measurements, corresponded by treatment with the differences in reduction of bacterial counts shown by scanning electron microscopy. A model of wet-processing conditions tested the effects of corrosive treatment of surfaces. Less bacterial attachment occurred after corrosive treatment on controls and electropolished samples. Electropolishing significantly reduced bacterial numbers and the effects of corrosive action compared to the controls. Thus, the multiple imaging techniques showed that engineered changes on stainless steel surfaces improved the resistance of the surface finish to bacterial attachment, biofilm formation, and corrosive action.

Bacteria↗

PubMed1999

Spatial regulation and surface chemistry control of monocyte/macrophage adhesion and foreign body giant cell formation by photochemically micropatterned surfaces.

A long-standing goal of biomedical device development has been the generation of specific, desired host blood and tissue responses. An approach to meeting this design criteria is precise surface modification that creates micropatterns of distinct physicochemical character to direct cell adhesion and behavior. For this study, poly(ethylene terephthalate) films were coated with poly(benzyl N, N-diethyldithiocarbamate-co-styrene) and sequentially exposed to monomer solutions for photoirradiation. A photomask was placed over different regions to generate micropatterned surfaces with graft polymer stripes of three distinct ionic characters. Human monocytes were cultured on these surfaces to ascertain whether adhesion and fusion of monocytes/macrophages could be controlled. Nonionic polyacrylamide greatly inhibited adhesion and induced clumping of the few monocytes that did adhere. Macrophage adhesion and spreading led to high degrees of interleukin-13 induced foreign body giant cell formation on both the anionic poly(acrylic acid), sodium salt, and benzyl N,N-diethyldithiocarbamate portions of the culture surface. In spite of the highest observed levels of monocyte/macrophage adhesion on cationic poly(dimethylaminopropylacrylamide), methiodide, the adherent cells were not competent to undergo fusion to form foreign body giant cells. These results suggest that inflammatory cell responses may be spatially controlled in a manner that may be ultimately exploited to improve the biocompatibility of medical devices.

Acrylic Resins↗

PubMed2003

Novel human endothelial cell-engineered polyurethane biomaterials for cardiovascular biomedical applications.

A tri-block coupling-polymer composed of 4,4'-methylenediphenyl diisocyanate and poly (ethylene oxide) (PEO), abbreviated MPEO, was used as the template surface-modifying additive (SMA), based on which selected amino acids (lysine, arginine, glycin, and aspartic acid) and RGD peptide were respectively conjugated as functional endgroups of the PEO spacer-arms through sulfonyl chloride-activation routes. After the immobilization of biofunctional factors, the SMA-MPEO derivatives were noncovalently introduced onto the biomedical poly(ether urethane) (PEU) surfaces by physical blending methods. The SMA synthesis and PEU surface modification were monitored and analyzed by nuclear magnetic resonance spectroscopy, attenuated total reflection-infrared spectroscopy, and X-ray photoelectron spectroscopy. The human umbilical vein endothelial cells (HUVECs) were collected and harvested manually by collagenase digestion. The cell culture was performed respectively on the MPEO derivative-modified PEU surfaces and also on the surfaces of the commercially available polystyrene cell-culture plates (TCPS) for control. The cell adhesion rates and cell proliferation rates of the in vitro cultivated HUVEC were measured using flow cytometry. The individual cell viability rates were determined with MTT assay. The cell morphologies of the living HUVECs were investigated by optical inverted microscopy, and more detailed information was acquired from scanning electrical microscopy. The results indicated that the efficacy of SMA functional endgroups was the dominant factor for HUVEC compatibility; the proper-sized PEO spacers (M(w) 2 k) could support and mobilize the functional endgroups, optimizing the surface (interface) environment for the cell growth. As the endgroups of the SMA-MPEO derivatives and the bio-functional factors, the basic amino acids (lysine and arginine) demonstrated similar performances to that of the widely acknowledged cell growth-promoter, RGD peptide, which were superior to TCPS. Therefore, these MPEO derivative-modified PEU materials are promising to serve as novel polymeric permanent implants or interventional devices for cardiovascular biomedical applications.

Biocompatible Materials↗

PubMed1994

In vitro plasma protein adsorption and kallikrein formation on 3-mercaptopropionic acid, L-cysteine and glutathione immobilized onto gold.

3-Mercaptopropionic acid (MPA), L-cysteine (L-cys), and glutathione (GSH) monolayers were immobilized onto gold and used in in vitro protein tests. The surfaces were characterized with ellipsometry, static contact angle measurements, atomic force microscopy, and Fourier transform infrared reflection absorption spectroscopy (FT-IRAS). After incubations in human plasma and antibody solutions, the surface antisera binding patterns were determined with ellipsometry. Using serum instead of plasma, complement activation was studied in the same fashion. Activated coagulation Factor XII and kallikrein formation on the surfaces and in the plasma were studied using a kallikrein-specific colorimetric assay. 3-Mercaptopropionic acid indicated contact activation of coagulation but L-cysteine did not. Glutathione displayed low deposition of plasma proteins, large deposition of proteins from serum, and did not promote kallikrein formation. None of the surfaces could be attributed complement activating properties, as determined by antibody deposition. The present study demonstrates that surface biology in complex model systems can be conveniently studied in vitro through systematic and well defined surface modifications.

3-Mercaptopropionic Acid↗