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At least 649 records · Page 36Linked to original sources

PubMed1998

Tissue reactions to bacteria-challenged implantable leads with enhanced infection resistance.

Tissue reactions to implantable pacemaker leads were investigated in an early infection model in rabbits. Both standard leads and surface-modified leads were used. The surface modification technique was applied to achieve controlled release of the antibiotic gentamicin. The insulating polyurethane tubing material of the leads was provided with an acrylic acid/acrylamide copolymer surface graft and then loaded with gentamicin. Implantation periods varied from day 4, to week 3 1/2, to week 10. We investigated tissue reactions in the absence of an infectious challenge and also the efficacy of surface-modified leads in preventing infection after challenge with Staphylococcus aureus was evaluated. It was demonstrated that the applied surface modification did not induce adverse effects although during early postimplantation an increase in infiltration of granulocytes and macrophages and wound fluid and fibrin deposition were observed. After bacterial challenge, standard leads were heavily infected at each explantation period, denoted by abscesses, cellular debris, and bacterial colonies. In contrast, little or no infection was observed, either macroscopically or by bacterial cultures, with the surface-modified leads. Microscopy showed little evidence of the bacterial challenge, and that primarily at day 4. It was concluded that the applied surface modification demonstrated enhanced infection resistance and thus represents a sound approach to the battle against infectious complications with biomaterials.

Acrylamide↗

PubMed2005

Behaviour of endothelial cells seeded on thin polyelectrolyte multilayered films: a new biological scaffold.

The surface modification using thin polyelectrolyte multilayered films was proposed as a new scaffold material for different cell lines. In this study, we evaluated the possible use of polyelectrolyte multilayers as surface modification for the development of endothelial cells. In order to control the behaviour of endothelial cells, cell viability by MTT assay was studied. Moreover, the endothelial cell phenotype was checked and the expression of a leukocyte adhesion molecule (ICAM-1) was quantified. The behaviour of the cells on two polyelectrolyte multilayers was compared to cells on polystyrene, and two polyelectrolyte monolayers (terminating the multilayer architectures). The results have shown a better cell viability on the polyelectrolyte multilayers, inducing a higher cell number compared to polyelectrolyte monolayers after 1 and 3 days of culture. Moreover, the cells showed a normal morphology of cytoskeleton. The phenotype of the endothelial cells was kept and a low level of leukocyte adhesion molecules was observed. In conclusion, the polyelectrolyte multilayers can be considered as a potential surface modification procedure to enhance the development of endothelial cells on hydrophobic substrate and which can be applied to vascular tissue engineering.

Biocompatible Materials↗

PubMed2006

Higher sensitivity secondary ion mass spectrometry of biological molecules for high resolution, chemically specific imaging.

To expand the role of high spatial resolution secondary ion mass spectrometry (SIMS) in biological studies, numerous developments have been reported in recent years for enhancing the molecular ion yield of high mass molecules. These include both surface modification, including matrix-enhanced SIMS and metal-assisted SIMS, and polyatomic primary ions. Using rat brain tissue sections and a bismuth primary ion gun able to produce atomic and polyatomic primary ions, we report here how the sensitivity enhancements provided by these developments are additive. Combined surface modification and polyatomic primary ions provided approximately 15.8 times more signal than using atomic primary ions on the raw sample, whereas surface modification and polyatomic primary ions yield approximately 3.8 and approximately 8.4 times more signal. This higher sensitivity is used to generate chemically specific images of higher mass biomolecules using a single molecular ion peak.

Animals↗

PubMed1998

Biocompatibility, cell adhesion, and degradation of surface-modified biodegradable polymers designed for the upper urinary tract.

OBJECTIVES: The aim of this study was to develop a short bioresorbable ureteric stent and to characterize polymers and their surface modifications with respect to biocompatibility, degradation kinetics, cell adhesion properties, and incorporation of biologically active substances. Poly(D,L-lactide) PDLLA, poly(D,L-lactide-co-glycolide) PDLLA-co-GLY, and poly(D,L-lactide-co-trimethylenecarbonate) PDLLA-co-TMC were chosen as basic polymers. Surface modification was performed by plasma-induced graft polymerization and included grafting with hydroxyethylmethacrylate (HEMA), oligo(ethyleneoxide)-monomethacrylate (OEOMA), and acrylic acid (AAC). Biocompatibility of the polymers was assessed in vitro applying parameters of cell morphology, proliferative activity, and cell adhesion. All polymers were biocompatible and exerted no toxic effect on urothelial cell lines and on primary human urothelial cell cultures. A markedly reduced cell adhesion could be achieved in polymers grafted with HEMA, OEOMA, and AAC. Our results indicate that surface modification of bioresorbable polymers by grafting with HEMA, OEOMA, or AAC is an efficient approach to improve surface properties with respect to biocompatibility and cell adhesion properties.

Absorption↗

PubMed2006

A novel carbon electrode material for highly improved EDLC performance.

Porous materials, developed by grafting functional groups through chemical surface modification with a surfactant, represent an innovative concept in energy storage. This work reports, in detail, the first practical realization of a novel carbon electrode based on grafting of vinyltrimethoxysilane (vtmos) functional group for energy storage in electric double layer capacitor (EDLC). Surface modification with surfactant vtmos enhances the hydrophobisation of activated carbon and the affinity toward propylene carbonate (PC) solvent, which improves the wettability of activated carbon in the electrolyte solution based on PC solvent, resulting in not only a lower resistance to the transport of electrolyte ions within micropores of activated carbon but also more usable surface area for the formation of electric double layer, and accordingly, higher specific capacitance, energy density, and power capability available from the capacitor based on modified carbon. Especially, the effects from surface modification become superior at higher discharge rate, at which much better EDLC performance (i.e., much higher energy density and power capability) has been achieved by the modified carbon, suggesting that the modified carbon is a novel and very promising electrode material of EDLC for large current applications where both high energy density and power capability are required.

Journal Article↗

PubMed2003

Modification of polymer surfaces: optimization of approaches.

Modification of polymer surfaces to achieve a surface with enhanced compatibility is an important means of obtaining improved biomaterials. Techniques are available for altering the hydrophilicity or charge of a surface, attaching macromolecules or attempting to resemble cell membranes. Relevant to the clinical success of a modified surface is the modification procedure and a procedure based on incorporation as opposed to surface treatment has potential advantages. The modification of plasticized vinyl chloride (PVC) by the incorporation of cyclodextrins is described. In comparison to unmodified PVC controls, cyclodextrin incorporation reduced fibrinogen adsorption, with the extent of reduction dependent on the type and quantity of cyclodextrin incorporated.

Adsorption↗

PubMed1999

Modification of Surface Charge Properties during Kaolinite to Halloysite-7Å Transformation.

The surface charge properties of well and poorly ordered kaolinite and halloysite-7Å, representing three different stages of kaolinite to halloysite-7Å transformation identified in the kaolin deposit of São Vicente de Pereira (Portugal), were studied. Mineralogical (X-ray diffraction, Fourier transformation-infrared) and chemical data (analytic electron microscopy) showed that the gradual transformation from kaolinite to halloysite-7Å minerals was accompanied by an increase in hydration and a decrease in Si/Al ratio. In particular, the replacement of Si(IV) by Al(III) in the tetrahedral layer caused an electrical charge unbalance and a modification of surface charge properties during the kaolinite to halloysite transformation. Accordingly, the cation exchange capacity (CEC) gradually increases when passing from well-ordered kaolinite to halloysite-7Å, attesting the direct correspondence existing among the structural order of the samples, number of tetrahedral substitutions, and CEC. Electrophoretic experiments provided further evidences of the origin of surface charge properties and the variation encountered during kaolinite to halloysite-7Å transformation. The curves of zeta-potential versus pH show the same pH dependency for the three minerals, but a gradual increase of zeta-potential when passing from well ordered kaolinite to halloysite-7Å through the poorly ordered kaolinite. The results can unambiguously be attributed to the increase of permanent charge due to the higher degree of isomorphic substitution, more than to the increase of structural and ionizable water. Copyright 1999 Academic Press.

Journal Article↗

PubMed2006

Modification of surface antigens in blood CD8+ T-lymphocytes in COPD: effects of smoking.

In contrast to the effects of cigarette smoke on T-lymphocyte subsets in the airways, it has not yet been determined whether smoking has immunomodulatory effects on surface antigens of peripheral blood T-lymphocytes and, if that is the case, whether these effects differ in smokers with and without chronic obstructive pulmonary disease (COPD). The present authors have, therefore, examined the expression of the surface activation marker CD28, the levels of cytotoxic effector lymphocytes (CD27-/CD45RA+) and the expression of the lung type (Tc)1-specific chemokine receptor CXCR(3)+ on peripheral blood CD8+ T-lymphocytes. The present authors have also studied the chemotactic activity of CD8+ T-lymphocytes on monocyte chemotactic protein (MCP)-1 and compared 13 nonsmoking controls, 12 smokers with COPD and 14 smokers without airflow limitation. There was a decrease in the total count of CD8+ T-cells and an increase in the CD4+/CD8+ ratio in smokers with COPD compared with smokers without COPD and controls. Expression of the Tc1-specific chemokine receptor CXCR(3)+ by CD8+ T-cells was increased in smokers with COPD compared with smokers without COPD and controls. The expression of activated and of cytotoxic effector CD8+ T-cells in smokers with and without COPD showed an increase compared with controls. CD8+ T-cells from smokers with and without COPD showed a decrease in chemotactic activity to MCP-1 compared with controls. In conclusion, chronic obstructive pulmonary disease may be a systemic immunomodulatory disease associated with the modification of surface antigens in blood CD8+ T-lymphocytes.

Antigens, CD↗

PubMed1999

An assessment of the strength of NG108-15 cell adhesion to chemically modified surfaces.

The strength of adhesion of NG108-15 cells to glass substrates modified with adsorbed proteins (laminin and poly-ornithine) or modified with covalently bound peptides (tri-ornithine and Tyr-Ile-Gly-Ser-Arg) was quantitatively assessed, by determining the shear stresses necessary to denude the cells from substrates using a spinning disk device. The shear stresses required to detach NG108-15 cells from glass modified with either adsorbed poly-ornithine or with both poly-ornithine and laminin were significantly (P < 0.05) higher than the shear stresses required to detach the cells from plain glass substrates. Covalent surface modifications resulted in higher strengths of NG108-15 adhesion than were exhibited on surfaces modified with adsorbed proteins. NG108-15 cell adhesion strength was maximal on surfaces covalently modified with only amine groups (without any peptides or proteins). These results indicate that general (i.e., not necessarily receptor-specific) surface modification strategies, which increase the net surface charge of a substrate, will elicit strong adhesion of NG108-15 cells.

Cell Adhesion↗

PubMed2003

The properties of chitosan-gelatin membranes and scaffolds modified with hyaluronic acid by different methods.

The objective of the present study was to investigate the properties of chitosan-gelatin membranes or scaffolds, which were modified by incorporation of hyaluronic acid in the surface or bulk phase through co-crosslinking with N,N-(3-dimethylamino-propyl)-N'-ethyl carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in 2-morpholinoethane sulfonic acid (MES) buffer. The comparative study on properties of surface modification (HA(S)) and polyblend membranes (HA(C)) revealed that gelatin was enriched on the surface of HA(C), while hyaluronic acid was enriched on the surface of the HA(S). The HA(S) membranes made by surface modification method had a characteristic surface morphology. The corresponding scaffolds were prepared through freeze-drying. The incorporation of hyaluronic acid improved flexibility and fibroblasts adhesion, while slowing down the rate of biodegradation of chitosan-gelatin scaffold. Human fibroblasts adhered and proliferated well on the membranes or scaffolds in vitro.

Biocompatible Materials↗

PubMed2006

Electrophoretic mobility and molecular distribution studies of poly(amidoamine) dendrimers of defined charges.

Generation 5 ethylenediamine (EDA)-cored poly(amidoamine) (PAMAM) dendrimers (E5, E denotes the EDA core and 5 the generation number) with different degrees of acetylation and carboxylation were synthesized and used as a model system to investigate the effect of charge and the influence of dendrimer surface modifications on electrophoretic mobility (EM) and molecular distribution. The surface-modified dendrimers were characterized by size-exclusion chromatography, 1H NMR, MALDI-TOF-MS, PAGE, and CE. The focus of our study was to determine how EM changes as a function of particle charge and molecular mass, and how the molecular distribution changes due to surface modifications. We demonstrate that partially modified dendrimers have much broader migration peaks than those of fully surface functionalized or unmodified E5 dendrimers due to variations in the substitution of individual dendrimer surfaces. EM decreased nonlinearly with increases in surface acetylation for both PAMAM acetamides and PAMAM succinamic acids, indicating a complex migration activity in CE separations that is not solely due to charge/mass ratio changes. These studies provide new insights into dendrimer properties under an electric field, as well as into the characterization of dendrimer-based materials being developed for medical applications.

Acetylation↗

PubMed2000

Expanding baculovirus surface display. Modification of the native coat protein gp64 of Autographa californica NPV.

To create a tool for eukaryotic surface display, this approach is aimed at demonstrating a direct modification of the native envelope protein gp64 of Autographa californica NPV without disturbing viral infectivity. Short affinity-tag peptides, the biotin mimic streptagII, and the gp41 amino-acid motif ELDKWA of HIV-1, specific for the human monoclonal antibody 2F5, were engineered into the baculovirus major coat protein gp64 and presented on the viral surface. Two different streptag peptides were inserted at the naturally occurring NotI site at amino-acid 278 of gp64. Additionally, the ten-amino-acid peptide GG-ELDKWA-GG, containing the epitope of mAb 2F5, was introduced into gp64 envelope protein at the same position. In all cases we were able to propagate viable virus-achieving infectious titers in the range of wild-type AcMNPV. Streptag and ELDKWA-epitope surface localization on purified virus particles was demonstrated by flow cytometry and Western blot analysis. We could also show selective retention of mutant viruses by specific interaction between chimeric virions and their target counterparts, recognizing the epitope or the streptag peptide in the viral envelope. These data provide evidence that altering the surface properties of the baculovirus virion could be of value in improving baculovirus display technology and developing new applications.

Amino Acid Sequence↗

PubMed1998

[Characterization of the properties of differentially modified titanium surfaces for dental implantology. 2: In vitro biocompatibility studies].

The aim of the present study was to determine whether specific surface modifications are capable of improving the biocompatibility of a titanium surface, and whether there is a correlation between the physico-chemical properties of the implant material and its biocompatibility. To this end, the properties of titanium surfaces were modified using various methods or the latter were coated with various materials. Plasma treatments under different atmospheric conditions (N2-plasma, SO2-plasma, acetylene plasma) as well as plasma polymerization were used to affect the biological response. Characterization of the physico-chemical surface properties by means of X-ray photoelectron spectroscopy (XPS), contact angle measurements and the calculation of surface tensions or surface energy provided important information on the interactions at the interface between the implant material and the aqueous environment. The influence of the respective surface modification on cell proliferation, cell viability and the activity of mitochondrial dehydrogenases was evaluated in specific in vitro tests with human gingiva fibroblasts. It was show that different modifications of the titanium samples induce different biological responses of the gingiva fibroblasts. The results confirm the existence of correlations between thermodynamic surface properties and cellular reactions under in vitro conditions.

Cell Division↗

PubMed2003

Cytomorphometric analysis and surface ultrastructure of developing decidua.

A scanning electron microscopic (SEM) and morphometric analysis of the topographical changes occurring in the uterine luminal epithelial layer in association with decidual tissue (DT) formation in guinea pigs was undertaken in order to elucidate the surface ultrastructural characteristics which occur during the process of endometrial differentiation. Experimentally induced decidua formation was promoted by mechanical stimulation of the antimesometrial luminal surface during the period of maximal uterine sensitivity to stromal differentiation. DT-associated remodeling of the uterine epithelial layer was subsequently examined by light and SE microscopic analysis for apical epithelial and luminal contour alterations associated with decidua growth. Cytological changes in the luminal surface associated with DT induction included sparse microvillus growth from the apical epithelial surface, accompanied by the appearance of prominent apical membrane surface protrusions and endometrial gland openings as compared with non-DT-stimulated control samples. Decidua surface growth was characterized by a short, sparse epithelial microvillus pattern present over a highly contoured luminal uterine surface on which contoured gland openings were both numerous and prominent. These surface modifications contrasted with the flat, non-decidualized luminal surface contour which was covered by distinct, microvilli-laden, apical cell membranes, and defined by prominent intercellular membrane borders. The uterine surface at the time of maximal DT formation (i.e. growth) closely resembled that of a uterine luminal surface undergoing apoptosis and subsequent cellular reabsorption, characterized by disrupted cell surface membranes, sparse microvillus surfaces and prominent epithelial contours reflecting stromal tissue and vasculature involution. These data indicate that the alterations in the uterine luminal surface associated with DT formation are reminiscent of the endometrial changes associated with the initiation of early placentation, and may be used as a model for the analysis of the role of epithelial cell surface modifications associated with the induction and support of interstitial blastocyst implantation and early decidua formation.

Animals↗

PubMedDate not supplied

In vitro studies of immobilized heparin and sulfonated polyurethane using epifluorescent video microscopy.

In situ surface modification techniques to improve the blood compatibility of blood contacting surfaces of medical devices have been developed by the authors. The techniques include heparin immobilization and sulfonated polymer grafting onto a polyurethane (PU) surface by using either ozone oxidation or photo reaction. These modified PUs were evaluated using an epifluorescent video microscope combined with a parallel plate flow cell. The epifluorescent video microscope system measured the amount of platelet coverage on the PU surfaces using whole human blood containing mepacrine labeled platelets perfused at a wall shear rate of 100 sec-1 for 20 min. Platelet activation and complement activation were also measured. Both immobilized heparin and sulfonated PUs showed significantly lower levels of platelet adhesion than the control PU. The platelet activation levels of these modified PUs also correspond to the results of the platelet adhesion. As for complement activation, heparin the immobilized surface showed the least complement activation, while sulfonated PU and the control PU showed higher levels of complement activation. In situ surface modification techniques, which use either ozone oxidation or photo reaction, are useful in a variety of medical devices even of a complex design, such as membrane oxygenators or artificial hearts.

Allylamine↗

PubMed2006

Plasma-based processes for surface wettability modification.

In this article, we describe a method to create rough features on silicon surfaces by reactive etching of a photoresist layer. The roughness and, consequently, the wettability of the surfaces can be modified by modifying the duration of plasma etching. Hydrophobic materials deposited on the rough silicon surface can be modified until a superhydrophobic behavior is obtained, whereas hydrophilic materials become more hydrophilic. The elaboration technique described herein offers an inexpensive and rapid method for the creation of tunable roughness on silicon surfaces with large areas.

Hydrophobic and Hydrophilic Interactions↗

PubMed2002

Design and function of a dendrimer-based therapeutic nanodevice targeted to tumor cells through the folate receptor.

PURPOSE: We sought to develop nanoscale drug delivery material that would allow targeted intracellular delivery while having an imaging capability for tracking uptake of the material. A complex nanodevice was designed and synthesized that targets tumor cell through the folate receptor. METHODS: The device is based on an ethylenediamine core polyamidoamine dendrimer of generation 5. Folic acid, fluorescein, and methotrexate were covalently attached to the surface to provide targeting, imaging, and intracellular drug delivery capabilities. Molecular modeling determined the optimal dendrimer surface modification for the function of the device and suggested a surface modification that improved targeting. RESULTS: Three nanodevices were synthesized. Experimental targeting data in KB cells confirmed the modeling predictions of specific and highly selective binding. Targeted delivery improved the cytotoxic response of the cells to methotrexate 100-fold over free drug. CONCLUSIONS: These results demonstrate the ability to design and produce polymer-based nanodevices for the intracellular targeting of drugs, imaging agents, and other materials.

Carrier Proteins↗

PubMed2004

Hyaluronic acid grafting mitigates calcification of glutaraldehyde-fixed bovine pericardium.

Pathologic calcification is the leading cause of the clinical failure of glutaraldehyde-fixed bovine pericardium used in bioprosthetic valves. A novel surface modification of glutaraldehyde fixed bovine pericardium was carried out with high molecular weight hyaluronic acid (HA). HA was chemically modified with adipic dihydrazide (ADH) to introduce hydrazide functional groups onto the HA backbone. Glutaraldehyde-fixed bovine pericardium (GFBP) was modified by grafting this HA to the free aldehyde groups on the tissue via the hydrazide groups. Following a 2-week subcutaneous implantation in osteopontin (OPN)-null mice, the calcification of HA-modified bovine pericardium was drastically reduced (by 84.5%) compared to positive controls (tissue without HA-modification) (p = 0.005). The calcification-mitigating effect of HA surface modification was also confirmed by microscopic analysis of explanted tissue stained with Alizarin Red S for calcium.

Animals↗