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PubMed2003

Fibroblast growth on surface-modified dental implants: an in vitro study.

A major consideration in designing dental implants is the creation of a surface that provides strong attachment between the implant and bone, connective tissue, or epithelium. In addition, it is important to inhibit the adherence of oral bacteria on titanium surfaces exposed to the oral cavity to maintain plaque-free implants. Previous in vitro studies have shown that titanium implant surfaces coated with titanium nitride (TiN) reduced bacterial colonization compared to other clinically used implant surfaces. The aim of the present study was to examine the support of fibroblast growth by a TiN surface that has antimicrobial characteristics. Mouse fibroblasts were cultured on smooth titanium discs that were either magnetron-sputtered with a thin layer of titanium nitride, thermal oxidized, or modified with laser radiation (using a Nd-YAG laser). The resulting surface topography was examined by scanning electron microscopy (SEM), and surface roughness was estimated using a two-dimensional contact stylus profilometer. A protein assay (BCA assay) and a colorimetric assay to examine fibroblast metabolism (MTT) were used. Cellular morphology and cell spreading were analyzed using SEM and fluorescence microscopy. Fibroblasts on oxidized titanium surfaces showed a more spherical shape, whereas cells on laser-treated titanium and on TiN appeared intimately adherent to the surface. The MTT activity and total protein were significantly increased in fibroblasts cultured on titanium surfaces coated with TiN compared to all other surface modifications tested. This study suggests that a titanium nitride coating might be suitable to support tissue growth on implant surfaces.

3T3 Cells↗

PubMed2003

XPS, AES, and AFM as tools for study of optimized plasma functionalization.

The plasma-based surface modification of polymer materials with desirable bulk properties is a useful way to obtain polymers with tailor-made surface properties. This is necessary because the surface properties of most engineering polymers in use today are less then optimum for many applications. New functionalities such as biocompatibility, adhesion, special functional groups as well as lubricative, friction and wear-and-tear properties are demanded. By optimization of the process parameters during a low pressure plasma treatment, most of these requirements can be fulfilled. A specific functionalization with, e.g., carboxyl, amino, epoxy or hydroxyl groups as well as the generation of ultra thin layers with those functionalities is possible. The most challenging problem is not only to find parameters which do not lead to a fragmentation of the monomeric structure, but moreover the adhesion of the thin films to the substrates must overcome a stability test without delamination. To optimize plasma processes, with their great variety of parameters influencing the obtained surface properties, several surface analytical techniques are indispensable. XPS, AES as well as AFM are helpful tools to characterize the modified sample surfaces and consequently optimize the set of parameters for the glow discharge treatment. With XPS the retention of the monomer structure can be controlled. AES depth profiling clarifies the elemental composition of gradient layers, necessary for a good adhesion of scratch-resistant coatings. AFM visualizes the surface morphology which is important for, e.g., the friction properties of plasma-coated substrates.

Journal Article↗

PubMed2003

X-ray photoelectron spectroscopy for detection of the different Si-O bonding states of silicon.

X-ray photoelectron spectroscopy (XPS) was used to detect the bonding between a silica particle surface and attached silanes. In addition to the commonly recorded Si 2p spectrum, the Si 1 s level is also accessible when monochromatic Ag Lalpha X-rays are applied. Furthermore, the spectrum of the Si 1 s level shows a fine structure. After spectrum deconvolution, we assigned the fitted spectral peaks to Si-C bonds of the silanes and to the Si-O bonds of the silica network. The recorded Si 1 s spectra were deconvoluted into peaks originating from Si-C bonds and the Si-O-Si silica network. To check the results of spectrum deconvolution, several differently functionalized silanes containing stoichiometric amounts of heteroatoms were applied for silica surface modification. We conclude that spectra deconvolution of the Si 1 s signal is an appropriate means for quantification of surface attached silane molecules.

Journal Article↗

PubMed2003

[The influence of a new surface treatment of silicone intracoular lenses with fluoralkylsitan on the adherence of endophthalmitic bacteria in vitro]].

INTRODUCTION: Dynasilan is a fluoroalkylsilan which is able to bind to surface active molecules of intraocular lenses (IOLs), thereby offering a new option for surface modification of silicone lenses. The purpose of this in vitro study was to investigate the influence of this new surface treatment on the adherence of two typical endophthalmitis-inducing bacteria ( Staphylococcus epidermidis, Propionibacterium acnes). MATERIALS AND METHODS: A total of 14 Dynasilan-treated and 14 untreated silicone lenses were incubated at 37 degrees C for 24 h in brain heart infusion broth (10(8) CFU/ml) either with Staphylococcus epidermidis or with Propionibacterium acnes for 1 h. Subsequently, the adherent bacteria were resuspended using ultrasonification at 35 kHz for 3 x 45 s. After a dilution series and incubation at 37 degrees C for 24 h or 3 days the colonies were counted. RESULTS: On untreated IOLs incubated with Staphylococcus epidermidis the average number of bacteria was 3.6 x 10(7)/ml, and on treated IOLs the number of counted colonies was reduced to 1.09 x 10(7)/ml. Incubated with Propionibacterium acnes the average number of adherent bacteria on untreated IOLs was 4.75 x 10(4)/ml and on modified IOLs the number was reduced to 2.94 x 10(4)/ml. CONCLUSION: Dynasilan surface treatment may reduce the adherence of Staphylococcus epidermidis and Propionibacterium acnes on silicone intraocular lenses. Further studies regarding the stability of this treatment, its biocompatibility and influence on lens epithelial cell adhesion are in progress.

Bacterial Adhesion↗

PubMed1992

ESCA investigation of low-temperature ammonia plasma-treated polyethylene substrate for immobilization of protein.

A low-temperature radiofrequency plasma excited in anhydrous ammonia was used to modify polyethylene substrate surfaces for covalent immobilization of proteins. Electron spectroscopy for chemical application (ESCA) was used for surface characterization of polyethylene to a depth scale of 7 nm. The data revealed that surface modification is extensive and occurs in seconds at low discharge power. Primary amino functionalities were detected on the polyethylene surface and the level is dependent on plasma parameters. 125I-labelled antibodies covalently attached to amino groups via glutaraldehyde allowed the conditions for optimum level of primary amine to be established. Both ESCA data and protein loadings are in excellent agreement.

Ammonia↗

PubMed2004

Hemocompatibility of polyacrylonitrile dialysis membrane immobilized with chitosan and heparin conjugate.

Chitosan (CS)/heparin (HEP) polyelectrolyte complex (PEC) was covalently immobilized onto the surface of polyacrylonitrile (PAN) membrane. The effect of surface modification on the protein adsorption and platelet adhesion, metabolites permeation and anticoagulation activity of the resulting membrane was investigated. Surface characterization such as water contact angle, and X-ray photoelectron spectroscope were performed. The immobilization of PEC caused the water contact angle to reduce, thereby indicating the increase in the hydrophilicity. Protein adsorption, platelet adhesion, and thrombus formation were all reduced by the immobilization of HEP. Anticoagulant activity was evaluated with activated partial thrombin time (APTT), prothrombin time (PT), fibrinogen time, and thrombin time (TT). The results revealed that PEC-immobilizing membrane can improve antithrombogenicity of PAN membrane. In addition, the PEC-immobilized membranes can suppress the proliferation of Pseudomonas aeruginosa. In vitro cytotoxicity test showed leachable substance released was below cytotoxic level. The pure water permeability results show little variation due to PEC-immobilization. Thus PEC-immobilization can endow the PAN membrane hemocompatibility and antibacterial activity while retaining the original permeability.

Adsorption↗

PubMed2006

An overview of prion biology and the role of blood filtration in reducing the risk of transfusion-transmitted variant Creutzfeldt-Jakob disease.

Prions are infectious proteins believed to be responsible for a variety of progressive and fatal neurodegenerative diseases, collectively referred to as transmissible spongiform encephalopathies (TSE). By 1996, it was recognized that ingestion of beef from cattle afflicted with a TSE known as bovine spongiform encephalopathy, could result in a devastating human TSE known as variant Creutzfeldt-Jakob disease (vCJD). Two recent reports of probable transfusion-transmitted vCJD have raised concerns about the safety of the blood supply. The relatively long asymptomatic latency of vCJD, as well as the lack of sensitive and specific antemortem tests, increase the risk that asymptomatic, infected individuals may become blood donors. To this point, donor deferral has been a strategy used to reduce this risk. Nevertheless, this strategy may be unreliable and, furthermore, may threaten blood availability. Leukoreduction has also been helpful in reducing cell-associated infectious prion, which has been reported to reduce up to 42% of the infectivity in blood. Proprietary prion affinity surface modifications have been developed and applied to filters, which exploit an understanding of the unique chemical characteristics of prion surfaces. These have been successfully adapted to existing high-efficiency blood filter matrices for the reduction of prions present in blood components for transfusion.

Chromatography, Affinity↗

PubMed2005

Nonwetting process for achieving surface functionalization of chemically stable poly(tetrafluoroethylene).

Using a low-energy Ar+ ion-beam with and without a reactive gas, chemically stable poly(tetrafluoroethylene) (PTFE) films were modified to have special surface features. The adhesion strength between the PTFE and the copper was significantly improved because of both changes in the surface topography and chemical interactions due to PTFE functionalization (oxidation and amination). The surface modification altered the failure mode from adhesive failure for the unmodified PTFE/Cu interface to cohesive failure for the surface-modified PTFE/Cu layer interface.

Journal Article↗

PubMedDate not supplied

Microfabricated surface designs for cell culture and diagnosis.

Grooved and holed surfaces with a well fabricated design may serve as microsubstrates for cell culture and microreactors for diagnosis. In this study, the authors prepared chemically treated, micrometer scale grooved and holed glass surfaces by combined surface modification and ultraviolet (UV) excimer laser ablation techniques, as follows. 1) Microcell-culture substrate: Amino group attached glass surfaces, prepared by the treatment with an aminopropylsilane, were condensed with a carboxylated radical initiator. Subsequently, polyacrylamide was grafted by surface initiated radical polymerization to create a very hydrophilic surface layer. Ultraviolet excimer laser beams (KrF: 248 nm) were irradiated through a microscope onto surfaces to create grooves or holes that were 10 and 50 microns in width or diameter, respectively. The depth, depending on the irradiation light strength, ranged from a few to several tenths of a micrometer. On endothelial cell (EC) seeding, ECs adhered and grew on the bottoms of the grooved or holed surface where glass was exposed on ablation. Little cell adhesion was observed on non ablated, grafted surfaces. Endothelial cells aligned along the groove, resulting in very narrow tube like tissue formation, whereas ECs tended to form a multilayered spherical aggregate in a hole. A single cell resided in a 10 microns square hole. 2) Microreactor for diagnosis: The glass surface, treated with a fluorinated silane, was ablated to create round holes. On addition of a few microliters of water, water could be quantitatively transferred into a hole because of the water repellent characteristics of non ablated, fluorinated glass. As a model of a microreactor, enzyme reactions to affect different levels of glucose were carried out in tiny holed surfaces.

Acrylic Resins↗

PubMed2004

Blood compatibility of polyurethane surface grafted copolymerization with sulfobetaine monomer.

Surface modification is an effective way to improve the hemocompatibility and remain bulk properties of biomaterials. Recently, polymer tailed with zwitterions was found having good blood compatibility. In this study, the grafting copolymerization of sulfobetaine onto polyurethane surface was obtained through two steps. In the first step, polyurethane film coupled with vinyl groups was obtained through the reaction between the carboxyl group of acrylic acid (AA) and the NH-urethane group of polyurethane by dicyclohexylcarbodiimide (DCC). In the second step, sulfobetaine was grafted copolymerization on the surface using AIBN as an initiator. The reaction process was monitored with ATR-IR spectra and X-ray photoelectron spectroscopy (XPS) spectra. The wettability of films was investigated by water contact angle measurement. The blood compatibility of the grafted films was evaluated by platelet adhesion in platelet rich plasma (PRP) and protein absorption in bovine fibrinogen (BFG). Low platelet adhesion was observed on the grafted films incubated in PRP for 1 and 3 h, respectively. The protein absorption was reduced on the grafted films after incubated in bovine fibrinogen for 2 h. All of these results revealed that the improved blood compatibility was obtained by grafting copolymerization with zwitterionic monomer of sulfobetaine onto polyurethane film. In addition, introducing vinyl groups onto surface through DCC and AA is a novel method to functionalize polyurethane for further modification.

Acrylates↗

PubMed1998

[Surface treatments for dental titanium castings].

Because pure titanium is highly reactive at high temperature, its casting surface is easily coated with a thick contaminated layer that affects its physical and chemical properties, and consequently a stable superficial oxide membrane develops in the presence of air or water even at room temperature, which makes the surface discolored. Therefore, surface treatments for pure titanium castings are more important than those for other dental alloy castings. This article reviews the methods of surface treatments for dental titanium castings in four aspects: physical finishing, chemical finishing, electro-chemical finishing and surface modification technology.

Dental Casting Investment↗

PubMed1995

Fused-silica capillaries with surface-bound dextran layer crosslinked with diepoxypolyethylene glycol for capillary electrophoresis of biological substances at reduced electroosmotic flow.

This report is concerned with the introduction of novel surface modification involving the covalent attachment of branched, high molecular weight dextrans and subsequent crosslinking with polyether chains on the inner surface of fused silica capillaries with the aim of producing hydrophilic capillaries with reduced electroosmotic flow (EOF). Three different molecular mass dextrans, namely 45, 71 or 150 kDa were covalently attached to the capillary surface, and subsequently crosslinked with diepoxypolyethylene glycol (PEG). This chemistry produced stable coating over a wide range of conditions including high and low pH aqueous solutions. Moreover, the various dextran-PEG-coated capillaries exhibited reduced electroosmotic flow. These features of the dextran-PEG coatings were useful for the separations of basic and acidic proteins, and provided high resolution separation for closely related acidic monosaccharides and sialooligosaccharides.

Carbohydrate Sequence↗

PubMed2002

Covalent DNA immobilization on polymer-shielded silver-coated quartz crystal microbalance using photobiotin-based UV irradiation.

The use of a commercial, silver-coated quartz crystal microbalance (QCM) as a disposable, low-cost, and reliable DNA sensor is presented. This is an incorporation of polymer-based silver electrode shielding and photochemistry-based surface modification for covalent DNA immobilization. To prevent undesired oxidation, the silver electrodes are coated with thin polystyrene films. The polymer surfaces are then modified by a photoreactive biotin derivative (photobiotin) under UV irradiation. The resulting biotin residues on the polymer-shielded surface react with a tetrameric avidin. Consequently a biotin-labeled DNA probe can be immobilized through a biotin-avidin-biotin bridge. A 14-mer single-stranded biotin-DNA probe and a 70-mer single-stranded DNA fragment containing complementary or noncomplementary sequences are used as a model system for DNA hybridization assay on the proposed sensors. The shielding ability of the polystyrene coatings after photo irradiation is investigated. The DNA probe binding capacity, hybridization efficiency, and kinetics are also investigated.

Affinity Labels↗

PubMed1997

Immobilization of the cell-adhesive peptide Arg-Gly-Asp-Cys (RGDC) on titanium surfaces by covalent chemical attachment.

Surface modification of acid-pretreated titanium with 3-aminopropyltriethoxylsilane (APTES) in dry toluene resulted in covalently bonded siloxane films with surface coverage that was relatively controllable by regulating the reaction conditions. A hetero-bifunctional cross-linker, N-succinimidyl-3-maleimidopropionate (SMP), reacted with the terminal amino groups, forming the exposed maleimide groups. Finally, a model cell-binding peptide, Arg-Gly-Asp-Cys (RGDC), was immobilized on the surface through covalent addition of the cysteine thiol groups to the maleimide groups. X-ray photoelectron spectroscopy, radiolabelling techniques, and ellipsometry were used to quantify and characterize the modified surfaces.

Journal Article↗

PubMed2005

Surface modifying substances that reduce apparent yeast cell hydrophobicity.

OBJECTIVE: To determine whether several topical compounds and other chemical entities are able to diminish the surface hydrophobicity of yeast cells. METHOD: Hydrophobicity of yeast cells was determined by binding styrene microspheres to the surface of untreated yeast or yeast pre-incubated with various substances with potential for cell surface modification. The degree of microsphere adherence to yeast cells was measured by flow cytometry. RESULTS: A significant reduction in cell surface hydrophobicity was observed when yeast was incubated in protein-containing media. Other compounds that effectively reduced microsphere binding were various formulations of K-Y and heparin. Divalent cations (Ca+ + , Mg+ + , Zn+ + , Cu + + ) were also potent inhibitors of microsphere adherence. It was possible to remove substances contributing to microsphere binding by chemical extraction of the yeast. Yeast having reduced microsphere binding activity also showed diminished binding of concanavalin A. CONCLUSIONS: Several commercially available compounds were able to block binding of styrene microspheres to yeast. Some of the binding activity appeared to be attributable to mannose-containing surface components. These findings have implications for formulating therapeutic products that might block yeast binding to tissues.

Candida albicans↗

PubMed1986

Aluminum lactate treatment alters the lung biological activity of quartz.

Previous studies of surface modification of quartz particles have suggested that the biological activity of silica is at least in part related to its surface properties. In the present study, we exposed the tracheal lobe of 8 sheep to either 100 ml saline (saline group), 100 mg of quartz (Minusil-5) in 100 ml saline (SI group) or 100 mg of Al lactate treated quartz in 100 ml saline (SI-Al group). The 24 sheep were studied by bronchoalveolar lavage at days 0, 12, 24, 40, 60 and by autopsy at day 60. In the saline group, BAL analyses were as previously reported [1]. In the SI group, we found significant and sustained increases in total BAL cells (x 2, P less than 0.05), macrophages and lymphocytes (x 2, P less than 0.05), neutrophils (x 5-10, P less than 0.01), IgG (x 1.2-1.8, P less than 0.05), fibronectin (x 2-3, P less than 0.05), lactate dehydrogenase (x 3, P less than 0.01) and alkaline phosphatase (x 2, P less than 0.05). Histologically, a macrophagic and lymphocytic alveolitis was observed at day 60. In the SI-Al group, these changes were significantly attenuated and in the above parameters, SI-Al group did not differ from saline group after day 24. These data of BAL and histology of the sheep tracheal lobe model document clearly that aluminum lactate treatment alters the biological activity of quartz.

Animals↗

PubMed1997

Grafting of PEO to glass, nitinol, and pyrolytic carbon surfaces by gamma irradiation.

Glass, nitinol, and pyrolytic carbon surfaces were grafted with poly (ethylene oxide) (PEO) and PEO-containing Pluronic surfactants by gamma irradiation. These substrates were coated with a primer layer of trichlorovinylsilane (TCVS), which allows grafting of organic polymers. The TCVS-coated substrates were adsorbed with PEO or Pluronics and exposed to 0.3 Mrad of gamma radiation to graft the polymer to the surface. PEO-grafted substrates were characterized by contact angle measurement, X-ray photoelectron spectroscopy, fibrinogen adsorption, and platelet adhesion and activation. Surface modification with PEO reduced fibrinogen adsorption by as much as 99%. Platelet adhesion was significnatly reduced or prevented on the modified surfaces. Protein- and platelet-resistance effects were independent of hydrophilicity of the PEO-grafted surfaces. Polymer grafting by gamma radiation to TCVS-coated substrates provides a facile process to improve thromboresistance of inorganic biomaterials.

Alloys↗

PubMed1998

Adsorption of proteins onto poly(ether urethane) with a phosphorylcholine moiety and influence of preadsorbed phospholipid.

In a previous report we demonstrated that the blood compatibility of poly(ether urethane) (PEU) was improved by grafting phosphorylcholine (PC) groups on the surface. The improved blood compatibility was indicated by decreased platelet adsorption/activation and reduced thrombin formation at the polymer surface in experiments in which the surfaces were contacted with platelet-rich plasma in vitro. In the present study, we investigated the effect of grafted PC groups at a PEU surface on protein and phospholipid adsorption. Adsorption of human fibrinogen (Fg), human serum albumin (Alb), human high-molecular-weight kininogen (HMWK), and dioleoyl phosphatidylcholine (DOPC) vesicles was measured by ellipsometry. For this purpose, thin PEU films were cast on silicon wafers. The polymer film was photochemically modified with a PC-containing aryl azide. The presence of PC groups on the polymer surface was demonstrated by ESCA (Electron Spectroscopy for Chemical Analysis). The hydrophilicity of the polymer surface increased by the surface modification, as indicated by a decrease of the contact angle from 59 degrees before to 43 degrees after modification. Our data show that the presence of PC groups has little effect on the adsorption of proteins to a PEU surface. The highest adsorption was observed for Fg (0.49 microgram/cm2 on PC-modified PEU and 0.50 microgram/cm2 on PEU), followed by HMWK (0.28 microgram/cm2 on both PC-modified PEU and PEU), and Alb (0.16 microgram/cm2 on PC-modified PEU and 0.18 microgram/cm2 on PEU). Protein adsorption was further studied on a "biomembrane-like" DOPC bilayer formed on hydrophilic silicon. We found no protein adsorption on this DOPC bilayer. The adsorption of small unilamellar DOPC vesicles on the polymer surfaces amounted to about 0.06 microgram/cm2 (corresponding to circa 30% of monolayer coverage) and was similar for PC-modified PEU and PEU. Despite this partial surface coverage, preadsorbed DOPC on the polymer surface diminished the subsequent adsorption of proteins considerably. These results show that the mere presence of phosphorylcholine groups on a PEU surface is insufficient to suppress protein adsorption. The highly ordered structure of natural phospholipid bilayers seems to be required to suppress protein adsorption effectively.

Adsorption↗