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PubMed2005

Response of primary fibroblasts and osteoblasts to plasma treated polyetheretherketone (PEEK) surfaces.

Polyetheretherketone (PEEK) is a synthetic polymer with suitable biomechanical and stable chemical properties, which make it attractive for use as an endoprothetic material and for ligamentous replacement. However, chemical surface inertness does not account for a good interfacial biocompatibility, and PEEK requires a surface modification prior to its application in vivo. In the course of this experimental study we analyzed the influence of plasma treatment of PEEK surfaces on the cell proliferation and differentiation of primary fibroblasts and osteoblasts. Further we examined the possibility of inducing microstructured cell growth on a surface with plasma-induced chemical micropatterning. We were able to demonstrate that the surface treatment of PEEK with a low-temperature plasma has significant effects on the proliferation of fibroblasts. Depending on the surface treatment, the proliferation rate can either be stimulated or suppressed. The behavior of the osteoblasts was examined by evaluating differentiation parameters. By detection of alkaline phosphatase, collagen I, and mineralized extracellular matrix as parameters for osteoblastic differentiation, the examined materials showed results comparable to commercially available polymer cell culture materials such as tissue culture polystyrene (TCPS). Further microstructured cell growth was produced successfully on micropatterned PEEK foils, which could be a future tool for bioartificial systems applying the methods of tissue engineering. These results show that chemically inert materials such as PEEK may be modified specifically through the methods of plasma technology in order to improve biocompatibility.

Animals↗
PubMed2006

Evaluation of mammalian cell adhesion on surface-modified porous silicon.

Porous silicon is a promising biomaterial that is non-toxic and biodegradable. Surface modification can offer control over the degradation rate and can also impart properties that promote cell adhesion. In this study, we modified the surface of porous silicon surface by ozone oxidation, silanisation or coating with collagen or serum. For each surface, topography was characterised using atomic force microscopy, wettability by water contact angle measurements, degradation in aqueous buffer by interferometric reflectance spectroscopy and surface chemistry by Fourier-transform infrared spectroscopy. The adhesion of rat pheochromocytoma (PC12) and human lens epithelial cells to these surfaces was investigated. Cells were incubated on the surfaces for 4 and 24 h, and adhesion characteristics were determined by using a fluorescent vital stain and cell counts. Collagen coated and amino silanised porous silicon promoted cell attachment for both cell lines whereas cells attached poorly to ozone oxidised and polyethylene glycol silanised surfaces. We showed that the two cell lines had different adhesion characteristics on the various surfaces at different time points. The use of the vitality assays Alamar Blue (redox based assay) and neutral red (active cellular uptake assay) with porous silicon was also investigated. We reveal incompatibilities between certain resazurin (Alamar Blue), lysosomal incorporation assays (neutral red) and porous silicon.

Animals↗
PubMed1997

Role of physiological conditions in the oropharynx on the adherence of respiratory bacterial isolates to endotracheal tube poly(vinyl chloride).

Pneumonia is a major problem in intensive care patients and can be induced by pathogenic bacteria adhering to poly(vinyl chloride) (PVC) endotracheal (ET) tubes. This study examines the influence of surface properties on the adherence of the respiratory isolates Staphylococcus aureus and Pseudomonas aeruginosa to PVC. In particular, the influence of respiratory tract physiological conditions, 5% CO2 and saliva, on adherence was investigated. In general, decreased adherence to PVC was observed when bacteria were grown in CO2. When these CO2-grown bacteria were treated with saliva their adherence to PVC significantly increased; however, their adherence was significantly reduced to saliva-treated PVC. Treatment of both bacterial isolates with saliva decreased their negative zeta potential, a factor which may directly contribute to the observed increased microbial (saliva pretreated) adherence to PVC. Cell surface hydrophobicity (CSH) was evaluated by measuring the initial rates of microbial removal from a buffered aqueous phase, to ensure the absence of electrostatic interactions, to an organic phase (xylene). Under physiological conditions, CSH did not appear to be a dominant factor in biomaterial adherence as the CSH of S. aureus was decreased by saliva treatment but was unchanged for Ps. aeruginosa. Additionally, CSH also differed for the two isolates when grown in CO2, significantly decreasing with S. aureus but remaining unaltered with Ps. aeruginosa. Saliva treatment of PVC also decreased the advancing and receding contact angles of the biomaterial and its surface roughness, which may be a factor in the decreased adherence of saliva-treated bacteria to this surface. Alternative biomaterials or surface modifications appear necessary for the desired improvements in ET tube effectiveness. This study highlights the influence of physiological conditions on biomaterial and bacterial surface characteristics and subsequent interactions. It is imperative that the physiological conditions predominating in the clinical area of biomaterial use be considered when investigating device biocompatibility.

Bacterial Adhesion↗
PubMed2001

Determining optimal surface roughness of TiO(2) blasted titanium implant material for attachment, proliferation and differentiation of cells derived from human mandibular alveolar bone.

In the complex process of bone formation at the implant-tissue interface, implant surface roughness is an important factor modulating osteoblastic function. In this study, primary cultures of osteoblast-like cells, derived from human mandibular bone, were used. The aim was to examine the effect of varying surface roughness of titanium implant material on cellular attachment, proliferation and differentiation. A recognized method of increasing surface roughness and enlarging the surface area of titanium implants is by blasting with titanium dioxide particles: the four specimen types in the study comprised surfaces which were machine-turned only, or blasted after turning, with 63-90 microm, 106-180 microm, or 180-300 microm TiO(2) particles, respectively. The specimens were analyzed by scanning electron microscopy and confocal laser scanning. The turned samples had the smoothest surfaces: average height deviation (S(a)) of 0.20 microm. The roughest were those blasted with 180-300 microm particles, S(a) value 1.38 microm. Blasting with intermediate particle sizes yielded S(a) values of 0.72 microm and 1.30 microm, respectively. Cell profile areas were measured using a semiautomatic interactive image analyzer. Figures were expressed as percentage of attachment. DNA synthesis was estimated by measuring the amount of [(3)H]-thymidine incorporation into trichloroacetic acid (TCA) insoluble cell precipitates. The specific activity of alkaline phosphatase was assayed using p-nitrophenylphosphate as a substrate. The ability of the cells to synthesize osteocalcin was investigated in serum-free culture medium using the ELSA-OST-NAT immunoradiometric kit. After 3 h of culture, the percentage of cellular attachment did not differ significantly between specimens blasted with 180-300 micromparticles and the turned specimens. All blasted surfaces showed significantly higher [(3)H]-thymidine incorporation than the turned surfaces (P<0.05), with the highest on the surfaces blasted with 180-300 microm particles. Osteocalcin synthesis by the cells in response to stimulation by 1,25(OH)2D3, was also significantly greater (P<0.05) on the surfaces blasted with TiO(2) particles. However, analysis of alkaline phosphatase activity disclosed no significant differences among the four surface modifications. It is concluded that in this cellular model, the proliferation and differentiation of cells derived from human mandibular bone is enhanced by surface roughness of the titanium implant. However, increasing the size of the blasting particles to 300 microm does not further increase the initial attachment of the cells compared to turned surfaces and those blasted with 63-90 microm particles.

Adolescent↗
PubMed1997

Ion implantation and protein coating of detachable coils for endovascular treatment of cerebral aneurysms: concepts and preliminary results in swine models.

OBJECTIVE: Complete anatomic obliteration remains difficult to achieve with endovascular treatment of wide-necked aneurysms using Guglielmi detachable platinum coils (GDCs). Ion implantation is a physicochemical surface modification process resulting from the impingement of a high-energy ion beam. Ion implantation and protein coating were used to alter the surface properties (thrombogenicity, endothelial cellular migration, and adhesion) of GDCs. These modified coils were compared with standard GDCs in the treatment of experimental swine aneurysms. METHODS: In an initial study, straight platinum coils were used to compare the acute thrombogenicity of standard and modified coils. Modified coils were coated with albumin, fibronectin, or collagen and underwent Ne+ ion implantation at a dose of 1 x 10(15) ions/cm2 and an energy of 150 keV. Coils were placed in common iliac arteries of 17 swine for 1 hour, to evaluate their acute interactions with circulating blood. In a second study, GDCs were used to treat 34 aneurysms in an additional 17 swine. GDCs were coated with fibronectin, albumin, collagen, laminin, fibrinogen, or vitronectin and then implanted with ions as described above. Bilateral experimental swine aneurysms were embolized with standard GDCs on one side and with ion-implanted, protein-coated GDCs on the other side. The necks of aneurysms were evaluated macroscopically at autopsy, by using post-treatment Day 14 specimens. The dimensions of the orifice and the white fibrous membrane that covered the orifice were measured as the fibrous membrane to orifice proportion. Histopathological evaluation of the neck region was performed by light microscopy and scanning electron microscopy. RESULTS: Fibronectin-coated, ion-implanted coils showed the greatest acute thrombogenicity (average thrombus weight for standard coils, 1.9 +/- 1.5 mg; weight for fibronectin-coated coils, 8.6 +/- 6.2 mg; P < 0.0001). By using scanning electron microscopy, an intensive blood cellular response was observed on ion-implanted coil surfaces, whereas this was rare with standard coils. At Day 14, greater fibrous coverage of the necks of aneurysms was observed in the ion-implanted coil group (mean fibrous membrane to orifice proportion of 69.8 +/- 6.2% for the ion-implanted coil group, compared with 46.8 +/- 15.9% for the standard coil group; P = 0.0143). CONCLUSION: The results of this preliminary experimental study indicate that ion implantation combined with protein coating of GDCs improved cellular adhesion and proliferation. Future application of this technology may provide early wound healing at the necks of embolized, wide-necked, cerebral aneurysms.

Animals↗
PubMed1987

[Effect of neuraminidase and x-rays (2 Gy and 8 Gy) on microvilli and membrane invaginations of Ehrlich ascites tumor cells in monolayer culture].

A monolayer culture (Eagle basal medium plus 10% of fetal calf serum) of Ehrlich ascites tumor cells was exposed to X-radiation with 2 Gy and 8 Gy and treated with Vibrio cholerae neuraminidase alone or combined with sublethal X-ray irradiation (2 Gy). Pictures of the Ehrlich ascites tumor cells taken with the electron microscope were investigated in order to find out any cell surface modifications due to membrane invaginations and microvilli. The results showed that the rate of microvilli as well as that of membrane invaginations became higher with the increasing X-ray dose (2 Gy; 8 Gy). Following to neuraminidase treatment there was a considerable augmentation of membrane invaginations as compared to control cells, whereas the number of microvilli was slightly reduced. As it has been already described before, the influence of neuraminidase produced an increased endocytosis activity and a strengthening of the cytoskeleton. Combined treatment with neuraminidase and sublethal X-radiation (2 Gy) caused a higher rate of membrane invaginations than each method alone; the number of microvilli was slightly increased by combined treatment. The conclusion is drawn that these structure modifications are due to reparation processes induced by radiation on the one hand and to an enzymic action of neuraminidase on the cell surface on the other hand.

Animals↗
PubMed2005

The effect of irradiation modification and RGD sequence adsorption on the response of human osteoblasts to polycaprolactone.

Using techniques of tissue engineering, synthetic substitutes can be applied for the repair and regeneration of damaged bone. It has been found that material surface properties are crucial for cell adhesion and spreading, i.e. cell activities that are related directly to the ability of osteoblasts to proliferate. This fact has promoted the strategy of creating an ECM-like layer onto materials, so as to influence the cell response. In this study human bone-derived osteoblasts have been used to test the effects of surface modification by low energy ion beams of a poly epsilon-caprolactone (PCL) substrate and subsequent RGD adsorption. Osteoblasts were seeded and grown onto untreated and irradiated poly epsilon-caprolactone films, with or without RGD-adsorption step, and viability, morphology, and spreading of the osteoblasts were studied at different time endpoints. Differences were observed in the organization of cytoskeleton within cells: stress fibers were more evident in irradiated samples vs. untreated and total cell adhesion was higher. Surface characterization by X-ray Photoelectron Spectroscopy, Atomic Force Microscopy, and surface free energy measurements showed that the polar character of PCL, i.e., the acid-base term, was increased following irradiation treatment. Moreover the irradiated PCL had a nano-sized topography, which also could improve osteoblasts adhesion. We found that the treatment of the surface with ion beam is per se improving osteoblasts adhesion and spreading onto PCL. Furthermore, also if a significant RGD adsorption was obtained for irradiated PCL surfaces, it was found that in the investigated conditions it seems to have only a minor effect on the cell response. This study suggests that new strategies involving irradiation-based treatments can be adopted to promote the initial steps of bone deposition onto synthetic surfaces, exploiting the surface-induced reorganization of the ECM matrix.

Adsorption↗
PubMed2005

A study of biologically active peptide sequences (P-15) on the surface of an ABM scaffold (PepGen P-15) using AFM and FTIR.

Cellular response to any biomaterial surface is governed by a number of factors including topography, surface chemistry, surface charge, structural heterogeneity, and physiological conditions. Understanding these factors at the nanoscale level is crucial to develop improved biomaterials. Any changes in these properties due to surface modifications need to be addressed properly, as they could have significant impact on the cellular interaction with biomaterials. In this study, the topography and surface chemistry of commercially available tissue engineered xenograft, PepGen P-15 [comprised of a synthetic peptide P-15 irreversibly attached to anorganic bovine bone mineral (OsteoGraf/-N)] was studied using Atomic Force Microscopy (AFM), and Fourier Transform Infrared Spectroscopy (FTIR). FTIR confirmed the presence of the peptide on the surface of PepGen P-15. Changes in the peptide conformation, which includes a decrease in the beta-strand accompanied by an increase in unordered structures/random coil structures after attachment on OsteoGraf/-N is observed. Specific functional groups, which are involved in the binding mechanism, are identified. The results suggest that the attachment of the peptide on OsteoGraf/-N occurs via a specific surface docking ionic interaction involving the C-terminal carboxylic group on the peptide with positive domains generated by hydroxyl vacancies on the apatite surface.

Animals↗
PubMed2006

Fluorescence spectroscopic studies on plasma-chemically modified polymer surfaces with fluorophore-labeled functionalities.

Molecular engineering of polymer surfaces that includes the attachment of functional molecules to existing or previously generated reactive chemical groups like e.g., -OH, -NH2, or -CHO requires simple strategies and tools for the controlled generation of surface functionalities and their derivatization as well as for their identification and eventually quantification. Here, we systematically investigate the plasma-chemical surface modification of polypropylene films in combination with dansyl labeling chemistry and conventional, yet costly, XPS and highly sensitive fluorescence spectroscopy for the detection of surface groups. Based on these results, the potential of and requirements on the fluorometric characterization and quantification of surfaces functionalities are discussed.

Fluorescent Dyes↗
PubMed2004

Polyurethane vascular catheter surface grafted with zwitterionic sulfobetaine monomer activated by ozone.

Polyurethane (PU) is a conventional biomedical material with favorable biocompatibility and excellent mechanical properties and widely used in making vascular catheter, but its antithrombogenic property is not good enough to make it as a more demanding applicable biomaterial. Surface modification is an effective way to improve the hemocompatibility for biomaterials. The purpose of present study was to use ozonization method to modify the surface of PU vascular catheter slice to improve its antithrombogenicity by grafting N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a zwitterionic sulfobetaine monomer. PU vascular catheter (PUVC) grafted with DMMSA (PUVC-g-PDMMSA) was characterized by ATR-FTIR and XPS. ATR-FTIR and XPS investigation confirmed the graft polymerization. The blood compatibility of the grafted films was evaluated by platelet rich plasma (PRP) platelet adhesion study and scanning electron microscopy (SEM) was used to observe the morphology of platelet using PU vascular catheter (PUVC) as the reference. No platelet adhesion was observed for the grafted PUVC slice incubated with PRP at 37 degrees C for 120 min. It is significant that this new zwitterionic sulfobetaine grafted PUVC have improved antithrobogenicity. It is effective that the inner surface of vascular catheter with inner diameter in only 3mm can be grafted with PDMMSA by using ozonization method.

Betaine↗
PubMed2006

Improving dispersion of nanometer-size diamond particles by acoustic cavitation.

A novel acoustic-dispersion method for fine diamond particles was developed. Two samples of nanometer-sized diamond particles were used. They had primary particle sizes of 5 nm (ND5) and 150 nm (ND150). Disaggregation of agglomerated particles using ultrasound and surface modification of ND5 and ND150 were investigated. The ND5 and ND150 particles aggregated to secondary particles, having sizes on the order of micrometers. The surfaces of ND5 and ND150 particle were modified due to chemical reactions and the particles were disaggregated by acoustic cavitation. The ND5 particles were disaggregated to give an average particle size of about 100 nm by ultrasound exposure with average acoustic intensities higher than 800 W/m(2). The agglomerated ND150 particles with size of 15 microm were disaggregated to reach an average particle size of about 300 nm by ultrasound exposure with an average acoustic intensity higher than 2000 W/m(2). The surfaces of ND5 and ND150 particles were found to be modified with hydroxyl groups resulting from acoustic cavitation. This could lead to a well dispersed solution of nanometer-sized diamond particles in water.

Journal Article↗
PubMed2003

Control of electroosmotic flow and wall interactions in capillary electrophoresis capillaries by photografted zwitterionic polymer surface layers.

A novel capillary with covalently bonded zwitterionic surface modification was prepared by photograft polymerization of the zwitterionic monomer N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine, onto the inner surface of a UV-transparent fused-silica capillary. Although the zwitterionic moieties in the resulting polymeric "tentacles" comprise both a positive quaternary ammonium group and a negative sulfonate group, the coating has a net zero charge. The electroosmotic flow (EOF) was therefore extensively suppressed on the grafted capillary compared to the native silica capillary and to the silica capillary that had been activated for graft polymerization by reaction with 3-(methacryloyl)oxypropyltrimethoxysilane. It was also found that the EOF can be varied by adding chaotropic anions or divalent cations such as perchlorate ion and magnesium ion to the running buffer, due to the interaction between these ions and zwitterionic functional group. This provides a new way of altering the EOF and the wall interaction without changing the pH or the overall ionic strength of the separation buffer. The influence of pH and ionic strength of separation buffer on the EOF were also investigated to optimize the separation conditions. Good separations of a mixture containing eight inorganic anions were achieved within 5 min under optimal conditions by capillary zone electrophoresis. The newly prepared capillary was also well suited for the separation of peptides or proteins.

Anions↗
PubMed2006

Fabrication and investigation of nanostructures on transition metal dichalcogenide surfaces using a scanning tunneling microscope.

Nanometer-scale holes have been fabricated on the surfaces of the semiconducting transition metal dichalcogenides (TMDCs) molybdenum ditelluride (MoTe2) and molybdenum disulfide (MoS2) by applying voltage pulses from the tip of a scanning tunneling microscope (STM) operating in ultrahigh vacuum (UHV). It was found that the tip geometry (tip shape and sharpness) influences the formation and structure of the atomic-scale nanostructures. Threshold voltage ranges for the surface modification of MoTe2 (3.0 +/- 0.3 V) and MoS2 (3.4 +/- 0.3 V) were determined. Negative sample voltage pulses applied to a p-type MoTe2 surface produced much larger and deeper nanometer-scale holes when compared with those produced by positive voltage pulses. The existence of threshold voltages and the pulse polarity dependence of nanostructure fabrication suggests that an electric field evaporation mechanism is applicable. Support for this mechanism was obtained by nanostructuring metallic TMDC NbSe2, where both the produced features and the threshold voltages (3.0 +/- 0.3 V) were similar for both positive and negative voltage pulses.

Journal Article↗
PubMed1998

A histomorphometric evaluation of screw-shaped implants each prepared with two surface roughnesses.

Four different surface modifications were designed. Forty screw-shaped implants were divided into 4 groups, 10 screws in each. Every screw was prepared with 2 different surface topographies. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using 1 height, 1 spatial and 1 hybrid descriptive parameter. After 12 weeks in rabbit bone all screws were histomorphometrically evaluated. Blasted surfaces demonstrated more bone in contact to implant surface compared with turned surfaces. Most bone in close contact to implant surface was found for a surface blasted with 75 microns sized particles, numerically characterized with an average height deviation (Sa) of 1.4 microns, an average wavelength (Scx) of 11.6 microns and a developed surface area ratio (Sdr) of 1.5.

Aluminum Oxide↗
PubMed1992

Plaque formation in vivo and bacterial attachment in vitro on permanently hydrophobic and hydrophilic surfaces.

Highly hydrated polyethylene oxide (PEO) films represent one type of surface modification which may interfere with biofilm formation. Protein adsorption and saliva-mediated bacterial adherence were investigated in vitro on normal and hydrophobized glass surfaces and on glass surfaces with immobilized PEO films. More protein and bacteria bound to untreated compared to hydrophobized and PEO-treated glass. Pellicle and plaque formation was also studied in vivo on ceramic crown surfaces either untreated, hydrophobized or with immobilized PEO films. Pellicle and plaque formation was similar on the untreated ceramic and PEO surfaces. Less plaque seemed to collect on these surfaces compared to adjacent normal tooth surfaces. Almost no plaque accumulated on the hydrophobic crown surface and it was virtually devoid of stainable pellicle. Even after 7 days in the mouth without oral hygiene this surface was very hydrophobic and the disclosing solution could not spread.

Actinomyces↗
PubMed1990

The effect of chemical modification of quartz surfaces on particulate-induced pulmonary inflammation and fibrosis in the mouse.

One of the critical steps in the development of crystal-induced lung diseases is thought to be the interaction of crystal surfaces with cell membranes. The effect of chemical modifications of the surface of alpha-quartz on the development of lung disease has been investigated by treating quartz with various organosilanes. The functional groups attached to the quartz surfaces were (-CN), (-CH3), (-NH2), and -(N(CH3)3+). After intratracheal injection of each modified crystal at a constant surface area into mice, pulmonary inflammation and fibrosis were assessed 6 wk postexposure to the crystals by lung wet weight (lung index) and by the level of hydroxyproline in the lung. The crystals showing the highest degree of biologic activity were native quartz, which has a negative charge, -N(CH3)3+ modified quartz, which has a positive charge, and -CN modified quartz, which has no charge. One of the crystals with chemical groups capable of hydrogen bonding, the -NH2 modified quartz, was as unreactive as the crystal preparation modified with a hydrophobic group, -CH3. If the -CH3 and -NH2 modified quartz are compared as a less reactive group with the more reactive native quartz and -N(CH3)3+ modified quartz, these experiments suggest that electrostatic interactions may be more important in determining effective biologic activities than are hydrogen bonding interactions.

Animals↗
PubMed2004

[The effect of the surface morphology of Ti-implants on the proliferation activity of fibroblasts and osteoblasts].

It is known that surface morphology greatly influences the osseointegration of dental implants. The goal of the experiments conducted by the authors was to study in vitro the effect of various surface modifications on the activity of bone and connective tissue cells. In the experiments they introduced NIH3T3 fibroblast and MCH3T3 osteoblast cells were cultured the surface of ten titanium disks with various morphology in 24-multiwell plates. The cells were let grow on the surface of the disks for two days in a culture medium. One group of the disks underwent scanning electronmicroscopy and the changes in the number and form of cells on the surfaces were studied under various magnifications. From the surface of the second group the cells were lysed and were counted in a Bürker's chamber. After counting the cells they were lysed in a lysis buffer and their protein concentrations were measured with the help of a spectrophotometer. The authors found that only a morphological study of the cells is possible under SEM, they could not detect a quantitative difference in the number or activity of the cells. Upon counting the cells and determining their protein concentration the best result were yielded by the surface roughened by aluminium oxide. In growing fibroblasts the titanium oxide treated surfaces provided good results, while in the case of the osteoblasts the laser treated disks were more successful.

Cell Proliferation↗