Biomedical subjects

J Lausmaa

Publications and source records attributed to J Lausmaa.

At least 19 recordsLinked to original sources

PubMed2001

Interactions between human whole blood and modified TiO2-surfaces: influence of surface topography and oxide thickness on leukocyte adhesion and activation.

An in vitro model (Nygren et al., J Lab Clin Med 129 (1997) 35-46) was used to investigate interactions between leukocytes and four modified TiO2-surfaces. Surface topography was measured using scanning electron microscopy and optical profilometry while Auger electron spectroscopy was used to determine surface composition and oxide thickness. The surfaces were either smooth or rough with either thin or thick oxides. All surfaces consisted of TiO2 covered by a carbonaceous layer. The surfaces were incubated with capillary blood for time periods of between 8 min and 32 h. Immunofluorescence techniques together with computer aided image analysis and chemiluminescence technique were used to detect cell adhesion, expression of adhesion receptors and the zymosan-stimulated respiratory burst response. Leukocyte adhesion to the surfaces increased during the first hours of blood-material contact and then decreased. Polymorphonuclear granulocytes were the dominating leukocytes on all surfaces followed by monocytes. Cells adhering to rough surfaces had higher normalized expression of adhesive receptors than cells on smooth surfaces. Maximum respiratory burst response occurred earlier on the smooth than on the rough surfaces. In conclusion, topography had a greater impact than oxide thickness on most cellular reactions investigated, but the latter often had a dampening effect on the responses.

Antigens, CD↗

PubMed2001

Structure and surface of TiNi human implants.

The surface and the "bulk" structure of TiNi implants were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS), and scanning Auger microprobe analysis (AES). TiNi implants were compared with otherwise identically prepared non-implanted specimens, and sputter-cleaned and reoxidized samples. Non-implanted and implanted samples had essentially the same surface topography and microstructure. Ti, O, and C were the dominant elements detected on the surface. Trace amounts (approximately 1 at%) of Ni and Ca, N, Si, B, and S were also detected. Ti was present as TiO2 on the surface, while nickel was present in metallic form. A significant difference in Ni peak intensity was observed when retrieved or non-implanted control samples (a very low nickel content) were compared with sputter-cleaned and reoxidized samples (well-detected nickel). It is evident that the method of passivation is crucial for nickel loosening. No major changes occurred in the TiNi samples bulk structure or in the surface oxide during the implantation periods investigated.

Biocompatible Materials↗

PubMed2001

Contamination of polyethylene cups with polymethyl methacrylate particles: an experimental study.

The articulating surfaces of 6 ultra-high molecular weight polyethylene cups were exposed to curing polymethyl methacrylate (PMMA) bone-cement and examined with scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Three of the cups were exposed to blood and bone-cement, and the rest were exposed to bone-cement only. After removal of the bone-cement bulk, PMMA particles were found and identified in all 6 cups. The particles were verified by identifying zirconium with energy-dispersive x-ray fluorescence spectroscopy in 5 cups and with LA-ICPMS in 1 cup. The degree of surface contamination was estimated with LA-ICPMS. The number of zirconium-containing particles detected was on average 10 to 20/mm2. PMMA bone-cement left in polyethylene cups during polymerization can contaminate the articulating surface with adherent PMMA particles.

Bone Cements↗

PubMed1999

Surface characterization, protein adsorption, and initial cell-surface reactions on glutathione and 3-mercapto-1,2,-propanediol immobilized to gold.

Monolayers of glutathione (GSH) and 3-mercapto-1,2-propanediol (MG) on gold were tested for their bioreactivity by assessing the degree of inflammatory reaction as manifested by the adherence and activation of platelets and white blood cells (wbc) after exposure to blood ex vivo. Surface composition was characterized by XPS, and noncontact optical profilometry was used to determine surface roughness. The thickness and composition of the adsorbed protein layers were measured by ellipsometry/antibody techniques in vitro. Cell adhesion and activation were quantified by acridine orange staining, fluorescein-diacetate staining, and by specific antibodies against cell membrane antigens. Distinct differences among the surfaces were observed relative to the amounts and composition of adsorbed plasma proteins and the adhesion and activation of platelets (CD62P-exposure) and wbc (CD11b/CD18-exposure). GSH surfaces, which adsorbed the least amount of plasma protein, caused the least adherence and activation of platelets (CD62P), followed by the highest activation of wbc (CD11b/18). The MG surfaces caused a rapid recruitment and activation of platelets (CD62P), followed by a lower activation of wbc (CD11b/18). Thus it appears that measurements of the initial adsorption of plasma protein from anticoagulated plasma and of the adhesion and activation of platelets after 8 min of exposure to whole blood cannot be used to predict accurately the adhesion and activation behavior of inflammatory cells after longer periods (2 h) of exposure on different surfaces.

Adsorption↗

PubMed1999

Adsorption and coadsorption of water and glycine on TiO2.

Adsorption of water, ions, and biomolecules constitutes the first events occurring at biomaterial-biosystem interfaces. In this work, the adsorption and coadsorption of water and glycine on TiO2 were studied by thermal desorption spectroscopy (TDS). The first water monolayer desorbs in three peaks around 180K, 300K, and 400K, which are assigned to water molecularly adsorbed at oxygen sites, at Ti4+ sites, and to recombination of dissociated water, respectively. A fourth desorption peak (160K), appearing at coverages > 0.8 monolayer, is attributed to water clusters and multilayers. The water-TiO2 interaction is changed if the surface is annealed in vacuum, which leads to increased hydroxylation. Desorption spectra from glycine overlayers evaporated on TiO2 in situ show that around 40% of the first monolayer desorbs as intact molecules ( approximately 300-450 K) and the remainder as dissociation fragments and surface reaction products around 600 K. At coverages > 0.6 monolayers, intact molecules desorbing from cluster multilayers at 310 K are detected. The glycine desorption spectra are unaffected by coadsorbed water. In contrast, coadsorption of glycine displaces water from more strongly bound states in the monolayer to more weakly bound states and clusters, making the surface more hydrophobic. The study shows that TDS is a powerful method for characterizing biomaterial surfaces with regard to their interaction with biologically relevant molecules.

Adsorption↗

PubMed1999

Surface analysis of failed oral titanium implants.

The aim of the present study was to investigate the surface topography, composition, and oxide thickness of consecutively failed, oral Brånemark implants in order to determine possible causes for failure. The failure criterion was lack of osseointegration manifested as implant mobility. Ten implants were retrieved before loading (early failures) and 12 during a period of function up to 8 years (late failures). At retrieval, early losses did not display any clinical sign of infection. All late failures were radiographically characterized by peri-implant radiolucency and did not show infectious signs with one exception. No implant seemed to be lost due to peri-implantitis (plaque-induced progressive marginal bone loss). Twelve implants were analyzed by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and depth profiling using a blind protocol. Two pristine fixtures, which underwent the same preparation as the failed implants, were used as controls. In the SEM, control samples were essentially free from macroscopic contamination, whereas failed implants contained varying amounts of tissue residues. AES showed that all surfaces consisted of Ti oxide and varying amounts of additional elements, with C dominating in most cases. Nitrogen and sometimes Na, Ca, P, Cl, S, and Si were detected. The Si contamination was most likely due to ion leaching from the glass vials used for storage. Depth profiles showed a typical oxide thickness of 5-8 nm for all samples. In conclusion, no significant changes in the oxide layer composition or thickness as a result of implantation were observed. The results do not indicate any material-related cause for the failures of these implants. Possible reasons for these failures were impaired healing, asymptomatic infection, and overload.

Adult↗

PubMed1997

Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials.

Glow discharge plasma treatment is a frequently used method for cleaning, preparation, and modification of biomaterial and implant surfaces. The merits of such treatments are, however, strongly dependent on the process parameters. In the present work the possibilities, limitations, and risks of plasma treatment for surface preparation of metallic materials are investigated experimentally using titanium as a model system, and also discussed in more general terms. Samples were treated by different low-pressure direct current plasmas and analyzed using Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), atomic force microscopy, scanning electron microscopy, and light microscopy. The plasma system is a home-built, ultra-high vacuum-compatible system that allows sample introduction via a load-lock, and precise control of pressure, gas composition and flow rate, etc. This system allows uniform treatment of cylindrical and screw-shaped samples. With appropriate plasma parameters, argon plasma remove all chemical traces from former treatments (adsorbed contaminants and other impurities, and native oxide layers), in effect producing cleaner and more well-controlled surfaces than with conventional preparation methods. Removal (sputtering) rates up to 30 nm/min are possible. However, when inappropriate plasma parameters are used, the result may be increased contamination and formation of unintentional or undesired surface layers (e.g., carbides and nitrides). Plasma-cleaned surfaces provide a clean and reproducible starting condition for further plasma treatments to form well-controlled surface layers. Oxidation in pure O2 (thermally or in oxygen plasmas) results in uniform and stoichiometric TiO2 surface oxide layers of reproducible composition and thicknesses in the range 0.5-150 nm, as revealed by AES and XPS analyses. Titanium nitride layers were prepared by using N2 plasmas. While mild plasma treatments leave the surface microstructure unaffected, heavy plasma treatment can give rise to dramatic morphologic changes. Comparison of these results with corresponding analyses of commercial implants and electropolished and/or anodically oxidized samples shows that the plasma treatment offers superior control of the surface status. However, it is also shown that improper control of the plasma process can produce unwanted and irreproducible results.

Argon↗

PubMed1997

Adhesion and activation of platelets and polymorphonuclear granulocyte cells at TiO2 surfaces.

The initial reactions of two TiO2 surfaces with blood were investigated by short-time exposure to capillary blood and analysis of surface-adsorbed plasma proteins and surface-adhering cells by using immunofluorescence techniques. Antibodies directed against platelet membrane antigen and P-selectin were used to visualize platelet adhesion and activation. Acridine orange and anti-CD11b were used to detect adhesion and activation of polymorphonuclear granulocytes (PMNs). Antibodies against thrombospondin were used as markers for platelet alpha-granules. The fluorescence intensity was quantitated by computer-aided image analysis. Commercially pure, polished sheet titanium was oxidized in two different ways: (1) the natural oxide was dissolved with hydrofluoric acid and a new oxide layer was grown by oxidation in nitric acid, or (2) annealing was performed at 700 degrees C in air. Auger electron spectroscopy and x-ray photoelectron spectroscopy showed that both surfaces had similar composition consisting of TiO2 covered by a carbonaceous surface contamination layer. The thickness of the oxide layer was 4 nm on the acid-oxidized surface and 39 nm on the annealed surface. Optical profilometry and scanning electron microscopy showed that the acid-oxidized surface was rough and the annealed surface was smooth. The fibrinogen/prothrombin-thrombin ratio in the initial protein film differed between the surfaces. The number of adhering platelets was larger at the surface with a high surface concentration of adsorbed fibrinogen. Platelet activation (CD62) and priming of PMNs (CD 11b) were also significantly higher on the acid-oxidized surface. The results indicate that non-self recognition of biomaterials is an array of transient reactions comprising protein-material, protein-cell, and cell-cell interactions.

Biocompatible Materials↗

PubMed1997

Bone response to surface modified titanium implants - studies on the tissue response after 1 year to machined and electropolished implants with different oxide thicknesses.

The bone formation around titanium implants with varied surface properties was investigated after 1 year in rabbits. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits. Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads. There were no significant differences between the differently prepared implant groups. Our study shows that a high degree of bone contact and bone formation is achieved after 1 year with titanium implants which are modified with respect to oxide thickness and surface topography. There is no indication that a reduction of surface roughness, which in the initial phase decreases the rate of bone formation, had any influence on the amount of bone after 1 year in rabbit cortical bone.

Journal Article↗

PubMed1997

Surface characterization and biological evaluation of spark-eroded surfaces.

Forty commercially pure titanium implants were prepared with a spark-eroding process in order to create highly increased surface roughnesses. Two degrees of roughness were achieved by altering the applied current. Surface topographical characterization was performed with SEM and an optical profilometer. The surface composition and oxide layer were investigated using Auger scanning microscopy. In the present study, there was a large difference between the stipulated and measured surface roughness, indicating the need for a careful surface characterization in each new study. After 12 wk in rabbit bone, no statistically significant difference was found with respect to peak removal torque and histomorphometric analyses. The results from the present study provide no support for further increase of the surface roughness than that possible to achieve with a blasting technique.

Journal Article↗

PubMed1997

Structure of the interface between rabbit cortical bone and implants of gold, zirconium and titanium.

The role of surface properties (chemical and structural) for the interaction between biomaterials and tissue is not yet understood. In the present study, implants made of titanium, zirconium (transition metals with surface oxides) and gold (metallic surface) were inserted into the rabbit tibia. Light microscopic (LM) morphometry showed that after 1 and 6 mo the gold implants had less amount of bone within the threads and a lower degree of bone-implant contact than the titanium and zirconium implants, which did not differ from each other. These quantitative differences were supported by LM and ultrastructural observations of the interface. The ultrastructural observations in addition demonstrated that the layer of non-collagenous amorphous material located between the implant and the calcified bone was appreciably thicker around zirconium than around titanium implants. The factors potentially responsible for the observed morphological differences in the bone around the different material surfaces are discussed.

Journal Article↗

PubMed1996

Torque and histomorphometric evaluation of c.p. titanium screws blasted with 25- and 75-microns-sized particles of Al2O3.

A comparison was made between screw-shaped c.p. titanium implants blasted with either 25- or 75-microns particles of Al2O3. The implant surfaces were investigated with respect to topography and composition before implantation in rabbit bone. Grit blasting with 25- or 75-microns particles produced two different surface roughnesses, but no significant difference in the surface composition for the two surfaces. After 12 weeks insertion time in the rabbit tibia and femur, a higher removal torque and more bone-to-metal contact was found for the implants blasted with 75-microns particles compared with the 25-microns-blasted ones.

Aluminum Oxide↗

PubMed1996

Bone response to surface-modified titanium implants: studies on the early tissue response to machined and electropolished implants with different oxide thicknesses.

The bone formation around titanium implants with varied surface properties is investigated. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits (1, 3 and 6 weeks). Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition, between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads at 6 weeks. The smooth, electropolished implants, irrespective of anodic oxidation, were surrounded by less bone than the machined implants after 1 week. After 6 weeks the bone volume as well as the bone-implant contact were lower for the merely electropolished implants than for the other three groups. Our study shows that a high degree of bone contact and bone formation are achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, the result with the smooth (electropolished) implants indicates that a reduction of surface roughness, in the initial phase, decreases the rate of bone formation in rabbit cortical bone.

Animals↗

PubMed1994

Titanium with different oxides: in vitro studies of protein adsorption and contact activation.

Adsorption of albumin (HSA) and fibrinogen (Fib) from human blood plasma onto titanium surfaces with varying oxide properties was studied with an enzyme-linked immunosorbent assay. The intrinsic activation of blood coagulation (contact activation) was studied in vitro using a kallikrein-sensitive substrate. The sample surfaces were characterized with Fourier transform Raman spectroscopy. Auger electron spectroscopy and atomic force microscopy. Low Fib and high HSA adsorption was observed for all titanium samples except for the radio frequency plasma-treated and water-incubated samples, which adsorbed significantly lower amounts of both. Oxide thickness and carbon contamination showed no influence on protein adsorption or contact activation. Smooth samples with a surface roughness (Rrms) < 1 nm showed some correlation between surface wettability and adsorption of Fib and HSA, whereas rough surfaces (Rrms > 5 nm) did not. To varying degrees, all titanium surfaces indicated activation of the intrinsic pathway of coagulation as determined by their kallikrein formation in plasma.

Adsorption↗

PubMed1994

Bone response to surface modified titanium implants: studies on electropolished implants with different oxide thicknesses and morphology.

In a series of experimental studies, bone formation was analysed around systematically modified titanium implants. In the present study, machined, electropolished and anodically oxidized implants were prepared, surface characterized and inserted in the cortical bone of rabbits (7 wks and 12 wks). SEM, scanning Auger electron spectroscopy and atomic force microscopy revealed no differences in surface composition but marked differences in oxide thickness, surface topography and roughness. Light microscopic morphology and morphometry showed that all implants were in contact with bone, and had a large proportion of bone within the threads. The smooth, electropolished implants were surrounded by less bone than the machined implants with similar oxide thickness, (4-5 nm) and the anodically oxidized implants with thicker oxides (21 nm and 180 nm, respectively) after 7 wks. These studies show that a high degree of bone contact and bone formation can be achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, it appears that a reduction of surface roughness may influence the rate of bone formation in rabbit cortical bone.

Animals↗

PubMed1994

Site-specific adhesion of Staphylococcus epidermidis (RP12) in Ti-Al-V metal systems.

Staphylococcus epidermidis (RP12) adhesion patterns were studied on the following titanium (Ti)-aluminium (Al)-vanadium (V) metal systems: (i) microfabricated samples consisting of Ti, Al and V islands deposited onto Ti or V substrata, (ii) pure Ti, Al and V metals, and (iii) medical grade Ti6Al4-V alloy. All of these surfaces were covered with their respective oxides formed upon exposure of the metals to air. Quantitative analysis of the number of cells bound per unit area indicates that S. epidermidis (RP12) exhibits greatest adhesion to pure V surfaces. When exposed to surfaces having controlled spatial variations in chemical composition on the 10 microns scale (microfabricated samples), the bacteria preferentially populate V islands versus Ti or Al substrata. In the case of the biphasic Ti6Al4V alloy, the bacteria tend to adhere to V-rich, mixed phase regions and phase boundaries. These findings demonstrate that enhanced and preferential adhesion of S. epidermidis (RP12) occurs on V surfaces in Ti-Al-V metal systems and suggest that bacterial interactions are influenced by surface oxide composition.

Alloys↗

PubMed1994

Material-tissue interfaces: the role of surface properties and processes.

The introduction of a foreign material into living tissue--intentionally as in biomedical applications (implants, protheses, drugs) or unintentionally as when minerals or fibers are inhaled--results in the creation of interfaces between the material and the surrounding tissue. This article identifies and discusses the possible role of material surface properties and molecular processes occurring at such interfaces. For kinetic and thermodynamic reasons, surfaces are different from the corresponding bulk of the material, and contain reactive (unsaturated) bonds, which in turn lead to the formation of surface reactive layers (e.g., surface oxides on metals) and adsorbed contamination layers. The encounter with the biological environment leads to further surface reactions modifying the surface, and to the adsorption of water, ions, and biomolecules, which are continuously exchanged. The exact nature of the dynamic, adsorbed water, ions, and biomolecule coating in turn influences the behavior of cells approaching the material surface, and hence the tissue response.

Animals↗

PubMed1991

Preparation of ultra-thin oxide windows on titanium for TEM analysis.

Using submerged jet electropolishing, extremely thin (less than 10 nm), continuous, thermal oxide "windows" have been prepared on polycrystalline titanium (Ti). The preparation technique is described in detail. It has allowed a systematic investigation of the structure of thermal surface oxide layers on Ti in the thickness range 6-40 nm, corresponding to oxidation temperatures 100-450 degrees C. Auger electron spectroscopy was used for oxide characterization and for depth profiling to determine oxide thickness. The thinnest oxides, less than 10 nm, are amorphous, morphologically homogeneous, and with essentially no contrast in the transmission electron microscopy (TEM) pictures. As the oxide thickness is increased up to 40 nm, a texture corresponding to the grain structure of the oxidized metal becomes gradually more visible. At the same time the oxide becomes increasingly more crystalline. The results are compared with previously published corresponding results for thicker anodic oxides on Ti.

Microscopy, Electron↗