bluuebunny/crossref_metadata_2025 huggingface dataset:
Short‐term cell‐attachment rates: A surface‐sensitives test of cell–substrate compatibility
Authors: Vogler E. A. , Bussian R. W.
Published: December 2004

Mechanisms of cell deposition from a sessile liquid phase and adherence to various plastic substrates have been investigated by measurement of short‐term (<120 min) cell‐attachment rates. Sigmoidal attachment‐rate curves were fit with a three‐parameter variant of a logistic equation to quantify parameters related to initial rate and equilibrium‐adherence. For substrates on which cell adhesion was low, initial rates were estimated from slopes of linear bestfit equations. Average variations in adherence parameters for three cell lines, MDCK (epithelioid), VERO, and AHL‐1 (fibroblastic) to tissue‐culture grade polystyrene dishes were less than 10% (standard‐error‐of‐mean/mean × 100) over extended periods of more than two months, so that attachment measurements could be repetitively applied with the same cell stocks continuously subcultured in the laboratory. Developed techniques were applied to a variety of plastics and the results tabulated. Comparison of adherence parameters for ionomer and polyethylene films, both with and without adsorbed fetal‐bovineserum proteins, demonstrated that surface carboxyl groups were important in protein adsorption and cellular adherence. Attachment rates of MDCK to polystyrene were dependent on starting cell number whereas equilibrium adherence did not vary significantly over a wide range of inoculum concentrations. It was concluded from theoretical considerations that initial rates of MDCK attachment were sensitive to and dependent on electrostatic barriers to formation of close substrate contacts whereas equilibrium‐adherence levels were controlled by short‐range forces such as interfacial energies and formation of receptor‐ligand complexes.
Controlled release using a new bioerodible polyphosphazene matrix system
Authors: Laurencin C. T. , Koh H. J. , Neenan T. X. , Allcock H. R. , Langer Robert
Published: December 2004

Polyphosphazenes possess polymer backbones consisting of nitrogen and phosphorous formally separated by alternating single and double bonds. Their potential for biomedical applications stems from the fact that polymers with a wide array of properties can be synthesized using the same starting compound, poly(dichlorophosphazene), through changes in side chain substituents, and that many of these compounds synthesized have been found to biodegrade to harmless products. In this article, studies of a novel monolithic bioerodible polyphosphazene matrix system for controlled drug delivery are presented. Poly(imidazole methylphenoxy) phosphazene is synthesized and shown to be bioerodible. The versatility of drug delivery devices fabricated using this polymer is shown through studies of release of macro‐molecules and low molecular weight drugs. Initial histological evaluations of this particular polyphosphazene are also presented.
Newly made antibacterial braided nylon sutures. I. In vitro qualitative and in vivo preliminary biocompatibility study
Authors: Chu C. C. , Tsai W. C. , Yao J. Y. , Chiu Sindy S.
Published: December 2004

A new type of braided nylon thread with a silver compound coating was made for the purpose of designing a biocidal suture material. The study used standard bacterial culture techniques to evaluate the antibacterial prop‐erty of the new Ag‐coated nylon thread. Seven types of bacterial species were tested; S. aureus, E. coli, P. aeruginosa, K. pneumoniae, S. dysenteriae, S. maruslene, and P. mirabilis. The commercial size 2/0 Nurolon suture from Ethicon served as the control. A weak direct current ranging from 0.4–400 μA was applied to the specimens to examine whether the biocidal property of silver could be enhanced by current. The antibacterial property was evaluated by the width and sterility of the clear zone in the bacterial culture plates. It was found that the new nylon thread exhibited very good to moderate bactericidal property toward these seven bacterial species. P. aeruginosa was the most sensitive species, while P. mirabilis was the least sensitive one. Application of direct current through the Ag‐coated specimens positively enhanced their antibacterial property and the degree of enhancement depended on the direct current level. The material also exhibited an antibacterial property toward well‐established bacterial colonies, but the effect was less strong than the case when direct current was applied simultaneously with incubation. Silver ions released from the coated nylon thread were responsible for the observed antibacterial property; and the application of a weak direct current to the material enhanced this effect. A preliminary biocompatibility study of this new material in rat gluteal muscle indicated that the new material caused less inflammatory reaction than the control Nurolon suture up to 60 days after implantation.
Use of chemically purified and cross‐linked bovine pericardium as a ligament substitute
Authors: Chvapil Milos , Gibeault David , Wang Ti‐Fen
Published: December 2004

This study tested the reaction of a periarticular tissue to implanted pericardial membrane, substituting a segment of patellar ligament. Bovine pericardium was chemically purified and cross‐linked with monomeric glutaraldehyde under pH, temperature and time conditions minimizing the polymerization of the cross‐linking agent. Eight rats had both knee joint patellar ligaments excised. One side served as a control (simple suture), the other dissected ligament was replaced with a strip of pericardium. After 18 days and 12 weeks the dissected ligaments were analyzed by morphological methods. An unexpected fast ingrowth of cells and vessels was observed at 18 days. At 12 weeks new collagen deposits within pericardial patch were seen with striking biodegradation of the implant. Thus, using a new method of cross‐linking the collagenous matrix with glutaraldehyde we see no evidence of glutaraldehyde cytotoxicity, as documented by our previous work.
Characterization of the tissue proliferated at the blood interface of carbon/ceramic composites
Authors: Chignier Elza , Guidollet Jeanine , Dureau Georges , Grousson Brigitte , Buttazzoni Bernard , Louisot Pierre , Elloy Rosy
Published: December 2004

The present study focuses on cell adhesion/differentiation and material stability of surfaces of the three carbon/ceramic composites implanted in intra‐atrial position in dogs for 1 year. Before implantation their surface was characterized by scanning electron microscopy. After harvesting, the tissue proliferated on the blood interface was examined by histology, scanning, and transmission electron microscopy, wavelength dispersive and x‐ray spectrometry, electrophoretic and enzymatic characterization of glycosaminoglycans (GAGs) which were compared to endocardiac tissue as control samples. One year after implantation, the pattern of GAGs in the newly developed tissue was characterized by: (1) a constant increase of the total GAGs present on all carbon composites, (2) a significant increase of dermatan sulfate (p < 0.05), (3) a significant increase of chondroitin sulfate (p < 0.05), (4) a significant decrease of heparan sulfate in Group 1, whereas this GAG fraction was increased in Groups 2 and 3. Cellular surface differentiation towards endothelial‐like cells occurred in places particularly in groups 1 and 3, whereas only fibrous tissue was found covering the implants in Group 2. Fibroblastic cells with dense intracellular deposits, which produced emission of Si, Ca, and C energy as well as extracellular lipidic containing inclusions were observed. The macromolecular modifications were associated with (1) the absence of endothelial lining, (2) the migration of carbon and silicon particles, and (3) the occurrence of calcifications and lipidic inclusions. These results suggest that the relative smoothness of these materials could be responsible for the development of a tissue that did not adhere to the biomaterial, indicating that cell adhesion and functional differentiation are in intimal relationship with the physical‐chemical structure of the material surface.
Molecular and supramolecular structure of adsorbed fibrinogen and adsorption isotherms of fibrinogen at quartz surfaces
Authors: Nygren Håkan , Stenberg Manne
Published: December 2004

The adsorption of fibrinogen to quartz surfaces was measured by ellipsometry, ELISA, and electron microscopy. The initial adsorption at low concentrations was diffusion rate limited as determined by the ELISA and by counting the number of adsorbed molecules at electron micrographs. From ellipsometry, ELISA, and electron microscopy measurements it was found that the surface concentration of adsorbed fibrinogen increased continuously over four decades in bulk concentration of fibrinogen. At a hydrophilic quartz surface a plateau level of the adsorption isotherm was found at a surface concentration of 0.1 pmol/cm2 where the adsorbed molecules had a mean intermolecular distance of 10 ± 5 nm between neighbors. At higher surface concentrations the molecules were densely packed and formed a layer where single molecules could not be identified. Adsorbed fibrinogen showed different structure at hydrophobic and hydrophilic quartz surfaces. At a hydrophilic surface, the fibrinogen molecules appeared as a 46 nm nodose rod consisting of 6–7 nodes with a diameter of 4 nm. At a hydrophobic surface, the molecule appeared as a binodular or trinodular rod with a node diameter of 5–9 nm, connected with a thin filament to form a 40‐nm rod. Adsorption from higher concentrations of fibrinogen in solution resulted in adsorbed spheric structures with a diameter of 18–24 nm at the hydrophobic surface and in end‐to‐end polymers at the hydrophilic quartz membrane.
Physical and hydrodynamic factors affecting erythrocyte adhesion to polymer surfaces
Authors: Chang G. , Absolom D. R. , Strong A. B. , Stubley G. D. , Zingg W.
Published: December 2004

Using a flow cell design which ensures fully developed laminar flow, the influence of various hydrodynamic and physical factors in determining the extent of erythrocyte adhesion to various polymer surfaces has been examined. Specifically we have investigated the effect of exposure time, flow rate, erythrocyte concentration, and substrate surface tension on the extent of erythrocyte adhesion. The results indicate: (1) the extent of erythrocyte adhesion is most extensive on the more hydrophobic surfaces; (2) the rate of adhesion is higher on the more hydrophobic surfaces; (3) saturation coverage occurs after 7–10 min of exposure to the erythrocyte suspension for all substrates examined. No „lag‐time”︁ in the onset of adhesion was observed; (4) The level of saturation depends on the bulk erythrocyte concentration, increasing with increasing cell concentration; (5) the extent of adhesion decreases with an increase in flow rate; and (6) substrate surface defects such as roughness have a major effect on the pattern of erythrocyte adhesion.
AES analysis of stainless steel corroded in saline, in serum and in vivo
Authors: Zabel David D. , Brown Stanley A. , Merritt Katharine , Payer Joe H.
Published: December 2004

Auger electron spectroscopic (AES) studies were conducted to examine the surface film of stainless steel specimens which had been subjected to passive and anodic corrosion in vitro and in vivo. Anodic corrosion was accelerated by the application of a +500 mV (SCE) potential for 30 minutes. Experiments performed in 0.9% saline indicated little alteration in the nature of the surface film compared to a freshly prepared control specimen. Auger analysis of specimens in 10% serum or in vivo revealed that passive film thickness was dependent on the corrosive environment. The films of specimens immersed under freely corroding conditions in 10% serum or in vivo were similar to the control film. Accelerated corrosion performed in 10% calf serum resulted in significant film thickening. The thickest films were from accelerated corrosion in vivo. The mechanism for the altered surface films produced by corrosion in vivo or in serum as compared to saline needs to be investigated further.
Hydrophilic microporous polyurethane versus expanded PTFE grafts as substitutes in the carotid arteries of dogs. A limited study
Authors: Martz Hugues , Paynter Royston , Slimane Saidi Ben , Beaudoin Gilles , Guidoin Robert , Brzone Juan , Simhon Haim Ben , Satin Richard , Sheiner Nathan
Published: December 2004

A novel, microporous, hydrophilic polyether urethane‐urea (PEUU) vascular graft was compared with expanded PTFE in the canine carotid artery. At implantation times ranging from 4 h to 6 months, all the PEUU grafts were found to be occluded while of the PTFE grafts, only those implanted for 1 week and 6 months were blocked. Histopathological analysis of the explanted grafts and their capsules revealed an on‐going inflammatory reaction at the anastomotic sites of the PEUU grafts.
Use of an enzyme linked immunosorbent assay (ELISA) for quantification of proteins on the surface of materials
Authors: Merritt Katharine , Edwards Christopher R. , Brown Stanley A.
Published: December 2004

This study demonstrates the usefulness of an enzyme linked immunosorbent assay (ELISA) for detection and quantification of protein on the surface of materials. Bovine serum albumin (BSA) and bovine gamma globulin (BGG) were the proteins used. Titanium and stainless steel were the materials tested. The proteins were detected with the use of rabbit antiserum specific for BSA and for BGG. This reaction was quantitated by the use of horseradish peroxidase conjugated goat anti‐rabbit gamma globulin. The technique is described in detail. The technique was demonstrated to be suitable for quantitation of protein from 0.01 mg/mL to 0.1 mg/mL on the surface of 3 mm × 10 mm materials. The technique was also demonstrated to be suitable for determining the surface area of solid materials. It is a simple technique and suitable for most biomaterials laboratories.
Effect of proteins and pH on fretting corrosion and metal ion release
Authors: Merritt Katharine , Brown Stanley A.
Published: December 2004

The objectives of this study were to determine the effect of proteins and protein charge on the corrosion of stainless steel. As Zwitter ions, proteins have a positive charge in solutions acidic to their isoelectric point (pI) and a negative charge in solutions basic to the pI. Fretting corrosion rates of stainless‐steel plates and screws as determined by weight loss and metal ion release were studied in saline and protein solutions with the pH adjusted to 3, 5, and 8. Alterations in pH did not affect the corrosion rate in saline solutions. However, alterations of the pH in albumin solutions did affect the corrosion rate. In protein solutions acidic to the isoelectric point the presence of the positively charged albumin did not alter the corrosion rates as compared to that in saline. However, the presence of negatively charged proteins in solutions basic to their isoelectric points decreased the amount of corrosion. Thus, the effect of proteins on fretting corrosion is dependent on the charge on the protein. When the release of nickel was compared to the release of chromium, it was shown that the release was in proportion to the composition of the alloy when fretting corrosion took place in saline. The nickel/chromium ratio in the albumin and gamma globulin solutions was increased relative to that predicted indicating preferential release of nickel in protein solutions.
An in vitro evaluation of the hemostatic activity of topical agents
Authors: Eloy Rosy , Baguet Joel , Christé Georges , Rissoan Marie Clotilde , Paul Jacqueline , Belleville Jean
Published: December 2004

An in vitro method has been developed for human non‐anticoagulated blood to evaluate the enhancing effect of hemostatic agents on both plasmatic and cellular activation of the coagulation cascade. The coagulation time and the sequential generation of fibrinopeptide A (FpA) have been used as parameters. The kinetics of generation of FpA has been modelized and mathematically analyzed using the latence time, the slope of the linear part of the curve, and the time necessary to reach half maximal amplitude of FpA in the tube. A very precise evaluation of the hemostatic activity of five different molecules, four being collagenous in nature, is given.
In vitro simulation of biocompatibility of Ti‐Al‐V
Authors: Bruneel Noël , Helsen Jef A.
Published: December 2004

The presented data are the result of a reappraisal of the biocompatibility properties of titanium alloys. An in vitro study has been conducted using Hanks' solution with four different additional compounds (EDTA, l‐leucine, Na‐citrate, and 8‐hydroxyquinoline). A measurable dissolution rate was observed for Ti and Al in a solution contaning EDTA and for Ti, Al, and V for a solution containing Na‐citrate. The dissolution kinetics are discussed and explained in terms of the composition of the surface layers. The results contain useful introductory information for an extended study of media allowing representative in vitro simulation of the in vivo behavior of titanium alloys.
Kinetics of cell adhesion to polymer surfaces
Authors: Absolom D. R. , Thomson C. , Hawthorn L. A. , Zingg W. , Neumann A. W.
Published: December 2004

Results of the kinetics of adhesion of granulocytes as well as fresh and glutaraldehyde‐fixed erythrocytes, suspended in Hanks Balanced Salt Solution (HBSS; pH 7.2, ionic strength of 0.15) to various polymeric substrates are presented. Cell adhesion increases rapidly initially and reaches a plateau value after approximately 30 minutes. There is no evidence for a lag‐time in the onset of cell adhesion, suggesting that electrostatic double‐layer forces are negligible under these experimental conditions. For the experiments in which the cells are suspended in HBSS, which has a surface tension larger than that of the cells, the level of cell adhesion increases with decreasing surface tension of the polymeric substrates. An additional experiment with fresh human granulocytes suspended in HBSS containing 10% dimethyl sulfoxide was also performed. The surface tension of the resulting liquid medium is below that of the cells and the pattern of adhesion is reversed, in agreement with the predictions of a thermodynamic model for cell adhesion. The slightly different behavior of siliconized glass as a substrate is discussed in terms of „screening”︁.
Poly(dimethylsiloxane)‐poly(ethyleneoxide)‐heparin block copolymers. I. Synthesis and characterization
Authors: Grainger D. W. , Kim S. W. , Feijen J.
Published: December 2004

Amphiphilic block copolymers containing poly(dimethylsiloxane), poly(ethylene oxide), and heparin (PDMS‐PEO‐Hep) have been prepared via a series of coupling reactions using functionalized prepolymers, diisocyanates, and derivatized heparins. All intermediate steps of the synthesis yield quantifiable products with reactive end‐groups, while the final products demonstrate bioactive, covalently bound heparin moieties. Due to the solvent systems required, commercial sodium heparin was converted to its benzyltrimethyl ammonium salt to enhance its solubility. The same procedure was applied to heparin degraded by nitrous acid in order to covalently couple it in solutions with the semitelechelic copolymers. As might be expected, this derivatization reduces the apparent bioactivity of the heparin. However, preliminary findings suggest that the bioactivity can be restored by reforming the heparin sodium salt.
Development of Ni‐4 wt.% Si thermoseeds for hyperthermia cancer treatment
Authors: Chen J.‐S. , Poirier D. R. , Damento M. A. , Demer L. J. , Biancaniello F. , Cetas T. C.
Published: December 2004

Ferromagnetic alloys, used in the form of „thermoseeds”︁ for surgical implantation, have been developed and used to induce localized hyperthermia in cancerous growths. Alloys of nickel with approx. 4 wt.% Si were chosen for this study because they have Curie temperatures in the desired range of 45–60°C. The thermoseeds were prepared by using either a special casting technique or casting and swaging followed by homogenization. The effects of these different processing schedules on the magnetic behavior of these alloys are discussed. In particular, the importance of minimizing oxidation during melting and heat treating, and the effects of homogenizing the thermoseeds on the relative permeability at temperatures near the Curie temperature are pointed out. The best processing schedule is casting small ingots while avoiding oxidation, followed by swaging, drawing, and homogenization. Actual induction heating experiments and the results from magnetization tests indicate that Ni‐4 wt.% Si alloys prepared in this manner can be used as thermoseeds with predictable Curie temperatures. These thermoseeds can be used to obtain nearly uniform and constant temperatures in tumors with variable blood flows.
In vitroandin vivometal ion release
Authors: Brown Stanley A. , Farnsworth Lilian J. , Merritt Katharine , Crowe Timothy D.
Published: December 2004

A series of experiments was conducted to studyin vitroandin vivometal ion release and the urine excretion of metal ions. Metal salts were injected and urine analyzed. Anodic potentials were applied to stainless steel and cobalt‐chromium‐molybdenum (CCM) specimens to cause an acceleration of corrosion rates. Corrosion experiments were done in saline, 10% serum and in a subcutaneous space in hamsters. Corrosion rates were determined by measurements of weight loss and calculations of net charge transfer. Metal ion concentrations were determined with graphite furnace atomic absorption spectroscopy, and were calculated from total charge using Faraday's law. The results with stainless steel showed that the weight loss and metal ion release from stainless steelin vitroandin vivocan be calculated using Faraday's Law, assuming release in proportion to alloy composition. The results with CCM indicated that release ratesin vitrocan be used to determine the proportionality of releasein vivo. All the nickel and most of the cobalt was rapidly excreted, while less than 50% of the chromium was excreted. The excretion of metals following salt injection orin vivocorrosion were very similar.
Cell adhesion to a series of hydrophili–hydrophobic copolymers studies with a spinning disc apparatus
Authors: Horbett T. A. , Waldburger J. J. , Ratner B. D. , Hoffman A. S.
Published: December 2004

Adhesion of cells to substrates strongly influences many of their functions and therefore plays an important role in a variety of processes, including phagocytosis, hemostasis, and the response of tissue to implanted materials. In previous studies, the influence of substrate hydrophilicity on cell adhesion has not been separated from effects due to major differences in other properties of the substrate, such as charge, rigidity, and the specific chemical composition of the materials. In addition, very few careful studies of the force required for cell detachment from various substrates have been performed. In this study, 3T3 cell detachment from a chemically homologous series of copolymers based on hydroxyethylmethacrylate (HEMA) and ethylmethacrylate (EMA) was measured with a spinning‐disc apparatus. The spinning‐disc technique allowed measurements of cell detachment over a wide range of applied shear stress on each sample. Cell detachment did not occur until a critical value of shear stress was exceeded. The critical shear stress of detachment decreased linearly with increasing HEMA content, from 18 dynes/cm2 on poly‐EMA to 0 on the polymers containing 83% or more HEMA. “Plating efficiency,” calculated as the fraction of cells initially applied which remained after dip rinsing the surfaces, did not vary significantly among most of the copolymers. Dip rinsing, however, exposes the cells to only one, relatively low shear stress (estimated to be somewhat less than 3 dynes/cm2). The existence of a critical shear stress for 3T3 cell detachment suggests that cell adhesion to surfaces cannot be fully understood with single shear stress methods because cells may attach with a wide range of strengths which are either all above or all below the applied shear stress. The influence of surface hydrophilicity on cell adhesion and the variety of forces which may contribute to this phenomenon are discussed.
Preparation and properties of a biomaterial: HEMA grafted SBS by γ‐ray irradiation
Authors: Hsiue Ging‐Ho , Yang Jen‐Ming , Wu Ryh‐Lih
Published: December 2004

Solvent‐cast films of styrene‐butadienestyrene triblock copolymer (SBS) were synthesized and a poly(2‐hydroxyethylmethacrylate) (PHEMA) layer was grafted onto these films using Co 60 γ‐ray irradiation. The IR absorption spectrum of the graft copolymer was taken and its surface morphology studied by a scanning electron microscope. The degree of grafting and the mechanical properties of SBS, SBS‐g‐HEMA, and PHEMA were measured. In order to study its biocompatibility, contact angle and blood clotting time experiments were performed. The degree of grafting was related to the soaking time, film thickness and total irradiation dosage. However, it levelled off at 7% when the total dosage reacehed 1 Mrad. It was found that the mechanical properties of SBS‐G‐HEMA were the same as those of SBS and were superior to those of PHEMA. The blood compatibility of SBS‐g‐HEMA as measured by the Lee‐White clotting test was better than that of SBS and polystyrene and was quite similar to that of PHEMA.
Biocompatibility of six elastomers in vitro
Authors: Bakker D. , van Blitterswijk C. A. , Daems W. Th. , Grote J. J.
Published: December 2004

The biocompatibility of two silicone rubbers, Silastic and Dow Corning Elastomer, and of a polyether and a polyester urethane, a polyether polyester copolymer, and polypropylene oxide was assessed in vitro. These elastomers were selected for assessment as a possible alloplastic tympanic membrane. For these studies use was made of rat middle ear mucosa explants and serially cultured epithelium. The quantitative results were based on epithelial growth curves, the morphological picture was based on the findings in epithelium, and the aging of a biomaterial was simulated. Epithelium morphology was investigated by scanning and transmission electron microscopy and x‐ray microanalysis. Quantitative results showed that on Dow Corning Elastomer and polypropylene oxide, cell proliferation was significantly lower compared to normal growth curves. The morphological findings were negative for polypropylene oxide, and did not discriminate between the other biomaterials under study. The simulation results indicated better biocompatibility for the polyurethanes and the polyether polyester copolymer compared with that of polypropylene oxide and both silicone rubbers. Under the simulation conditions, cells exposed to Silastic showed siliconcontaining inclusions. These in vitro results suggest that the biocompatibility of the polyurethanes and the polyether polyester copolymer is better than that of both silicone rubbers and polypropylene oxide.
Effects of a grooved epoxy substratum on epithelial cell behavior in vitro and in vivo
Authors: Chehroudi B. , Gould T. R. , Brunette D. M.
Published: December 2004

The effects of grooved epoxy substrata on epithelial (E) cell behavior were studied in vitro and in vivo. V‐shaped grooves, 10 μm deep, were produced in silicon wafers by micromachining, a process which was developed for the fabrication of microelectronic components. The grooved substrata were replicated in epoxy resin. More E cells attached to grooved surfaces than to adjacent smooth surfaces. Clusters of E cells were markedly oriented by the grooved surfaces in comparison to the adjacent smooth surfaces where the orientation was random. Grooved and smooth epoxy implants were placed percutaneously in the parietal area of rats. One week after implantation E cells were found to adhere tightly to the implant surfaces. In the grooved portion of the implant E cells interdigitated into the grooves and had rounded nuclei. Histomorphometric measurements indicated that there was a shorter length of epithelial attachment and a longer length of connective tissue attachment in the grooved, compared to the smooth, portion of implants. After 10 days the epithelial attachment had migrated down the length of the protruding smooth portion of the implant and was located on the base of the implant. However, epithelium remained attached to the grooved portion of the implant. These observations indicate that grooved surfaces have the potential to impede epithelial downgrowth on percutaneous devices.
Colonization of n‐butyl‐2‐cyanoacrylate tissue adhesive by Staphylococcus epidermidis
Authors: Olson Merle E. , Ruseska Ivanka , Costerton J. William
Published: December 2004

In vitro adhesion of Staphylococcus epidermidis to cyanoacrylate tissue adhesive surfaces was investigated by employing a modified Robbins device. Bacterial colonization of n‐butyl‐2‐cyanoacrylate tissue adhesive polymer surfaces was demonstrated by employing scanning electron microscopy, epifluorescence technique, and aerobic plate counts. The S. epidermidis was found to rapidly colonize the n‐butyl‐2‐cyanoacrylate polymer surface producing a biofilm composed of embedded bacteria in an extensive amorphous matrix that totally occludes the material surface. The results indicate that the bacteriocidal properties of the polymer to this bacteria are weak or absent.
The corrosion fatigue properties of surgical implants in a living body
Authors: Morita Masafumi , Sasada Tadashi , Hayashi Hitoshi , Tsukamoto Yukio
Published: December 2004

Fatigue fracture of artificial implants in the human body, caused by the repeated application of stress, is well documented. It is known that the fatigue strength of implant materials decreases when they are exposed under in vivo corrosion conditions. There are, however, no investigations concerning the effect of body fluids on the fatigue characteristics of commonly used biomaterials. Accordingly, fatigue tests on machined stainless‐steel AISI 316, and COP alloy rods have been conducted in the right lower leg of rabbit. These specimens were piereced through the hole drilled at the middle of the tibial bone. A cyclic tensile stress of frequency 5 or 10 Hz was applied to the rods. From the results, it was found that the fatigue strength at 5 × 106 cycles for AISI 316 under the in vivo environment was 680 MPa compared to 830 MPa in air and similarly for COP alloy, was 680 MPa in the living body compared to 800 MPa in air. These remarkable changes in fatigue strength associated with the in vivo environments are considered to be due to the corrosive action of body fluids on the biomaterials.
Serotonin and β‐thromboglobulin release reaction from platelet as triggered by interaction with polypeptide derivatives
Authors: Kang Inn‐Kyu , Ito Yoshihiro , Sisido Masahiko , Imanishi Yukio
Published: December 2004

The effect of wettability of 14 polypeptide derivatives upon adhesion and activation of platelets was investigated with reference to release reactions from adhered platelets, using radioisotope labeling and radio‐immunoassay method. The serotonin release was more significant from platelets adhered to polymer materials to which a large number of platelets are adhered. However, no clear relationship was found between adhesion of platelets and β‐thromboglobulin release from adhered platelets. Therefore, stimuli inducing serotonin release and β‐thromboglobulin release were considered to be from different origins. The trend in β‐thromboglobulin release was well correlated with the extent of morphological change of adhered platelets as observed by scanning electron microscope. It was suggested that the determination of released β‐thromboglobulin in association with the measurement of platelet adhesion could be useful for evaluation of blood compatibility of materials.
Development of a new system for evaluating the biocompatibility of implant materials using an osteogenic cell line (MC3T3‐E1)
Authors: Itakura Yoshinobu , Kosugi Arihito , Sudo Hiroko , Yamamoto Shigehisa , Kumegawa Masayoshi
Published: December 2004

A new culture system was developed to clarify the biocompatibility of implant materials with bone tissue using the MC3T3‐E1 osteogenic cell line. The cells were inoculated onto specimens such as aluminium oxide, titanium, dental casting silverpalladium alloy (PD), and a plastic coverslip. To study the effects of these materials on cell growth, differentiation, and calcification, DNA and protein content, alkaline phosphatase activity, and calcium content, respectively, were determined. The results from biochemical analysis suggest titanium and aluminium oxide to have adequate biocompatibility, while PD has an irritant effect on cell metabolism. It is clear that an objective view of the differentiation and calcification processes of osteogenic cells can be understood through such analysis. From the results of this study, our culture system appears suitable for evaluating the biocompatibility of implant materials with bone tissue.
Human monocyte/macrophage activation and interleukin 1 generation by biomedical polymers
Authors: Miller K. M. , Anderson J. M.
Published: December 2004

In vitro cell culture techniques were used to evaluate the effect of several clinically significant biomedical polymers on monocyte activation and Interleukin 1 (IL1) production. Isolated human peripheral blood monocytes were cultured in the presence of a panel of five biomedical polymers routinely used in a variety of clinical applications: Polyethylene (PE), silica‐free polydimethylsiloxane (PDMS), woven Dacron fabric, expanded polytetrafluoroethylene (ePTFE) and the segmented polyurethane, Biomer. Monocytes generated IL1 in the presence of all five materials. Maximal levels of IL1 were generated at 24 h in monocyte‐polymer cultures supplemented with serum and additionally stimulated with lipopolysaccharide (LPS). No difference was observed due to serum source. Results from cultures supplemented with fetal bovine serum were not significantly different from those obtained with human serum supplemented cultures. The thymocyte proliferative activity generated by monocytes in the presence of these biomedical polymers was neutralized by a specific polyclonal anti‐IL1 antiserum. Statistically significant differences in IL1 production were observed between polymers, allowing their classification according to reactivity into high (Dacron, PE), intermediate (ePTFE) and low (Biomer, PDMS) reactive groups.
Effect of particle size on the in vitro and in vivo degradation rates of poly(DL‐lactide‐co‐glycolide) microcapsules
Authors: Visscher G. E. , Pearson J. E. , Fong J. W. , Argentieri G. J. , Robison R. L. , Maulding H. V.
Published: December 2004

Three different sieve size fractions of ergotcontaining biodegradable microcapsules were examined both in vitro and in vivo. The sieve sizes and average particle diameter, (μm), were: less than 45–75 (X̄ = 30); 75–106 (X̄ = 79), 106–177 (X̄ = 130). These microcapsules contained ca. 9% drug and were produced from 50:50 poly(DL‐lactide‐co‐glycolide). The objective was to determine the effect of particle size on in vivo and in vitro degradation rates. The microcapsules were injected into rat gastrocnemius muscle and excised and examined at various time points up to 70 days. Initially a minimal tissue response was noted which was characterized by a sharply localized acute inflammatory reaction. Following this, connective tissue and foreign body giant cells engulfed the microcapsules at 20–30 days. Only vestiges of the microcapsules were found surrounded by minimal connective tissue and foreign body giant cells after 60–70 days. The tissue reaction was a minimal, sharply localized foreign body giant cell and connective tissue process for all three size groups of microcapsules. The largest microcapsules (X̄ = 130 μm) exhibited a slightly greater tendency to undergo in vivo and in vitro degradation relative to the other groups. However, it can be concluded that over the microcapsule size ranges examined minimal differences in the degradation properties of the polymeric matrices and consequently those of the microcapsules were noted.
Experimental implantation of hydrogel into the bone
Authors: Korbelář P. , Vacík J. , Dylevský I.
Published: December 2004

The present study deals with the application and possibilities of insoluble hydrophilic gels (poly(2‐hydroxyethyl methacrylate)) as substitutes of bone tissue experimentally. Their biocompatibility is examined with regard to the porous qualities of the implant and to its chemical structure, and their behavior in the cancellous and compact bone is evaluated. It was found that the modifications of hydrogels used in the experiment are biocompatible, with the compatibility increasing in proportion to increasing porosity. The nonporous and microporous hydrogels are not compatible and are demarcated. The sintered macroporous gel is surrounded by a thin fibrin membrane. By adding methacrylic acid to the hydrogel surface, adhesion increases markedly. Marked destruction also appears in the polymer especially in the cancellous bone. By an active destruction of the polymer, no direct phagocytosis can be proved. Upon breakdown of the implant in the compact bone the activity of the macrophages is delayed. When the gel without methacrylic acid is used alone, destruction does not occur even after 193 days. When methacrylic acid is added to the polymer surface, destruction does occur and the implant is filled only by bone trabeculae.
Correlations between mouse 3T3 cell spreading and serum fibronectin adsorption on glass and hydroxyethylmethacrylate–ethylmethacrylate copolymers
Authors: Horbett Thomas A. , Schway Michael B.
Published: December 2004

The interaction of cells with solid surfaces is important in many settings, including the response of tissue to implanted materials. Protein adsorption to the surfaces plays a critical role in controlling cell interactions with surfaces. However, few comprehensive studies of both cell behavior and protein adsorption in complex protein mixtures (e.g., serum) have been done so the connection between these events is not well understood. In particular, methods to systematically perturb both protein adsorption and cell behavior in order to understand their relationship have been lacking. To induce changes in cell and protein behavior, the effects of serum dilution and substrate surface chemistry were studied. Surface chemistry was varied by using a series of polymers and copolymers of hydroxyethyl methacrylate (HEMA) and ethylmethacrylate (EMA) varying in their hydrophobic/hydrophilic balance. Large changes in cell spreading and fibronectin adsorption were observed when either serum concentration or polymer type was varied. The spreading of 3T3 cells in serum was found to be well correlated with the amount of fibronectin adsorption to the substrates. Attachment was not correlated with fibronectin adsorption, especially on glass preadsorbed with diluted serum. For 3T3 cells and perhaps other cells that have a receptor for a protein which is present in the medium, the amount of adsorption of this protein to the substrate appears to be a critical factor controlling cell interactions with the substrate.
Blood compatibility of surfaces modified by plasma polymerization
Authors: Yeh Y.‐S. , Iriyama Y. , Matsuzawa Y. , Hanson S. R. , Yasuda H.
Published: December 2004

Tubular blood‐contacting polymeric materials were modified by plasma polymerization and evaluated in the baboon with respect to their capacity to induce both acute and chronic arterial thrombosis. Polymer surface composition was determined by electron spectroscopy for chemical analysis. Steady‐state arterial thromboembolism was initiated by introducing tubular segments into chronic arteriovenous shunts. Rates of platelet destruction induced by the test materials were calculated from 111In‐platelet survival measurements. Nine plasma polymers based on tetrafluoroethylene, hexafluoroethane, hexafluoroethane/H2, and methane, when deposited on silicone rubber, consumed platelets at rates ranging from 1.1–5.6 × 108 platelets/cm2‐day. Since these values were near the lower detection limit for this test system, the plasma polymers were considered relatively nonthrombogenic. Acute thrombus formation was initiated by inserting expanded Teflon (Gore‐Tex PTFE) vascular grafts into the shunt system. 111In‐platelet deposition was measured by scintillation camera imaging over a 1‐h exposure period. Standard PTFE grafts (10 cm × 4 mm i. d.) accumulated approximately 1 × 1010 platelets over this interval. While modification of PTFE grafts with a plasma polymer based on hexafluoroethane/H2 did not alter graft surface morphology, platelet deposition was reduced by 87% as compared to the controls (p < 0.001). We conclude that both the surface chemistry and texture of prosthetic materials influence thrombogenesis. The method of plasma polymerization may be useful for assessing the importance of these variables independently and, perhaps, for minimizing certain adverse blood–material interactions.
Analysis of the biocompatibility of ALCAP ceramics in rat femurs
Authors: Mattie D. R. , Bajpai P. K.
Published: December 2004

Ceramics composed of aluminum, calcium, and phosphorus oxides (ALCAP) were tested for compatibility as bone replacement biomaterials. Implantation of ALCAP ceramics in rat femurs had no deleterious effect on body weights, organ/body weight ratios, muscle, bone, blood, and kidney function. Aluminum resorbed from ALCAP ceramic bone implants was excreted in the urine and was not deposited in adjacent muscle. Plasma levels of aluminum were not elevated in rats implanted with ALCAP ceramics. Alkaline phosphatase activity of excised implant sites indicated greater bone formation in ALCAP ceramic implants than in bone autografts. Radiographs and implant histology demonstrated excellent bone association with implants and ingrowth of new bone into ALCAP ceramic implants. ALCAP ceramics are biocompatible and suitable for reconstruction of bone.
Designing to counteract the effects of initial device instability: Materials and engineering
Authors: Kay John F.
Published: December 2004

Implants for hard tissue replacement have evolved over the last few decades, but a critical assessment of their design reveals that most dental implants and most orthopedic appliances for any given indication are basically similar in design to their commercial competitors. Some unique features are contained in the outer 0.7 mm, but shadow pictures of the devices could almost be superimposed upon one another. Near‐optimal designs have evolved for the materials systems commonly in use. The fight to minimize initial instability of implants, which leads to failure, has caused certain attachment mechanisms to emerge as acceptable, based upon research that indicates firm fixation in bone has resulted in longer average implant lifetime. The problem of initial stabilization is one of materials and design, both of which are necessary for a successful implant system. The nonmetallic calcium phosphate glass and ceramics technology available today provides materials that may counteract the effects of initial device instability by not relying on mechanical means of retention, alone, but chemical as well.
The effect of plasma‐sprayed calcium phosphate ceramic coatings on the metal ion release from porous titanium and cobalt‐chromium alloys
Authors: Ducheyne Paul , Healy Kevin E.
Published: December 2004

Bone tissue ingrowth in porous materials is enhanced by the deposition of bioactive calcium phosphate ceramic linings onto the pore walls. These bioactive coatings can be deposited using several methods which yield a variety of coating efficiencies and thereby influence the mechanisms and kinetics of ion release from the metal. We analyzed the effect of plasmaspraying hydroxyapatite onto titanium and cobalt–chromium alloys by measuring the release of Ti, Al, V, Co, and Crin vitro. Plasma‐sprayed coatings significantly reduced the Ti and Al release from titanium‐based alloy specimens. The tendencies of release from the cobalt‐based specimens are less pronounced. The data substantiate that neither localized enhanced passive dissolution of metal ions nor ceramic shielding of the metal occurs. The Scanning Auger Electron Microprobe Spectroscopic data suggest that the dissipation of thermal and kinetic energy of the ceramic particle at the time of impact can produce compositional and structural changes in the metal surfaces. The resulting effects are significant for the titanium alloy but less significant for the Co–Cr alloy system.
A comparative clinical study of solid and granular porous hydroxylapatite implants in human periodontal osseous defects
Authors: Kenney E. B. , Lekovic V. , Carranza F. A. , Dimitrijeric B. , Han T. , Takei H.
Published: December 2004

Solid and granular porous hydroxylapatite implants were compared in the surgical treatment of angular interproximal periodontal defects in 10 subject. After completion of initial therapy, presurgical measurements of pocket depth, attachment level, gingival recession, gingival fluid and tooth mobility were recorded. Six months after the surgery the measurements were repeated. The use of both forms of porous hydroxylapatite resulted in reduction in pocket depth, and probebale attachment level gains as well as gingival recession and reduction of gingival fluid and tooth mobility. These changes were similar for both granular and solid forms of porous hydroxylapatite.
In vivo histologic and biomechanical characterization of a biodegradable particulate composite bone cement
Authors: Gerhart Tobin N. , Renshaw Andrew A. , Miller Richard L. , Noecker Robert J. , Hayes Wilson C.
Published: December 2004

A biodegradable particulate composite bone cement consisting of a crosslinked gelatin matrix and tricalcium phosphate particles was implanted intraosseously in rabbits for up to 12 weeks. Cured cylindrical implants were inserted in holes drilled in the proximal tibial metaphysis. Sequential fluorochrome labeling and radiographs were done, and specimens were processed for decalcified and nondecalcified histology. At 4 weeks, the cross‐sectional diameter of the implant was slightly greater than at implantation. There was considerable dissolution of the matrix and some new bone ingrowth. At 12 weeks, the diameter was reduced to half the original diameter and bone had grown throughout the matrix. In the distal femur, freshly mixed cement was used to stabilize an osteochondral fracture. Mechanical testing of the cement‐stabilized fracture revealed a decrease in compressive strength and modulus at 4 weeks followed by an increase to greater than initial values at 12 weeks. Over time, the osteochondral fragment subsided into the underlying cement, but the subsidence did not correlate with mechanical strength. This osteochondral fracture model permits measurement of the overall material properties of a cement simultaneously weakened by resorption and reinforced by ingrowing bone.
An evaluation of two configurations of tricalcium phosphate for treating craniotomies
Authors: Hollinger Jeffrey O. , Schmitz John P. , Mizgala James W. , Hassler Craig
Published: December 2004

Biodegradable beta‐tricalcium phosphate disks (TCP) of two configurations were inserted into 15‐mm‐diameter craniotomy wounds and nontreated control sites were evaluated in 60 rabbits. There were no adverse tissue reactions and no apparent difference in the clinical appearance of the 12‐ and 24‐week implanted disks. By 36 weeks and continuing to 48 weeks, the omnidirectional TCP (OTCP) implants were degrading more rapidly than the unidirectional TCP (UTCP) implants, with degradation progressing centripetally and replacement by woven bone and maturing lamellar bone. Host‐implant interface of both TCP configurations was a bone bond without interposed soft tissue. TCP disks may be clinically useful for craniotomy repair.