bluuebunny/crossref_metadata_2025 huggingface dataset:
Microencapsulation of mammalian cells in a HEMA‐MMA copolymer: Effects on capsule morphology and permeability
Authors: Crooks Colin A. , Douglas Jon A. , Broughton Richard L. , Sefton Michael V.
Published: December 2004

A new process for preparing uniform microcapsules with a hydroxyethyl methacrylate‐‐methyl methacrylate copolymer (HEM A‐MMA) has been devised. Capsule diameters were 900‐‐1000 μm in diameter, (± 10–20 μm, ± SD) depending on the precipitation conditions. The process involved the coextrusion of polymer solution (in PEG 200) and the mammalian cell suspension (here erythrocytes) through a needle assembly which is submerged in a layer of hexadecane which is in turn sitting above a stirred isotonic aqueous solution in a volumetric flask. The needle is repeatedly withdrawn from the hexadecane overlayer shearing a droplet from the needle tip which falls into the water, where the solvent is extracted to precipitate the polymer around the cells to yield the capsules. The morphology of the capsule wall was altered by changing the precipitation bath from phosphate buffered saline (PBS) to 0.3 M glycerol. This resulted in greater macroporosity in the wall, presumably because of the faster precipitation due to the higher solvent/precipitant compatibility with 0.3 M glycerol. The permeability to a series of test solutes (glucose, inulin, albumin, and alcohol dehydrogenase, ADH) increased by a factor of ∼ 2, presumably because of the increased macroporosity. Addition of 15% water to the polymer solvent enhanced the macroporosity, presumably by bringing the system closer to the cloud point; however, there was no corresponding increase in permeability. There was a significant decrease in permeability between that of albumin (∼69,000 D) and ADH (∼150,000 D) suggesting that the molecular weight cutoff of these capsules was on the order of 100,000 D as desired. This process is now being evaluated for the encapsulation of pancreatic islets and other cells of potential clinical interest.
The bone–titanium interfacein vitro
Authors: Davies J. E. , Lowenberg B. , Shiga A.
Published: December 2004

Commercially pure 5‐mm‐diameter titanium (cpTi) discs received droplet inoculations of cells derived from rat bone marrow and were maintained in supplemented culture medium for 2–3 weeks. The cells and extracellular matrix (ECM) were processed for observation by light (LM), scanning (SEM), and transmission electron (TEM) microscopy. The latter was achieved by freeze‐fracturing the solid metal from the resin‐embedded tissue using a method which preserved the interface. Surface staining of whole discs revealed cells separated from the metal substratum by areas of ECM which stained positively using von Kossa's method to identify mineralization. At SEM, the ECM comprised dense interwoven collagen fiber networks which were partially obscured by globular masses (GMs). Individual GMs were associated with collagen fibers, especially at fiber intersections. EDAX line scan analysis confirmed the presence of Ca and P in these areas which were assumed to be spheritic foci of calcification since the Ca and P peaks diminished in areas which demonstrated only collagen fibers or the underlying cpTi. TEM examination confirmed the presence of globular mineralization and also revealed the presence of an interfacial zone between the metal substratum and the mineralized ECM elaborated by osteoblasts during the culture period. The interfacial zone comprised two layers, a bonding zone containing few collagen fragments and a ruthenium red positive layer containing more densely packed collagen fibers. We believe that this is the first report of both the formation of bonelike tissue on solid titanium substratain vitroand demonstration of an interface which bears close morphological similarities to that known to developin vivo.
The effect of protein and urine on uropathogen adhesion to polymer substrata
Authors: Hawthorn Lesleyann , Reid Gregor
Published: December 2004

Uropathogenic adhesion was measured using a range of polymer materials with differing surface tension properties. Experiments were carried out in the presence of phosphate buffered saline (controls), Tamm Horsfall protein (THP), and human urine with quantitation by image analysis. The results showed that THP did not bind to the polymer materials and therefore did not act as a receptor surface for type 1 fimbriated Escherichia coli. However, the THP did interfere with adhesion by binding directly to these organisms as well as to Pseudomonas aeruginosa, Staphylococcus epidermidis, and, to a lesser extent, Proteus mirabilis. Incubation of the uropathogens in THP and urine resulted in altered adhesion profiles to polymer surfaces, with no single trend apparent. The results emphasize that fluid components, particularly proteins, and substratum surface tension influence bacterial adhesion to biomaterials.
The effect of fluid shear stress upon cell adhesion to fibronectin‐treated surfaces
Authors: Truskey George A. , Pirone John S.
Published: December 2004

Cell attachment to and spreading upon a surface is mediated by adhesion molecules, such as fibronectin. The role of fibronectin in maintaining cell adhesion was examined by measuring cell attachment following exposure of cells to laminar flow in a parallel‐plate flow channel. 3T3 fibroblasts were allowed to adhere to glass slides with or without preadsorbed fibronectin for 2 h before exposure to shear stresses ranging from 5 to 140 dyne/cm2. For cells which adhered to glasss surfaces, cell loss was biphasic with a significant loss of cells during the first 2 min of flow, followed by a much slower decline in the number of attached cells with time. Following exposure to shear stresses greater than 5 dyne/cm2, the number of attached cells decreased exponentially as the shear stress increased. The distribution of adhesive stresses among the population of cells was log‐normal with a median of 50 dyne/cm2, a mean of 82 dyne/cm2 and a standard deviation of 108 dyne/cm2. After exposure to flow for 2 h, the adhesive stress of the remaining cells decreased to a mean value of 50 dyne/cm2. Cell adhesion after exposure to flow was increased by preadsorbing fibronectin to the glass surface. The initial loss of cells from fibronectin‐treated glass following exposure to flow correlated with the degree of cell spreading. Preadsorbed fibronectin resulted in a greater number of bonds between the surface and the cell, which in turn promoted cell spreading and increased the adhesive strength of the cell.
In vitro toxicity test of 2‐cyanoacrylate polymers by cell culture method
Authors: Tseng Yin‐Chao , Tabata Yasuhiko , Hyon Suong‐Hyu , Ikada Yoshito
Published: December 2004

The inhibition of Swiss 3T3 cell growth by the microspheres prepared from various 2‐cyanoacrylate polymers was investigated to assess their cell toxicity. Poly(ethoxyethyl 2‐cyanoacrylate) and poly(methyl 2‐cyanoacrylate) microspheres inhibited cell growth in a smaller amount than poly‐(isobutyl 2‐cyanoacrylate) and poly(ethyl 2‐cyanoacrylate) microspheres. The extent of cell growth inhibition by the microspheres decreased with the increasing molecular weight, regardless of the kind of polymers used. Every kind of the microspheres was degraded releasing formaldehyde in the culture medium. The cell growth inhibition by the medium containing the microspheres was observed within 24 h for poly(ethoxyethyl 2‐cyanoacrylate) and poly(methyl 2‐cyanoacrylate). The extent of inhibition was in a linear proportion with the amount of formaldehyde released. It is concluded that the cell toxicity of 2‐cyanoacrylate polymers is attributed to formaldehyde released upon polymer degradation.
Quantitative in vivo studies of hyperemia in the course of the tissue response to biomaterial implantation
Authors: Bouet T. , Schmitt M. , Desuzinges C. , Eloy R.
Published: December 2004

Hyperemia associated with an inflammatory response has been investigated in rats, by using four different experimental models, i.e., “positive” and “negative” polymer implants from the pharmacopea, operative control, and abscess induced by turpentine oil. 133Xenon clearance, infrared thermography and Laser Doppler Flowmetry (LDF) were used to monitor the subcutaneous local hemodynamic changes from 1 to 40 postoperative days. LDF proved to be a sensitive, reproducible method, able to discriminate positive from negative implants already at the 3rd postoperative day and up to 40 days. This increased local blood flow was also visualized at the site of positive implants at the 14th and 21st postoperative days by means of 133Xe Clearance. Additional information obtained by infrared thermography allowed discrimination between positive implants and control sites but only at the very early stage (1 to 3 days). The significance of the different data collected by the three techniques was correlated with histological events occurring at the different implant sites. LDF may therefore represent a useful technique for noninvasive semiquantitative assessment of tissue response to biomaterials.
Friction properties of the interface between porous‐surfaced metals and tibial cancellous bone
Authors: Rancourt D. , Shirazi‐Adl A. , Drouin G. , Paiement G.
Published: December 2004

Friction tests between cancellous bone cubes and porous‐surfaced metal plates were conducted in order to determine the mechanical properties of the interface in a knee porous‐surfaced metal implant. Bone specimens were obtained from fresh frozen amputated tibiae and three metal plates were chosen: titanium bead porous‐surfaced, titanium fiber mesh porous‐surfaced, and smooth stainless steel. Results show that the friction curve is highly nonlinear. Friction coefficients measured vary between 0.3 and 1.3. The friction coefficient of the interface is independent of the excision site of the bone cubes and of the magnitude of the rate of relative displacement at the interface. The friction coefficient appears to vary slightly with the normal contact pressure for all the metal surface. Both porous surfaces have statistically a higher friction coefficient than the smooth surface. This is likely due to the presence of surface asperities whereby the metal ploughs the bone surface. However, no significant difference is observed between bead and fiber mesh types.
A hydrophilic plasma polymerized film composite with potential application as an interface for biomaterials
Authors: Marchant Roger E. , Johnson Steven D. , Schneider Bernard H. , Agger Mary Patricia , Anderson James M.
Published: December 2004

A hydrophilic polymer composite film (approx. 420 nm thick), with potential application as an interface for biomaterials has been prepared on nonorganic substrates, which include glass, silicon, and aluminum foil, using a glow discharge plasma polymerization technique. A thin film (110 nm thick) polymerized from hexane provided an adherent protective coating for the substrate material, and covalent bonding sites for the outer layer polymerized fromN‐vinyl‐2‐pyrrolidone. This outer layer provided the hydrophilic surface or interface. The two layers were copolymerized for a short period during transition between monomers to provide an intimate covalently bonded diffuse interphase. Preliminaryin vitroandin vivobiocompatibility studies indicate that the hydrophilic film is non‐cytotoxic, and does not increase the inflammatory response when compared with negative controls.
The effects of bulk versus particulate titanium and cobalt chrome alloy implanted into the rabbit tibia
Authors: Goodman S. B. , Fornasier V. L. , Lee J. , Kei J.
Published: December 2004

Twenty‐eight mature New Zealand white female rabbits were allocated into 4 groups of 7 rabbits. Group 1 received a coiled wire of cobalt chrome alloy (Vitallium) (16 gauge × 1 cm). Group 2 received an equal weight of cobalt chrome particles averaging 15.4 μm in diameter. Group 3 received a coiled wire implant of commercially pure (C.P.) titanium (16 gauge × 1 cm). Group 4 received the same weight of C.P. titanium particles averaging 3.8 μm. The implants were placed through a drill hole in the proximal right tibia; the left tibia served as a prepared but nonimplanted control. The animals were killed after 16 weeks and quantitative histology was performed on undecalcified sections of the implant area. Bulk cobalt chrome and titanium implants were surrounded by a thin, incomplete, fibrous tissue layer with decreased numbers of cells. Trabeculae of bone were present within this connective tissue envelope. Fingerlike projections of bone enveloped the implant where it abutted endosteal bone. Clumped and loosely scattered cobalt chrome and titanium particles were surrounded by a minimal amount of fibrous connective tissue. Smaller particles were present within cells. Hematopoietic cells abutted the bulk or particulate implants directly. There was no evidence of acute or chronic inflammation or foreign body reaction. These results should be contrasted with those of Howie et al. in which intraarticular cobalt chrome particles stimulated a rapid proliferation of macrophages and synovial degeneration after 1 week. This may be due to a direct toxic effect of metals in an intra‐articular environment, the smaller particle size used in that study, or to abrasive injury to the hyaline cartilage and subsequent synovitis. Our results underscore the general inert properties of these metals in the short term, when implanted into bone in the sizes and physical forms chosen.
Marrow cell induced osteogenesis in porous hydroxyapatite and tricalcium phosphate: A comparative histomorphometric study of ectopic bone formation
Authors: Ohgushi Hajime , Okumura Motoaki , Tamai Susumu , Shors Edwin C. , Caplan Arnold I.
Published: December 2004

To investigate the bone formation ability of porous hydroxyapatite (HA) and tricalcium phosphate (TCP), ceramic discs were implanted with or without rat marrow cells into subcutaneous sites in syngeneic rats. The discs of HA and TCP had identical microstructures: pore size was 190–230 μm, porosity was 50–60%, and they were fully interconnected. Implants without marrow cells (discs themselves) did not show bone formation, whereas implants with marrow cells showed bone formation in the pores of the ceramics. The bone formation of both HA and TCP occurred initially on the surface of the ceramic and progressed towards the center of the pore. The de novo bone was quantitated from decalcified serial sections of the implants. One month after implantation with marrow cells, the percentage fractions of the pore area filled with bone for implanted HA and TCP were 16.9 and 15.1, respectively. At 2 months after implantation with marrow cells, the fractions of bone were 34.3 and 30.9, respectively. These results indicate that both HA and TCP ceramics can show comparable osteogenic ability in the presence of marrow cells.
A histomorphological study on self‐reinforced polyglycolide (SR‐PGA) osteosynthesis implants coated with slowly absorbable polymers
Authors: Vasenius Jarkko , Vainionpää Seppo , Vihtonen Kimmo , Mero Matti , Mäkelä Antero , Törmälä Pertti , Rokkanen Pentti
Published: December 2004

A total of 150 osteotomies of rabbits' distal femur were fixed with absorbable self‐reinforced polyglycolide (SR‐PGA) rods coated with slowly absorbable polymers. In order to reduce the degradation rate of the SR‐PGA construction rods were coated with n‐butyl‐2‐cyanoacrylate, polydioxanone (PDS), poly‐beta‐hydroxybutyrate (PHBA), or poly‐l‐lactide (PLLA). Biocompatibility and the rate of biodegradation were evaluated in histological, histomorphometric, microradiographic, and oxytetracycline labeling studies. PDS, PHBA, and PLLA coatings showed good biocompatibility although there were scattered fluid accumulations around the rod in each group. Cyanoacrylate coating seemed to inhibit cartilage regeneration and cause the formation of considerable amount of connective tissue around the implant. The PGA core of the rod had totally degraded in 24 to 36 weeks in each coating group. Cyanoacrylate and PDS coatings were not detectable after 6 weeks while PHBA and PLLA coatings were still observed after 48 weeks. There were five (14%) non‐unions in the cyanoacrylate coating group, one (3%) in the PHBA coating group caused by a purulent infection and none in the PDS and PLLA coating groups.
Radiofrequency plasma deposition of oxygen‐containing films on polystyrene and poly(ethylene terephthalate) substrates improves endothelial cell growth
Authors: Ertel Sylvie I. , Ratner Buddy D. , Horbett Thomas A.
Published: December 2004

Polystyrene and poly(ethylene terephthalate) substrates were modified by radiofrequency plasma deposition with organic vapors comprised of carbon, oxygen, and hydrogen (acetone, methanol, glutaraldehyde, formic acid, allyl alcohol, and ethylene oxide). The treatments resulted in the deposition of a film at least 100 Å thick containing up to 26% atomic oxygen at the surface. A high oxygen incorporation was observed for vapors with a large oxygen‐to‐carbon ratio. Bovine aortic endothelial cell growth measured on acetone, methanol, and glutaraldehyde films was linearly correlated with the oxygen content of the treated surfaces. Nitrogen was incorporated in the surface by blending nitrogen gas into the organic vapors used for plasma deposition. The resulting nitrogen‐containing substrates exhibited a high affinity for serum fibronectin but a moderate cell growth.
Ultra‐high‐strength absorbable self‐reinforced polyglycolide (SR‐PGA) composite rods for internal fixation of bone fractures: In vitro and in vivo study
Authors: Törmälä P. , Vasenius J. , Vainionpää S. , Laiho J. , Pohjonen T. , Rokkanen P.
Published: December 2004

The ultra‐high‐strength, self‐reinforced (SR) absorbable polymeric composites, consisting of reinforcement elements, like fibers, and of matrix polymer which have the same chemical element composition as reinforcement, were defined. A method to manufacture self‐reinforced, absorbable polyglycolide (SR‐PGA) rods of polyglycolide sutures (Dexon) by sintering them partially together at elevated temperature and pressure was presented. The rods with nominal diameters of 1.5 mm, 2.0 mm, 3.2 mm, and 4.5 mm showed initial bending modulus and strength values of 8–15 GPa and 220–405 MPa, respectively. Their initial shear strengths were 165–255 MPa. The smallest rods (diam. 1.5 mm) lost their mechanical strength after implantation in the subcutis of rabbits in 4–5 weeks while the thickest rods retained their strength over 8 weeks. The ultra‐high‐strength SR‐PGA rods were concluded to be suitable for fixation of cancellous bone fractures, osteotomies, and epiphyseal plate fractures where the fixation is not exposed to excessive mechanical stresses and where the loads are predominantly of a shear nature.
Calcium phosphate materials containing alumina: Raman spectroscopical, histological, and ultrastructural study
Authors: Bertoluzza A. , Simoni R. , Tinti A. , Morocutti M. , Ottani V. , Ruggeri A.
Published: December 2004

Variable alumina quantities were added to two types of calcium phosphate materials–hydroxyapatite ceramics with Ca/P = 1.67 and calcium metaphosphate glass with Ca/P = 1–in order to increase their mechanical properties. Raman spectroscopy shows that alumina interacts with the phosphate group of these materials, while thermomechanical analysis shows that their elastic modulus has a value similar to that of bone. Histological sections demonstrate that the surface in close contact with ceramic materials shows a good integration between bone and biomaterial. All ceramic specimens are penetrated by well‐stained, presumably glycoprotein, matrix, that consistently forms a thin network in close contact with the implant. After 6 weeks bone growing on both ceramic and glass shows signs of maturation with a lamellar structure and an apparently normal mineralization. In the case of the glass, inside this newly formed bone, were often observed two layers, the internal one showing a well defined lamellar structure.
Fibrin–antibiotic mixtures: An in vitro study assessing the possibility of using a biologic carrier for local drug delivery
Authors: Greco F. , de Palma L. , Spagnolo N. , Rossi A. , Specchia N. , Gigante A.
Published: December 2004

An in vitro study assessing the kinetics of drug release from antibiotic–fibrin seal compounds and the antibacterial efficacy of the delivered drug has been performed. Antibiotic sensitivity and the amount of drug released was measured by means of agar diffusion test. Standard and experimental curves were established for each antibiotic and each bacterial test in order to evaluate the quantities of the drug released during each 24 h period. The reconstitution of lyophilized human fibrin with an aqueous solution containing an antibiotic resulted in only minor modification of the clotting process, with the exception of those solutions containing cefotaxim and mezlocillin which failed to clot altogether and were excluded from further study. The evaluation of the kinetics of elution of the antibiotics from the fibrin clots showed that all of the antibiotics had been almost completely released by 96 h. The delivered amount of each drug was enough to maintain the Minimal Inhibitory Concentration (MIC) until the 4th day of culture for the most of antibiotics, resulting in a prolonged release of the drug.
Plasma‐sprayed coatings of tetracalciumphosphate, hydroxyl‐apatite, and α‐TCP on titanium alloy: An interface study
Authors: Klein Christel P. A. T. , Patka P. , van der Lubbe H. B. M. , Wolke J. G. C. , de Groot K.
Published: December 2004

In order to study the interaction of calcium phosphate coatings with bone tissue, coated titanium cylinders with a standard size were implanted in dog femora. Coatings were made by plasma spraying powders of hydroxylapatite, β‐whitlockite, and tetracalciumphosphate particles. The plasma spraying process tuns β‐whitlockite into α‐TCP. Bone bonding and bone formation were evaluated by mechanical push‐out tests and histological observations. Hydroxylapatite and tetracalciumphosphate coatings show an interface strength after 3 months of implantation of 34.3 ± 6.5 MPa and 26.8 ± 3.9 MPa, respectively, while α‐TCP and blanco titanium lead to an interface strength of 10.0 ± 3.5 MPa and 9.7 ± 1.3 MPa, respectively. Histological examinations revealed that hydroxylapatite and tetracalciumphosphate give rise to an excellent bone formation, while α‐TCP and blanco titanium evoked remodeling and less bone contact.
Interaction of poly(sodium vinyl sulfonate) and its surface graft with antithrombin III
Authors: Ito Yoshihiro , Liu Lin‐Shu , Imanishi Yukio
Published: December 2004

Poly(sodium vinyl sulfonate) (PVS) was found to be 1/14 times as active as heparin in inducing the conformational change and activation of antithrombin III. The conformational change of antithrombin III was investigated in terms of the intrinsic fluorescence of tryptophan residue, the extrinsic fluorescence using 1,6‐diphenyl‐1,3,5‐hexatriene as fluorescent probe, and Fourier‐transform infrared spectroscopy. It was evident in the experiment using 2,4,6‐trinitrobenzene sulfonate that PVS elicited the activity of antithrombin III by interacting with amino groups of the protein as does heparin.

Sodium vinyl sulfonate was graft‐polymerized onto polyetherurethane (PEU) film that was treated with glow discharge in advance. PVS‐grafted PEU film adsorbed antithrombin III easily and, like ungrafted PVS, induced conformational change and activation of antithrombin III. However, the mechanism of interaction of the PVS graft with antithrombin III did not seem to be completely the same as that of ungrafted PVS in solution.
Fibroblast stimulation by monocytes cultured on protein adsorbed biomedical polymers. I. Biomer and polydimethylsiloxane
Authors: Bonfield T. L. , Colton E. , Anderson J. M.
Published: December 2004

The studies presented in this paper evaluate the modulatory role of protein preadsorbed polydimethylsiloxane (PDMS) and Biomer on the secretion of fibroblast stimulating growth factors from human monocytes/macrophages. The results of these studies show that Biomer and PDMS selectively activate human monocytes to produce fibroblast “progression‐like” and to a lesser extent “competence‐like” stimulating growth factors. Polydimethylsiloxane stimulated the monocytes/macrophages to produce more “progression‐like” fibro‐blast stimulating growth factors than Biomer. The induction of “competencelike” fibroblast stimulating activity from the monocytes was enhanced by preadsorption of PDMS with human derived fibrinogen, fibronectin, IgG, hemoglobin, or albumin. This phenomenon was not observed with protein preadsorbed Biomer. These studies support the hypothesis that protein preadsorbed polymers will selectively modulate monocyte/macrophage activation and induction of growth factors which have the potential to participate in tissue‐implant interactions in vivo.
Improved biocompatability of silicone rubber by removal of surface entrapped air nuclei
Authors: Kalman P. G. , Ward C. A. , McKeown N. B. , McCullough D. , Romaschin A. D.
Published: December 2004

Biomaterials activate the complement system which is important since C3a promotes platelet aggregation and release, and C5a activates neutrophils that may augment coagulation. Tiny air nuclei (microbubbles) are found in the surface roughness of biomaterials on exposure to a liquid, therefore two interfaces exist: (a) a blood/biomaterial, and (b) a blood/air interface. Experiments were carried out that documented that air bubbles activate complement and augment in vitro platelet aggregation in human plasma. The air nuclei were removed from the surface of silicone rubber by a technique termed denucleation to determine if complement activation and platelet aggregation could be reduced. We observed a significant reduction in C3a and C5a in the plasma samples incubated with denucleated silicone rubber as compared to the control samples (p < 0.001, ANOVA). The plasma incubated with the denucleated silicone caused reduced platelet aggregation as compared to the plasma incubated with the control silicone when added to a platelet suspension (p < 0.001, ANOVA). Surface chemical analysis by x‐ray photoelectron spectroscopy (XPS) showed no change in the silicone rubber surface after the denucleation procedure.
Human endothelial cell interactions with surface‐coupled adhesion peptides on a nonadhesive glass substrate and two polymeric biomaterials
Authors: Massia S. P. , Hubbell J. A.
Published: December 2004

The attachment, spreading, spreading rate, focal contact formation, and cytoskeletal organization of human umbilical vein endothelial cells (HUVECs) were investigated on substrates that had been covalently grafted with the cell adhesion peptides Arg‐Gly‐Asp (RGD) and Tyr‐Ile‐Gly‐Ser‐Arg (YIGSR). This approach was used to provide substrates that were adhesive to cells even in the absence of serum proteins and with no prior pretreatment of the surface with proteins of the cell adhesion molecule (CAM) family. This approach was used to dramatically enhance the cell‐adhesiveness of substrates that were otherwise cell‐nonadhesive and to improve control of cellular interactions with cell‐adhesive materials by providing stably bound adhesion ligands. Glycophase glass was examined as a model cell‐nonadhesive substrate prior to modification, and polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE) were examined as representative materials for biomedical applications. The peptides were surface‐coupled by their N‐terminal amine to surface hydroxyl moieties using tresyl chloride chemistry. Prior to peptide grafting, the PET and PTFE were surface hydroxylated to yield PETOH and PTFE‐OH. The PET‐OH was less cell‐adhesive and the PTFE‐OH was much more cell‐adhesive than the native polymers. Radioiodination of a C‐terminal tyrosine residue was used to quantify the amount of peptide coupled to the surface, and these amounts were 12.1 pmol/cm2 on glycophase glass, 139 fmol/cm2 on PET‐OH, and 31 fmol/cm2 on PTFE‐OH. Although the glycophase glass did not support adhesion or spreading even in the presence of serum, the RGD‐ and YIGSR‐grafted glycophase glass did support adhesion and spreading, even when the only serum protein that was included was albumin. Although PET and PTFE‐OH supported adhesion when incubated in serum‐supplemented medium, neither of these materials supported adhesion with only albumin present, indicating that cell adhesion is mediated by adsorbed CAM proteins. When these materials were peptide‐grafted, however, extensive adhesion and spreading did occur even when only albumin was present. Since the peptide grafting is quite easily controlled and is temporally stable, while protein adsorption is quite difficult to precisely control and is temporally dynamic, peptide grafting may be advantageous over other approaches employed to improve long‐term cell adhesion to biomaterials.
The effect of cells on biomaterial calcification: Experiments with in vivo diffusion chambers
Authors: Rosanova I. B. , Mischenko B. P. , Zaitsev V. V. , Vasin S. L. , Sevastianov V. I.
Published: December 2004

The results of these in vivo experiments show that bovine pericardium can undergo calcification without direct contact with tissue. It is clear that the direct interaction of cells with implanted samples both promotes and accelerates the process of calcification. Moreover, dietary calcium supplements, calcium chloride and vitamin D can intensify the rate and extent of this process.
Torsional properties of implant grade titanium
Authors: Zardiackas Lyle D. , Disegi John , Givan Daniel
Published: December 2004

The purpose of this research was to evaluate the torsional strength and ductility of CP titanium in the as received condition, heat treated below the α → β transition temperature, and glass bead blasted. Results were compared to as‐received samples of implant quality 316L stainless steel. Little or no effect of any of the treatments was noted. The torsional strength of all titanium samples was comparable to 316L stainless and the torsional ductility of the titanium was significantly greater than 316L stainless (p <.01). These results are significantly different than those obtained when torsion testing bone screws of the same material. A hypothesis is proposed for the differences in these results.
A new biodegradable copolymer of glycolic acid and lactones with relatively low molecular weight prepared by direct copolycondensation in the absence of catalysts
Authors: Fukuzaki Hironobu , Yoshida Masaru , Asano Masaharu , Kumakura Minoru , Mashimo Tooru , Yuasa Hisako , Imai Kyoichi , Yamanaka Hidetoshi , Kawaharada Umeko , Suzuki Keiji
Published: December 2004

Relatively low‐molecular‐weight copolyesters of glycolic acid (GA) with lactones such as γ‐butyrolactone (BL), δ‐valerolactone (VL), and ϵ‐caprolactone (CL) were synthesized by copolycondensation without catalysts. The resulting copolyesters are intended as carriers for drug delivery systems. Copolyesters with approximately 85 mol% GA (number‐average molecular weight (Mn): 2900 ± 100) are crystalline and solid and show a parabolic‐type in vivo degradation pattern. The in vivo degradation of amorphous‐pasty poly (GA/CL) (approximately 50/50 mol%) changed from parabolic‐type to lineartype to S‐type pattern as their molecular weight increased. A luteinizing hormonereleasing hormone agonist, D‐Leu,6 desGly10 ‐LHRH ethylamide monoacetate (LHRH agonist), was incorporated into small cylinders with these copolyesters. An initial burst of LHRH agonist was observed for cylinders prepared with parabolic‐type degrading copolyesters, in contrast to a marked delay in LHRH agonist release for cylinders prepared with S‐type degrading copolyesters. The resulting daily dose of drug was maintained an approximately constant, though decreasing stepwise with time. For example, the daily amount of LHRH agonist released in vivo from a cylinder prepared with poly(GA/CL) (50/50 mol%; Mn = 4500) was 61 ± 39 μg/day throughout an experimental period of 10 weeks with a corresponding pharmacological effect on the rat prostate.
Bone‐bonding ability of P2O5‐Free CaO · SiO2 glasses
Authors: Ohura Kouichiro , Nakamura Takashi , Yamamuro Takao , Kokubo Tadashi , Ebisawa Yukihiro , Kotoura Yoshihiko , Oka Masanori
Published: December 2004

An apatite‐ and wollastonite‐containing glass‐ceramic (A · W‐GC) has been reported to form a tight bond with living bone through an apatite layer formed on its surface. This layer is considered to be formed by dissolution of Ca2+ and HSiO3− ions from the glass‐ceramic into the surrounding body fluids. In order to confirm this proposed mechanism for the surface reaction of A · W‐GC, three kinds of glass in the systems CaOSiO2, CaOSiO2CaF2, and CaOSiO2P2O5 were implanted into the tibiae of rabbits for 3 or 8 weeks. Contact microradiography and SEM‐EPMA showed that all three kinds of glass formed a Ca, P‐rich layer in combination with a Si‐rich layer on their surfaces within 3 weeks and formed a direct bond with bone via these layers. The detaching test, performed 8 weeks after implantation, showed that the loads required to detach the implants from the bone were almost equal for the phosphorus‐free and the phosphorus‐containing glasses. It was concluded that even P2O5‐free CaO · SiO2 glass formed a Ca,P‐rich layer on its surface and bonded tightly with living bone. If glasses and glass‐ceramics release at least Ca2+ and HSiO3− ions, this would be sufficient for them to form the Ca,P‐rich layer on their surfaces in vivo, enabling them to bond directly with bone.
Quantification of gas denucleation and thrombogenicity of vascular grafts
Authors: Bensen Christopher V. , Vann Richard D. , Koger Kim E. , Klitzman Bruce
Published: December 2004

In vitro methods were developed to measure the air content of vascular graft walls and the thrombogenicity of this air. Gas content (volume %) of expanded polytetrafluoroethylene (ePTFE) grafts from different sources ranged from 75.5 ± 0.4% to 61.8 ± 0.3%. Exposure of Vitagraft ePTFE to a vacuum prior to saline immersion replaced 87.5% of the gas nuclei with saline (denucleation). Acetone and ethanol immersion produced 98.9% and 94.3% denucleation, respectively. Denucleation was essentially complete when vacuum exposure was followed by hydrostatic pressure treatment at 500 psig or greater. The influence of gas content on thrombogenicity was determined by immersing graft samples in whole canine blood and weighing the adherent thrombus. Denucleation significantly reduced adherent thrombus weight compared with control grafts (p < 0.001). Air in Vitagraft walls was responsible for 84% of the adherent thrombus weight at four minutes. The described methods could be employed to assess the hemocompatibility of various biomaterials.
A light and electron microscopic study of the effects of surface topography on the behavior of cells attached to titanium‐coated percutaneous implants
Authors: Chehroudi B. , Gould T. R. L. , Brunette D. M.
Published: December 2004

Previous studies using light microscopy have demonstrated that micromachined grooved surfaces inhibit epithelial (E) downgrowth and affect cell orientation at the tissue/implant interface. This study investigates the ultrastructure of the epithelial and connective‐tissue attachment to titanium‐coated micromachined grooved, as well as smooth control, implant surfaces. V‐shaped grooves, 3, 10, or 22 μm deep, were produced in silicon wafers by micromachining, replicated in epoxy resin, and coated with 50‐nm titanium. These grooved, as well as smooth, titanium‐coated surfaces were implanted percutaneously in the parietal area of rats and after 7 days processed for electron microscopy. The tissue preparation technique used in this study enabled us to obtain ultrathin sections with few artifacts from the area of epithelial and connective‐tissue attachment. The histological observations demonstrated that E cells closely attached to, and interdigitated with, the 3‐μm and 10‐μm grooves. In contrast, E cells were not found inside the 22‐μm‐deep grooves and made contact only with the flat ridges between the grooves. As a general rule, fibroblasts (F) were oriented parallel to the long axis of the implants and produced a connective tissue capsule with 3‐μm and 10‐μm‐deep grooved surfaces as well as smooth surfaces. On the 22‐μm‐deep grooved surfaces, however, F inserted obliquely into the implant. The attachment of F to the titanium surface was mediated by two zones; a thin (≈︁20 nm), amorphous, electron dense zone immediately contacting the titanium surface, and a fine fibrillar zone extending from the amorphous zone to the cell membrane. As oblique orientation of F has been associated with the inhibition of epithelial downgrowth, micromachined grooved surfaces of appropriate dimensions have the potential to improve the performance of percutaneous devices.
The minimum surface fibrinogen concentration necessary for platelet activation on dimethyldichlorosilane‐coated glass
Authors: Park K. , Mao F. W. , Park H.
Published: December 2004

Albumin and fibrinogen were competitively adsorbed onto dimethyldichlorosilane‐coated glass (DDS‐glass) and platelet activation was examined as a function of the surface fibrinogen concentration. The weight ratio of albumin to fibrinogen in the adsorption solution was varied from 10 to 700. Platelet activation was quantitated by the area and circularity of spread platelets. When the DDS‐glass was coated with albumin alone, platelets were only contact adherent and could not spread at all. After competitive adsorption of fibrinogen and albumin, however, platelets were able to spread on the surface. Platelet activation increased linearly as the surface fibrinogen concentration increased up to 0.02 μg/cm2. Platelets were able to activate fully if the surface fibrinogen concentration was 0.02 μg/cm2 or higher, even though the surface was dominated by albumin. It appears that platelets can activate fully as long as only a small fraction (2–15%) of the surface is covered with tightly bound fibrinogen.
Cytotoxicity of a BIS‐GMA dental composite before and after leaching in organic solvents
Authors: Anne Rathbun M. , Craig Robert G. , Hanks Carl T. , Filisko Frank E.
Published: December 2004

Cell culture techniques were used to determine the source of cytotoxic agents in a commercial BIS‐GMA composite. The material was polymerized according to the manufacturer′s directions and leachable components were removed by room temperature extraction in ethanol, chloroform, or toluene. The leachable components in the extracts were identified using infrared spectrographic analysis. Thin layer chromatographic analysis was used to determine the number of constituents. These constituents were separated by gas chromatography and then identified by mass spectrographic analysis. Succinic dehydrogenase activity and radioactive labeling with tritiated leucine were used to evaluate cell metabolism and protein synthesis, respectively. The infrared analysis of the extracts showed that the primary component was unreacted BIS‐GMA. Trace amounts of 2‐hydroxy‐4‐methoxy‐benzophenone, a light stabilizer, as well as a phenyl ester of benzoic acid which was probably degraded from BIS‐GMA, were detected by the mass spectrographic method. The removal of leachable components caused a 90% decrease in toxicity compared to the nonextracted BIS‐GMA samples. The extracted BIS‐GMA samples showed no cellular response compared to the Teflon negative control.
The periapical tissue reactions to a calcium phosphate cement in the teeth of monkeys
Authors: Hong Y. C. , Wang J. T. , Hong C. Y. , Brown W. E. , Chow L. C.
Published: December 2004

A calcium phosphate cement, Grossman sealer, and Sargenti N2 were compared under conditions where root canals of monkey incisors were deliberately overfilled and the apical tissue responses were evaluated histologically. The periapical tissues exposed to Sargenti N2 revealed severe irritation at all times through the 6‐month experimental period. The reactions to Grossman sealer were milder but persisted throughout the observation period. The calcium‐phosphate‐cement treated animals showed mild tissue irritation after 1 month, but thereafter the adverse tissue reactions were minimal. New bone formation adjacent to the cement was also observed. These results point to the possibility that calcium phosphate cement might be used in simplified endodontic procedures. The compatibility of calcium phosphate cement with the periapical tissue suggests that the cement may have other applications in dentistry and medicine.
Quantitative analysis of in vivo tissue responses to titanium‐oxide‐ and hydroxyapatite‐coated titanium alloy
Authors: Hayashi K. , Uenoyama K. , Matsuguchi N. , Sugioka Y.
Published: December 2004

We have previously studied a large number of histological specimens of biomaterials and found that regions with and without an intervening fibrous membrane coexisted in many specimens. Therefore, it appears necessary to perform an evaluation of the entire specimen when histologically assessing the affinity of bone for a biomaterial. Accordingly, we performed a quantitative histological evaluation of hydroxyapatite (HAP)‐ and titanium‐ oxide(TiO2)‐coated Ti‐6Al‐4V and uncoated Ti‐6Al‐4V (control) by determining the affinity index. This was defined as the length of bone directly opposed to the implant/the total length of the bone‐‐implant interface X 100%. The test materials were inserted into the distal epiphyseal region of the femurs of adult dogs, and follow‐up quantitative histological comparisons were performed from 4 weeks to 96 weeks. The HAP‐coated implants had the highest affinity index 4 weeks after insertion, and this superiority was maintained up to 96 weeks. There was a significant difference in affinity index between HAP‐coated implants and control implants (P < 0.001), while TiO2‐coated implants showed no significant difference in comparison to the control.
The role of an endothelial cell lining in limiting distal anastomotic intimal hyperplasia of 4‐mm‐I.D. Dacron grafts in a canine model
Authors: Graham Linda M. , Brothers Thomas E. , Vincent Christopher K. , Burkel William E. , Stanley James C.
Published: December 2004

The effect of an endothelial cell (EC) lining on intimal hyperplasia at the distal anastomosis of Dacron grafts was assessed in a canine model. Enzymatically derived autologous EC were used to seed 14 to 17 cm long, 4 mm I.D., knitted Dacron aortoiliac grafts implanted in an end‐to‐side manner in six dogs (Group I). Unseeded grafts were similarly implanted in six control dogs (Group II). All animals received acetylsalicylic acid (325 mg po qd) 24 h prior to graft placement and for 2 weeks postoperatively. Distal anastomotic intimal hyperplasia (AIH) and luminal surface EC coverage were quantitated at the conclusion of a 16‐week study period. Patency for Group I and Group II grafts were 90% and 55%, respectively (p = 0.07). Maximum AIH, defined as the maximum reduction of luminal cross‐sectional area at the distal anastomosis, was not significantly different between Group I (13.1 ± 8.0%) and Group II (15.1 ± 7.3%) conduits. However, AIH was inversely related to the extent of luminal EC coverage (r = −0.6, p < 0.05), thus greater endothelialization was associated with decreased AIH. These data support the idea that EC coverage of the luminal surface of prosthetic vascular grafts may limit the development of AIH.
Postadsorptive transitions in fibrinogen adsorbed to Biomer: Changes in baboon platelet adhesion, antibody binding, and sodium dodecyl sulfate elutability
Authors: Chinn Joseph A. , Posso Sylvia E. , Horbett Thomas A. , Ratner Buddy D.
Published: December 2004

Residence‐time‐dependent changes in fibrinogen after its adsorption to Biomer were examined by measuring platelet adhesion and antibody binding to the adsorbed protein, and the amount of adsorbed fibrinogen which could be eluted by sodium dodecyl sulfate (SDS). Baboon fibrinogen was first adsorbed (from either pure solution or dilute plasma) to Biomer, which was then stored in either buffer or buffered albumin solution prior to testing. Subsequently, the adherent protein layer was either probed for fibrinogen capable of mediating platelet adhesion using 111In radiolabeled, washed platelet suspensions under both static and shearing conditions, or for fibrinogen capable of binding antibody using a direct enzyme linked immunosorbent assay (ELISA). Alternatively, the surface with the adsorbed protein layer was soaked in a 3% SDS solution, and the amount of 125I radiolabeled fibrinogen retained was measured. Decreases in platelet and antibody binding, and in the SDS elutability of the adsorbed fibrinogen after it was stored in buffer were detected, although different rates of decrease were observed for each method. When the protein‐coated surfaces were stored in buffered albumin solution rather than buffer, the decrease in the reactivity of fibrinogen was prevented. While each of the three assays measures a different property of adsorbed fibrinogen, this study suggests that the adherent protein undergoes time dependent conformational changes which render it less reactive toward platelets and antibodies, and more resistant to elution by SDS.
Negative cilia concept for thromboresistance: Synergistic effect of PEO and sulfonate groups grafted onto polyurethanes
Authors: Han Dong Keun , Jeong Seo Young , Kim Young Ha , Min Byoung Goo , Cho Han Ik
Published: December 2004

In order to investigate the interaction between various sulfonated polyurethanes (PUs) and blood, a commercial PU surface was chemically modified by poly(ethylene oxide) (PEO), dodecanediol(DDO), and propane sultone to give hydrophilic, hydrophobic, and negative sulfonated surfaces, respectively. The blood compatibility of modified PUs was evaluated by an in vitro platelet adhesion test, activated partial thromboplastin time (APTT), and prothrombin time (PT) measurements as well as an ex vivo rabbit A‐A shunt method. In the platelet adhesion test, the hydrophilic PEO grafted PUs showed less platelet adhesion than untreated PU and hydrophobic DDO grafted PU. Sulfonated PU‐PEO exhibited a lower degree of adhesion and shape change of platelet. The APTT and PT, especially APTT, of the sulfonated PUs were extended, whereas those of PU‐PEO and PU‐DDO did not show any significant change compared with untreated PU. Meanwhile, in the ex vivo experiment, hydrophilic PEO grafted PUs showed longer occlusion times than untreated PU or hydrophobic DDO grafted PU. In addition, the incorporation of SO3 groups at the end of PU‐DDO and PU‐PEO, particularly PU‐PEO‐SO3, exhibited an enormous prolongation in occlusion time, indicating a synergistic effect of the hydrophilic PEO and the negative SO3 groups on thromboresistance. These occlusion times corresponded well to in vitro evaluation results: the less adhesion and shape change of platelet and the longer APTT and PT, the more extended the ex vivo occlusion time.
Preparation of thermo‐responsive membranes. II
Authors: Nozawa Iwao , Suzuki Yosuke , Sato Shuji , Sugibayashi Kenji , Morimoto Yasunori
Published: December 2004

Two types of liquid crystal (LC)‐immobilized membranes were prepared by a soaking method and sandwich method to control the permeation of indomethacin, as a model drug, in response to local and systemic fever. Monooxyethylene trimethylolpropane tristearate (MTTS) was used as a model LC because it has a gel‐liquid crystal phase transition temperature near the body temperature, 39–40°C in phosphate buffered saline (pH 7.4). Two porous polypropylene (PP) membranes were soaked into 20% MTTS chloroform solution in the soaking method, and two PP membranes were poured with the melted MTTS and pressed in the sandwich method. Thermo‐response efficacy of the soaked membrane was dependent upon the content of MTTS in MTTS membrane, and the MTTS content above the void volume of PP membrane (38%) was needed for high efficacy. On the other hand, the sandwich membrane exhibited higher thermo‐response efficacy than the soaked membrane, because more LC was embedded in the pores of sandwich membrane than that of the soaked membrane. The sandwich membrane permeation of indomethacin was sharply controlled by temperature changes between 32 and 38°C.