bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing correlations between fibrinogen adsorption and surface properties using multivariate statistics
Authors: Pérez‐Luna Víctor H. , Horbett Thomas A. , Ratner Buddy D.
Published: May 2005

A multivariate model based on the partial least squares algorithm (PLS) was constructed in order to establish a correlation between the surface properties of common polymeric materials and the amount and retention of fibrinogen adsorbed from a complex mixture. Surface characterization was performed by means of static secondary ion mass spectroscopy (SIMS), electron spectroscopy for chemical analysis (ESCA), and by contact angle measurements of several liquids on those materials.125I‐fibrinogen was adsorbed from a 1% plasma solution in buffer and the amount adsorbed after 2 h was determined. After 5 days of residence time in buffer, the adsorbed fibrinogen was eluted with a 1% solution of the surfactant sodium dodecyl sulfate (SDS). The percent of fibrinogen that remained on the surfaces after elution is referred to as fibrinogen retention. Correlations between surface properties and the amounts of fibrinogen adsorbed or fibrinogen retention were established. These models also show the most important variables that are related to the protein behavior on these surfaces. © 1994 John Wiley & Sons, Inc.
Recombinant human bone morphogenetic protein‐2 is superior to demineralized bone matrix in repairing craniotomy defects in rats
Authors: Marden Leslie J. , Hollinger Jeffrey O. , Chaudhari Anshumali , Turek Tom , Schaub Robert G. , Ron Eyal
Published: May 2005

The purpose of this study was to measure bone‐regenerative effects of recombinant human bone morphogenetic protein‐2 (rhBMP‐) in rat calvarial critical‐size defects (CSDs). CSDs (8 mm in diameter) were treated with either: (1) 2.2 µg rhBMP‐ combined with insoluble collagenous bone matrix (ICBM), (2) 6.5 µg rhBMP‐ plus ICBM, (3) ICBM alone, or (4) demineralized bone matrix (DBM), for 7, 14, or 21 days. Multiple linear regression showed that rhBMP‐ had a significant time‐ and dose‐dependent effect on bone regeneration (P < .05). After 7 days, new calcifying cartilage and remineralizing ICBM, with an occasional zone of new woven bone, was evident in defects treated with rhBMP‐/ICBM. By 14 days, both doses of rhBMP‐ reconstituted with ICBM had induced more bone formation than ICBM alone or DBM, and 6.5 µg was superior to 2. 2 m̈g. There was no evidence of adverse cellular response. This study shows for the first time that rhBMP‐ could restore osseous form to a calvarial defect. In addition, osteoregeneration was accelerated by the higher dose of rhBMP‐. © 1994 John Wiley & Sons, Inc.
Thermal stability of sodium hyaluronate in aqueous solution
Authors: Lowry Karen M. , Beavers Ellington M.
Published: May 2005

Since its identification 60 years ago as a ubiquitous component of the body of mammals, hyaluronic acid has been widely studied, primarily in the fields of medicine and biology. On the other hand, our research has dealt with hyaluronic acid as a chemical intermediate in the synthesis of novel lubricious coatings, and in this connection data were needed on stability of aqueous solutions of the polymer over a range of temperatures from 25–100°C. The investigation reported here provides that information, obtained by exposing samples in sealed ampules in baths a controlled temperatures and determining the resultin change in viscosity of the solutions. Data of this kind have not previously been reported on sodium hyaluronate free from the proteins and other organics normally associate with the polymer in its natural environment. © 1994 John Wiley & Sons, Inc.
Analysis of the general features of the soft tissue response to some metals and ceramics using quantitative histomorphometry
Authors: Therin M. , Christel P. , Meunier A.
Published: May 2005

This article analyzes the general features of the tissue response to orthopedic biomaterials when implanted in the paraspinal muscles in rats for periods between 1 week and 1 year. Using a computer‐assisted cell counting method, it was shown that the membrane thickness was a stable parameter that poorly correlated with the other histomorphometric parameters except fibrocyte distance parameters. Macrophages were significant in number only in the short term and were always located at the implant‐tissue interface. At 4 weeks, the period corresponding to which macrophages disappeared, fibrocytes were found nearer the interface than at earlier periods and did not migrate for up to 52 weeks, although their densities decreased to 50% of their initial values. Therefore, it can be histomorphometrically confirmed that (1) the presence of an implant induced a delay in the healing process; (2) the immune system was not usually involved in the response to bulk metals; and (3) at early time periods, the presence of PMN cells was correlated to the long‐term number of macrophages. On the contrary, the histomorphometric findings suggested that around the tested materials, a large number of macrophages did not induce an immediate or a delayed fibrocyte proliferation. If one considers that a low fibrocyte surface density is related to activated cells surrounded by a matrix high in collagen content, then the large number of macrophages induced the stimulation of collagen synthesis by the fibrocytes already included in the membrane. Accordingly, in the short‐term, a high fibrocyte density and few macrophages may be a criterion for testing biocompatibility. © 1994 John Wiley & Sons, Inc.
Isolation and characterization of metallic wear debris from a dynamic intervertebral disc prosthesis
Authors: Schmiedberg Stefan K. , Chang Dennis H. , Frondoza Carmelita G. , Valdevit Antonio D. C. , Kostuik John P.
Published: May 2005

A dynamic intervertebral disc prosthesis (DIDP) has been developed. It consists of a CoCrMo body and uses Ti6A14V springs to replicate the mechanical function of the lumbar joint. Wear studies have been performed previously on the DIDP using two specialized simulators to test the wear properties of the moving parts of the disc prosthesis. A pin‐in‐slot simulator generates wear that would occur in the hinge‐pin assembly of the prosthesis. A spring‐in‐pocket simulator approximates the conditions under which the springs would wear against the body of the prosthesis. The spring‐pocket interface is responsible for the production of approximately 90% of the total wear occurring in the prosthesis, and is therefore the main focus of this study. Bovine serum with a preservative has been used as a lubricant in both simulators. The spring‐in‐pocket simulator compares the effects of two different manufacturing techniques of CoCrMo (HIPing and forging) on their wear characteristics against Ti6A14V springs. Debris from the spring‐in‐pocket simulator has been isolated from the serum lubricant and characterized using scanning electron microscopy techniques. The morphology of the Ti6Al4V fragments is rough and irregularly shaped. The size of these fragments ranges from <1 μm. to > 30 μm. The forged CoCrMo alloy debris has an irregular polyhedral shape, with sizes in the same range as the spring fragments. The morphology of the HIPed CoCrMo debris is spherical with a size range <5 m̈m to >30 μm. Length and width measurements of micron‐size particles were made with the particle measurement feature of the scanning electron microscope. Micron‐size particles were found in all stations. This article provides a unique way to isolate and analyze debris from serum lubricants used in simulators. © 1994 John Wiley & Sons, Inc.
Titanium fiber mesh anchorage for percutaneous devices applicable for peritoneal dialysis
Authors: Paquay Y. C. G. J. , De Ruijter J. E. , van Der Waerden J. P. C. M. , Jansen J. A.
Published: May 2005

In previous experiments a new type of percutaneous device for implantation in soft tissue was designed. The subcutaneous component of the new device consists of a sintered titanium fiber web. The percutaneous devices are inserted by a so‐called „two‐phase”︁ surgical technique with an intervening healing period of 3 months between the insertion of the subcutaneous flange and the placement of the percutaneous part. From a clinical point of view, this time interval is too long. Therefore, the aim of this study was to investigate a possible reduction of the intervening healing period. The implants were inserted in the backs of 18 rebbits. In each rabbit, six implants were placed with intervals of 1 week. Consequently, at the end of the experiment, in each rabbit six implants were present with implantation periods ranging from 5–10 weeks. After 10 weeks, the animals were sacrificed and the implants with their surrounding tissues were processed histologically. Light microscopic and histomorphometric analysis demonstrated that there was no difference in tissue response between the various implantation periods. Furthermore, it was found that the fiber mesh material showed good biocompatible behavior. In conclusion, the experiment has demonstrated that for titanium mesh percutaneous devices a 5‐week healing period is sufficient between the installation of the subcutaneous and percutaneous parts. © 1994 John Wiley & Sons, Inc.
Studies on calcium phosphate precipitation: Effects of metal ions used in dental materials
Authors: Okamoto Y. , Hidaka S.
Published: May 2005

The effects of 26 metal ions, of which 23 are used in dental materials, on the conversion of amorphous calcium phosphate (ACP) to hydroxyapatite (HAP) in vitro were studied. From the effects on both the rate of HAP transformation and induction time, effects of metal ions were classified into three types; inhibitory (in the order: nickel, tin, cobalt, manganese, copper, zinc, gallium, thallium, molybdenum, cadmium, antimony, magnesium, and mercury); ineffective (cesium, titanium, chromium, iron [ferrous], iridium, palladium, platinum, silver, gold, aluminum, and lead); and stimulatory (iron [ferric] and indium). These results suggest that metal ions used in dental materials may modify the precipitation of oral calcium phosphate. © 1994 John Wiley & Sons, Inc.
Dual constant composition kinetics characterization of apatitic surfaces
Authors: Paschalis E. P. , Wikiel K. , Nancollas G. H.
Published: May 2005

The use of calcium phosphate phases as implant materials in forms such as ceramic hydroxyapatite (CHAP) and hydroxyapatite plasma‐coated implants (HPCTI) as well as the synthetic phases is now quite well established. Although conventional physical chemical charaterization methods such as X‐ray diffraction may indicate the exclusive presence of hydroxyapatite (HAP), there is little doubt that other calcium‐containing surface impurities play important roles in the initial reactions that take place when such materials are brought into contact with aqueous phases. These surface impurities usually dissolve rapidly with the release of excess calcium and hydroxide ions. Based on the constant composition (CC) method, the dual constant composition (DCC) approach has been developed for investigating the dissolution kinetics behavior of these apatitic materials in an attempt to characterize and modify the surfaces, and possibly to predict their behavior when placed in vivo. The results of this study confirm the presence of highly reactive heterogeneous calcium‐containing phases on the surface of materials such as CHAP and HPCTI, as evidenced by the release of appreciable amounts of calcium and hydroxyl ions upon introduction of these surfaces in saline solutions. Furthermore, these calcium phosphate phases exhibited a unique dissolution behavior when compared with synthetically prepared phases such as HAP and β‐tricalcium phosphate (β‐TCP), as suggested by the observation that they dissolve in solutions supersaturated with respect to HAP. © 1994 John Wiley & Sons, Inc.
Surface energy characterization of unalloyed titanium implants
Authors: Kilpadi Deepak V. , Lemons Jack E.
Published: May 2005

Osteointegration is dependent on a variety of biomechanical and biochemical factors. One factor is the wettability of an implant surface that is directly influenced by its surface energy. This investigation used the Zisman plot to determine critical surface energy. The effects of surface treatment, bulk grain size, and surface roughness on the critical surface tension of unalloyed titanium (Ti) were examined. Radio frequency glow discharge‐treated Ti had the highest critical surface tension, followed by the passivated and heat‐sterlized conditions. Titanium with no surface treatment had the lowest critical surface tension. The surface energy of Ti with an average grain size of 23 μm was not significantly different from that with a grain size of 70 μm. Surface roughness was shown to cause significant difference in measurements and definitely should be considered in studies of this kind. © 1994 John Wiley & Sons, Inc.
Atomic force microscopy studies of the interaction of a dentin adhesive with tooth hard tissue
Authors: Cassinelli C. , Morra M.
Published: May 2005

The usefulness of atomic force microscopy (AFM) in the study of dental biomaterials was investigated. Two basic points were addressd: the first is the use of an atomic force microscope for the imaging of tooth hard tissue; the second is a study by AFM of the interaction of a liquid adhesive (Gluma) with dentin. Results show that dental tissues are readily imaged by AFM and that high‐resolution images of the dentin ultrastructure can be obtained. As to the dentin adhesive, it was possible to elucidate the mechanism of action of Gluma. In particular, polymerization of the hydroxyethylmethacrylate present in the Gluma mixture was observed to occur in <30 seconds. © 1994 John Wiley & Sons, Inc.
Inflammatory response and degradation of three types of calcium phosphate ceramic in a non‐osseous environment
Authors: van der Meulen J. , Koerten H. K.
Published: May 2005

The cellular response and inflammatory reaction to three types of calcium phosphate ceramic spheres, namely fluorapatite (FA), hydroxyapatite (HA), and β‐tricalcium phosphate (TCP), were investigated. The degradation at ultrastructural level of these ceramics was also studied. The mouse peritoneal cavity was used as a model compartment for this study. To minimize the influence of a wound reaction, the spheres were implanted by injection. Intraperitoneal injection of lates beads of 6.4 and 25.7 μm showed that an inflammatory reaction is influenced by the size of injected particles; therefore, ceramic spheres with the same average diameter (11.3 μm) were used. After 2 and 4 days and 1, 2, 4, 8, 12, and 24 weeks, the spheres were harvested. All materials gave rise to a short, mild inflammatory reaction. The ceramic spheres aggregated rapidly, and foreign body granulomas were formed within 2 weeks. Degradation of all materials was observed in this study, and degradation products were frequently seen both intracellularly and extracellularly. After 2 weeks TCP and HA showed the formation of crystals at their surface and between individual grains of the spheres. This was most prominently seen with TCP. At 4 weeks, HA and TCP granulomas showed the formation of extracellular, globular deposits between macrophages or multinucleated giant cells and fragments of the ceramic. They consisted of an organic matrix containing apatite‐like crystals and iron, and had an average diameter of 10 μm. The number of deposits was the highest for TCP. For FA, calcium phosphate precipitation and the formation of deposits was not observed before the 8‐week interval and remained at a low level. © 1994 John Wiley & Sons, Inc.
Effect of 2‐amino oleic acid exposure conditions on the inhibition of calcification of glutaraldehyde cross‐linked porcine aortic valves
Authors: Chen Weiliam , Kim John D. , Schoen Frederick J. , Levy Robert J.
Published: May 2005

Postimplant calcific degeneration is a frequent cause of clinical failures of glutaraldehyde cross‐linked porcine bioprosthetic heart valves (BPHV). It was demonstrated previously that 2‐amino oleic acid (AOA) used as a bioprosthesis treatment was highly effective in mitigating aortic valve cusp but not aortic wall calcification. Our main objective was to study the efficacy of various AOA exposure conditions for inhibiting calcification of both cusps and aortic wall tissues using rat subdermal implants. BPHV tissues were treated with a saturated AOA solution for different time intervals before experimentation. Aortic wall AOA levels were consistently lower than that of the cusps after the same exposure times. The diffusion of calcium ion across both cusp and aortic wall tissues was evaluated, and the results demonstrated that there was an AOA exposure time‐dependent retardation of calcium ion penetration for cusp but not aortic wall. An 8‐month extraction study was performed to determine the stability of AOA binding. When Tween 80 was used as an extraction medium, cusp and aortic wall retained 12.9 and 48.7%, respectively, of their initial AOA levels. AOA inhibition of calcification in rat subdermal implants (60 days) was found to be exposure time‐dependent with maximum treatment time (120 h), resulting in the lowest calcium levels (20.1 ± 10.3 and 71.4 ± 5.4 μg/mg of cusp and aortic wall, respectively) as compared with control (219.1 ± 6.8 and 104.9 ± 8.5 μg/mg of cusp and aortic wall respectively). The significance of AOA binding on BPHV tissue was determined by either blocking or reducing BPHV's (cusp and aortic wall) free aldehyde residues with lysine or NaBH4, respectively, before AOA treatment. For aortic cusps, the AOA contents after 72 h were 98.3 ± 2.7, 34.2 ± 3.6, and 54.1 ± 3.0 nM/mg of tissue for AOA (control), lysine‐pretreated (plus AOA) and NaBH4‐pretreated (plus AOA) tissues, respectively. However, their calcium levels after 60 days of rat subdermal implant were all comparable (i. e., 48.1 ± 6.2, 38.2 ± 9.1, and 47.0 ± 15.0 μg calcium per mg of tissue). Similar results were observed on BPHV aortic wall. It can thus be concluded that AOA inhibition of BPHV calcification is exposure time‐dependent, but the efficacy of AOA for aortic wall is less than that noted for aortic cusps, perhaps because of lower AOA bindings and differences in calcium diffusion kinetics. © 1994 John Wiley & Sons, Inc.
Formation and characterization of anodic titanium oxide films containing Ca and P
Authors: Ishizawa Hitoshi , Ogino Makoto
Published: May 2005

Commercially pure titanium was anodized in an electrolytic solution that was dissolved calcium and phosphorus compounds in water, and an AOFCP (anodic titanium oxide film containing Ca and P) was formed. It was found that sodium β‐glycerophosphate (β‐GP) and calcium acetate (CA) were suitable for the electrolytes to form the AOFCP having an equivalent Ca/P ratio to hydroxyapatite (HA). The AOFCP was characterized by scanning electron microscopy (SEM), an energy‐dispersive X‐ray microanalysis (EDX), and X‐ray diffraction (XRD). Numerous micropores and microprojections were observed on the AOFCP by SEM. The composition of the AOFCP, which was measured by EDX, changed according to β‐GP and CA concentration, and the electrolytic voltage. Ca and P in the AOFCP seem to be incorporated into the TiO2 matrix from CA and β‐GP in the electrolyte during the anodic oxidation. Despite the existence of Ca and P in the AOFCP, no calcium phosphate peak was detected by XRD, and the AOFCP consisted of anatase and only a little rutile. The AOFCP, whose contents of Ca and P were low, had a high adhesive strength after soaking in a simulated body fluid for 300 days. When the AOFCP having an equivalent Ca/P ratio to HA was hydrothermally heated at 300°C, HA crystals were precipitated on the AOFCP and completely covered the surface. © 1995 John Wiley & Sons, Inc.
Initial bone matrix formation at the hydroxyapatite interface in vivo
Authors: de Bruijn J. D. , van Blitterswijk C. A. , Davies J. E.
Published: May 2005

Dense, sintered, slip‐cast hydroxyapatite rods were implanted transfemorally in young adult rats. The femora were excised after 2 and 4 weeks and, following fixation, either embedded in methyl methacrylate for light microscopy, decalcified and prepared for transmission electron microscopy, or freeze fractured in liquid nitrogen for scanning electron microscopic analysis. The latter was performed on the two tissue fragments that remained after freeze fracturing, from which the first contained the implants and the second comprised tissue that had been immediately adjacent to the hydroxyapatite rods. Undecalcified light microscopic sections revealed extensive bone tissue formation around and in contact with the hydroxyapatite rods. The initial bone matrix apposed to the implant surface, as demonstrated with scanning electron microscopy, was either composed of globular deposits or an organized network of collagen fibers. The deposits, which ranged in size from 0.1–1.1 μm, fused to form a cement‐like matrix to which collagen fibers were attached. Degradation of the hydroxyapatite surface resulted in the presence of unidirectionally aligned crystallites, with which the newly formed bone matrix was closely associated. Ultrastructural analysis of the bone‐hydroxyapatite interface with transmission electron microscopy revealed a 50–600‐nm‐wide collagen‐free granular zone, comprising one or more 40–100‐nm‐thick electron‐dense layer(s). These structural arrangements most probably partially represent the globular deposits and proteinaceous material adsorbed onto and partially in the degrading hydroxyapatite surface. Although the latter change in surface topography may have enhanced bonding of the cement‐like matrix to the hydroxyapatite, the cause for this change in topography and the type of bond formed are, at present, unknown. © 1995 John Wiley & Sons, Inc.
Immunofluorescence and confocal laser scanning microscopy studies of osteoblast growth and phenotypic expression in three‐dimensional degradable synthetic matrices
Authors: Attawia Mohamed A. , Devin Jessica E. , Laurencin Cato T.
Published: May 2005

In the development of three‐dimensional cell‐polymer synthetic matrices for tissue regeneration, visualization of cells growing in these porous structures can be difficult. The focus of this study was the development and use of a novel method that would allow for visualization of osteoblasts inside opaque matrices. The morphologic responses and phenotypic characterization of osteoblasts as they attach, spread, and migrate through a porous three‐dimensional biodegradable polymer‐ceramic matrix in vitro were studied using immunofluorescence and confocal laser scanning microscopy (CLSM). CLSM offers several advantages over the most commonly used imaging methods [traditional light microscopy and scanning electron microscopy (SEM)]. CLSM filters out‐of‐focus background and provides more structural details of cells. In addition, CLSM does not require extensive sample preparation as does SEM. When used in conjunction with fluorescence‐labeled antibodies to identify cells and their products, it can characterize morphology of growing cells and successfully determine phenotypic function. Using monoclonal antibody to osteocalcin, a bone cell‐specific protein, cells throughout the matrix were found to have preserved osteoblast‐like phenotype with growth. The morphology of cells throughout the matrix was found to be similar to osteoblast cells grown on tissue culture polystyrene and consisted of spread polygonal forms. Using the technique of CLSM with immunofluorescent antibodies, we have demonstrated for the first time that these three‐dimensional degradable polymer matrices can support osteoblast growth and phenotypic expression throughout its structure. © 1995 John Wiley & Sons, Inc.
Low‐voltage scanning electron microscopic imaging of ultrahigh‐molecular‐weight polyethylene
Authors: Pienkowski David , Jacob Robert , Hoglin Dennis , Saum Kenneth , Kaufer Herbert , Nicholls Paul J.
Published: May 2005

Submicron ultrahigh‐molecular‐weight polyethylene (UHMWPE) wear particles from total joint prostheses may contribute to implant failure through particle‐mediated aseptic loosening. The purpose of this study was to examine the microstructure of virgin UHMWPE powder to determine its morphology for future comparison with wear debris. A new method of low‐voltage scanning electron microscopy (LVSEM) in an oil‐free vacuum was applied, which produced high‐resolution images of UHMWPE micromorphology, while minimizing specimen damage and obviating the need for image processing. GUR 415 UHMWPE virgin powder particles were examined by using routine high‐voltage SEM, LVSEM, and image analyses. LVSEM showed that UHMWPE particles were composed of submicron‐size spherical subparticles connected by numerous nanometer‐size fibrils. These spherical subparticles had a highly textured surface morphology seen only by LVSEM. Fracture of the nanometer‐size fibrils was observed. Routine high‐voltage SEM obfuscates the intricate and delicate UHMWPE micromorphology as well as the damage done by the accompanying high‐voltage electron. This study suggests that the micromorphology of wear particles previously studied with routine high‐voltage SEM was overlooked or damaged, justifies the need for LVSEM in future studies, and raises the question of what is the true morphology of polyethylene wear debris retrieved from human tissues. © 1995 John Wiley & Sons, Inc.
Distribution of titanium and vanadium following repeated injection of high‐dose salts
Authors: Merritt Katharine , Brown Stanley A.
Published: May 2005

Titanium and its alloy of 6% aluminum and 4% vanadium are used extensively in orthopedic and dental surgery. However, in conditions of motion leading to wear, there is significant generation of wear products with deposition of black debris in the tissue. The questions remain as to how much of this debris is generated and to where it is transported. Previous studies have been hampered by low levels of detected elements giving values just above the background levels found in normal tissue and body fluids. The purpose of these experiments was to increase the body burden of titanium and vanadium by injecting larger doses of titanium and vanadium salts over an extended period of time. Each animal (Syrian hamster) received 100 μg of each element once a week for six weeks. The hamster was sacrificed on the seventh week and body fluids and tissue harvested. The results indicate that in the experimental animals there was transport of vanadium with levels above control in urine, plasma, liver, spleen, and the mineralized portion and organic portion of bone. Titanium had less transport but still showed levels in the experimental animals in plasma, kidney, liver, spleen, and both phases of bone above those in the control animals. Neither element was found above control levels in lung or red blood cells. The levels of titanium and vanadium in control bone were high, possibly indicating bone as a site for storage and accumulation of these elements when encountered in the activities of daily living. © 1995 John Wiley & Sons, Inc.
Endothelial cells on dacron vascular prostheses: Adherence, growth, and susceptibility to neutrophils
Authors: Tunstall Ann , Eberhart Robert C. , Prager Morton D.
Published: May 2005

Human umbilical vein endothelial cells (HUVEC) on knitted and woven Dacron prostheses were compared with HUVEC on smooth surfaces (tissue culture polystyrene, PET film, and Natrix) with regard to adherence, growth, and susceptibility to injury by neutrophils (PMN). These are properties of importance for successful seeding or coating of prostheses. For prosthetic material of given macroscopic dimensions, more endothelial cells (EC) adhered than to smooth surfaces. However, the prostheses had a greater effective surface area as determined by the number of EC at confluency. When this parameter was taken into account, fewer EC were found adherent to prosthetic material per unit effective surface area than for the smooth surface substrates. Growth on prostheses was clearly inferior to that on smooth surfaces, and EC on prostheses were more susceptible to attack by activated PMN than on smooth surfaces. These differences may reflect the topographic differences in cells attached to fibers where they assume more distorted shapes by stretching to span fibers. © 1995 John Wiley & Sons, Inc.
Attachment and growth of cultured fibroblast cells on silk protein matrices
Authors: Minoura Norihiko , Aiba Sei‐Ichi , Gotoh Yohko , Tsukada Masuhiro , Imai Yohji
Published: May 2005

The attachment and growth of L‐929 cells on films made of Bombyx mori silk proteins—fibroin and sericin and their mixtures—was studied by a cell culture method. Both cell attachment and growth were dependent on a minimum of around 90% sericin in the mixture. The results from electron micrography as well as from the DSC measurements supported the notion that the mixture of the two proteins fibroin and sericin has a phase‐separated structure in the solid state. The observed minimum of sericin in the cell attachment and growth is thought to be a result of this phase‐separated structure. Films of pure component proteins (i.e., 100% fibroin or sericin) exhibited as high a cell attachment and growth as collagen, a widely used mammalian cell culture substrate. However, a morphological study of the attached cells revealed that the cells attached to silk fibroin were extended and had a spindle shape, just like the cells attached to collagen, while the cells attached to the silk sericin had a different shape. It is concluded, therefore, that the attachment condition on silk fibroin is ideal for the viability, growth and function of the cells. © 1995 John Wiley & Sons, Inc.
Cytotoxicity testing of poly(anhydride‐co‐imides) for orthopedic applications
Authors: Attawia Mohamed A. , Uhrich Kathryn E. , Botchwey Edward , Fan Miranda , Langer Robert , Laurencin Cato T.
Published: May 2005

The cytotoxicity of a series of poly(anhydride‐co‐imides) with osteoblast‐like cells (MC3T3‐E1) was evaluated. The imide component of the copolymers was based on trimellitylimidoglycine (TMA‐gly), and the anhydride component was based on either sebacic acid (SA) or 1,6‐bis(carboxyphenoxy)hexane (CPH). Cell adhesion and proliferation on surfaces of the polymer discs were observed by environmental scanning electron microscopy (ESEM). During the first 24 h of attachment, cells showed normal morphology when cultured on the various copolymers of CPH. Concurrently, the effects of polymer breakdown products on osteoblast‐like cells were evaluated by studying their proliferation (cell numbers), viability (dye exclusion), and morphology (light microscopy). Cell cultures in the presence of these breakdown products resulted in normal morphologies and reached confluency after 7 days. This initial in vitro evaluation with osteoblast‐like cells suggests that the poly‐(anhydride‐co‐imides) may be viable carriers for osteoblasts. © 1995 John Wiley & Sons, Inc.
Prevention of bone loss by percutaneous estradiol implants in ovariectomized rats
Authors: Yamamura Keiko , Iwata Hisashi , Osada Takashi , Yano Kohji , Yotsuyanagi Toshihisa , Nabeshima Toshitaka
Published: May 2005

This study was conducted to investigate whether hydroxyapatite (HAP) is appropriate as a percutaneous drug carrier for estradiol (E2) for the suppression of bone loss. Ten‐week‐old female Sprague–Dawley rats were subjected either to bilateral ovariectomy (OVX) or to sham surgery (control). Ovariectomized rats were implanted percutaneously with E2‐HAP disks containing low, medium or high doses of estradiol (50, 250, or 500 μg E2/rat, respectively). Ovariectomized rats without implant and OVX rats implanted only with HAP served as additional controls. All rats were sacrificed 90 days after surgery. At the end of the experiment, bone mineral density of the lumbar spine was measured by dual energy X‐ray absorption, and serum E2 was assayed by radioimmunoassay. The bone mineral density of OVX and HAP‐treated OVX rats decreased by 18% compared to sham surgery rats, but decreased by only 13, 7, and 3% in rats treated with 50, 250, and 500 μg E2/rat, respectively. The in vitro release of E2 from E2‐HAP devices was determined by an HPLC method. Estradiol release from the HAP devices followed almost a zero‐order kinetics. Estradiol remained intact in E2‐HAP implants for up to six months when stored at 5, 25, and 40°C. This study indicates that E2‐HAP implants are effective in suppressing bone loss in the spine of OVX rats in a dose‐dependent manner. © 1995 John Wiley & Sons, Inc.
Antithrombin activity of surface‐bound heparin studied under flow conditions
Authors: Lindhout T. , Blezer R. , Schoen P. , Willems G. M. , Fouache B. , Verhoeven M. , Hendriks M. , Cahalan L. , Cahalan P. T.
Published: May 2005

Polyacrylamide‐grafted polyetherurethane sheets were modified by end‐point and multipoint attachment of heparin. The surface‐bound heparin was firmly attached. No release of heparin activity could be detected when the surface was rinsed at a wall shear rate of 2000 s−1. Uptake of antithrombin and thrombin inactivation were investigated under well‐defined flow conditions by the use of a spinning device with an attached disk‐shaped heparinized surface. It is demonstrated that the rate of thrombin inactivation at the antithrombin‐heparin surface equals the maximal rate of transport of thrombin toward the surface when the surface coverage of antithrombin exceeds 10 pmol/cm2. This result indicates that a higher intrinsic catalytic efficiency of a surface does not necessarily result in a higher antithrombin activity. We varied the heparin content of the surfaces between 0 and 35 μg/cm2 by increasing the number of functional groups to which heparin could be covalently attached. The uptake of antithrombin increased with the heparin content of the surface, but the stoichiometry decreased from 2 to 0.5 pmol antithrombin/μg heparin. Apparently, antithrombin could not bind to heparins buried in the poly(acrylamide) layer. The rate of thrombin inactivation at surfaces with low heparin content (2 μg/cm2) fells below the transport limit of thrombin and became proportional with the heparin content of the surface. Although the contribution of surface‐bound heparin to the neutralization of fluidphase thrombin was found to be negligible compared with the effect of fluid‐phase antithrombin at physiologic relevant concentrations, these heparinized surfaces markedly delayed the onset of thrombin generation in platelet‐rich plasma. It is concluded that the inhibition of locally produced thrombin might contribute to the thromboresistance of the heparinized surface. © 1995 John Wiley & Sons, Inc.
Role for interleukin‐4 in foreign‐body giant cell formation on a poly(etherurethane urea) in vivo
Authors: Kao Weiyuan John , McNally Amy K. , Hiltner Anne , Anderson James M.
Published: May 2005

Interleukin‐4 (IL‐4) was previously shown to induce extensive macrophage fusion to form foreign‐body giant cells (FBGCs) in vitro. In the present study, our goal was to extend these findings to an in vivo test environment on biomaterials. The subcutaneous cage‐implant system was modified for mice to elucidate IL‐4 participation in mediating FBGC formation in vivo. Exudate leukocyte concentrations from cages containing poly(etherurethane urea) (PEUU A′) and empty cage controls indicated a similar inflammatory response that turned toward resolution by 14 days postimplantation, thus confirming the applicability of the cage‐implant system in mice. FBGC kinetic analysis showed that the formation of mouse FBGCs occurs through the fusion of adherent macrophages at a constant rate up to 14 days of implantation. Purified goat anti‐mouse IL‐4 neutralizing antibody (IL4Ab) or normal goat nonspecific control IgG (gtIgG) at various concentrations, or recombinant murine IL‐4 (muIL4) was injected into the implanted cages containing PEUU A′ every 2 days for 7 days. The injection of IL4Ab significantly decreased the FBGC density on PEUU A′ cage‐implanted in mice, when compared with the nonspecific IgG or PBS injection controls. Conversely, the FBGC density was significantly increased by the injection of muIL4 when compared with nonspecific IgG and PBS injection controls. Adherent macrophage density, FBGC morphology, FBGC average size, and size distribution were not significantly different among IL4Ab, nonspecific control gtIgG, muIL4, and PBS control groups. Our data suggest that IL‐4 participates in FBGC formation on biomaterials in vivo. © 1995 John Wiley & Sons, Inc.
Surface‐modified poly(methyl methacrylate) enhances adsorption and retains anticandidal activities of salivary histatin 5
Authors: Edgerton M. , Raj P. A. , Levine M. J.
Published: May 2005

Denture‐induced stomatitis is a common intraoral disease which is associated with high levels of Candida albicans adhesion to a denture surface. The aim of this study was to produce a surface‐modified denture resin, which is usually manufactured from poly(methyl methacrylate) (PMMA), carrying an immobilized anticandidal protein. PMMA was modified by surface polymerization of methyl methacrylic acid to enhance adsorption of a potent candidacidal salivary protein, histatin 5. The modified PMMA showed higher surface adsorption and desorption of histatin 5 than the unmodified material. Because histatin 5 destabilizes C. albicans cell membranes and allows efflux of intracellular molecules, candidacidal activity was monitored by dye release from fungal cells. Adsorbed histatin 5 did not release dye from the yeast cells; however, dye was detected as histatin was desorbed from the surface. In an adhesion assay, modified PMMA decreased human submandibular–sublingual saliva (HSMSL) mediated adherence of yeast cells to the polymer. Precoating histatin 5 onto unmodified PMMA also abolished HSMSL‐mediated adhesion. These experiments show that dental acrylic may be surface modified and loaded with histatin 5 as a means of controlled release of histatin 5 to an affected area. This surface modification may additionally reduce adhesion of C. albicans cells to the saliva‐coated material. © 1995 John Wiley & Sons, Inc.
Structural evaluation of human and sheep bone and comparison with synthetic hydroxyapatite by FT‐Raman spectroscopy
Authors: Rehman I. , Smith R. , Hench L. L. , Bonfield W.
Published: May 2005

The composition of whole human and sheep cortical bone tissue, and of a synthetic hydroxyapatite (P120), were compared using Fourier transform Raman (FT‐Raman) spectroscopy. Deproteination procedures to remove the bulk of the collagen present in bone tissue allowed isolation of the mineral phase. A comparison of the spectra obtained from both whole and deproteinated bone with those of synthetic hydroxyapatite showed direct correlation only in the region of 952 cm−1 (symmetric PO mode). In contrast, human and sheep bone were very closely matched in both, the organic and inorganic structures. The results demonstrate that deproteination of bone is not a necessary precursor to obtain spectral information. © 1995 John Wiley & Sons, Inc.
A study of reversibly inactivated lipases for use in a morphine‐triggered naltrexone delivery system
Authors: Nakayama G. R. , Roskos K. V. , Fritzinger B. K. , Heller J.
Published: May 2005

A key component of an implant that can be triggered by external morphine to release naltrexone is an inactivated enzyme that can be activated by morphine and which can then rapidly remove a protective coating surrounding a bioerodible polymer containing dispersed naltrexone. In this article we describe a lipase that has been conjugated with O3‐carboxymethylmorphine, morphine‐β‐3‐glucuronide and O3‐carboxypropylmorphine. The enzyme conjugate was then inactivated by complexation with affinity‐purified goat polyclonal antimorphine antibodies. Antibody lipase interactions were measured by pH Stat and ELISA techniques. Affinity constants of the antibodies determined by radioimmunoassay using tritium‐labeled morphine were 4.10 × 106, 3.18 × 106 and 3.38 × 107, respectively. While a concentration of 10−5 M morphine was required to restore lipase activity, it is likely that a combination of correct morphine tether and correct affinity‐purified antibody can increase sensitivity to the desired 10−8−10−9 M morphine level. Thus, a functioning device can almost certainly be constructed. However, it is unlikely that reactivation times of 1–2 h necessary for clinical usefulness in treatment of narcotic addiction can be achieved. © 1995 John Wiley & Sons, Inc.
X‐ray powder diffraction patterns of calcium phosphates analyzed by the Rietveld method
Authors: Keller Ludwig
Published: May 2005

Least‐square refinement of x‐ray powder diffraction patterns analyzed by the Rietveld method can yield structural information which had been unattainable or at least elaborate to obtain by conventional pattern analysis. The Rietveld method calculates a powder pattern on the basis of a structural model as well as the characteristics of the instrument used, and minimizes the differences between the intensities observed and the intensities calculated. The method is applied on patterns produced powders or polycrystalline solids on conventional powder diffractometers. For materials containing more than one crystalline phase with known structures such as hydroxyapatite (HA) and whitlockite (β‐TCP), pattern analysis yields phase quantification without internal or external standards. Refinement of the lattice parametersa0andc0determines the degree of dehydroxylation in plasma‐sprayed HA coatings. The presence of amorphous Ca phosphates in HA coatings is detected by background modeling. The calculation of entire powder patterns allows discrimination of small concentrations of poorly crystallized Ca phosphate phases against the background, and prevents gross aberrations in estimating secondary phases. Even defect structures such as an OH‐deficient HA lattice can be detected through slight differences in diffracted intensity by which the pattern calculated deviates from the pattern observed. © 1995 John Wiley & Sons, Inc.
Adhesion and spreading of human skin fibroblasts on physicochemically characterized gradient surfaces
Authors: Ruardy T. G. , Schakenraad J. M. , van der Mei H. C. , Busscher H. J.
Published: May 2005

In this study, adhesion and spreading of human skin fibroblasts on gradient surfaces of dichlorodimethylsilane (DDS) coupled to glass was investigated. Gradient surfaces were prepared by the diffusion technique and characterized by the Wilhelmy plate technique for their wettability and by scanning x‐ray photoelectron spectroscopy for their chemical surface composition. A linear relation between the gradient length, based on advancing water contact angles, and the square root of the diffusion time of DDS was observed. XPS analysis and the cellular experiments were carried out on gradient surfaces prepared using diffusion time of 3 h. A continuously varying chemical composition over the length of the gradient surfaces observed with the Si/O elemental surface concentration ratio being highest on the hydrophobic end of the gradient surfaces. In the presence of serum proteins, human skin fibroblasts seeded on these gradient surfaces showed a preferential adhesion onto the steepest part of the gradient, probably due to an optimal local wettability and/or local chemistry. Furthermore, it was shown that the spread area of human fibroblasts increased over the length of the gradient surface when going from the hydrophobic to the hydrophilic end. Summarizing, this study shows that the use of gradient surfaces to study cellular responses to materials surface properties, like wettability, yields more‐convincing conclusions than the use of a variety of materials with different wettabilities due to the control of the specific surface chemistry of gradient surfaces. © 1995 John Wiley & Sons, Inc.
Noncontact microstrain measurements in orthodontic wires
Authors: Kirkpatrick Sean J. , Duncan Donald D.
Published: May 2005

A technique is presented that allows for highly sensitive and highly accurate measurements of microstrain in biomaterials. It is particularly useful for measuring strains in materials where the use of conventional extensometers or strain gauges is impracticable, such as in reinforcement fibers and orthodontic wires and in hostile environments. The technique is based on the well known technique of observing translating laser speckle with a linear‐array charge‐coupled device (CCD) camera. However, it employs a relatively new data processing algorithm involving a twodimensional frequency transform of the data. Advantages of the technique include: insensitivity to slow surface microstructure changes, insensitivity to zero‐mean noise processes, compact design, modest resolution requirements, and the fact that it is truly noncontact. Strain rate measurements were made on an 0.028‐gauge round stainless steel orthodontic wire as an example of this technique. The Young's modulus of the wire based on the speckle technique was 2.04 × 1011 Nm−2, which is very close to the textbook value. © 1995 John Wiley & Sons, Inc.
Mechanical and histological investigation of hydrothermally treated and untreated anodic titanium oxide films containing Ca and P
Authors: Ishizawa H. , Fujino M. , Ogino M.
Published: May 2005

In a previous study a new method for forming thin hydroxyapatite (HA) layers on titanium was described. Titanium was anodized at 350 V in an electrolytic solution containing sodium β‐glycerophosphate and calcium acetate, and an anodic titanium oxide film containing Ca and P (AOFCP) was formed on the surface. Then numerous HA crystals were precipitated on the AOFCP during hydrothermal treatment in high‐pressure steam at 300°C. In this study three types of hydrothermally treated films differing in amounts of precipitated HA crystals and tensile adhesive strength, and untreated films were histologically and mechanically investigated in a transcortical rabbit femoral model for 8 weeks of implantation using light microscopy, scanning electron microscopy (SEM), and push‐out tests. Machined titanium and HA ceramics served as control materials. The push‐out shear strength and bone apposition of the AOFCP significantly increased after hydrothermal treatment, and were equivalent to those of HA ceramics, although the HA layer on the AOFCP was thin at 1–2 μm. From SEM observation of the pushed‐out specimen, it was found that the thin HA layer had directly bonded to bone but the AOFCP had not. The push‐out strength of the hydrothermally treated film resulted from the chemical bonding of the bone–HA layer interface, while that of the untreated film resulted from mechanical interlocking force between bone and the microprojections. There was a small difference in bone apposition but no significant difference in push‐out strength with the amount of precipitated HA crystals on the treated films. Among the treated films, the film formed at the lowest electrolyte concentration showed the lowest bone apposition because of incomplete covering by the HA crystals, and showed the highest stability against mechanical failure because the adhesive strength was very high at about 38 MPa. Also, the hydrothermally untreated anodic oxide films, whose surfaces were rough as a result of the large microprojections, showed much higher push‐out strength and bone apposition than titanium. The good hard‐tissue compatibility may be attributed to the surface roughness and the possible inhibition of titanium ion release from the specimen. © 1995 John Wiley & Sons, Inc.