bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlations between mouse 3T3 cell spreading and serum fibronectin adsorption on glass and hydroxyethylmethacrylate–ethylmethacrylate copolymers
Authors: Horbett Thomas A. , Schway Michael B. 
Published: December 2004

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

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

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

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

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

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

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

AbstractBiodegradable beta‐tricalcium phosphate disks (TCP) of two configurations were inserted into 15‐mm‐diameter craniotomy wounds and nontreated control sites were evaluated in 60 rabbits. There were no adverse tissue reactions and no apparent difference in the clinical appearance of the 12‐ and 24‐week implanted disks. By 36 weeks and continuing to 48 weeks, the omnidirectional TCP (OTCP) implants were degrading more rapidly than the unidirectional TCP (UTCP) implants, with degradation progressing centripetally and replacement by woven bone and maturing lamellar bone. Host‐implant interface of both TCP configurations was a bone bond without interposed soft tissue. TCP disks may be clinically useful for craniotomy repair.
Brain tissue reaction to permselective polymer capsules
Authors: Winn Shelley R. , Aebischer Patrick , Galletti Pierre M. 
Published: December 2004

AbstractThe brain tissue reaction to permselective polymer capsules implanted in rats was evaluated for 1 to 54 weeks. The polymer capsules were well tolerated in all animals and no recognizable neurological or behavioral deficits were associated with the implants. Necrosis at the brain/polymer interface, as assessed with Nissl stain, was not observed. Foreign body giant cells were consistently absent. Immunocytochemically identified reactive neuroglial cells showed a remarkably low‐grade tissue response to the synthetic material be yond the first 2 weeks of observation. Immunolabeled cortical neurons revealed conserved columnar arrays around the implants. Transmission electron microscopy showed a minimal degree of collagen deposition compared to implants in peripheral sites, and normal synapses within a few micrometers from the brain/polymer interface, supporting the prospect of biocompatible, immunoisolated xenografts in the central nervous system.
Effect of substrate condition and substituted phenols and methacrylates on toluene diisocyanate/dentin bond strengths
Authors: Stackhouse James A. , Kristol David S. , Von Hagen Stanley , Rao Gururajan 
Published: December 2004

AbstractOne aim of this in vitro investigation was to determine the effect of substituting four phenols and two methacrylates with vinyl functions on the dentin bond strengths of several new experimental dentin bonding agents. Another objective was to determine the effect of postextraction age and dentin level within the tooth on tensile bond strengths of these toluene diisocyanate‐derived adhesives. Extracted third molars were divided into postextraction age groups and sectioned into three slices ∼400 m̈m thick. The four substituted phenols were: eugenol, o‐methoxyphenol, o‐chlorophenol, and p‐cresol. Substituted methacrylates with vinyl ligands were 2‐hydroxyethyl methacrylate (HEMA) and 6‐hydroxyhexyl methacrylate (HHMA). Results showed that adhesives made with o‐chlorophenol, p‐cresol, and methoxyphenol with HEMA were the best, while those made with eugenol and HHMA were the worst. The post extraction age of the tooth and the dentin depth had no consistent effect on most adhesive bond strengths which were generally around 10.3 MPa (1500 psi).
Compressed poly(vinyl alcohol)‐polycaprolactone admixture as a model to evaluate erodible implants for sustained drug delivery
Authors: Wang Paul Y. 
Published: December 2004

AbstractAn implant may release a drug either by diffusion concurrent with dissolution of the polymeric implant material without depolymerization (Type A) or by bioerosion involving depolymerization (Type B). The Type A material may induce immune response, while the erosion of Type B polymer releases fragments which could cause toxicity problems. It is proposed that a combination of the two types of polymers may attenuate the intensity of immune response and toxicity, because the presence of one in an implant of the same weight reduces the amount of the other. However, it is important to determine first, if sustained delivery may be achieved by such an implant. In this study, partially hydrolyzed poly(vinyl acetate) (PVA) and polycaprolactone (PCL) were chosen as the model Type A, and B polymers, respectively, to evaluate this objective in vitro. Pellet discs were prepared to assess the effects of compression, proportion of PVA to PCL, acetyl content of PVA, PCL hydrolysis catalyst and drug loading, using methylene blue (MB) as a model drug. Results showed that sustained delivery could be effected, but PCL erosion did not occur as planned. Therefore, PCL served only as a passive component of the implant, while PVA was eroded with the release of MB. Consequently, it was inferred that a polymer may not be required as a passive component, which suggested the use of other compounds of known biocompatibility. Tests with insulin in a compressed solid admixture with cholesterol showed that reduction of hyperglycemia in diabetic Wistar rat could be effected reproducibly for at least 2 weeks. Thus, the present study, originally planned to test a proposed concept, indicates that many nonpolymeric materials of known biocompatibility may be suitable for drug delivery implants as well.
Platelet shape change and cytoskeletal reorganization on polyurethaneureas
Authors: Goodman S. L. , Grasel T. G. , Cooper S. L. , Albrecht R. M. 
Published: December 2004

AbstractUnderstanding how platelet activation responses are affected by polymers having varied surface physicochemical properties can lead to improved materials for vascular applications. The in vitro responses of human platelets were studied upon adherence to four polyurethaneureas with different soft segments, as well as to Biomer, and to Formvar. Platelets were observed by video‐enhanced light microscopy (VLM) as they adhered to polymer films. Platelets were subsequently prepared for high‐voltage transmission electron microscopy (HVEM) to view the cytoskeleton and other ultrastructural features. Scanning electron microscopy (SEM) was then used to characterize cell surface morphology and to survey platelet populations. Shape change and cytoskeletal reorganization differed on the various surfaces. The extent of shape change and cytoskeletal reorganization was related to polyurethane surface energetic properties. While the most extensive shape change was observed on the hydrophilic and polar Formvar surface, the least shape change was observed on a polyethylene oxide soft segment polyurethane with similar surface‐water energetic properties. Therefore properties other than surface‐water energetics must be involved in determining platelet responses to different classes of polymers. HVEM also showed that cytoskeletal reorganization proceeded to completion only on Formvar. Polyurethane adherent platelets, although appearing fully spread by SEM or VLM, never exhibited complete cytoskeletal reorganization.
Transient adsorption of fibrinogen on foreign surfaces: Similar behavior in plasma and whole blood
Authors: Brash J. L. , ten Hove P. 
Published: December 2004

AbstractThe adsorption of fibrinogen from both human whole blood and plasma to a number of “foreign” surfaces is reported. Adsorption was measured as a function of plasma or blood dilution using radioiodine labeling. We showed previously that adsorption of fibrinogen from plasma exhibits a maximum at a plasma dilution of about 100:1, and have attributed this behavior to competition from other plasma proteins. (The same phenomenon is manifest as a time transient in fibrinogen adsorption.) In the present work we show that exactly the same trends are observed in whole blood. For each of the four surfaces, glass, siliconized glass, collagencoated glass and polyethylene, the adsorption of fibrinogen as a function of dilution is the same in whole blood as in plasma. Each of these surfaces shows a unique dependence of fibrinogen adsorption on plasma or blood dilution. On cuprophane and a hydrophilic polyether urethane there is essentially no adsorption of fibrinogen from blood or plasma. For the hydrophilic polyurethane this result may be artifactual, but the absence of fibrinogen binding to cuprophane in blood or plasma is real since fibrinogen is found to be adsorbed in monolayer amounts from buffer.
Titanium‐coated dacron® velour: A study of interfacial connective tissue formation
Authors: Yan John Y. J. , Cooke Francis W. , Vaskelis Paul S. , von Recum Andreas F. 
Published: December 2004

AbstractPolyethylene terephthalate in textile form (Dacron®) has been used extensively as a surgical implant material for applications such as vascular grafts and percutaneous access devices. It is moderately histocompatible eliciting a chronic inflammatory reaction predominnately in tissue which has grown into the pores of the fabric. Titanium implants on the other hand, induce only the slightest inflammatory response and connective tissue adhesion to the titanium oxide surface is excellent. It was, therefore, hypothesized that a titanium coating on Dacron® fabric might improve its histocompatibility while leaving its desirable mechanical properties unaffected. To test this idea, Dacron® velour specimens were coated with titanium by vacuum deposition and were implanted together with uncoated controls in rabbits subcutis. After various implantation times, the specimens were recovered and the associated tissue was examined histologically. Qualitative and semiquantitative analysis revealed that tissue ingrowth quantity and quality was highly variable, not only between test and control specimens, but also between animals and even between specimens within the same animal. This indicated that there may be a number of factors influencing tissue ingrowth that were not adequately controlled in this study. The titanium coating which was undoubtedly highly oxidized had a profound qualitative and quantitative effect on fibroblast activity (ground substance formation) and fibroblast adhesion to the Dacron® fibers. The results obtained after these short‐term implantation periods indicate that titanium coating affects the quality of the interfacing tissue and may actually improve long‐term histocompatibility. Long‐term studies will have to confirm these preliminary data.
Platelet adhesion onto protein‐coated and uncoated polyetherurethaneurea having tertiary amino groups in the substituents and its derivatives
Authors: Ito Yoshihiro , Sisido Masahiko , Imanishi Yukio 
Published: December 2004

AbstractInteractions of platelet with novel polyetherurethaneurea and its heparinized derivative were investigated. Platelet adhesion onto the material and release of serotonin or adenosine phosphate from platelet‐rich plasma (PRP) were suppressed by an introduction of amino groups to polyetherurethaneurea, by quaternization of the polymer. When the material was precoated with one of major plasma proteins and the protein‐coated materials were taken to contact with washed platelet suspension (WP), the dependence of platelet adhesion and activation on the properties of polymers was different from that observed for PRP interaction. Platelet adhesion and activation were promoted according to the nature of coating proteins in the order albumin < γ‐globulin < fibrinogen and with increasing degree of denaturation of coating proteins. When the polymer materials were coated with proteins by immersing in aqueous solution containing two kinds of plasma proteins, adhesion behaviors of platelet were similar to those observed for PRP—uncoated material interaction. These experimental facts indicate that the selectivity of platelet for proteincoated material cannot be assessed by the interaction of WP with materials coated with a single kind of protein. It was concluded that material surface to which albumin is selectively adsorbed without denaturation does not stimulate adhering platelets for release reactions.
Attachment and growth of fibroblast cells on polypeptide derivatives
Authors: Kang Inn‐Kyu , Ito Yoshihiro , Sisido Masahiko , Imanishi Yukio 
Published: December 2004

AbstractAttachment and growth of mouse fibroblast cells on polypeptide derivatives with different wettabilities were studied in the presence or absence of serum proteins. In the presence of serum, a peak level of cell attachment was observed for substrates with a contact angle of around 70°. However, no relationship was found between cell attachment and water contact angle of the substrate in the absence of serum. Ca2+‐dependent cell attachment was observed on hydrophobic polypeptides in the absence of serum proteins. This suggests that Ca2+‐dependent membrane proteins function as mediators for cell attachment to hydrophobic polypeptides. In the presence of serum proteins, it was found that cell attachment is affected by the metabolism, Ca2+, and the cytoskeleton of the cell. Cell growth rate on hydrophilic polypeptide substrates was higher than that on intermediate or hydrophobic polypeptide substrates. This demonstrates that the strong interaction between cells and substrates will be unfavorable for a dewebbing process during mitosis.