bluuebunny/crossref_metadata_2025 huggingface dataset:
Rabbit eye irritation caused by wearing toxic contact lenses and their cytotoxicities: In vivo/in vitro correlation study using standard reference materials
Authors: Tsuchiya Toshie , Arai Tadashi , Ohhashi Jyunichi , Imai Kiyoshi , Kojima Hajime , Miyamoto Satoru , Hata Hideyo , Ikarashi Yoshiaki , Toyoda Kazuhiro , Takahashi Michihito , Nakamura Akitada
Published: May 2005

To clarify the relationship between eye irritancy and cytotoxic potential induced by irritant materials, we made lenses coated with standard reference materials (SRMs) prepared from various amounts of zinc diethyldithiocar‐bamate (ZDEC) and polyurethane (PU).

Zinc diethyldithiocarbamate was classified as a mild irritant by the Draize eye irritation test. When ZDECSRM coated contact lenses were applied to rabbit eyes, Draize scores increased in proportion to both the ZDEC and PU concentrations used for coating. Furthermore, correlation with the cytotoxic potential (γ = −0.93) was better than with lactate dehydrogenase (LDH) activities of tears from rabbit eyes wearing these coated lenses (γ = 0.78). In conclusion, in vivo eye irritancy induced by wearing lenses could be estimated quantitatively with the cytotoxic potentials using a colony assay. Further‐more, we could compare different sensitivities caused by the same set of SRMs among three different sites of tissue. As a result, the order of sensitivity was eye > muscle ≫ skin. © 1993 John Wiley & Sons, Inc.
Cell growth on immobilized cell growth factor. 6. Enhancement of fibroblast cell growth by immobilized insulin and/or fibronectin
Authors: Ito Y. , Inoue M. , Liu S. Q. , Imanishi Y.
Published: May 2005

A cell growth factor protein (insulin) and/or a cell‐adhesion protein (fibronectin) were immobilized on surface‐hydrolyzed poly(methyl methacrylate) membranes. The growth of mouse fibroblast cells STO was accelerated by the immobilized insulin. This acceleration was enhanced by introduction of spacer arms. Coimmobilization of insulin and fibronectin was very effective for the acceleration of cell growth. © 1993 John Wiley & Sons, Inc.
Cell growth on immobilized cell growth factor. 9. Covalent immobilization of insulin, transferrin, and collagen to enhance growth of bovine endothelial cells
Authors: Liu Shu Qin , Ito Yoshihiro , Imanishi Yukio
Published: May 2005

Bovine endothelial cells were cultivated on the surface of polyurethane membranes or tubes immobilized with insulin, transferrin, and/or collagen, and growth was measured. For the purpose of immobilization, amino groups were introduced on the membranes or tubes by glow‐discharge treatment in the presence of ammonia gas. The proteins were coupled to the amino groups on the surfaces by using dimethyl suberimidate (DMS) or water‐soluble carbodiimide (WSC). Growth of bovine endothelial cells was higher on immobilized insulin or transferrin using DMS than that using WSC. The cell growth was higher on immobilized insulin or transferrin than on free insulin or transferrin, respectively. Though immobilized collagen did not affect the cell growth, coimmobilization with insulin or transferrin brought about greater acceleration of cell growth. In addition, the immobilized collagen was indispensible to maintain the endothelial cells on the material surface for a long time. The endothelial cells grown in the polyurethane tubes, on which insulin and collagen are coimmobilized, kept a normal cobblestone‐like appearance and maintained the ability to secrete prostacyclin for 9 months. © 1993 John Wiley & Sons, Inc.
Selective neuronal cell attachment to a covalently patterned monoamine on fluorinated ethylene propylene films
Authors: Ranieri John P. , Bellamkonda Ravi , Jacob Jules , Vargo Terrence G. , Gardella Joseph A. , Aebischer Patrick
Published: May 2005

The patterned covalent surface addition of a monoamine to fluorinated ethylene propylene films (FEP) controls both cellular attachment and differentiation in defined media conditions. A radio frequency glow discharge (RFGD) process was used to replace FEP surface fluorine atoms with hydroxyl groups. The primary amine was then covalently attached by polymerizing aminopropyl‐triethoxysilane (APTES) via the hydroxyl functionalities. The selective attachment of cells to the APTES regions was determined to be dependent upon the initial adsorption of albumin to the patterned FEP membrane. Albumin was determined to enhance cellular attachment to the APTES regions and prevent attachment to the unmodified FEP areas for both an NB2a neuroblastoma cell line and primary rat endothelial cells. If albumin were not preadsorbed onto the membrane, selective attachment to the modified regions would not occur. Radiolabeling albumin with 125I demonstrated the preference of albumin for adsorption onto the monoamine surface where the cells preferentially attached. Both hydrophobic and ionic forces contributed to the adsorption process. Although selective cellular attachment to the patterned APTES regions could be achieved by albumin preadsorption to the surface, the neuroblastoma cells did not significantly differentiate unless additional serum components were supplemented to the media. © 1993 John Wiley & Sons, Inc.
Dissolution, leaching, and Al2O3 enrichment at the surface of bioactive glasses studied by solution analysis
Authors: Andersson Ö. H. , Rosenqvist J. , Karlsson K. H.
Published: May 2005

Five glass compositions in or near the bioactive region in the system SiO2Na2OCaOP2O5Al2O3 were studied in vitro by immersion in Tris buffer. The Si concentration can be taken as a measure of the amount of dissolved glass, whereas the Na concentration can be used to estimate the thickness of the Si‐rich (Si gel) layer. Upon immersing a bioactive glass into Tris buffer, a surface layer of a few micrometer thickness is dissolved during the first 8 h. During the first few hours of immersion, the rate of dissolution of the glass network is equal to or exceeds that of the growth of the Si‐rich layer. If the glass contains Al2O3, most of the aluminum that would be released due to dissolution of the silica network is enriched in the Si‐rich surface layer that forms due to leaching. Al2O3 is not only bonded by the Si gel but also interferes with formation of culcium phosphate. © 1993 John Wiley & Sons, Inc.
Determination of the 3‐D morphology of degradable biopolymer implants undergoing in vivo resorption
Authors: Schliephake H. , Klosa D. , Rahlff M.
Published: May 2005

A technique is presented that allows the visualization of the degradation process of biopolymers. Serial thick‐section specimens containing cross‐sections of polydioxanone implants (PDAs) were realigned for 3‐D reconstruction using a double‐embedding technique. The outlines of the cross‐sectioned implants were traced using an automatic image analysis system and converted into x, y, and z coordinates. The reconstruction of the implant body was achieved by the stepwise analysis of vertical relationships between two adjacent section levels. The surface was approximated by triangulation and calculated from the surface triangles. Visualization was achieved by introducing the data into commercially available software using z‐buffering and Gouraud shading. The geometric precision of the reembedding technique was found to be 0.8–1.5% of the screen width; recovering experiments showed a good approximation to the actual physical volume of unresorbed implants (±2.6%). The error of volume determination due to the limited resolution in the z direction was calculated to be acceptable (<5.0%) in isotropic objects where the ratio between the radius of the surface curvature and the distance between the sections is >4. Results indicate that large devices of PDAs are degraded in vivo in a fashion similar to that previously described for in vitro degradation of PLA molded screws by a surface/center differentiation with formation of hollow residuals after 17 weeks and complete degradation with phagocytosis of microparticles after 26 weeks. © 1993 John Wiley & Sons, Inc.
Apatite formation on three kinds of bioactive material at an early stage in vivo: A comparative study by transmission electron microscopy
Authors: Neo M. , Nakamura T. , Ohtsuki C. , Kokubo T. , Yamamuro T.
Published: May 2005

Apatite formation on the surface of three kinds of bioactive material at an early stage after implantation in bone was studied using transmission electron microscopy (TEM). The materials were apatite‐ and wollastonite‐containing glass‐ceramic (A‐W GC) as a surface‐active glass‐ceramic, dense sintered hydroxyapatite (HA) as a surface‐active ceramic, dense sintered β‐tricalcium phosphate (β‐TCP) as a resorbable ceramic. Particles of these materials, ranging from 100–300 μm in diameter, were implanted into rat tibviae, and specimens were prepared at 3, 7, 10, and 14 days after implantation. For A‐W GC, dissolution of the glassy and probably wollastonite phase was observed in the surface region on and after the third day, and a collagen‐free thin apatite layer on the surface of the material was evident on and after the seventh day. This apatite layer was observed before the mineralization of the surrounding bone matrix and was sometimes evident even where the material bordered on the bone marrow. On and after the tenth day, the surrounding bone matrix calcified and A‐W GC‐bone bonding through an apatite layer was completed. For HA, a mineralized collagen‐free layer was observed on the surface of the ceramic on and after the tenth day. This layer was always present near calcifying bone and it was difficult to distinguish from immature bone. For β‐TCP, such a surface mineralized layer was rarely evident, even just before bone‐ceramic contact, and finally the bone bonded to β‐TCP directly. Cell‐mediated degradation of β‐TCP was frequently observed. In conclusion, surface apatite formation differed among these materials, reflecting their bioactivity and suggesting differences in their bone‐bonding mechanisms. © 1993 John Wiley & Sons, Inc.
In vivo transport and excretion of corrosion products from accelerated anodic corrosion of porous coated F75 alloy
Authors: Brown Stanley A. , Zhang Kan , Merritt Katharine , Payer Joe H.
Published: May 2005

Corrosion of porous coated cobalt chromium specimens surgically implanted subcutaneously in hamsters was accelerated by application of a fixed anodic potential. Corrosion current measurements were utilized for prediction of metal ion release based on Faraday's law. Daily urine samples were collected pre‐ and post‐stimulation, and, at animal sacrifice, organs and blood samples were taken for chemical analysis. By using in vitro release data from previous studies, and efficiency correction factors, the amount of metal ion release was calculated. The results demonstrated rapid and complete excretion of nickel and molybdenum. Most of the cobalt was excreted, with elevation of cobalt levels in liver, kidney, and lung. Chromium excretion was much lower due to significant red cell binding and in vivo storage, especially in the kidney and spleen. © 1993 John Wiley & Sons, Inc.
Effects of hydroxyapatite implants on primary mineralization during rat tibial healing: Biochemical and morphometric analyses
Authors: Schwartz Z. , Braun G. , Kohavi D. , Brooks B. , Amir D. , Sela J. , Boyan B.
Published: May 2005

The effect of 40‐ to 60‐mesh hydroxyapatite (HA) granules (Calcitek, Inc., Carlsbad, CA) on the process of primary mineralization during bone healing was examined following insertion of the HA granules into rat tibial bone after marrow ablation. Response to HA was assessed by monitoring morphometric and biochemical changes in matrix vesicles, which are extracellular organelles associated with initial calcification. Following insertion of HA, matrix vesicle‐enriched membranes (MVEMs) were isolated from the tissue adjacent to the implant and from the endosteum of the contralateral limb at 3,6,14, and 21 days and from a nonimplanted control group (t = 0). MVEM alkaline phosphatase‐ and phospholipase A2‐specific activities were increased on days 6 (peak) and 14; phosphatidylserine content was also elevated on days 6 and 14 (peak). Comparable changes were seen in the contralateral limb but at lesser magnitudes. Morphological changes were observed as well. The number of matrix vesicles/μm2 matrix increased on days 6 (peak) and 14. The mean diameter of the matrix vesicles was elevated on days 6 (peak), 14, and 21. Mean distance from the calcifying front increased on day 6 but was decreased on days 14 and 21. These results indicated that HA behaves like bone‐bonding implants in that there is a stimulation of matrix vesicle enzymes, increased phosphatidylserine content, and increase numbers of matrix vesicles. However, the increases occur only after 6 days postimplantation, indicating a delay in response when compared to normal healing. This delay is confirmed by the morphometric measurements. HA causes a reduction in the response associated with marrow ablation. In addition, the effects of HA are comparable locally and systemically but with different intensity. These observations suggest that osteogenic cells are able to compensate for the inhibitory effects of HA and primary calcification involves normal matrix vesicle production and maturation, if somewhat delayed and reduced in magnitude. The ability to support primary mineral formation may contribute to the successful bonding of HA with surrounding osseous tissue. © 1993 John Wiley & Sons, Inc.
Magnitude and polarity of a fluoroethylene propylene electret substrate charge influences neurite outgrowth in vitro
Authors: Makohliso Solomzi A. , Valentini Robert F. , Aebischer Patrick
Published: May 2005

Positively charged coating materials such as polylysine improve neuronal attachment in vitro. Due to the structural complexity of these charged molecules, it is unclear whether neuronal effects are due to charge or to physicochemical effects, or both. Polymeric materials with charge storage capabilities and defined surface properties may provide a model in which electrical charge and surface property effects can be separated. Fluorinated ethylenepropylene (FEP) films can store negative or positive charges injected through a corona charging process, thus generating a negative or positive external electrostatic field. In the present study, mouse neuroblastoma (Nb2a) cells were cultured on positive, negative, and uncharged FEP substrates, in both serum‐containing and serum‐free media. Cell attachment, differentiation, and neurite outgrowth were assessed 24, 48, 72 and 96 h after plating. Electron spectroscopy for chemical analysis (ESCA), contact angle analysis, and scanning electron microscopy (SEM) revealed no differences in surface chemistry and topography between positive, negative, and uncharged FEP. No significant differences in the levels of cell attachment on positive, negative, and uncharged substrates were observed. Significantly higher levels of neurite outgrowth, however, were observed with positive substrates as compared to negative and uncharged substrates, in both media conditions. Substrates charged to +1000 V showed greater levels of outgrowth compared to +500 and +3000 V, suggesting the presence of an optimal range of charge for neurite outgrowth. These results show that cell/charge interactions mediate cell effects on electrically charged substrates with identical surface chemistry, topography and adhesivity. © 1993 John Wiley & Sons, Inc.
Effect of the conformation and orientation of adsorbed fibronectin on endothelial cell spreading and the strength of adhesion
Authors: Iuliano Denise J. , Saavedra Steven S. , Truskey George A.
Published: May 2005

The effect of surface hydrophobicity upon the conformation of the cell binding domain of fibronectin (Fn) and the influence of Fn conformation on bovine aortic endothelial cell (BAEC) adhesion were examined. The free sulfhydryl group of Fn located near the cell binding domain was selectively labeled with acrylodan, a polarity sensitive fluor. Fluorescence emission was monitored in solution and upon adsorption to hydrophilic glass and hydrophobic silanized glass. The acrylodan‐labeled Fn emission maximum shifted to longer wavelengths upon adsorption and the shift was greater for acrylodan‐labeled Fn adsorbed to hydrophilic glass than hydrophobic silane, suggesting that the acrylodan was in a more solvent accessible environment on glass than silane. BAEC, suspended in serum‐free medium, attached for 15 or 120 min onto glass or silane surfaces containing preadsorbed Fn, after which cell spreading and the strength of adhesion in a parallel plate flow chamber were measured. Cell spreading was similar on both surfaces after 15 min attachment, but BAECs were more spread on glass than silane after 120 min. At low surface concentrations of Fn, BAECs were more adherent on glass than silane. At higher surfaces concentrations, adhesion was similar. After a 2‐h incubation in serum‐free medium, cells on glass showed more extensive development of focal contacts as determined by immunofluorescent staining for vinculin. Cell adhesion under flow was reduced on silane by inhibition of protein synthesis with cycloheximide, suggesting that cell attachment to silane was promoted by cellular synthesis of Fn. The results indicate that changes in the conformation of the Fn cell binding domain affect Fn affinity for its cell surface receptor. © 1993 John Wiley & Sons, Inc.
Platelet‐mediated adhesion of Staphylococcus epidermidis to hydrophobic NHLBI reference polyethylene
Authors: Wang I‐Wen , Anderson James M. , Marchant Roger E.
Published: May 2005

The effects of platelets and plasma proteins on the adhesion of Staphylococcus epidermidis strain RP62A to hydrophobic NHLBI reference polyethylene was quantitatively studied using a rotating disk system to generate well‐defined shear conditions simulating the hemodynamics of human blood circulation. Bacterial adhesion was quantified by adhesive coefficient, the percentage of bacteria transported to the surface that becomes adherent. The results showed that surface modification by adsorption of plasma proteins reduced the adhesion of S epidermidis as compared to the bare polymer surface. This surface modification was not sufficient to eliminate completely bacterial adhesion, even at the highest physiologic shear stress level. S epidermidis did adhere strongly to polyethylene surface modified by platelets. This is readily evident as approximately 50% of the adherent S epidermidis were bound to contact‐activated platelets which occupied only 4% of the surface area. Adhesive coefficients to platelets were significantly greater than to the protein‐adsorbed polyethylene surface by at least one order of magnitude (P ≤ .01) across the range of physiological shear conditions investigated. These studies show that it is biologic surface modification by contact‐activated platelets, and not plasma proteins, which mediates S epidermidis adhesion to polyethylene. © 1993 John Wiley & Sons, Inc.
Production of prostacyclin and fibrinolysis modulators by endothelial cells cultured in the presence of polyethylene terephthalate
Authors: Cenni Elisabetta , Ciapetti Gabriela , Cavedagna Daniela , Di Leo Alessandro , Pizzoferrato Arturo
Published: May 2005

The aim of this study was the evaluation of the in vitro production of prostacyclin, and of tissue plasminogen activator (tPA) and its inhibitor, PAI‐1, by human endothelial cells cultured in the presence of polyethylene terephthalate (PET). After a 48 h contact between the cells and the polymer, the concentration of 6‐keto‐PGF1α, a stable metabolite of prostacyclin, tPA, and PAI‐1, was assayed on the supernatants. Contact of the endothelial cells with PET produced a highly significant reduction of 6‐keto‐PGF1α with respect to control cultures. Tissue plasminogen activator concentration in the supernatants of the cultures in contact with the material was similar to that observed in the controls, while PAI‐1 production was significantly reduced. It can be concluded that the contact between endothelial cells and PET determines a reduction in the platelet aggregability and an increase of the fibrinolytic activity due to a decrease in PAI‐1, while tPA concentration remains unchanged. © 1993 John Wiley & Sons, Inc.
Prosthetic replacement of the rabbit medial meniscus
Authors: Messner Karola , Gillquist Jan
Published: May 2005

Implants of polyurethane‐coated polyester (Dacron), polyurethane‐coated PTFE (Teflon), or uncoated PTFE were used to substitute the medial rabbit meniscus, and were observed over a 3‐month period. Joint mechanics were similar for sham‐operation, meniscectomy, or substitution with a coated implant. Joints with an uncoated PTFE prosthesis tended to be less compliant and to show greater load dissipation during relaxation. Cartilage indentation showed softening with all alternatives compared to sham‐operation. Ingrowth into the prosthesis periphery was best with the PTFE implants. Both types of coated prosthesis retained their original shape, in contrast to the uncoated prostheses. To the naked eye the cartilage appeared unaffected only after sham‐operation or implantation of a coated PTFE prosthesis. Osteophyte formation was common with all alternatives except sham‐operation. We conclude that replacement of the medial meniscus with coated prostheses, especially the PTFE, was better than meniscectomy or using the uncoated prosthesis. However, cartilage softening and osteophyte formation indicate that joint mechanics were not restored to normal. © 1993 John Wiley & Sons, Inc.
Effect of esterase on methacrylates and methacrylate polymers in an enzyme simulator for biodurability and biocompatibility testing
Authors: Bean T. A. , Zhuang W. C. , Tong P. Y. , Eick J. D. , Yourtee D. M.
Published: May 2005

Current in vitro biocompatibility methods do not evaluate the degradation of biomaterials after contact with enzymes that might be present in the oral or systemic environment. In this study, two methods of in vitro enzyme degradation and a method for the separation of the degradative products by high performance thinlayer chromatography (HPTLC) are reported. In the first method two dental adhesives, Scotchbond and Scotchbond II, and two dental composites, Helimolar and P‐50, were evaluated. These materials were incubated with four different enzymatic preparations for periods of up to 72 h. The enzymes were lipase, esterase, and liver enzyme extracts from both mouse and rat. Chloroform soluble products extracted from the aqueous phase were examined by HPTLC for decomposition products resulting from enzyme activity. The second method was similar, but analyzed the aqueous fraction directly without chloroform extraction. In this method five dental restorative materials, P‐50, P‐30, Scotochbond II, Silux, and Silux Plus, were incubated with a nonspecific porcine liver esterase. In addition to the polymerized biomaterials. Monomers containing methacrylic acid units were also hydrolyzed with esterase and analyzed by ion chromatography to establish the sensitivity of the enzyme simulator. Each biomaterial presented thin‐layer zones not present before enzymatic action. These experiments provide support that aqueous enzymatic action may facilitate the hydrolytic weakening of polymeric biomaterials. © 1994 John Wiley & Sons, Inc.
Effect of pretreating porous webs on stromal fibroplasia in vivo
Authors: Trinkaus‐Randall V. , Banwatt R. , Wu Xin Yi , Leibowitz H. M. , Franzblau C.
Published: May 2005

We have previously demonstrated that keratocytes penetrate and deposit collagen after a porous web is inserted into interlamellar corneal pockets. In these studies our goal was to determine whether pretreatment of the porous discs were followed in vivo for a period of 42 days. The criteria we used to determine whether pretreatment affected wound healing were: collagen deposition, extent of fibroplasia, the synthetic rate of keratocytes within the disc, and lack of edema. Our results indicate that preseeding with stromal keratocytes enhanced the overall synthetic rate and specifically enhanced the amount of collage deposited within the web. © 1994 John Wiley & Sons, Inc.
Cellular uptake of titanium and vanadium from addition of salts or fretting corrosion in vitro
Authors: Maurer A. M. , Merritt K. , Brown S. A.
Published: May 2005

The use of titanium and titanium‐6% aluminum‐4% vanadium alloy for dental and orthopedic implants has increased in the last decade. The implants are presumed to be compatible because oseointegration, bony apposition, and cell attachment are known. However, the cellular association of titanium and vanadium have remained unknown. This study examined the uptake of salts or fretting corrosion products. Titanium was not observed to be toxic to the cells. Vanadium was toxic at levels greater than 10 μg/mL. The percentage of cellular association of titanium was shown to be about 10 times that of vanadium. The percentage of cellular association of either element was greater from fretting corrosion than from the addition of salts. The presence of vanadium did not affect the cellular uptake of titanium. The presence of titanium decreased the cell association of vanadium. © 1994 John Wiley & Sons, Inc.
Synthetic scleral reinforcement materials: I. Development and in vivo tissue biocompatibility response
Authors: Jacob‐LaBarre Jean T. , Assouline Michael , Byrd Thomas , McDonald Marguerite
Published: May 2005

The surgical treatment of pathological myopia involves the placement of a band cut from donor sclera around the back of the globe to provide support and to prevent elongation that leads to retinal detachment and blindness. In the search for a synthetic material that would overcome the disadvantages of the donor tissue band, we tested 11 types of band made from 14 polymers in rabbit eyes. Bands were cut from porous and solid materials, as well as porous patches affixed to the posterior surface. Criteria for suitability and biocompatibility included ease of placement and suturing, stable positioning, and absence of long‐term tissue response on a cellular level. Testing included evaluation by the surgeons performing the implantations, measurement of the distance between the band and the globe, determination of fibrous capsule thickness and amount of collagen deposition, and enumeration of macrophages accumulated at the band/capsule interface. Based on the results of these studies, two of the porous materials (expanded polytetrafluoroethylene and porous polyurethane fabric) and two of the composite materials (porous polyurethane fabric coated with polyacrylonitrile and silicone with microvilli cut into the posterior surface) were selected for further study. © 1994 John Wiley & Sons, Inc.
Morphologic variation in plasma‐sprayed hydroxyapatite‐bioactive glass composite coatings in Hank's solution
Authors: Lin J. H. Chern , Liu M. L. , Ju C. P.
Published: May 2005

Pure hydroxyapatite (HA), pure bioactive glass (BG), and a new series of (HA/BG) composite coatings were plasmasprayed onto a commercial Ti6A14V substrate. Changes in morphology and phases of these coatings after immersion in Hank's physiologic solution were investigated using XRD and SEM. Results indicated that the as‐sprayed BG coating has an essentially amorphous structure with a very rough surface. After 7 days of immersion, the BG surface started to dissolve, and weak XRD peaks of apatite started to develop. Small amounts of CaO, β‐TCP, Ca4P2O5, as well as a glassy film, were found on the as‐sprayed pure HA surface, most of which dissolved in 7 days. The XRD intensity of apatite in pure HA slowly increased with immersion time until, on the 10th day, the intensity started to drop, and 10 days later, the intensity rose again. This undiscovered “drop and rise” phenomenon was observed for the HA/BG composite coatings in an even more dramatic way. The presence of HA accelerates the dissolution of bioactive glass. © 1994 John Wiley & Sons, Inc.
Adhesion of lactobacilli to urinary catheters and diapers: Effect of surface properties
Authors: Reid Gregor , Lam Dominique , Bruce Andrew W. , van der Mei Henny C. , Busscher Henk J.
Published: May 2005

Thirteen strains of lactobacilli were tested for their ability to adhere to commercial devices used in the urinary tract. Although it appeared that the most hydrophilic organisms adhered in highest numbers, there was no significant correlation between water contact angle and adhesiveness to catheters. Five organisms tested were found to be highly adherent to Huggies commercial diapers. Loss in hydrophobicity upon serial culture of Lactobacillus fermentum B‐54 was not due to a proteinaceous S layer, although protein involvement per se cannot be ruled out. It was evident that, not only can members of the normal female urogenital flora adhere to commonly used commercial prostheses, but their ability to attach is related to hydrophilic as well as hydrophobic surface components. © 1994 John Wiley & Sons, Inc.
Complement activation on solid surfaces as determined by C3 deposition and hemolytic consumption
Authors: Liu Li , Elwing Hans
Published: May 2005

Complement activation was investigated on hydrophilic and hydrophobic glass beads incubated in serum. Very little complement activation was detected with these surfaces, as indicated by a hemolytic assay and by measurement of the amount of iC3b appearing in the solution. However, preadsorption with IgG at the hydrophobic and hydrophilic beads resulted in complement activation on both surfaces. We also investigated dependent deposition of C3 at hydrophobic and hydrophilic silicon surfaces when the complement was activated. The chemistry of those surfaces is similar to the hydrophobic and hydrophilic beads. Ellipsometry, an optical method, was used for determination of the amounts of oraganic material deposited at the surface. C3 deposition was observed at the IgG precoated hydrophobic surface but not at the IgG‐coated hydrophilic surface. The absence of C3 deposition at the hydrophilic surface was probably due to reversible binding of IgG. However, precoating of the hydrophilic surface with a double layer of IgG and anti‐IgG resulted in C3 deposition also at the hydrophilic surface. The results illustrate that methods based on measuring deposition of C3 at surfaces, such as immunofluorescence or ellipsometry, cannot exclude surface‐associated complement activation that is probably due to reversible binding of the complement components of the activated molecule. On the other hand, it has previously been shown that determination of complement activation in solution with the use of a C3a assay cannot exclude surface‐associated activation due to immobilization of C3a at the surface.1 This methodologic question is an important issue because factors such as C3a and C5a act as soluble anaphylatoxins, whereas deposited factors such as C3 act as cellular receptors. © 1994 John Wiley & Sons, Inc.
Cyclic fatigue and fracture in pyrolytic carbon‐coated graphite mechanical heart‐valve prostheses: Role of small cracks in life prediction
Authors: Dauskardt R. H. , Ritchie R. O. , Takemoto J. K. , Brendzel A. M.
Published: May 2005

A fracture‐mechanics based study has performed to characterize the fracture toughness and rates of cyclic fatiguecrack growth of incipient flaws in prosthetic heart‐valve components made of pyrolytic carbon‐coated graphite. Such data are required to predict the safe structural lifetime of mechanical heart‐valve prostheses using damagetolerant analysis. Unlike previous studies where fatiguecrack propagation data were obtained using through thickness, long cracks (∼2–20 mm long), growing in conventional (e.g., compact‐tension) samples, experiments were performed on physically small cracks (∼100–600 μm long), initiated on the surface of the pyrolytic‐carbon coating to simulate reality. Small‐crack toughness results were found to agree closely with those measured conventionally with long cracks. However, similar to well‐known observations in metal fatigue, it was found that based on the usual computations of the applied (far‐field) driving force in terms of the maximum stress intensity, Kmax, small fatigue cracks grew at rates that exceeded those of long cracks at the same applied stress intensity, and displayed a negative dependency on Kmax; moreover, they grew at applied stress intensities less than the fatigue threshold value, below which long cracks are presumed dormant. To resolve this apparent discrepancy, it is shown that long and small crack results can be normalized, provided growth rates are characterized in terms of the total (near‐tip) stress intensity (incorporating, for example, the effect of residual stress); with this achieved, in principle, either form of data can be used for life prediction of implant devices. Inspection of the long and small crack results reveals extensive scatter inherent in both forms of growth‐rate data for the pyrolytic‐carbon material. © 1994 John Wiley & Sons, Inc.
The delay method: A new surgical technique for enhancing the bone‐binding capability of HAP implants to bone surrounding implant cavity preparations
Authors: Ogiso Makoto , Yamashita Yasuo , Tabata Tsuneo , Ramonito Ree , Borgese Diego
Published: May 2005

To confirm the efficacy of a new apatite‐implantation technique, in vivo research was undertaken on 12 dogs. The project was designed to determine the time‐dependent effects on alveolar tissues surrounding implant cavity preparations without implantation in bone. In addition, a group of hydroxyapatite (HAP) implants was placed immediately after cavity preparation (conventional method). A second group was placed after a delay of 2 weeks (delay method). Hemorrhagic infiltration occurred within the cavity and into the surrounding fatty marrow, a phenomenon attributed to cavity preparation. Subsequent to absorption of infiltrated blood cells into the surrounding marrow, fibrous tissue was formed, followed by osseous formation initiated by the original bone. Formation of newly formed, thin trabeculae reached a peak at 14 days. Most of the original marrow near the cavity, where few trabeculae were originally present, was transformed into thin trabecular‐forming areas. In addition, sinusoidal capillaries and hematopoiesis were formed at the site. At 30 days, the number of new trabeculae and sinusoidal capillaries formed decreased, and adipose cells began to appear. These results indicate that tissue surrounding the prepared cavity was centrally activated at 14 days, and that this activation may be beneficial in the biologic ability of an apatite implant to advantageously affect bone binding and chemical bonding activity. It is concluded that bone formation was faster and wider around implants placed by the delay method than that surrounding conventionally placed implants. These results indicate that more efficient bone formation around implants was encouraged by bone activation stimulated during the 14 day delay period. © 1994 John Wiley & Sons, Inc.
Theoretical analysis of in vivo macrophage adhesion and foreign body giant cell formation on strained poly(etherurethane urea) elastomers
Authors: Kao Weiyuan John , Hiltner Anne , Anderson James M. , Lodoen G. A.
Published: May 2005

Quantitative description of foreign body giant cell (FBGC) formation on poly(etherurethane urea) (PEUU) surfaces as a function of time can conceivably predict the effects of polymer characteristics on cellular responses in vivo. In the present study, the formation of FBGCs on strained and unstrained PEUUs was quantified with two parameters: the density of adherent macrophages present initially that participate in FBGC formation (do) and the rate constant for cell fusion (k); both kinetic parameters were used to calculate the time‐dependent FBGC density (dfc). Relationships were sought between results of the cellular analysis and the extent of environmental stress cracking (ESC), as characterized by scanning electron microscopy. Surface degradation was semiquantified with percent light transmittance.

The materials used were: base PEUU, base PEUU with 1% Santowhite® antioxidant powder, base PEUU with 5% Methacrol 2133F® antifume agent, and base PEUU with both 1% Santowhite® and Methacrol 2138F®. A comparison of unstrained base PEUU with base PEUU strained to 400% elongation indicated that the rate of cell fusion, but not do and dfc, increased in the presence of strain. In all strained samples, additives that strongly affected the ESC also influenced FBGC kinetic parameters. Strained PEUU containing Santowhite® had the lowest do, the slowest rate of cell fusion, and lowest dfc, and the least incidence of ESC. The results suggest that the incidence of ESC in PEUU was decreased in the presence of Santowhite®, which also lowered the number of adherent macrophages participating in FBGC formation, the rate of FBGC formation and the subsequent FBGC density. These studies also indicate that strain in PEUUs does not directly modulate the adherent macrophage and FBGC density. Further studies are necessary to delineate the relationship between PEUU strain and adherent macrophage and FBGC activation, which leads to the exocytosis of degrading agents and the observed incidence of biodegradation. © 1994 John Wiley & Sons, Inc.
In vitro Plasma protein adsorption and kallikrein formation on 3‐mercaptopropionic acid, L‐cysteine and glutathione immobilized onto gold
Authors: Lestelius M. , Liedberg B. , Lundström I. , Tengvall P.
Published: May 2005

3‐Mercaptopropionic acid (MPA), L‐cysteine (L‐cys), and glutathione (GSH) monolayers were immobilized onto gold and used in in vitro protein tests. The surfaces were characterized with ellipsometry, static contact angle measurements, atomic force microscopy, and Fourier transform in frared reflection absorption spectroscopy (FT‐IRAS). After incubations in human plasma and antibody solutions, the surface antisera binding patterns were determined with ellipsometry. Using serum instead of plasma, complement activation was studied in the same fashion. Activated coagulation Factor XII and Kallikrein formation on the surfaces and in the plasma were studied using a kallikreinspecific colorimetric assay. 3‐Mercaptopropionic acid indicated contact activation of coagulation but L‐cysteine did not. Glutathione displayed low deposition of plasma proteins, large deposition of proteins from serum, and did not promote kallikrein formation. None of the surfaces could be attributed complement activating properties, as determined by antibody deposition. The present study demonstrates that surface biology in complex model systems can be conveniently studied in vitro through systematic and well defined surface modifications. © 1994 John Wiley & Sons, Inc.
In vivo and electron microscopic studies of rat liver after intravenous injection of polyamino acid microspheres
Authors: Li C. , McCuskey P. , Kan Z. , Yang D. J. , Wright K. C. , Wailace S.
Published: May 2005

In vivo and electron microscopy were used to study the hepatocellular responses of rat livers to intravenously injected polymeric microspheres. Two microsphere preparation with different surface characteristics and degradability were used in this study. In vivo microscopy revealed that both poly(benzyl L‐glutamate) (PBLG) and poly(hydroxypropyl L‐glutamine) (PHPG) microspheres caused disturbance in the microcirculation of rat liver up to 2 months after injection. The observed changes included stagnant flow and adherence of white blood cells to the endothelial lining of venules and sinusoids. Kupffer cell (KC) activation following phagocytosis of microspheres was evidenced by the enlargement of KCs and increased number of KCs taking up fluorescent latex particles. Electron microscopy of rat livers revealed a wide range of hepatocellular injury associated with the administration of PBLG and PHPG microspheres. These results indicate that a small amount of remaining microspheres is sufficient to induce continuous disturbance to hepatic microcirculation and that particulate drug carriers should be designed to be rapidly degraded so that the return to normal liver function is possible. © 1994 John Wiley & Sons, Inc.
Joint resurfacing using allograft chondrocytes and synthetic biodegradable polymer scaffolds
Authors: Freed L. E. , Grande D. A. , Lingbin Z. , Emmanual J. , Marquis J. C. , Langer R.
Published: May 2005

Cartilage implants which could potentially be used to resurface damaged joints were created using rabbit articular chondrocytes and synthetic, biodegradable polymer scaffolds. Cells were serially passaged and then cultured in vivo on fibrous polyglycolic acid (PGA) scaffolds. Cell‐PGA constructs were implanted in vivo as allografts to repair 3‐mm diameter, full thickness defects in the knee joints of adult rabbits, and cartilage repair was assessed histologically over 6 months. In vitro, chondrocytes proliferated on PGA and regenerated cartilaginous matrix. Collagen and glycosaminoglycan (GAG) represented 20 to 8% of the implant dry weight (dw), respectively, at the time of in vivo implantation; the remainder was PGA and unspecified components. Implants based on passaged chondrocytes had 1.7‐times as much GAG and 2.6‐times as much collagen as those based on primary chondrocytes. In vivo, cartilaginous repair tissue was observed after implantation of PGA both with and without cultured chondrocytes. Six month repair was qualitatively better for cell‐PGA allografts than for PGA alone, with respect to: (1) surface smoothness, (2) columnar alignment of chondrocytes, (3) spatially uniform GAG distribution, (4) reconstitution of the subchondral plate, and (5) bonding of the repair tissue to the underlying bone. These pilot studies demonstrate that it is feasible to use cell‐polymer allografts for joint resurfacing in vivo. © 1994 John Wiley & Sons, Inc.
Magnetically directed poly(lactic acid) 90Y‐microspheres: Novel agents for targeted intracavitary radiotherapy
Authors: Häfeli Urs O. , Sweeney Siobhan M. , Beresford Beverly A. , Sim Edward H. , Macklis Roger M.
Published: May 2005

High energy β‐emitting radioisotopes like Yttrium‐90 have a radiotoxic range of about one centimeter. For cancer treatment they must be brought near the tumor cells and kept there for as long as they are radioactive. We developed as carriers for the ionic form of 90Y a matrix‐type polymeric drug delivery system, poly(lactic acid) (PLA) microspheres. This radiopharmaceutical could be selectively delivered to the target site after incorporating 10% Fe3O4 (magnetite) which made the magnetic microspheres (MMS) responsive to an external magnetic field. Furthermore, MMS are biodegradable and slowly hydrolyze into physiologic lactic acid after the radioactivity is completely decayed. Previously prepared 10–40 μm MMS were radiochemically loaded to high specific activity with 90Y at a pH of 5.7. Stability studies showed that approximately 95% of added 90Y is retained within the PLA matrix after 28 days (>10 half‐lives) at 37°C in serum, and electron microscopy showed that the microspheres retained their characteristic morphologic appearance for the same time period. Cytotoxicity studies with SK‐N‐SH neuroblastoma cells growing in monolayer showed that the radiocytotoxicity of the microspheres could be directed magnetically to either kill or spare specific cell populations, thus making them of great interest for targeted intracavitary tumor therapy. We are currently optimizing this system for use in the treatment of neoplastic meningitis. © 1994 John Wiley & Sons, Inc.
Numerical analysis of extracellular fluid flow and chemical species transport around and within porous bioactive glass
Authors: García A. J. , Ducheyne P.
Published: May 2005

Modeling of the physical phenomena present at the biomaterial‐tissue interface provides a valuable tool for examining the underlying mechanisms which influence the overall behavior of the implant‐host system. Based on histological data from a previous implantation study (E. Schepers, M. De Clercq, P. Ducheyne, and R. Kempeneers, “Bioactive glass particulate materials as a filler for bone lesions,” J. Oral Rehab.; 18, 439–452, 1991, Ref. 1) which documented the differentiation of mesenchymal cells to cells expressing the osteoblastic phenotype in porous bioactive glass, a finite element momentum and mass transport model was constructed. In this analysis, the extracellular compositional variations and fluid flow conditions around and within porous bioactive glass granules were determined. Numerical simulations demonstrated that the interstitial fluid flow around these granules (300–360 μm) is viscosity dominated (low Reynolds number flow) and that the fluid inside the granules remains stagnant. This velocity field results in shear stresses proportional to the velocity gradient at the granule‐fluid interface outside the particles and no shear stresses inside the particles. A parametric study on the effect of interstitial fluid flow on chemical species (Na+, Ca+2, HPO4−2) transport outside the granules revealed three domains. At low velocities (0–0.1 μm/s), the transport of species is diffusion controlled. At intermediate velocities (1.0–10 μm/s), diffusion and convection contribute to the species transport. The concentration of chemical species is nearly uniform at high velocities (100–800 μm/s). For all three cases, the transport of chemical species within the granules is diffusion controlled. The differences in transport mechanisms and interstitial fluid flow conditions lead to variations in concentrations, reaction rates, and shear stresses between the inside and the outside of the glass granules. These differences may influence cellular migration, attachment, differention, and the overall response to these bioactive materials.
Interactions of human von Willebrand Factor with a hydrophobic self‐assembled monolayer studied by atomic force microscopy
Authors: Siedlecki Christopher A. , Eppell Steven J. , Marchant Roger E.
Published: May 2005

Human von Willebrand Factor (vWF) was studied by atomic force microscopy under physiologic buffer on a hydrophobic octadecyltrichlorosilane self‐assembled monolayer. The self‐assembled monolayer deposited on glass was sufficiently smooth (root mean square roughness = 0.25 ± 0.12 nm) to permit identification of adsorbed vWF. Adhesion of the protein to the hydrophobic substrate was sufficient to allow repeated scanning by the atomic force microscope probe, and images of vWF on a submolecular scale were obtained. The frictional force between the surface and the protein was sufficient to withstand an applied lateral force of 19 nN. This result shows that vWF experiences strong interaction with a hydrophobic surface in aqueous media. Statistical analysis of adsorbed vWF shows that the protein is composed of large globular domains with elliptical cross sections of average dimensions 56 ± 24 nm (major axis) 26 ± 19 nm (minor axis), and 2.8 ± 1.0 nm (height). Further analysis of the major axis dimension shows that the molecular chain of vWF contains two statistically different populations of domain size. However, no sequence order of the different population of domains within the individual molecule was found. On the basis of our analysis of the globular domains, we present a model describing the three‐dimensional structure of vWF protomer adsorbed on a hydrophobic surface in a physiologic solution. © 1994 John Wiley & Sons, Inc.