|Articles about Biomaterials|
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| The inflammatory potential of biphasic calcium phosphate granules in osteoblast/macrophage co-culture
Curran, J. M., J. A. Gallagher, et al. (2005), Biomaterials 26(26): 5313-20.
Abstract: Some biological properties of a range of biphasic calcium phosphate (BCP) granules were quantified using a co-culture model of primary unstimulated human osteoblasts and macrophages. The BCP granules were classified in terms of diameter and the ratio of tricalcium phosphate (TCP): hydroxyapatite (HA). All granules were 50% porous and sterilised by gamma-irradiation. Primary unstimulated human osteoblasts and macrophages were cultured in contact with the range of BCP granules for 1, 7 and 14 days. The response of the cells was determined and quantified by the assessment of viable cell adhesion to the substrate, using lactate dehydrogenase assay, and the production and release of the cytokines; interleukin 1beta, (IL-1beta), tumour necrosis factor alpha (TNF-alpha) and prostaglandin E2 (PGE2). Throughout the test period viable cell adhesion on all BCP granules was significantly lower than the tissue culture polystyrene control. Higher content TCP materials, (80% and 100% TCP) did not support viable cell adhesion after 1 day, lower content TCP materials, (20% and 50% TCP) granules did support viable cell adhesion throughout the time period. The percentage content of TCP was a more significant factor than granule size within the test conditions at all time points.
| The influence of a biomaterial on the closure of a marginal hard tissue defect adjacent to implants. An experimental study in the dog
Botticelli, D., T. Berglundh, et al. (2004), Clin Oral Implants Res 15(3): 285-92.
Abstract: OBJECTIVES: The present experiment was performed to determine the influence of Bio-Oss on hard tissue formation at sites that, following implant installation, presented a 1-1.25 mm wide marginal defect. MATERIAL AND METHODS: Four Labrador dogs were used. The premolars and first molars on both sides of the mandible were extracted. After 3 months, mucoperiosteal flaps were elevated and three experimental sites were prepared for implant installation in each side of the mandible. A step drill was used to widen the marginal 5 mm of the canal. Thus, following the placement of the implant (3.3 x 10 mm, SLA surface, Straumann AG, Waldenburg, Switzerland) a circumferential gap, about 1-1.25 wide and 5 mm deep, remained lateral to the titanium rod. The test sites in the left side of the mandible were first filled with a deproteinized cancellous bone mineral (Bio-Oss). The defect sites in the right side of the mandible (control sites) were left for spontaneous healing. A resorbable barrier membrane (Bio-Gide) was placed to cover the implant and the bone tissue in two sites of each quadrant, while the third site was left without membrane placement. The flaps were repositioned to cover all defect sites and were sutured. After 4 months of healing, block biopsies of each implant site were dissected and processed for ground sectioning. RESULTS: It was demonstrated that at 4 months, all types of defects were filled with newly formed bone and that the biomaterial placed in the marginal defect in conjunction with implant installation during healing became incorporated in the newly formed bone tissue. A high degree of contact was established between the Bio-Oss particles and the newly formed bone. CONCLUSION: Bio-Oss became integrated with the newly formed bone. In the model used, Bio-Oss did not enhance the process of bone formation and defect closure.
| The influence of anatomical features on the outcome of gingival recessions treated with coronally advanced flap and enamel matrix derivative: a 1-year prospective study
Berlucchi, I., L. Francetti, et al. (2005), J Periodontol 76(6): 899-907.
Abstract: BACKGROUND: Coronally advanced flap (CAF) is one of the most effective treatments of Miller Class I and II recessions. Even if excellent outcomes are reported in the literature, complete root coverage is not always predictable, since many surgical and host-related factors may affect the percentage of root coverage obtained. The aim of this clinical study was to evaluate if some anatomical features such as tissue thickness, papillae height and width, recession depth, and vestibular bone height may influence defect coverage of Miller Class I and II gingival recessions treated with CAF in combination with enamel matrix derivative (EMD). METHODS: Thirty healthy, non-smoking patients (13 men and 17 women; mean age 32.8 +/- 6.2 years) were enrolled. Each patient was treated for one single recession using a CAF with the adjunct of EMD. Clinical parameters at baseline and 6 and 12 months were recorded and compared by using paired Student t test. Data were subdivided in two groups according to the baseline recession depth (REC): REC < 4 mm (group 1) and REC > or = 4 mm (group 2). The relation between the anatomical parameters (papilla height, papilla width, crestal bone height, and flap thickness) and percent of root coverage was evaluated by multiple linear regression analysis. RESULTS: At 12 months, 91.7% of root coverage was obtained with a mean attachment gain of 3.23 mm. Better results in terms of percentage of root coverage were obtained when the baseline REC was < 4 mm compared to defects > or = 4 mm (96.5% versus 83.5%). Flap thickness was positively correlated to the percentage of root coverage. For gingival recessions > or = 4 mm, 100% root coverage was achieved only when tissue thickness was > or = 1 mm. Root coverage percentage was slightly related to papilla width in both groups, while it was associated with papilla height only in group 1 (P = 0.004). Only in patients in group 1 was the height of bone on the vestibular side related to the percentage of root coverage obtained (P = 0.003). CONCLUSIONS: The results of the present study suggest that baseline recession depth and flap thickness may influence the outcome of marginal tissue recession therapy with CAF plus EMD at 12 months. There is not a clear relation between root coverage and other anatomical features as papilla width, papilla height, and the amount of bone on the vestibular side.
| The influence of biomaterial on patterns of failure after cemented total hip replacement
Sott, A. H. and J. W. Rosson (2002), Int Orthop 26(5): 287-90.
Abstract: We examined aseptic loosening and osteolysis in 77 revised McKee-Arden total hip arthroplasties (THAs) using polyethylene cups and identical femoral stems made from either cobalt chrome alloy or titanium alloy. Time to failure was significantly shorter in the titanium group. Loosening and peri-prosthetic osteolysis occurred with significantly higher frequency in the titanium group compared to the cobalt chrome group.
| The influence of biomaterials on inflammatory responses to cardiopulmonary bypass
Courtney, J. M., B. M. Matata, et al. (1996), Perfusion 11(3): 220-8.
Abstract: The nature of cardiopulmonary bypass and the complexity of the inflammatory response make the detection and interpretation of a biomaterial influence difficult. However, if mediation of the inflammatory response is considered to be an appropriate clinical goal, alteration to the biomaterial influence merits further investigation.
| The influence of calcium phosphate biomaterials on human bone cell activities. An in vitro approach
Gregoire, M., I. Orly, et al. (1990), J Biomed Mater Res 24(2): 165-77.
Abstract: An in vitro method is described to assess the influence of synthetic calcium phosphate powders on osteoblast activities. Human osteoblast cell cultures were established from iliac crest. MC3T3-E1, an established osteogenic cell line, was employed as a control. Scanning and transmission electron microscopic observations clearly demonstrated the internalization of particles of calcium phosphate by the two osteoblast cell populations. As a consequence to the phagocytotic process, RNA transcription and protein synthesis were stimulated, as indicated by the measurements of labeled uridine, leucine and proline uptakes. From these data, it is proposed that such an in vitro model, using one of the specific cell types involved in the tissue responses to implants, could be useful to assess the biological response at the cell-biomaterial interaction.
| The influence of cellular seeding density in the microencapsulation of hybridoma cells
Arus, L., G. Orive, et al. (2005), J Biomater Sci Polym Ed 16(4): 521-9.
Abstract: The aim of this study was to assess the influence of different seeding densities on the function of hybridoma cells (clone 1B5, IgG 2alpha) producing an anti-angiogenic monoclonal antibody (mAb), microencapsulated using a high-voltage electrostatic field. Viable cells were microencapsulated in alginate/poly-L-lysine/alginate (APA) capsules and maintained in tissue culture. Cellular growth rates, production and release of mAb from the capsules were assessed. This study shows that hybridoma cells survive, proliferate and remain functionally competent for over one month in vitro after microencapsulation in APA capsules generated in an electrostatic field. However, the cell seeding density had to be at least 10(7) cells/ml for the microencapsulated cells to be viable and to produce and release mAb through the capsule membrane. The maximum monoclonal antibody concentration in this culture was 29.1 microg/ml by day 17, with a tendency to increase, but capsule breakage impeded the follow-up of this determination.
| The influence of Encephalitozoon cuniculi on neural tissue responses to implanted biomaterials in the rabbit
Ansbacher, L., M. F. Nichols, et al. (1988), Lab Anim Sci 38(6): 689-95.
Abstract: Laboratory rabbits are commonly used for testing the tissue response of neural device biomaterials. Rabbits of many colonies in the U.S. are infected by the intracellular microsporidian parasite, Encephalitozoon cuniculi, with rates of infection ranging from 15 to 76% (1). Several authors have suggested that infection by this parasite may alter immune system response and experimental results. We report that infection by E. cuniculi made the interpretation of results more difficult and altered the animals' responsiveness to implanted platinum wires coated with various polymers such as glow discharge methane, Parylene C, or polyimide. Edema, neuronal and glial reaction, and inflammatory responses to the coated wires were quantitated at four sites in each animal. Inconsistency of response in all measured parameters was found, both between animals and between sites in infected animals. Infected animals showed the greatest variability, primarily in the degree of inflammatory reaction. Parylene C was found to induce the most severe inflammatory reaction, an unexpected finding. No consistent reaction to any of the coating materials was found in this study. We believe that this variability in response was primarily due to infection by E. cuniculi. Our results suggest that rabbits should not be used for tissue compatibility testing of neural device biomaterials until the animals are free of E. cuniculi infestation as demonstrated by serologic screening.
| The influence of GFP-actin expression on the adhesion dynamics of HepG2 cells on a model extracellular matrix
Feng, Z., W. Ning Chen, et al. (2005), Biomaterials 26(26): 5348-58.
Abstract: Integrins belong to a family of important cell surface receptors which mediate the adhesion of most anchorage-dependent cells to nature extracellular matrix (ECM) and biomaterials. It is known that the binding of integrin with ECM proteins triggers mechanochemical responses of cytoskeleton. To date, the intricate interplay between integrin-ECM interaction and cytoskeleton dynamics leading to the regulation of cell morphogenesis on biomaterials remains largely unknown. In this study, green fluorescence protein (GFP)-actins were expressed in HepG2 cells for the temporal visualization of cytoskeletal structure of adherent cells on naturally derived materials. By combining confocal reflectance contrast microscopy and fluorescence microscopy, the adhesion contact dynamics, cytoskeleton remodeling and two-dimensional spreading of intact and GFP-actin expressing HepG2 cells on collagen and fibronectin-coated substrates are simultaneously probed during the initial cell seeding. First of all, our results show that the evolution of adhesion contact of HepG2 cells upon integrin-collagen or integrin-fibronectin interaction is impaired by GFP-actin expression. Also, the initial rate of cell deformation is reduced by 70% and 43% on fibronectin and collagen, respectively, upon GFP-actin expression. Interestingly, the steady-state adhesion energy of HepG2 cells remains unchanged and increases on fibronectin- and collagen-coated substrate, respectively, upon GFP-actin expression. Our highly integrated biophysical approach demonstrates that GFP-actins diffusively concentrate in the cytoplasmic cortex during initial cell seeding while adhesion contact evolves and cell spreads. Kinetics analysis on the adhesion contact formation demonstrates the intricate interplay between cytoskeleton property and ECM proteins in cell adhesion.
| The influence of physical and chemical agents on photooxidation of porcine pericardial collagen
Kozma, E. M., G. Wisowski, et al. (2005), Biomed Mater Eng 15(3): 137-44.
Abstract: Photooxidation is a method of tissue fixation resulting in protein crosslinking due to illumination in the presence of a dye. The aim of the study was to evaluate the impact of dyes, photooxidation time and the type of applied light on the porcine pericardial collagen crosslinking. The collagen modifications were evaluated on the basis of pericardial sensitivity to pepsin digestion. The hydrolysate components were evaluated qualitatively and quantitatively. All hydrolysates contained collagen alpha chains, their aggregates and degradation products. Methylene blue and methylene green-mediated 4 h photooxidation in the presence of visible light caused similar decrease in pericardium sensitivity to pepsin. However, both fixation types generated remarkable amounts of alpha chain degradation products. The prolongation of photooxidation time to 8 h did not increase the pericardial sample resistance to pepsin. Moreover, these sample hydrolysates revealed an elevated alpha chain content. Violet light mediated photooxidation did not alter pericardial sensitivity to pepsin when compared with fixation under visible light. Nevertheless, violet light fixed tissues displayed a decrease in collagen degradation products. The application of violet light in photooxidation of porcine pericardium will probably allow to obtain enzyme resistant bioprostheses with better mechanical properties compared with those obtained after visible light mediated process.
| The influence of polymer blend composition on the degradation of polymer/hydroxyapatite biomaterials
Dunn, A. S., P. G. Campbell, et al. (2001), J Mater Sci Mater Med 12(8): 673-7.
Abstract: The in vitro degradation of biodegradable polymer/ceramic composites was assessed in two different environments under both static and pseudodynamic conditions. The blends, consisting of polycaprolactone, poly(lactic-co-glycolic acid), and hydroxyapatite, have potential use in bone tissue engineering applications, thus it is essential to establish a standardized method of characterizing the degradation of new biomaterials. In this study, the variation in polymer blend ratio was examined to observe a change in degradation rate. The porous blends were degraded in water and serum-containing media. A previous study examined in vitro degradation in serum-free buffer. Molecular weight loss, gravimetric weight loss, pH changes and morphological changes were evaluated. The changes in porosity were observed with scanning electron microscopy and quantitatively assessed using image analysis. There was a significant difference in molecular weight loss and gravimetric weight loss between the blends after 10 weeks in vitro. Blends containing the greatest amount of poly(lactic-co-glycolic acid) degraded most rapidly.
| The influence of Surelease and sodium alginate on the in-vitro release of tamsulosin hydrochloride in pellet dosage form
Kim, M. S., S. W. Jun, et al. (2005), J Pharm Pharmacol 57(6): 735-42.
Abstract: The objective of this study was to prepare controlled-release pellets containing 0.2 mg tamsulosin hydrochloride using a pelletizer-equipped piston extruder and double-arm counter-rotating rollers with Surelease and sodium alginate. The release of tamsulosin HCl from pellets coated with the commercial aqueous ethylcellulose dispersion (Surelease) was investigated at different coating loads. In addition, the effect of sodium alginate on drug release was investigated by varying the ratio of sodium alginate to microcrystalline cellulose (MCC). Dissolution studies were first performed in 500 mL simulated gastric fluid (pH 1.2) containing 0.003% (w/w) polysorbate 80 and then in simulated intestinal fluids (pH 7.2). The morphology of pellet surfaces and cross sections were examined by scanning electron microscopy (SEM). Apparently, the spherical pellets were prepared using a pelletizer-equipped piston extruder and double-arm counter-rotating rollers. The release profiles of tamsulosin HCl from Surelease-coated pellets were significantly affected by changing the content of Surelease, the pH of the dissolution medium and the ratio of sodium alginate to MCC. The drug release rates not only decreased with increase in the coating load, but also increased when the pH of the dissolution medium was increased from 1.2 to 7.2 regardless of the sodium alginate-to-MCC ratio. Moreover, the drug release rate at pH 7.2 was gradually increased by increasing the ratio of sodium alginate to MCC. SEM showed smooth surfaces of Surelease-coated pellets. These results suggest that Surelease and sodium alginate would be useful excipients in the preparation of controlled-release pellets with the desired release profiles.
| The influence of surface porosity on gap-healing around intra-articular implants in the presence of migrating particles
Rahbek, O., S. Kold, et al. (2005), Biomaterials 26(23): 4728-36.
Abstract: The aim of the present study was to compare the effect of two different porous coatings on bone ongrowth and on the peri-implant migration of polyethylene (PE) particles. Porous-coated cylindrical implants with an either plasma-sprayed closed-pore coating (Pl) or titanium fiber metal open-pore coating (Fi) were inserted intra-articular in exact fit or with a 0.75 mm peri-implant gap. A weight-loaded implant device in the distal femur was used. We used a randomized paired design in eight dogs. PE particles were injected repeatedly intra-articular in the knee until the dogs were killed after 8 weeks. Fi implants had significantly more bone ongrowth 8 (0-21)% compared with Pl implants 0 (0-0)% in gap situations and reduced the number of peri-implant PE particles significantly. Among exact-fitted implants we found that peri-implant tissue around Pl implants consisted of significantly more fibrous tissue than around Fi implants. A sealing effect against the migration of PE particles was found for both Fi and Pl implants in exact fit.
| The influence of thrombus components in mediating bacterial adhesion to biomaterials
Lamba, N. M., J. N. Baumgartner, et al. (2000), J Biomater Sci Polym Ed 11(11): 1227-37.
Abstract: Thrombosis and infection represent the two largest limiting factors determining the long term success of implanted biomaterials. Infections associated with biomaterials are difficult to treat, and appear to evade the host defense systems. Mechanisms relating infection to thrombosis are described. Investigations into the role of receptors in mediating adhesion to thrombi are also discussed, in addition to strategies to reduce bacterial adhesion to biomaterial surfaces.
| The influence of various substances on the biomechanical behavior of lamina cribrosa and peripapillary sclera
Spoerl, E., A. G. Boehm, et al. (2005), Invest Ophthalmol Vis Sci 46(4): 1286-90.
Abstract: PURPOSE: Changes in the biomechanical properties of the lamina cribrosa (LC) and of the peripapillary sclera (ppSc) may play a role in the pathogenesis of glaucoma. The purpose of this study was to assess the influence of glyceraldehyde, methylglyoxal, and collagenase A on the mechanical properties of the LC and ppSc. METHODS: Two strips of 1-mm width were cut from each of 80 porcine eyes and 24 pairs of enucleated human eyes. One strip contained the LC and the other the adjacent superior ppSc. One half of the strips was divided into groups and treated with 0.5 M glyceraldehyde, 0.5 M methylglyoxal, and 0.1% collagenase A. The other strips served as the control. The stress strain relation was measured in the stress range of 0.02 to 6.0 MPa by a biomaterial tester. RESULTS: Stress values at 20% strain of the human LC changed from 1.97 +/- 1.48 to 3.40 +/- 1.60 MPa after incubation with glyceraldehyde (P = 0.029), from 2.42 +/- 2.22 to 5.46 +/- 1.91 MPa (P = 0.014) after incubation with methylglyoxal, and from 2.43 +/- 1.3 to 1.35 +/- 0.19 MPa after incubation with collagenase A. The stress values of human ppSc without glyceraldehyde were 3.40 +/- 2.59 and 7.45 +/- 4.46 MPa after incubation with glyceraldehyde (P = 0.047), 4.80 +/- 3.05 MPa without methylglyoxal and 16.10 +/- 5.53 MPa (P = 0.001) after incubation with methylglyoxal, 4.14 +/- 2.56 MPa without collagenase A, and 1.97 +/- 0.55 MPa after incubation with collagenase A. At a 20% strain, Young's moduli of the untreated LC were in the range of E = 11.8 to 15.6 MPa and E = 28.5 to 36.0 MPa of the untreated ppSc. CONCLUSIONS: Glyceraldehyde and methylglyoxal increase the stiffness of the LC and of the ppSc in human and in porcine eyes. These substances induce changes in the extracellular matrix according to the Maillard reaction as it occurs during the ageing process or in case of high blood glucose levels. Collagenase reduces the stiffness of the tissues.
| The inhibition of neutrophil antibacterial activity by ultra-high molecular weight polyethylene particles
Bernard, L., P. Vaudaux, et al. (2005), Biomaterials 26(27): 5552-7.
Abstract: Following infection, bacterial killing by polymorphonuclear leukocytes (neutrophils) is the main host defense against bacteria. Our hypothesis is that particles of ultra-high molecular weight polyethylene (UHMWP) may impair local neutrophil function and consequently reduce neutrophil bacterial killing. To determine how the in vitro phagocytic-bactericidal activity of neutrophils was affected by exposure to wear particles, tests were run comparing the effects of different particle composition, and different concentrations and sizes of UHMWP particles. There was a significant correlation between the number of particles and the decrease in neutrophil bactericidal activity (p<0.01), and the greatest effect was obtained with a concentration of 10(7) UHMWP/ml. There was a significant decrease in neutrophil bactericidal activity by incubation with particles of 0.1-5 microm (p<0.01), but not with larger size. The results suggest that neutrophil functional defects triggered by the presence of UHMWP particles may potentially contribute to the susceptibility of loose implants to bacterial infections.
| The interaction of heparinized biomaterials with human serum, albumin, fibrinogen, antithrombin III, and platelets
Nemets, E. A. and V. I. Sevastianov (1991), Artif Organs 15(5): 381-5.
Abstract: The influence of the method of heparin (HEP) immobilization on human serum albumin (HSA), fibrinogen (FG), and antithrombin III (AT-III) adsorption, platelet adhesion, and activation on the surface of polyvinylchloride, polyurethane Vitur, and a copolymer of styrene and divinylbenzene was measured. The negative correlation between the degree of irreversibility of plasma protein adsorption and the amount of adsorbed AT-III for HEP, immobilized onto the polymer surface passivated with HSA, FG, and plasma was found. The same negative correlation was observed between the amount of AT-III adsorbed on these systems and the number of adhered platelets. Schemes of the interaction of surface bound-HEP with AT-III, including the influence of an irreversibly adsorbed protein layer and adhered platelets, have been proposed. The essential role of AT-III in heparinized biomaterials/platelet interaction has been shown. A new method of combined immobilization of HEP and platelet adhesion inhibitor has been elaborated on.
| The interaction of selected semiconducting biomaterials with platelet-rich plasma and whole blood
Shih, C. C., C. M. Shih, et al. (2005), J Biomed Mater Res A 74(3): 325-37.
Abstract: Copper and silicon are used as biomaterials in various forms. Silicon is a well-known semiconductor and has two distinct types (n-type and p-type), depending on the dopants used. The oxides (e.g., CuO and Cu2O) on the copper surface also behave as semiconductors. The electrochemical properties of these two selected semiconducting biomaterials were investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and open-circuit potential (OCP) in an aerated Ringer's solution at 37 degrees C. Platelet-rich plasma (PRP) and whole blood from a healthy human donor were used to determine the degree of interaction with the selected semiconducting materials in vitro. Morphologies of adherent platelets and blood on these two biomaterials were examined by scanning electron microscopy (SEM). Experimental results indicated that the degree of interaction is a function of the electrochemical properties of these two biomaterials. Platelets and blood were found to react strongly with p-type biomaterials while little or no sign of interaction with n-type biomaterials was demonstrated. The difference in PRP and whole blood reactions between p-type and n-type semiconductors was quantified to be significant as p<0.05.
| The intraocular lens: challenges in the prevention and therapy of infectious endophthalmitis and posterior capsular opacification
Parsons, C., D. S. Jones, et al. (2005), Expert Rev Med Devices 2(2): 161-73.
Abstract: Cataract is the leading cause of visual impairment worldwide. In the UK, some 30% of the population over 65 years of age have visually impairing cataract. Importantly, 88% of those with treatable visual impairment from cataract are not in contact with any ocular healthcare service, representing a major potential healthcare need . In the USA, it has been estimated that 17.2% of the population (approximately 20.5 million) over 40 years of age have cataract in either eye and by 2020, this number is expected to rise to 30.1 million. Currently, cataract is responsible for 60% of Medicare costs associated with vision . Furthermore, as the populations of industrialized countries such as the UK and the USA continue to age, the costs associated with treatment of cataract can only be expected to increase. Consequently, the development of the intraocular lens to replace the cataractous lens and the advances in intraocular lens design and implantation represent a major development in cataract treatment. However, despite such advances, cataract surgery is not without complications, such as postoperative infectious endophthalmitis, a rare but potentially devastating condition, and posterior capsular opacification, a less serious but much more common problem. This review will examine the epidemiology of cataracts, the polymeric construction of intraocular lenses implanted during cataract surgery and the complications of postoperative infectious endophthalmitis and posterior capsular opacification with regard to therapeutic interventions and prophylactic strategies. Advances in biomaterial design and function will be discussed as novel approaches to prevent such postoperative complications.
| The intravascular magnetic suspension of a test device for in vivo hemocompatibility evaluation of biomaterials
Lederman, D. M., R. D. Cumming, et al. (1976), Trans Am Soc Artif Intern Organs 22: 545-53.
Abstract: To advance hemocompatibility evaluation techniques, a new in vivo method has been developed for the dynamic testing of candidate biomaterials in suitably-sized experimental animals. One of the salient features this method is that the material to be evaluated constitutes the blood contact surface of a slender body of revolution which is coaxially suspended in a large canine vessel by electromagnetic forces only. The insertion site of the specimen is distal and downstream to the test region, reducing the influence of thrombotic tissue substances. These experimental conditions also insure that the only chronically exposed foreign surface is that of the test material, whose interactions with blood components are not affected by contact with the vessel intima. As demonstrated in simulated Circulation Model experiments, macroscopic thromboembolic phenomena induced by the test material can be continuously monitored. Preliminary in vivo trials have verified the validity of the underlying principles; the feasibility of the required surgical techniques, and the adequate performance of the suspension system.
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