|Articles about Biomaterials|
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| Assessment of biomaterials as components of a reciprocating dialyser during canine dialysis
Davidson, G. W., 3rd, N. A. Peppas, et al. (1984), Biomaterials 5(4): 227-33.
Abstract: A recently reported device, the sorbent suspension reciprocating dialyser (SSRD), was investigated for use as a test system for biocompatibility of dialyser components. The device is easy to assemble and operate, and allows minimal blood contact with foreign material outside of dialyser components. Its constant pressure/variable flow rate operation allows quantification of degree of clotting of dialyser versus time. The effect of heparinization of the blood distribution gaskets (BDG) of the device on performance and dialyser lifetime was investigated. Heparin was bound to the surface of polyethylene gaskets by immersion in a solution of tridodecylmethylammonium chloride (TDMAC)--heparin complex for several hours. Gaskets were then assembled in an SSRD which was then used for experimental dialysis in dogs with AV shunts. Dialysers assembled using non-heparinized gaskets were used as controls. Blood coagulation tendency was quantified by the activated clotting time (ACT) and partial thromboplastin time (PTT), and these values correlated with the rate of clotting of the device. Heparinization of the gaskets resulted in the prevention of clotting in the dialyser until the final minutes of dialysis in all cases, in contrast to the constant decay of blood fill volume and evidence of clotting in the non-heparinized cases. However, dialyser lifetime was not significantly increased by gasket heparinization. At normal initial values of ACT (80-95 s) dialyser clotting occurred in 10-15 min. In tests with non-heparinized gaskets and systemically heparinized dogs, values obtained in the ACT test were observed to decrease during dialysis, indicating the disappearance of heparin from the blood. Both ACT and PTT tests show promise as predictors of dialyser lifetime.
| Assessment of bone repair associated with the use of organic bovine bone and membrane irradiated at 830 nm
Gerbi, M. E., A. L. Pinheiro, et al. (2005), Photomed Laser Surg 23(4): 382-8.
Abstract: OBJECTIVE: The aim of the present investigation was to assess histologically the effect of LLLT (GaAIAs, 830 nm, 40 mW, CW, (Phi) approximately 0.6 mm, 16 J/cm(2) per session) on the repair of surgical defects created in the femur of the Wistar Albinus rat. The defects were filled to lyophilized bovine bone (Gen-ox), organic matrix) associated or not to GTR (Gen-derm). BACKGROUND DATA: A major problem on modern Dentistry is the recovery of bone defects caused by trauma, surgical procedures or pathologies. Several types of biomaterials have been used in order to improve the repair of these defects. These materials are often associated to procedures of GTR. Previous studies have shown positive effects of LLLT on the repair of soft tissue wounds, but there are a few on its effects on bone healing. METHODS: Surgical bone defects were created in 42 animals divided into five groups: Group I (control, 6 animals); Group II (Gen-ox, 9 animals); Group III (Gen-ox + Laser, 9 animals); Group IV (Gen-ox + Gen-derm, 9 animals); Group V (Gen-ox + Gen-derm + Laser, 9 animals). The animals on the irradiated group received 16 J/cm(2) per session divided into four points around the defect (4 J/cm(2)) being the first irradiation immediately after surgery and repeated seven times at every 48 h. The animals were humanly killed after 15, 21, and 30 days. RESULTS: The results of the present investigation showed histological evidence of improved amount of collagen fibers at early stages of the bone healing (15 days) and increased amount of well organized bone trabeculae at the end of the experimental period (30 days) on irradiated animals compared to non irradiated ones. CONCLUSIONS: It is concluded that a positive biomodulative effect on the healing process of one defect associated or not to the use of organic lyophilized bone and biological bovine lyophilized membrane on the femur of the rat.
| Assessment of encrustation behaviour on urinary tract biomaterials
Gorman, S. P. and M. M. Tunney (1997), J Biomater Appl 12(2): 136-66.
Abstract: The effective clinical use of biomaterials within the urinary tract is often hindered by the associated problems of bacterial biofilm formation and encrustation which may cause obstruction or blockage of urethral catheters and ureteral stents. Methods for assessing encrustation formation on these devices are reviewed and novel urinary tract biomaterials which may be more effective at resisting encrustation are discussed.
| Assessment of heparin binding to the AN69 ST hemodialysis membrane: I. Preclinical studies
Chanard, J., S. Lavaud, et al. (2005), Asaio J 51(4): 342-7.
Abstract: The AN69 ST membrane was designed to render the surface of the native polyacrylonitrile polymer less cationic. This was achieved by layering the membrane with the polycationic biopolymer polyethyleneimine. This new membrane is able to bind heparin to its surface, through electrical interactions, without altering the reactivity of the sulfonate groups of the membrane, regularly distributed in the membrane bulk. The kinetics of unfractionated or low-molecular-weight heparins were studied in vitro and in vivo in sheep. Encouraging results were obtained indicating that heparin-coated hemodialyzers are potent anticoagulants. Priming the AN69 ST membrane-equipped hemodialyzer with heparin, as in regular hemodialysis, could allow drastic reduction of heparin consumption in hemodialysis.
| Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long-bone fracture model using a bone substitute
Florin, M., M. Arzdorf, et al. (2005), Vet Surg 34(3): 231-8.
Abstract: OBJECTIVE: To compare the mechanical properties of 4 stabilization methods for equine long-bone fractures: dynamic compression plate (DCP), limited contact-DCPlate (LC-DCP), locking compression plate (LCP), and the clamp-rod internal fixator (CRIF--formerly VetFix). STUDY DESIGN: In vitro mechanical study. SAMPLE POPULATION: Bone substitute material (24 tubes) was cut at 20 degrees to the long axis of the tube to simulate an oblique mid-shaft fracture. METHODS: Tubes were divided into 4 groups (n=6) and double plated in an orthogonal configuration, with 1 screw of 1 implant being inserted in lag fashion through the "fracture". Thus, the groups were: (1) 2 DCP implants (4.5, broad, 10 holes); (2) 2 LC-DCP implants (5.5, broad, 10 holes); (3) 2 LCP implants (4.5/5.0, broad, 10 holes) and 4 head locking screws/plate; and (4) 2 CRIF (4.5/5.0) and 10 clamps in alternating position left and right of the rod. All constructs were tested in 4-point bending with a quasi-static load until failure. The implant with the interfragmentary screw was always positioned on the tension side of the construct. Force, displacement, and angular displacement at the "fracture" line were determined. Construct stiffness under low and high loads, yield strength, ultimate strength, and maximum angular displacement were determined. RESULTS: None of the implants failed; the strength of the bone substitute was the limiting factor. At low loads, no differences in stiffness were found among groups, but LCP constructs were stiffer than other constructs under high loads (P=.004). Ultimate strength was lowest in the LCP group (P=.01), whereas yield strength was highest for LCP constructs (409 N m, P=.004). CRIF had the lowest yield strength (117 N m, P=.004); no differences in yield strength (250 N m) were found between DCP and LC-DCP constructs. Differences were found for maximum angular displacement at the "fracture" line, between groups: LPC
| Assessment of the elution of charcoal, cellulose acetate, and other particles from cigarettes with charcoal and activated charcoal/resin filters
Agyei-Aye, K., S. Appleton, et al. (2004), Inhal Toxicol 16(9): 615-35.
Abstract: This experiment was designed to study the release of cellulose acetate fibers, charcoal, and other particles from cigarettes with charcoal and activated charcoal/resin filters. For the first time in such studies, efforts were made to identify the particles that were eluted using other analytical techniques in addition to light microscopy. Other corrective measures were also implemented. During the studies it was found that trimming of larger filters to fit smaller filter housings introduced cellulose acetate-like particles from the fibers of the filter material. Special, custom made-to-fit filters were used instead. Tools such as forceps that were used to retrieve filters from their housings were also found to introduce fragments onto the filters. It is believed that introduction of such debris may have accounted for the very large number of cellulose acetate and charcoal particles that had been reported in the literature. Use of computerized particle-counting microscopes appeared to result in excessive number of particles. This could be because the filter or smoke pads used for such work do not have the flat and level surfaces ideal for computerized particle-counting microscopes. At the high magnifications that the pads were viewed for particles, constant focusing of the microscope would be essential. It was also found that determination of total particles by using extrapolation of particle count by grid population usually gave extremely high particle counts compared to the actual number of particles present. This could be because particle distributions during smoking are not uniform. Lastly, a less complex estimation of the thickness of the particles was adopted. This and the use of a simple mathematical conversion coupled with the Cox equation were utilized to assess the aerodynamic diameters of the particles. Our findings showed that compared to numbers quoted in the literature, only a small amount of charcoal, cellulose acetate shards, and other particles are released. It was also shown that those particles would have a low likelihood of reaching the lung.
| Assessment of the heparin-binding AN69 ST hemodialysis membrane: II. Clinical studies without heparin administration
Lavaud, S., B. Paris, et al. (2005), Asaio J 51(4): 348-51.
Abstract: Binding polyanionic unfractionated heparin over the modified AN69 polyacrylonitrile membrane, the surface electronegativity of which has been neutralized by polyethyleneimine (AN69-ST), renders the membrane more hemocompatible. This property was tested in two groups of long-term hemodialysis patients. Results were rated as massive or partial clotting of a dialyzer at the end of the session. Group I patients were included in a prospective, cross-over study comparing standard dialysis with hemodialysis without systemic administration of unfractionated heparin (n = 12, 123 sessions). In all instances, priming was made with 2 I saline containing 5,000 IU/l heparin. Only patchy or partial clotting was observed in 11% and 39% of the sessions with standard and heparin-free administration, respectively. Group II patients were included in an open, observational pilot study testing the effects of the heparin-coated membrane, without systemic administration of heparin, in patients at high risk of bleeding (n = 68, 331 sessions). Massive clotting was observed in six sessions only (less than 2%) and normal or slightly patchy dialyzers were found in 88% of the sessions. It is concluded that the dialysis AN69 ST membrane, after adequate priming at bedside, can be used without systemic administration of heparin for hemodialysis in patients at high risk of bleeding.
| Assessment of tissue ingrowth rates in polyurethane scaffolds for tissue engineering
Ramrattan, N. N., R. G. Heijkants, et al. (2005), Tissue Eng 11(7-8): 1212-23.
Abstract: The continuous development of new biomaterials for tissue engineering and the enhancement of tissue ingrowth into existing scaffolds, using growth factors, create the necessity for developing adequate tools to assess tissue ingrowth rates into porous biomaterials. Current histomorphometric techniques evaluating rates of tissue ingrowth tend either to measure the overall tissue content in an entire sample or to depend on the user to indicate a front of tissue ingrowth. Neither method is particularly suitable for the assessment of tissue ingrowth rates, as these methods either lack the sensitivity required or are problematic when there is a tissue ingrowth gradient rather than an obvious tissue ingrowth front. This study describes a histomorphometric method that requires little observer input, is sensitive, and renders detailed information for the assessment of tissue ingrowth rates into porous biomaterials. This is achieved by examining a number of computer-defined concentric zones, which are based on the distance of a pixel from the scaffold edge. Each zone is automatically analyzed for tissue content, eliminating the need for user definition of a tissue ingrowth front and thus reducing errors and observer dependence. Tissue ingrowth rates in two biodegradable polyurethane scaffolds (Estane and polycaprolactone-polyurethane [PCLPU]) specifically designed for tissue engineering of the knee meniscus were assessed. Samples were subcutaneously implanted in rats with follow-up until 6 months. Especially at the earlier follow-up points, PCLPU scaffolds showed significantly higher tissue ingrowth rates than Estane scaffolds, making the PCLPU scaffold a promising candidate for further studies investigating meniscus tissue engineering.
| Assessment of tissue reactions to biomaterials: a model system using the foreign body response in the mouse lung to intravenously injected divinyl copolymer beads
Hood, C. I., F. J. Schoen, et al. (1984), J Biomed Mater Res 18(9): 1031-41.
Abstract: We have developed a reproducible model of granuloma formation in the mouse lung using a narrow size range (45-53 micron) of divinyl benzene copolymer beads as a standard test material. Approximately 10,000 beads are given by intravenous injection into the tail veins of mice whence they embolize to the lung and incite granuloma formation. This delivery system eliminates the superimposed inflammatory reaction due to trauma that occurs when materials are directly implanted at the test site by surgical incision. Granuloma size was quantitated at intervals from 3 h to 6 weeks by tracing mid-bead granuloma areas on the ground glass screen of a light microscope at a known magnification and measuring the areas with a digitizer interfaced with a microcomputer programmed to prepare histograms and to merge data from replicate experiments. At 3 h only a few polymorphonuclear leukocytes could be observed adhering to the beads. At 48 h, the time of maximum granuloma size (mean area = 7501 micron2), the granulomas consisted of both polymorphonuclear and mononuclear leukocytes. After 6 weeks, the granulomas were smaller, composed predominantly of mononuclear leukocytes and had a mean area of 2893 micron2. This model system allows the analysis of a large number of measurements, is reproducible, and provides a useful method for comparing the hosts' inflammatory response to a variety of potential biomaterials, as well as for determining the effectiveness of antiinflammatory drugs.
| Assessment of urinary tract biomaterial encrustation using a modified Robbins device continuous flow model
Tunney, M. M., P. F. Keane, et al. (1997), J Biomed Mater Res 38(2): 87-93.
Abstract: Encrustation of biomaterials employed in the urinary tract remains a major problem resulting in obstruction or blockage of catheters and stents. Therefore, resistance to encrustation is a desirable feature of biomaterials employed in such devices. The novel assessment of biomaterial encrustation employing a continuous flow model based on a modified Robbins device is described. Artificial urine was used in conjunction with 5% CO2 to simulate the physiological environment within the upper urinary tract. The widely used urinary device biomaterials, silicone and polyurethane, were investigated in the model for hydroxyapatite and struvite encrustation. Scanning electron microscopy, energy dispersive X-ray analysis, and atomic absorption spectroscopy all showed that silicone was less prone to encrustation than polyurethane and that hydroxyapatite deposition was predominant on both surfaces. The model has the advantage that a large number of biomaterials may be investigated simultaneously because several Robbins devices may be placed in parallel. The model is recommended for comparative evaluation of biomaterial candidates for use in urinary tract devices.
| Assessments of thrombogenicity by three in vitro techniques. Student Research Award in the Undergraduate, Master Candidate, or Health Science Degree Candidate Category, 21st annual meeting of the Society for Biomaterials, San Francisco, CA, March 18-22, 1995
Skarada, D. J., G. R. Erickson, et al. (1995), J Biomed Mater Res 29(9): 1039-45.
Abstract: This study assessed three in vitro techniques designed to measure the thrombogenicity of vascular grafts. All techniques immersed vascular grafts in rotating blood. In the gravimetric analysis, the weight of adherent thrombi was recorded at 2 min intervals for 20 min. In the torque analysis, a microviscometer continuously recorded the amount of torque developed as the graft rotated for 20 min. In the thrombin analysis, the blood sample was analyzed for fibrinopeptide A production indicating fibrinogen cleavage. Expanded polytetrafluoroethylene grafts were treated by removal of air nuclei (denucleation), binding of heparin, or binding of polyethylene oxide (PEO). The gravimetric analysis determined that the time at which each group experienced clot initiation was as follows: control after 6 min, denucleation after 14 min, heparin after 18 min, and PEO after 10 min. Similarly, in the torque analysis all treatment groups significantly delayed the initial increase in torque from 8.0 min for control to 12.5 min for denucleation (P <.01), > 20 min for heparin (P <.01), and 12 min for PEO (p <.05). The thrombin analysis determined that coagulation activity was reduced relative to control at 12 min with the denucleation group (P <.05) and heparin group (P <.01) and at 18 min with all treatment groups (P <.01). The similarity of results among the techniques increases confidence that each measurement accurately predicts in vitro thrombogenicity.
| Assimilating cell sheets and hybrid scaffolds for dermal tissue engineering
Ng, K. W., W. Tham, et al. (2005), J Biomed Mater Res A 75(2): 425-38.
Abstract: Cell sheets can be used to produce neo-tissue with mature extracellular matrix. However, extensive contraction of cell sheets remains a problem. We devised a technique to overcome this problem and applied it to tissue engineer a dermal construct. Human dermal fibroblasts were cultured with poly(lactic-co-glycolic acid)-collagen meshes and collagen-hyaluronic acid foams. Resulting cell sheets were folded over the scaffolds to form dermal constructs. Human keratinocytes were cultured on these dermal constructs to assess their ability to support bilayered skin regeneration. Dermal constructs produced with collagen-hyaluronic acid foams showed minimal contraction, while those with poly(lactic-co-glycolic acid)-collagen meshes curled up. Cell proliferation and metabolic activity profiles were characterized with PicoGreen and AlamarBlue assays, respectively. Fluorescent labeling showed high cell viability and F-actin expression within the constructs. Collagen deposition was detected by immunocytochemistry and electron microscopy. Transforming Growth Factor-alpha and beta1, Keratinocyte Growth Factor and Vascular Endothelial Growth Factor were produced at various stages of culture, measured by RT-PCR and ELISA. These results indicated that assimilating cell sheets with mechanically stable scaffolds could produce viable dermal-like constructs that do not contract. Repeated enzymatic treatment cycles for cell expansion is unnecessary, while the issue of poor cell seeding efficiency in scaffolds is eliminated.
| Atiprimod is an inhibitor of cancer cell proliferation and angiogenesis
Shailubhai, K., S. Dheer, et al. (2004), J Exp Ther Oncol 4(4): 267-79.
Abstract: Atiprimod, a novel compound belonging to the azaspirane class of cationic amphiphilic drugs, exhibits both anti-proliferative and anti-angiogenic activities. Atiprimod inhibited proliferation of all human cancer cell lines included in the National Cancer Institute panel with IC50 values in the low micromolar range. Notably, metastatic cell lines were more sensitive to the compound compared to the non-metastatic cell lines derived from the same tumor tissue types. Atiprimod also induced apoptosis and activated both caspase-9 and caspase-3 in T84 colon carcinoma cells. Hence, the anti-proliferative activity could partly be due to its pro-apoptotic activity. Regarding angiogenesis in vitro, atiprimod inhibited both bFGF and VEGF induced proliferation and migration of human umbilical vein endothelial cells (HUVECs), resulting in disruption of cord formation. In addition, atiprimod also suppressed formation of new blood vessels in a chorioallantoic membrane assay. Previous studies have also shown that atiprimod treatment reduced production of IL-6, VEGF and inhibited activation of Stat3, a constitutively activated protein in majority of human cancers. Together these findings suggest that atiprimod acts on several molecules that are essential for tumor growth, invasion and metastasis.
| Atomic force microscopic observation of in vitro polymerized poly[(R)-3-hydroxybutyrate]: insight into possible mechanism of granule formation
Hiraishi, T., Y. Kikkawa, et al. (2005), Biomacromolecules 6(5): 2671-7.
Abstract: Atomic force microscopy (AFM) was used to study the formation and growth of poly[(R)-3-hydroxybutyrate] (PHB) structures formed in the enzymatic polymerization of (R)-3-hydroxybutyryl coenzyme A [(R)-3-HBCoA] in vitro. Poly(3-hydroxyalkanoate) (PHA) synthase (PhaC(Re)) from Ralstonia eutropha, a class I synthase, was purified by one-step purification and then used for in vitro reactions. Before the reaction, PhaC(Re) molecules were deposited on highly oriented pyrolytic graphite (HOPG) and observed as spherical particles with an average height of 2.7 +/- 0.6 nm and apparent width of 24 +/- 3 nm. AFM analysis during the initial stage of the reaction, that is, after a small amount of (R)-3-HBCoA had been consumed, showed that the enzyme molecules polymerize (R)-3-HBCoA and form flexible 3HB polymer chains that extend from the enzyme particles, resulting in the formation of an enzyme-nascent PHB conjugate. When a sufficient amount of (R)-3-HBCoA was used as substrate, the reaction rapidly increased after the first minute followed by a slow increase in rate, and substrate was completely consumed after 4 min. After 4 min, spherical granules continued to grow in size to form clusters over 10 um in width, and in later stages of cluster formation, the cluster developed small projections with a size of approximately 100-250 nm, suggesting qualitative changes of the PHB clusters. Moreover, the high-resolution AFM images suggested that globular structures of approximately 20-30 nm apparent width, which corresponds to the size of PhaC(Re), were located on the surface of the small PHB granule particles.
| Atomic force microscopy evaluation of aqueous interfaces of immobilized hyaluronan
Morra, M., C. Cassinelli, et al. (2003), J Colloid Interface Sci 259(2): 236-43.
Abstract: Hyaluronan (HA) was immobilized on aminated glass surfaces in three different ways: by simple ionic interaction and by covalent linking at low density and at full density. In agreement with previous reports, in vitro experiments show that the outcome of fibroblast adhesion tests is markedly affected by the details of the coupling procedure, suggesting that different interfacial forces are operating at the aqueous/HA interface in the three cases investigated. The interfacial properties of the HA-coated surfaces were probed by force-distance curves obtained with the atomic force microscope (AFM). This approach readily shows significant differences among the tested samples, which are directly related to the coupling strategy and to results of cell adhesion tests. In particular, the range of interaction between the tip and the surface is much lower when HA is covalently linked than when it is ionically coupled, suggesting a more compact surface structure in the former case. Increasing HA surface density minimizes the interaction force between the surface and the AFM tip, likely reflecting more complete shielding by the HA chains of the underlying substrate. In summary, these measurements clearly show the different nature of the aqueous interfaces tested, and underline the role of this analytical approach in the development and control of finely tuned biomaterial surfaces.
| Atomic force microscopy for characterization of the biomaterial interface
Siedlecki, C. A. and R. E. Marchant (1998), Biomaterials 19(4-5): 441-54.
Abstract: The molecular processes that occur at the interface of an implanted biomaterial determines the host response, including phenomena such as protein adsorption, conformational changes, and subsequent interactions with cellular components. Until recently, such processes could not be observed directly. Over the past decade, atomic force microscopy (AFM) has provided mechanistic insights into the molecular level interactions that occur at the biomaterial interface. Several unique operational modes have been developed which utilize intermittent contact with the sample and decrease applied shear forces. These dynamic modes also can be used to study the role of different structural components on biomaterial micromechanical properties. Force detection techniques allow molecular level studies of individual receptor-ligand binding events, and force mapping for determining structure/function relationships. Advancements in tip manufacturing, image processing techniques, the use of model surfaces and labeling all have contributed to the advancement of the AFM as a state-of-the-art research instrument. In this report, we examine the applicability of the AFM to the study of biomaterials and cell/molecular interactions.
| Atomic force microscopy study on specificity and non-specificity of interaction forces between Enterococcus faecalis cells with and without aggregation substance
Waar, K., H. C. van der Mei, et al. (2005), Microbiology 151(Pt 7): 2459-64.
Abstract: Enterococcus faecalis is one of the leading causes of hospital-acquired infections, and indwelling medical devices are especially prone to infection. E. faecalis expressing aggregation substance (Agg) adheres to biomaterial surfaces by means of positive cooperativity, i.e. the ability of one adhering organism to stimulate adhesion of other organisms in its immediate vicinity. In this study, atomic force microscopy (AFM) was used to measure the specificity and non-specificity of interaction forces between E. faecalis cells with and without Agg. Bacteria were attached to a substratum surface and a tip-less cantilever. Two E. faecalis strains expressing different forms of Agg showed nearly twofold higher interaction forces between bacterial cells than a strain lacking Agg [adhesive force (F(adh)), -1.3 nN]. The strong interaction forces between the strains with Agg were reduced after adsorption of antibodies against Agg from -2.6 and -2.3 nN to -1.2 and -1.3 nN, respectively. This suggests that the non-specific interaction force between the enterococci amounts to approximately 1.2 nN, while the specific force component is only twofold stronger. Comparison of the results of the AFM interaction forces with the positive cooperativity after adhesion to a biomaterial in a parallel-plate flow chamber showed that in the absence of strong interaction forces between the cells, positive cooperativity was also absent. In conclusion, this is believed to be the first time that the influence of specific antibodies on interaction forces between E. faecalis cells has been demonstrated by AFM, thereby experimentally distinguishing between specific and non-specific force components.
| Attachment and proliferation of osteoblasts and fibroblasts on biomaterials for orthopaedic use
Hunter, A., C. W. Archer, et al. (1995), Biomaterials 16(4): 287-95.
Abstract: Using a variety of cell types, cell attachment and growth was studied on prospective (polyethersulphone (PES) and polyetheretherketone) and currently used (titanium 318 alloy, cobalt chrome molybdenum alloy and ultra-high molecular weight polyethylene (UHMWPE)) orthopaedic biomaterials. Proliferation of fibroblasts and osteoblasts was measured using incorporation of tritiated thymidine into total DNA. Attachment of cells was assessed by indirect immunofluorescent labelling of vinculin, a component of the cell's focal adhesion plaque. The degree of cell attachment was quantified on the materials by determining the mean number of adhesion plaques and using an image analysis system to determine the mean total area of plaques per cell. Fibroblasts and osteoblasts responded differently to the materials tested. When grown on PES surfaces, rat tail fibroblasts synthesized significantly greater amounts of DNA than cells on all other surfaces, whilst fibroblasts on UHMWPE synthesized significantly less DNA than cells on all other materials. Interestingly, there was no significant difference between the amounts of DNA synthesized by osteoblasts grown on the various materials. Determination of the number of vinculin adhesion plaques per cell and the mean total area of the plaques per cell showed that the attachment of fibroblasts to UHMWPE was significantly reduced compared with other materials. In contrast there was no significant difference in the adhesion of osteoblasts to different materials. Scanning electron microscope (SEM) observations of cells on the materials correlated with the morphometric data. Cells with the greatest number and area of adhesion plaques were well spread and flattened whilst those with the least number of adhesion plaques were more rounded and less spread.
| Au(III), Pd(II), Ni(II), and Hg(II) alter NF kappa B signaling in THP1 monocytic cells
Lewis, J. B., J. C. Wataha, et al. (2005), J Biomed Mater Res A 74(3): 474-81.
Abstract: The transcription factor NFkappaB plays a key role in the tissue inflammatory response. Metal ions released into tissues from biomaterials (e.g., Au, Pd, Ni, Hg) are known to alter the binding of NFkappaB proteins to DNA, thereby modulating the effect of NFkappaB on gene activation and, ultimately, the tissue response to biomaterials. Little is known about the effect of these metals on key signaling steps prior to NFkappaB-DNA binding such as transcription factor activation or nuclear translocation, yet these steps are equally important to modulation of the pathway. Oxidative stress is known to alter NFkappaB proteins and is suspected to play a role in metal-induced NFkappaB signaling modulation. Our aim in the current study was to assess the effects of sublethal levels of Ni, Hg, Pd, and Au ions on NFkappaB activation and nuclear translocation in the monocyte, which is acknowledged as an important orchestrator of the biological response to materials and the pathogenesis of chronic disease. Sublethal concentrations of Au(III), Ni(II), Hg(II), and Pd(II) were added to cultures of human THP1 monocytic cells for 72 h. In parallel cultures, lipopolysaccharide (LPS) was added for the last 30 min to activate the monocytic cells. Then cellular cytoplasmic and nuclear proteins were isolated, separated by electrophoresis, and probed for IkappaBalpha degradation (activation) and NFkappaB p65 translocation. Protein levels were digitally quantified and statistically compared. The levels of reactive oxygen species (ROS) in the monocytic cells were measured as a possible mechanism of metal-induced NFkappaB modulation. Only Au(III) activated IkappaBalpha degradation by itself. Au(III) and Pd(II) enhanced LPS-induced IkappaBalpha degradation, but Hg(II) and Ni(II) suppressed it. Au(III), Ni(II), and Pd(II) activated p65 nuclear translocation without LPS, and all but Ni(II) enhanced LPS-induced translocation. Collectively, the results suggest that these metal ions alter activation and translocation of NFkappaB, each in a unique way at unique concentrations. Furthermore, even when these metals had no overt effects on signaling by themselves, all altered activation of signaling by LPS, suggesting that the biological effects of these metals on monocytic function may only be manifest upon activation. None of the metal ions elevated levels of ROS at 72 h, indicating that ROS were probably not direct modulators of the NFkappaB activation or translocation at this late time point.
| Augmented bone regeneration activity of platelet-rich plasma by biodegradable gelatin hydrogel
Hokugo, A., M. Ozeki, et al. (2005), Tissue Eng 11(7-8): 1224-33.
Abstract: This study investigates the ability of platelet-rich plasma (PRP) combined with biomaterials to enhance in vivo bone-repairing activity. A biodegradable hydrogel was prepared from gelatin, which has an affinity for various growth factors. Rabbit PRP was conventionally prepared by blood centrifugation and dropped onto freeze-dried gelatin hydrogel to obtain gelatin hydrogel incorporating PRP. Gelatin hydrogel incorporating PRP was applied to a bone defect of rabbit ulna to evaluate bone formation at the defect in terms of soft X-ray and histological examinations. As controls, fibrin incorporating PRP, empty gelatin hydrogel, and free PRP were applied to the defect; in addition, defect without any application was examined. Successful bone regeneration was observed at bone defect treated with gelatin hydrogel incorporating PRP, in marked contrast to the control groups. When in contact with gelatin, growth factors, such as platelet-derived growth factor and transforming growth factor beta(1), were released from the PRP. PRP growth factors are immobilized in the hydrogel through physicochemical interaction with gelatin molecules. The immobilized growth factors are released from the hydrogel in concert with hydrogel degradation. It is likely that the gelatin hydrogel permitted the controlled release of bioactive growth factors, resulting in factor-induced promotion of bone regeneration.
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