|Articles about Biomaterials|
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| Effects of bacterial adhesion with respect to the type of material, structure and design of intraocular lenses
Alava, J. I., N. Garagorri, et al. (2005), J Mater Sci Mater Med 16(4): 313-7.
Abstract: The properties of the biomaterials used to constitute lenses are important factors choosing a lens for human implantation because these can influence in posterior clinical evolutions of patients. In this study, different characteristics of intraocular lenses such as chemical composition, surface roughness and lens design have been investigated in terms of their influence into a pathological environment. Eight commercial lenses were tested by optical profiling, Infrared spectra with Fourier transformation (FTIR), water-material contact angle and scanning electron microscope (SEM) to know their chemical composition and structural characteristics. These lenses were then exposed to infectious conditions in order to evaluate their responses to the bacterial environment.
| Effects of bone morphogenetic protein-2 and hyaluronic acid on the osseointegration of hydroxyapatite-coated implants: an experimental study in sheep
Aebli, N., H. Stich, et al. (2005), J Biomed Mater Res A 73(3): 295-302.
Abstract: Research efforts aim at enhancing early osseointegration of cementless implants to improve early fixation and, thus, reduce the risk of loosening. The aim of the present study was to investigate whether bone morphogenetic protein (BMP) 2 had a positive effect on the osseointegration of hydroxyapatite-coated implants. Hydroxyapatite (HA) implants (perforated hollow cylinders and solid rods) were coated with BMP-2 and hyaluronic acid (HY) as the carrier or with HY alone. Uncoated HA implants served as controls. The osseointegration of the implants was evaluated either by light microscopy or by pullout tests after 1, 2, and 4 weeks of unloaded implantation in the cancellous bone of 24 sheep. The BMP-2 coating significantly increased bone growth into the implant perforations compared with HA-coated implants at 2 and 4 weeks. Bone-implant contact and interface shear strength of BMP-2 implants were lower than HA implants at 2 weeks. At 4 weeks, there was no significant difference in bone-implant contact and shear strength between BMP-2 and HA-coated implants. The BMP-2 coating enhanced gap healing but had no positive or even an inhibitory effect (at 2 weeks) on bone-implant contact and interface shear strength. In the clinical situation, a perfect press-fit implantation cannot be achieved, and BMP-2 may be beneficial for enhancing bone growth into gaps around cementless implants.
| Effects of bone morphogenetic protein-7 stimulation on osteoblasts cultured on different biomaterials
Acil, Y., I. N. Springer, et al. (2002), J Cell Biochem 86(1): 90-8.
Abstract: The objective of the present study was to investigate the effects of an in vitro stimulation of human osteoblasts by recombinant human bone morphogenetic protein-7 (rhBMP-7) on the collagen types and the quantity of the collagen cross-links synthesized in a three-dimensional culture on various biomaterials for bone replacement. Trabecular bone chips were harvested from human iliac crests, and cell cultures were established at standard conditions. One hundred and fifty nanograms per milliliter of rhBMP-7 was added. For the second passage a cell scraper was used to bring the cells into suspension, and 100 microl osteoblasts (at a density of 3.3 x 10(5)) were transferred onto nine blocks of either Bio-Oss, Tutoplast, or PepGen p-15. Blocks incubated with cells that were not treated with rhBMP-7 served as controls. Cell colonization of the biomaterials was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) after a period of 2, 4, and 6 weeks. Throughout the experiment medium, supernatants were collected and collagen was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Finally, the collagen cross-link residues hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) were quantified by HPLC. Within 4 weeks the cells became confluent on all of the studied biomaterials. All samples synthesized bone specific LP and collagen type I. However, in rhBMP-7-stimulated samples, the amount of HP and LP found was increased by 45% compared to non-stimulated samples. Cell proliferation and collagen synthesis was similar on the different biomaterials, but was consistently reduced in specimen not stimulated with rhBMP-7. In vitro stimulation of osteoblasts on Bio-Oss, Tutoplast, or PepGen p-15 with rhBMP-7 and subsequent transplantation of the constructs might lead to an enhanced osseointegration of the biomaterials in vivo.
| Effects of calcium ion implantation on human bone cell interaction with titanium
Nayab, S. N., F. H. Jones, et al. (2005), Biomaterials 26(23): 4717-27.
Abstract: The use of calcium ion (Ca) implantation of titanium (Ti), previously reported to encourage osseointegration in vivo, has been investigated using an in vitro model in order to understand the basic mechanisms involved in the response of target cells to such surfaces. Polished Ti discs were implanted with high, medium and low (1x10(17), 1x10(16), 1x10(15)ionscm-2) doses of Ca ions at 40 keV. The effects of different levels of Ca implantation on morphology, attachment and spreading of MG-63 cells seeded on the surface of control (non-implanted) Ti and Ca-Ti discs were assessed. Further, to understand cell-material interactions at a molecular level, the expression of beta1 and alpha5beta1 integrins and the formation of vinculin-positive focal adhesion plaques were examined. In addition, the effects of pre-immersion of the Ca (high)-Ti in tissue culture medium on cell attachment were measured and correlated with specific chemical changes at the Ti surface. Our findings suggest that Ca implantation can affect the adhesion of MG-63 cells both qualitatively and quantitatively. However, this effect appears to depend on the level at which Ca ions are implanted. Results showed that although cell adhesion on Ca (high)-Ti was initially reduced, it nevertheless was not only restored but substantially increased with progressing culture times. In addition, a significantly enhanced cell spreading, formation of focal adhesion plaques and expression of integrins were measured on this particular surface. In contrast, no marked differences were observed in cell behaviour on Ca-Ti (low and medium). Pre-immersion studies indicated that the decrease in cell attachment to Ca (high)-Ti at early time periods may be linked to the presence of Ca- and P-rich particles on the surface. The absence of these particles at 24 h was consistent with a significant increase in cell attachment.
| Effects of chitin/chitosan and their oligomers/monomers on release of type I collagenase from fibroblasts
Okamura, Y., A. Nomura, et al. (2005), Biomacromolecules 6(5): 2382-4.
Abstract: The effects of chitin/chitosan and their oligomers/monomers on the release of type I collagenase (MMP-1) from fibroblasts were evaluated using adult (adFB) and neonatal human fibroblasts (neFB) by a immunological assay. Release of MMP-1 from adFB increased significantly or tended to increase for all samples, while there was no significant change in MMP-1 levels with neFB. Because the oligomers and monomers of chitin and chitosan influenced MMP-1 activity, it was suggested that the elevated MMP-1 activity would continue until biodegradation of chitin and chitosan was complete.
| Effects of chitosan on human periodontal ligament fibroblasts in vitro and on bone formation in rat calvarial defects
Pang, E. K., J. W. Paik, et al. (2005), J Periodontol 76(9): 1526-33.
Abstract: BACKGROUND: The purpose of this study was to evaluate the effect of chitosan on human periodontal ligament fibroblasts (hPDLF) in vitro and on bone formation in rat calvarial defects in vivo. METHODS: Fibroblast populations were obtained from individuals with a healthy periodontium and cultured in alpha minimum essential medium (MEM) for the control group. For the experimental groups, cells were cultured in alpha-MEM containing chitosan at concentrations of 0.01, 0.1, 1, or 2 mg/ml. The 3-(4,5-dimethyl-thiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, reverse transcription-polymerase chain reaction (RT-PCR) and the assay of alkaline phosphatase (ALPase) activity were performed. Eight mm calvarial critical-sized defects were created in 30 male Sprague-Dawley rats. The animals were divided into three groups of 10 animals each. The defects were treated with either chitosan/absorbable collagen sponge (ACS) or ACS alone in the experimental groups or were left untreated (surgical controls). The animals were sacrificed at 2 or 8 weeks post-surgery and the treatment outcomes were evaluated using histological and histomorphometric parameters. RESULTS: The chitosan-induced proliferative responses of the hPDLF reached a plateau at a concentration of 0.1 mg/ml (P <0.05). When the hPDLF were stimulated with 0.1 mg/ml chitosan, both the mRNA expression of type I collagen and the ALP activity were significantly up-regulated (P <0.05). The surgical implantation of chitosan/ACS enhanced the new bone formation at 8 weeks post-surgery and the amount of new bone formation of the chitosan/ACS group was significantly greater than that of both the ACS alone group and the surgical control group (P <0.01). The new bone area and defect closure in the chitosan/ACS group were significantly greater than those in the ACS control and sham surgery control groups at 8 weeks (P <0.01). However, the chitosan/ ACS group exhibited significantly less bone density than both the ACS control and the sham surgery control group at 8 weeks (P <0.01). CONCLUSIONS: Chitosan (0.1 mg/ml) enhanced the type I collagen synthesis and facilitated the differentiation into osteogenic cells. Chitosan reconstituted with ACS has a significant potential to accelerate the regeneration of bone in rat calvarial critical size defects.
| Effects of cryopreservation on cell viability and insulin secretion in a model tissue-engineered pancreatic substitute (TEPS)
Mukherjee, N., Z. Chen, et al. (2005), Cell Transplant 14(7): 449-56.
Abstract: The use of encapsulated insulin-secreting cells constitutes a promising approach towards the treatment of insulin-dependent diabetes. However, long- term storage for off-the-shelf availability still remains an issue, which can be addressed by cryopreservation. This study investigated cryopreservation of a model tissue-engineered pancreatic substitute by two ice-free cryopreservation (vitrification) solutions (designated VS55 and PEG400) in comparison to a conventional freezing protocol. The model substitute consisted of insulin-secreting mouse insulinoma betaTC3 cells entrapped in calcium alginate/poly-L-lysine/alginate (APA) beads. Cell viability and static insulin secretion from the thawed cryopreserved groups were characterized and compared against fresh controls. Cell viability tests using alamarBlue showed that, compared to the fresh groups, the VS55 had the highest viability (p < 0.05), followed by both the PEG400 (p < 0.001) and the frozen groups (p < 0.001). In response to a square wave of glucose, the static insulin secretion data showed that the VS55 and PEG400 groups had similar induction levels against the fresh group, whereas the frozen group had the poorest secretion rate. Cryosubstitution of capsules showed ice formation in the frozen group but no ice in the vitrified groups. Microscopic observations revealed holes and/or tears within beads subjected to freezing, whereas no such abnormalities were detected in the vitrified samples. Overall, vitrification was found to be a promising preservation procedure for this encapsulated cell system.
| Effects of dental implant surfaces on the expression of bone sialoprotein in cells derived from human mandibular bone
Hilbig, H., T. Wiener, et al. (2005), Med Sci Monit 11(4): BR111-5.
Abstract: BACKGROUND: Protein adsorption is believed to be the first event that takes place after contact of natural tissue with an artificial surface. Bone sialoprotein (BSP) is one of the major noncollagenous proteins in the extracellular matrix of bone. The expression of BSP coincides with initial bone mineralization and is believed to be a center of crystallization for hydroxyapatite formation. MATERIAL/METHODS: We used a variety of four differently designed dental implant surfaces (SLA, CPT, ANOX, TICER) to investigate the effects on the development of adult human mandibular bone at days 5, 10, 15, 20, and 25 in vitro. The time course of the expression of BSP and labeling of fibroblasts was visualized immunohistochemically. The distribution patterns of cells were determined semiquantitatively on both the surface and the tissue-implant borderline. RESULTS: BSP immunoresponse increased from day 5 before decreasing after day 15 in vitro. The distribution of BSP-expressing cells changed during that time. Cell counts revealed that the time course of the settlement of cells depended on the design of the surface of the implant. The design of the border of the implant affected both the cell distribution patterns and the survivals of cells to a higher degree than did the design of the implant surface. CONCLUSIONS: Investigation of novel biomaterials for bone engineering represents an essential area for the design of tissue-engineering strategies. The hydroxyapatite-based implant material TICER could be a good scaffold to guide and promote the regeneration of bone tissue.
| Effects of dissolved calcium and phosphorous on osteoblast responses
Ma, S., Y. Yang, et al. (2005), J Oral Implantol 31(2): 61-7.
Abstract: The dissolution behavior of hydroxyapatite (HA) and its effect on the initial cellular response is of both fundamental and clinical importance. In this study, plasma-sprayed HA coatings were characterized by X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). Calcium (Ca) and inorganic phosphorous (Pi) ions released from plasma-sprayed HA coatings within 3 weeks were measured by flame atomic absorption and colorimetrically molybdenum blue complex, respectively. To investigate the effect of dissolution of HA coatings on osteoblast response, additional Ca and Pi were added into the cell culture media to simulate the dissolution concentrations. Human embryonic palatal mesenchyme cells, an osteoblast precursor cell line, were used to evaluate the biological responses to enhanced Ca and Pi media over 2 weeks. Osteoblast differentiation and mineralization were measured by alkaline phosphatase-specific assay and 1,25 (OH)2 vitamin D3 stimulated osteocalcin production. The coatings exhibited an HA-type structure. FTIR indicated the possible presence of carbonates on the coatings. A dissolution study indicated a continual increase in Ca and Pi over time. In the cell culture study, enhanced osteoblast differentiation occurred in the presence of additional Ca concentration in the cell culture media. However, additional Pi concentration in the cell culture media was suggested to slow down osteoblast differentiation and mineralization.
| Effects of fibrinogen residence time and shear rate on the morphology and procoagulant activity of human platelets adherent to polymeric biomaterials
Balasubramanian, V. and S. M. Slack (2001), Asaio J 47(4): 354-60.
Abstract: Fibrinogen readily adsorbs to the surface of biomaterials and, because of its demonstrated ability to support platelet adhesion and aggregation, plays a role in thrombotic events associated with the implantation of synthetic materials in the human body. Thus, understanding the factors influencing the interactions of fibrinogen with biomaterials, and how platelet responses are affected, is crucial for the development of synthetic materials exhibiting improved blood compatibility. In this study, the effects of fibrinogen residence time and shear rate on the procoagulant activity of adherent platelets, along with their morphologic status, as deduced from scanning electron microscopy, were investigated. To examine whether adherent platelets promoted the generation of thrombin, polymeric materials (polytetrafluoroethylene, polyethylene, and silicone rubber) preadsorbed with fibrinogen were exposed to platelet suspensions at different wall shear rates and then incubated with clotting factors for 5 minutes under static conditions. The amount of thrombin generated per platelet was calculated from the optical density of the color developed by adding substrate S-2238. Scanning electron microscopy images of the platelets revealed that the platelets exhibited different morphologies, depending on the shear rate and residence time of the adsorbed fibrinogen. Platelets ranged from their normal discoid shape observed primarily under static conditions, to that of fully spread platelets. Results from this study show that platelets, in the presence of shear forces, undergo activation on exposure to surfaces on which adsorbed fibrinogen has resided for short residence times rather than long residence times. Interestingly, studies examining the procoagulant responses of such adherent platelets demonstrated that the platelets attached to the fibrinogen coated materials did not promote significant thrombin generation. Such low prothrombinase activity of adherent platelets suggests that adsorbed fibrinogen, while capable of supporting platelet adhesion and spreading on biomaterials, does not necessarily enhance the procoagulant activity of adherent platelets.
| Effects of formulation factors on encapsulation efficiency and release behaviour in vitro of huperzine A-PLGA microspheres
Fu, X., Q. Ping, et al. (2005), J Microencapsul 22(1): 57-66.
Abstract: To develop a long-acting injectable huperzine A-PLGA microsphere for the chronic therapy of Alzheimer's disease, the microsphere was prepared by using o/w emulsion solvent extraction evaporation method based on a series of formulation design of the emulsion. The dialysis method was used for release analysis. The encapsulation efficiency and release amount of the microspheres were determined by UV/VIS spectrophotometry. The morphology of the microspheres was observed by scanning electron microscopy. The distribution of the drug within microspheres was observed by a confocal laser scanning microscope. The results indicated that the PLGA 15 000 microspheres possessed a smooth and round appearance with average particle size of 50 microm or so. The encapsulation percentages of microspheres prepared from PLGA 15 000, 20 000 and 30 000 were 62.75, 27.52 and 16.63%, respectively. The drug release percentage during the first day decreased from 22.52% of PLGA 30 000 microspheres to 3.97% of PLGA 15 000 microspheres, the complete release could be prolonged to 3 weeks. The initial burst release of microspheres with higher molecular weight PLGA could be explained by the inhomogeneous distribution of drug within microspheres. The encapsulation efficiency of the microspheres improved as the polymer concentration increase in oil phase and PVA concentration decreased in aqueous phase. The burst release could be controlled by reducing the polymer concentration. Evaporation temperature had a large effect on the drug release profiles. It had better be controlled under 30 degrees C. Within a certain range of particle size, encapsulation efficiency decreased and drug release rate increased with the reducing of the particle size.
| Effects of granulocyte-macrophage colony stimulating factor (GM-CSF) on biomaterial-associated staphylococcal infection in mice
Rozalska, B., A. Ljungh, et al. (1996), Microbiol Immunol 40(12): 931-9.
Abstract: Staphylococcal infections are a major complication in the usage of biomaterials. Different modifications of polymers have been made to reduce the incidence of such infections. We studied the effects of modifying heparinized polyethylene (H-PE) with mouse recombinant granulocyte-macrophage stimulating factor (rGM-CSF). The elimination of staphylococci (Staphylococcus aureus, S. epidermidis) from the peritoneum of mice implanted with rGM-CSF-coated H-PE was slightly more effective than the elimination of the bacteria from the peritoneum of animals implanted with uncoated H-PE. Most interestingly, the number of staphylococci present in the biofilms covering rGM-CSF-coated implants were significantly lower than the number of bacteria detected on the surface of H-PE not coated with rGM-CSF. In vitro, rGM-CSF restored the anti-bacterial potency of the phagocytes, which had been reduced by surface contact with H-PE. The results suggest that modification of biomaterials with rGM-CSF could be one way of preventing staphylococcal infections; especially in neutropenic disorders, which constitute the highest risk factor for foreign body-associated infections.
| Effects of growth factors on meniscal fibrochondrocytes
Pangborn, C. A. and K. A. Athanasiou (2005), Tissue Eng 11(7-8): 1141-8.
Abstract: To tissue engineer the knee meniscus, our laboratory follows a paradigm that includes biomaterial scaffolding, mechanical stimulation, and growth factor addition. The aim of this study was to study extracellular matrix (ECM) component uptake by meniscal fibrochondrocytes when stimulated with platelet-derived growth factor AB, transforming growth factor beta(1) (TGF-beta(1)), insulin-like growth factor type I, and basic fibroblast growth factor at various concentrations (low, medium, and high levels for each). Growth factors were applied to monolayer cultures for 3 weeks in a soluble form as part of the culture medium. Radiolabeling with [3H]proline and [(35)S]sulfate was performed to indicate collagen and glycosaminoglycan production, respectively. TGF-beta(1) is the only growth factor that increased the uptake of both components. It showed the most consistent behavior and the highest response. There is no conclusive evidence whether the high concentration of TGF-beta(1) (100 ng/mL) is better than the medium concentration (10 ng/mL). Therefore the results of this study demonstrate that TGF-beta(1) at either 10 or 100 ng/mL can be used to upregulate ECM production in monolayer cultures of meniscal fibrochondrocytes.
| Effects of hydrophilic plasticizers on mechanical, thermal, and surface properties of chitosan films
Suyatma, N. E., L. Tighzert, et al. (2005), J Agric Food Chem 53(10): 3950-7.
Abstract: Chitosan films were plasticized with four hydrophilic compounds, namely, glycerol (GLY), ethylene glycol (EG), poly(ethylene glycol) (PEG), and propylene glycol (PG). Our objective was to investigate the effect of plasticizers on mechanical and surface properties of chitosan films. The stability of plasticized films was observed by storage for 3 and 20 weeks in an environmental chamber at 50 +/- 5% RH and 23 +/- 2 degrees C. Plasticization improves the chitosan ductility, and typical stress-strain curves of plasticized films have the features of ductile materials, except the film made with 5% PG that exhibits as a brittle polymer and shows an antiplasticization effect. In most cases, the elongation of plasticized films decreases with the storage time, which might be due to the recrystallization of chitosan and the loss of moisture and plasticizer from the film matrix. Although at the beginning the mechanical properties of films made with PG, at high plasticizer concentration, are comparable to those of films made with EG, GLY, and PEG, their stability is poor and they tend to become brittle materials. The surface properties, analyzed by contact angle measurement, reveal that plasticization increases film hydrophilicity. It is found that GLY and PEG are more suitable as chitosan plasticizers than EG and PG by taking into account their plasticization efficiency and storage stability. Furthermore, a plasticizer concentration of 20% (w/w) with GLY or PEG seemingly is sufficient to obtain flexible chitosan film with a good stability for 5 months of storage.
| Effects of immobilized recombinant human bone morphogenetic protein-2/succinylated type I atelocollagen on cellular activity of ST2 cells
Tsujigiwa, H., H. Nagatsuka, et al. (2005), J Biomed Mater Res A 75(1): 210-5.
Abstract: The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) to induce ectopic bone formation requires a carrier. Type I atelocollagen, a biomaterial with a porous structure, excellent operational features, and biocompatibility, is an effective carrier for rhBMP-2. However, the conventionally used lyophilized rhBMP-2/collagen mixture does not necessarily give adequate bone-induction effect. In the present study, we examined the effect of immobilizing rhBMP-2 to type I atelocollagen on the cellular activity of ST2 cells. The following results were obtained: (1) rhBMP-2 was effectively immobilized to succinylated type I atelocollagen, indicating the usefulness of succinylated type I atelocollagen in immobilization; (2) studies of alkaline phosphatase activity confirmed the effectiveness of rhBMP-2 immobilized on succinylated atelocollagen in augmenting cellular activity.
| Effects of implantable biomaterials on radiation dosimetry
Stenson, K. M., J. M. Balter, et al. (1997), Head Neck 19(5): 384-90.
Abstract: BACKGROUND: It is generally known that radiation dose is enhanced in front of and reduced behind metallic plates. This study evaluates metallic, ceramic, and bioabsorbable facial-reconstruction materials for their differential effects on radiation dosimetry. METHODS: Commercially pure titanium (cpt), stainless steel (steel), titanium alloy (tia), hydroxyapatite (HA), and poly-L-lactide (PLA, a bioabsorbable polymer) were obtained for this study. The radiation doses distal (behind) and proximal (in front of) to the test material were measured with an ionization chamber placed at several distances from the test material. Therefore, transmission (proximal to plate) and backscattering (distal to plate) factors were generated at several distances for each material. RESULTS: Poly-L-lactide transmitted nearly 100% of the incident radiation beam. The metals had the greatest effect on transmission with steel, followed by cpt, tia, and HA showing the greatest reduction of incident beam. Poly-L-lactide revealed minimal backscattering. Greater backscatter of the incident radiation beam was seen from steel, followed by cpt and HA. Poly-L-lactide also behaved similar to water in transmission and backscatters properties during electron irradiation. CONCLUSIONS: Poly-L-lactide has a minimal effect on the radiation-dose distribution and may be beneficial as a reconstructive device for patients undergoing head and neck cancer radiotherapy. Hydroxyapatite showed a relatively minor effect, whereas the metals (steel, followed by cpt and tia) revealed the greatest detrimental effect on the radiation-dose distribution.
| Effects of mechanical compression of a fibrous tissue interface on bone with or without high-density polyethylene particles in a rabbit model of prosthetic loosening
De Man, F. H., W. Tigchelaar, et al. (2005), J Bone Joint Surg Am 87(7): 1522-33.
Abstract: BACKGROUND: The mechanisms leading to aseptic loosening of a total hip replacement are not fully understood. A fibrous tissue interface can be present around the implant. Hypothetically, component micromovements can compress this interface and cause increased fluid pressure according to biphasic models. We tested the hypothesis that compression of a fibrous membrane with or without the presence of high-density polyethylene particles leads to bone degradation. METHODS: A titanium implant was inserted in forty-five rabbit tibiae, and, after osseous integration was achieved, a fibrous tissue interface was generated. The animals were randomized to undergo a sham operation, treatment with compression of the fibrous membrane, treatment with high-density polyethylene particles, or treatment with both compression and particles. Morphometric analysis of the surrounding bone was performed on cryostat sections after Giemsa staining and staining of tartrate-resistant acid phosphatase activity. RESULTS: Forty specimens were available for analysis; five tibiae with an infection were excluded. After nine weeks, the controls showed vital bone, whereas the specimens treated with compression showed necrosis of bone and replacement of bone by cartilage in a discontinuous layer (p < 0.05 for both) but not fibrous tissue. Treatment with high-density polyethylene particles caused replacement of bone by fibrous tissue (p < 0.05) but not necrosis or cartilage formation. Compression combined with the presence of high-density polyethylene particles caused bone necrosis and loss of bone with replacement by cartilage and fibrous tissue (p < 0.05). CONCLUSIONS: In this in vivo study in rabbits, fibrous membrane compression led to bone necrosis and cartilage formation, possibly because of fluid pressure or fluid flow, whereas the presence of high-density polyethylene particles led to the loss of bone with replacement of bone by fibrous tissue. Cartilage formation may be a protective response to fluid pressure and/or fluid flow. Fibrous membrane compression may play an important role in the early stages of loosening of a total hip replacement.
| Effects of membrane adhesion barriers on wound healing reaction after glaucoma filtration surgery: a comparative study with Interceed and Seprafilm
Akyol, N., S. Aydogan, et al. (2005), Eur J Ophthalmol 15(5): 591-7.
Abstract: PURPOSE: To evaluate and compare the effectiveness of two adhesion barriers, Interceed and Seprafilm, on wound heal ing reaction after glaucoma filtration surgery. MATERIALS AND METHODS: Full-thickness filtration surgery was carried out on three groups, each containing four rabbits. Interceed and Seprafilm prepared in 3 x 4 mm dimensions was put on and around scleral opening in Groups 1 and 2, respectively. All groups received tobramycin and dexamethasone drops tid for 14 days. Intraocular pressure (IOP), anterior chamber depth, and bleb appearance were checked on the first, third, seventh, and 14th days. The rabbits were killed on the 14th day and the trabeculectomy area with overlying conjunctiva was excised. The samples were fixed wi th 10% formalin, buried in paraffin, and stained with hematoxylin and eosin. The surgical site and surrounding subconjunctival area were evaluated histopathologically for cell counts (fibroblast, lymphocyte, eosinophil, and macrophage), presence of edema and foreign body reaction, and potency of the fistula tract. RESULTS: Mean IOP at the first and third day examinations was significantly different between groups, but there was no statistically significant difference among the groups with respect to IOP, anterior chamber depth, or bleb appearance at the seventh and 14th days. The groups were similar with respect to number of fibroblasts, eosinophils, and neutrophils. Number of macrophages was significantly increased in Groups 1 and 2 and number of vessels was significantly decreased in Group 1. CONCLUSIONS: Neither of these two adhesion-preventing substances seems to suppress wound healing reaction after glaucoma filtration surgery. However, a diminished wound healing reaction was expected wi th a decreased number of vessels, such as in Group 1. Increased number of macrophages in both groups may result in a decreased level of some inflammatory mediators.
| Effects of moisture and temperature on the osteoinductivity of demineralized bone matrix
Han, B., Z. Yang, et al. (2005), J Orthop Res 23(4): 855-61.
Abstract: Demineralized bone matrix (DBM) is a well established osteoinductive bone graft material. It has been mixed with a variety of carriers to adjust to different forms of handling for a variety of applications. The impact of the various carriers on osteoinductivity remains largely unknown. Using an in vitro cell culture assay and in vivo intramuscular implantations into nude rats, the effects of moisture from water-based carriers and the storage temperature on osteoinductivity were studied. In the dry state, DBM can preserve its osteoinductive activity when temperatures reached 65 degrees C, but in the presence of moisture, the activity decreases with incubation time. Nearly 90% of the DBM activity is lost when maintained for 5 weeks at 65 degrees C. This study further indicates that the structure and stability of the collagen network in DBM not only provide a scaffold for osteogenitor cell proliferation and differentiation, but also controls the release rate of osteoinductive growth factors.
| Effects of nano HAP on biological and structural properties of glass bone cement
Fu, Q., N. Zhou, et al. (2005), J Biomed Mater Res A 74(2): 156-63.
Abstract: A novel type of glass-based nanoscale hydroxyapatite (HAP) bioactive bone cement (designed as GBNHAPC) was synthesized by adding nanoscale hydroxyapatite crystalline (20-40 nm), into the self-setting glass-based bone cement (GBC). The inhibition rate of nanoscale HAP and micron HAP on osteosarcoma U2-OS cells was examined. The effects of nanoscale HAP on the crystal phase, microstructure and compressive strength of GBNHAPC were studied, respectively. It was concluded that nanoscale HAP could inhibit the cell proliferation, whereas micron HAP could not, and that nanoscale HAP could be dispersed in the cement evenly and the morphology did not change significantly after a longer immersion time. XRD and FTIR results show nanoscale HAP did not affect the setting reaction of the cement. Furthermore, GBNHAPC had a higher compressive strength (92.6 +/- 3.8 MPa) than GBC (80.1 +/- 3.0 MPa). It was believed that GBNHAPC might be a desirable biomaterial that could not only fill bone defects but also inhibit cancer cell growth.
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