|Articles about Biomaterials|
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| Osteoporosis and biomaterial osteointegration
Fini, M., G. Giavaresi, et al. (2004), Biomed Pharmacother 58(9): 487-93.
Abstract: Biomaterial osteointegration depends not only on the properties of the implanted material but also on the characteristics and regenerative capability of the host bone. For this reason, researchers involved in biomaterial evaluation now place great importance on the various pathologies often present in orthopaedic patients which can negatively affect the success of surgical implants. Osteoporosis is undoubtedly one of the most frequently encountered of such diseases. Models reproducing the osteoporotic condition can be useful to understand the influence of the pathology on cell behaviour, bone regeneration and osteointegration processes, thus increasing our basic knowledge and allowing the development of surgical techniques and implant biomaterials more suitable for use in the surgical treatment of fractures in osteoporotic patients. The present paper is a literature review and, after a short description of how the presence of osteoporosis could influence bone regenerative processes, the results of the main studies on biomaterial biocompatibility and osteointegration both in vitro and in vivo in the presence of osteoporotic condition are reported. Both cell cultures and animal models are able to demonstrate the different response of bone to biomaterials by comparing healthy and pathological conditions. The use of pathological bone-derived cells and pathological animals is therefore recommended to test candidate orthopaedic materials.
| Ostrich pericardium, a biomaterial for the construction of valve leaflets for cardiac bioprostheses: mechanical behaviour, selection and interaction with suture materials
Paez, J. M., E. Jorge-Herrero, et al. (2001), Biomaterials 22(20): 2731-40.
Abstract: The mechanical behavior of ostrich pericardium was studied for the purpose of assessing its utility in the construction of bioprosthetic cardiac valve leaflets. The tissue was tested biaxially using a hydraulic simulator that subjected it to increasing stress until rupture. One hundred eighty trials were performed, 36 with unsutured pericardium and four series of 36 trials each with pericardium sutured with silk, Prolene, nylon or Gore-Tex. The samples were tested in pairs from three different pericardial regions. One sample from each pair (the predictive specimen) was assessed according to morphological and mechanical criteria, while the other (the predicted or selectable specimen) was subjected only to morphological analysis. The findings show that ostrich pericardium treated with glutaraldehyde according to standard methods has an excellent resistance to rupture in biaxial testing, withstanding stresses of up to 100 MPa, and never lower than 30 MPa. Its resistance to rupture is lowered by suturing, a loss that is less pronounced when silk sutures are used. The results with Gore-Tex are very homogeneous and the elastic behavior of the pericardium/suture unit appears to be similar to that of unsutured tissue, suggesting that the interaction between the two biomaterials is minor. Similar results were observed in the series sutured with Prolene and nylon. The use of paired samples makes it possible to closely estimate the mechanical behavior of the tissue in a given zone by determining that of its mate. The statistical study shows that this estimation is not conditioned by the suture employed, thus validating this approach and providing more precise criteria for tissue selection.
| Our first experience with Integra
Tymonova, J., M. Adamkova, et al. (2005), Acta Chir Plast 47(1): 5-9.
Abstract: The advantages of Integra have lead to an increase in its use after extensive burn injuries, in reconstructive surgery after burns, and abroad in general reconstructive surgery as well. At the Burn Center of FNsP Hospital in Ostrava Integra was used for the first time in March 2003. Since then, seven patients have undergone operations, involving the use of Integra in 14 body areas. In four of the patients scars after burns were corrected--on the neck, axilla, two on the trunk, two in the popliteal area and one between the toes. In three patients the artificial skin was applied after necronectomy. In a 7-month-old baby and in a 2-year-old child with burn injuries exceeding 25% of the body surface it was applied twice on the trunk, once on the upper extremity and once on the lower extremity. In an adult female Integra was applied on her neck and axilla after burns to a lesser extent. We have evaluated the scars one year after surgery in two patients. Cosmetic appearance was good in both of them. We have noted good functional result after the reconstruction of axilla. After reconstruction in the neck area and reconstruction of the necrectomy in the neck area and axilla, the functional results were average. The average functional results in both patients are probably due to poor compliance with the immobilization and following rehabilitation program.
| Outcome of 50 consecutive sinus lift operations
Papa, F., A. Cortese, et al. (2005), Br J Oral Maxillofac Surg 43(4): 309-13.
Abstract: We report 50 patients who had sinus lift operations between 1995 and 1999 using different grafting materials [autologous bone, heterologous bone, and hydroxyapatite]. The casenote were analysed clinically (intraoperative and postoperative results and complications), radiographically (amount of augmented bone 6 months postoperatively), and histologically (quality of the new bone 12 months postoperatively). Our aim was to find out if the various bone grafting materials used resulted in different outcomes after adjustment for significant predictors. We found that hydroxyapatite was associated with the lowest rate of loss of grafted material (median, 2.4 mm) followed by the autologous bone from iliac crest (2.8 mm). Bovine bone shown the highest loss (3.3 mm).
| Outcome of acetabular revision using an uncemented hydroxyapatite-coated component: two- to five-year results and review
Dorairajan, A., R. M. Reddy, et al. (2005), J Arthroplasty 20(2): 209-18.
Abstract: This is a retrospective review of 50 uncemented acetabular revisions with porous, hydroxyapatite-coated cups. The acetabulum alone was revised in 22 hips and both components were revised in 28 hips. The majority of hips (26) had type 2A (Paprosky) acetabular bone loss. All the revisions were carried out through a posterior approach. The mean duration of follow-up was 32 months (range, 24-52 months). Clinically, there was significant improvement in pain and moderate improvement in movement and mobility, and there is no radiological sign of failure of any cup so far. Re-revision was performed in 3 hips (6%) for recurrent dislocation. Our early results favor the use of this type of cup in acetabular revisions with moderate bone loss, but longer-term follow-up will be required. Key words: acetabulum, hydroxyapatite, revision, bone deficiency, complications.
| Outcome of the construction of a Blalock-Taussig shunt in adolescents and adults
Peries, A., A. A. Al-Hay, et al. (2005), Cardiol Young 15(4): 368-72.
Abstract: AIMS: The purpose of our study was to ascertain the outcome of the construction of a Blalock-Taussig shunt in patients aged 12 years and over. PATIENTS AND METHODS: We identified 21 patients in whom a Blalock-Taussig shunt had been constructed subsequent to the age of 12 years. Of the patients, 9 were female, and their median age was 18.5 years, with a range from 12 to 46 years. All had usual atrial arrangement, and the atrioventricular connections were concordant in 11, with univentricular atrioventricular connection in 10. Pulmonary atresia was present in 8 (38 per cent), and pulmonary stenosis, either valvar or subvalvar, in 13. An interposition graft had been placed between the subclavian and pulmonary arteries in 16 patients, and an end-to-side anastomosis between the arteries in 5. RESULTS: One patient had died in hospital, while 4 patients had died during the period of follow-up after initial construction of the shunt. Long-term follow-up was available in 86 per cent of patients. In the 3 patients lost to follow-up, the shunt had been known to be functioning at periods of 4, 8, and 10 years, respectively. Actuarial freedom from death after a period of 17 years was 76 per cent. In 8 patients, a period of 10 years had elapsed with the shunt patent, and a further 10 had a patent shunt after 5 years follow-up. Symptomatic improvement was reported in 16 (76 per cent) patients, although adverse cardiac events had occurred during follow-up in 17, including congestive heart failure in 3, atrial fibrillation in 3, and endocarditis in 2. In 2 patients, it had been possible to proceed to biventricular repair, one with tetralogy of Fallot, and the other having a Rastelli procedure. Further in 3 patients, it had been possible to construct the Fontan circulation, or one of its variants. One patient has undergone cardiac transplantation, while 2 are awaiting transplantation. CONCLUSIONS: Symptomatic improvement can be achieved by construction of a Blalock-Taussig shunt in older subjects, and the risks of surgery are low. Later repair may be feasible in some patients, but adverse cardiac events may follow the increased volume load on the systemic ventricle.
| Oxalate-degrading enzymes from Oxalobacter formigenes: a novel device coating to reduce urinary tract biomaterial-related encrustation
Watterson, J. D., P. A. Cadieux, et al. (2003), J Endourol 17(5): 269-74.
Abstract: BACKGROUND AND PURPOSE: The long-term placement of biomaterials within the urinary tract is limited by the development of encrustation. In a noninfected urinary environment, encrustation often results from the deposition of calcium oxalate on the biomaterial surface. There is an association between the absence of Oxalobacter formigenes, a commensal colonic bacterium capable of degrading oxalate, and calcium oxalate stone formation. This pilot study was designed to evaluate several oxalate-degrading enzymes produced by O. formigenes as a potential biomaterial coating to reduce urinary tract encrustation. MATERIALS AND METHODS: Circular silicone disks of 6-mm diameter were incubated for 48 hours in oxalylcoenzyme A decarboxylase (OXC), formyl-coenzyme A transferase (FRC), and coenzyme A, while control disks were incubated in distilled water. The adsorption of OXC and FRC was assessed using enhanced chemiluminescence (ECL) and atomic force microscopy (AFM). Coated and uncoated disks (20 of each) were implanted in the bladders of 40 female New Zealand White rabbits. After 30 days, the disks were recovered, and the degree of encrustation on the polymer surface was evaluated utilizing dry weight measurement, calcium atomic absorption spectroscopy (AAS), and scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDX). RESULTS: Both ECL and AFM demonstrated coating of the silicone disks with OXC and FRC. The mean dry weights of the coated and control disks following explantation were 0.591 +/- 0.438 g and 0.747 +/- 0.428 g, respectively (P = 0.307). The mean weight of calcium on the coated and control disks, as determined by AAS, was 154.1 +/- 96.25 mg and 258 +/- 181.35 mg, respectively (P = 0.008). CONCLUSIONS: The use of oxalate-degrading enzymes from O. formigenes to coat urinary biomaterials represents a novel paradigm to reduce biomaterial-related encrustation. Coating of silicone with oxalate-degrading enzymes from O. formigenes results in a modest reduction in encrustation with no apparent toxicity. Further studies are warranted.
| Oxidative and hydrolytic stability of a novel acrylic terpolymer for biomedical applications
Veleva, A. N., S. A. Khan, et al. (2005), J Biomed Mater Res A 74(1): 117-23.
Abstract: Oxidative and hydrolytic biostability assessment was carried out on a novel acrylic material made of hexamethyl methacrylate (HMA), methyl methacrylate (MMA), and methacrylic acid (MAA). To simulate the in vivo microenvironment, solutions of H2O2/CoCl2 and buffered solutions of cholesterol esterase (CE) and phospholipase A2 (PLA) were used. As controls, film specimens were incubated in deionized water. Samples were incubated in these solutions at 37 degrees C for 10 weeks before physical and mechanical properties were evaluated by size exclusion chromatography (SEC), 1H- nuclear magnetic resonance (1H-NMR), acid-base titration, and Instron tensile testing. The results from this study indicate excellent biostability of HMA-MMA-MAA terpolymers and thus their potential for use in biomedical devices for long-term implantation.
| Oxidative degradation and toxicity reduction of trichloroethylene (TCE) in water using TiO2/solar light: comparative study of TiO2 slurry and immobilized systems
Cho, I. H., J. H. Park, et al. (2005), J Environ Sci Health A Tox Hazard Subst Environ Eng 40(5): 1033-44.
Abstract: A solar-driven, photocatalyzed degradation system using TiO2 slurry and immobilized systems was constructed and applied to the degradation of trichloroethylene (TCE) contaminated water using TiO2 with solar light. The experiments were carried out under constant weather conditions on a sunny day. Solar photocatalytic treatment efficiency of the solar light/TiO2 slurry system was compared with that of the solar light/TiO2 immobilized system. The operation of the solar light/TiO2 slurry and immobilized systems showed 100% (TiO2 slurry system), 80% (TiO2 immobilized system) degradation of the TCE after 6 h, with a chloride production yield of approximately 89% (TiO2 slurry system), 72% (TiO2 immobilized system). The oxidants such as H2O2 and S2O8(2-) in the TiO2 slurry and immobilized systems increased TCE degradation rate by suppressing the electron/hole recombination process. The degradation rate and relative toxicity reduction of TCE followed the order of solar light/TiO2 slurry + S2O8(2-) > solar light/TiO2 slurry + H2O2 > solar light/TiO2 immobilized + S2O8(2-) > solar light/TiO2 slurry > solar light/TiO2 immobilized + H2O2 > solar light/TiO2 immobilized. Finally, following to the toxicity result, the acute toxicity was reduced by below toxicity endpoint (EC50 concentration) following the treatment. It means that many of the metabolites of TCE reduction are less toxic to Vibrio fischeri than the parent compound. Based on these results, TCE can be efficiently and safely treated in a solar-driven, photocatalyzed degradation system.
| Oxidized titanium implants (Nobel Biocare TiUnite) compared with turned titanium implants (Nobel Biocare mark III) with respect to implant failure in a group of consecutive patients treated with early functional loading and two-stage protocol
Jungner, M., P. Lundqvist, et al. (2005), Clin Oral Implants Res 16(3): 308-12.
Abstract: OBJECTIVES: The purpose of this study was to compare two implant types of similar shape but with different surfaces with respect to implant failure. MATERIAL AND METHODS: A total of 136 patients were treated with Nobel Biocare Implants between January 2001 and December 2002. Totally 394 implants were placed, of which 199 were oxidized titanium implants (Nobel Biocare TiUnite and 195 with turned titanium surface (Nobel Biocare Mark III. Sixty-three patients underwent a one-stage surgical protocol, of which 24 were objected to early functional loading. The remaining 73 patients were treated with a traditional two-stage surgical protocol. All patients were followed for a minimum of 5 months after loading of the implants. Implants were classified as survivals when clinically stable and fulfilling purported function without any discomfort to the patient, with no signs of infection or ongoing pathologic process. RESULTS: Seven implants were lost in five patients (two males and three females), six in the maxilla and one in the mandible. All failed implants were Mark III implants, inserted following the traditional two-stage protocol. The implant success rate was 98.2% for the whole-patient group, divided as a 100% success rate following the implants with oxidized surface (Nobel Biocare TiUnite compared with a success rate of 96.4% with implants with turned surface (Nobel Biocare Mark III).
| Oxidized titanium implants in reconstructive jaw surgery
Brechter, M., H. Nilson, et al. (2005), Clin Implant Dent Relat Res 7 Suppl 1: S83-7.
Abstract: BACKGROUND: Rehabilitation with implant-supported bridges in patients with insufficient bone volumes may require bone reconstructive procedures in conjunction with or prior to implant placement. Clinical follow-up studies using turned titanium and bone grafts have demonstrated higher failure rates than when used in nongrafted patients. Improved bone integration has been demonstrated for oxidized titanium implants; however, their clinical performance in bone reconstruction situations is not known. PURPOSE: This study was performed to analyze the survival and stability of oxidized titanium implants placed in patients subjected to reconstructive jaw surgery at one clinic. MATERIALS AND METHODS: Two hundred oxidized titanium implants (Mk III, TiUnite, Nobel Biocare AB, Goteborg, Sweden) were placed in 47 patients in conjunction with or secondary to six different reconstructive procedures owing to insufficient bone volume. In all six groups, implant stability was assessed by resonance frequency analysis and manually checked for rotation stability at implant insertion, at the time of abutment connection, and after a minimum of 12 months of loading of the prosthetic construction. Periapical radiographs were taken after a minimum of 12 months of loading (mean 21 months) for evaluation of the marginal bone levels. The mean clinical follow-up period was 30 months. RESULTS: Of the 200 implants, 199 were considered osseointegrated at the time of abutment surgery. At the 12-month postloading follow-up, another two implants were considered not stable. Three implants (1.5%) were ranked as unsuccessful. CONCLUSION: Clinical experience with 200 consecutive oxidized implants in various reconstruction situations shows a successful outcome, with only three failures (1.5%) during a mean follow-up period of 30 months.
| p130Rb2 and p27kip1 cooperate to control mobilization of angiogenic progenitors from the bone marrow
Vidal, A., S. Zacharoulis, et al. (2005), Proc Natl Acad Sci U S A 102(19): 6890-5.
Abstract: Neoangiogenesis involves both bone marrow-derived myelomonocytic and endothelial progenitor cells as well as endothelial cells coopted from surrounding vessels. Cytokines induce these cells to proliferate, migrate, and exit the cell cycle to establish the vasculature; however, which cell cycle regulators play a role in these processes is largely unknown. Here, we report that mice lacking the cell cycle inhibitors p130 and p27 show defects in tumor neoangiogenesis, both in xenografts and spontaneously arising tumors. This defect is associated with impaired mobilization of endothelial and myelomonocytic angiogenic progenitors from the bone marrow. This article documents the role of these molecules in angiogenesis and further suggests that cell expansion and mobilization from the bone marrow of angiogenic precursors are separable events.
| PAMAM dendrimer based macromolecules as improved contrast agents
Venditto, V. J., C. A. Regino, et al. (2005), Mol Pharm 2(4): 302-11.
Abstract: Dendrimers are an attractive platform for macromolecular imaging due to the presence of multiple terminal groups on the exterior of the molecule. Through application of appropriate metal ion chelates, large numbers of metal ions for imaging (paramagnetic or radioopaque) and therapy (radioactive particle emitters) may be conjugated to the dendrimer in combination with a targeting vector, through classic organic synthetic techniques. Thus, a large amount of these metal ions potentially may be site specifically delivered directly into the body with the dendrimer as the vehicle with the targeting vector directing the modified dendrimer. The development of targeted macromolecular agents with acceptable blood retention times and selective organ uptake then has the potential for various biological applications. A review of comparative studies of dendrimers with various externally appended imaging and targeting agents is presented herein.
| Partial generation of periodontal ligament on endosseous dental implants in dogs
Jahangiri, L., R. Hessamfar, et al. (2005), Clin Oral Implants Res 16(4): 396-401.
Abstract: OBJECTIVES: The objective of this pilot study was to investigate the feasibility of periodontal ligament (PDL) generation on an implant surface by approximating a tooth-to-implant contact using orthodontics. METHODS: Maxillary second premolars of six beagle dogs were extracted bilaterally. After 2 weeks of healing, hydroxyapatite (HA) coated titanium implants, 5 mm in length and 3.3 mm in diameter, were placed in the extraction sites. One side of the arch was used as control. Orthodontic tooth movement was initiated following implant placement to tip the first premolar roots into contact with the implant. This was achieved in 4-6 weeks as confirmed radiographically. Tooth-to-implant contact was maintained for further 6 weeks after which time, teeth were separated from implant contact orthodontically. After further 2 weeks of stabilization, the animals were sacrificed. Samples were analyzed by Faxitron radiographs before histology. Histology samples were prepared with Stevenel's Blue and Van Gieson stain and were subjected to polarized light microscopy. RESULTS: Histologic analysis revealed transfer and formation of PDL-like structure with formation of cellular cementum on the implant surfaces, in four out of six animals, where tooth-to-implant contact had been achieved. Direct bone-to-implant contact was noted in the areas coronal to the PDL-like tissue, an important sign to distinguish between PDL-like tissue and connective tissue that could originate from the coronal portion of a failing implant. Additionally, at the site of contact, the implant surface revealed some resorption of the HA coating. CONCLUSION: An animal model was established in which the proximity of tooth-to-implant contact lead to partial generation of PDL on a bioactive implant surface in four out of six animals.
| Particles of liquid-crystalline dispersions formed by (nucleic acid-rare earth element) complexes as a potential platform for neutron capture therapy
Yevdokimov, Y. M., V. I. Salyanov, et al. (2005), Int J Biol Macromol 37(4): 165-73.
Abstract: Microscopic size particles of the cholesteric double-stranded DNA (RNA) liquid-crystalline dispersions, containing the ions of the rare earth elements in their content, have been obtained for the first time. The properties of these particles differ from those of classical DNA cholesterics noticeably. The local concentration of the rare earth elements in a particle reaches 200mg/ml. The particles of the liquid-crystalline dispersion of the (DNA-gadolinium) complex maintain the properties for a long time. The combination of the microscopic size of particles, high concentration of gadolinium in particles and their stability opens a way to practical application of this new biomaterial.
| Particulate delivery systems for biodefense subunit vaccines
Bramwell, V. W., J. E. Eyles, et al. (2005), Adv Drug Deliv Rev 57(9): 1247-65.
Abstract: Expanding identification of potentially protective subunit antigens and correlates of protection has provided a basis for the introduction of safer vaccines. Despite encouraging results in animal models, the significant potential of particulate delivery systems in vaccine design has not yet translated into effective vaccines available for use in humans. This review article will focus on the current status of the development of particulate vaccines, mainly liposomes and bio-degradable polymers, against potential agents for biowarfare: plague, anthrax, botulinum, and smallpox; and filoviruses: Marburg and Ebola.
| Partitioning and concentrating biomaterials in aqueous phase systems
Johansson, G. and H. Walter (2000), Int Rev Cytol 192: 33-60.
Abstract: Aqueous phase separation is a general phenomenon which occurs when structurally distinct water-soluble macromolecules are dissolved, above certain concentrations, in water. The number of aqueous phases obtained depends on the number of such distinct macromolecular species used. Aqueous two-phase systems, primarily those containing poly(ethylene glycol) and dextran, have been widely used for the separation of biomaterials (macromolecules, membranes, organelles, cells) by partitioning. The polymer and salt compositions and concentrations chosen greatly affect the physical properties of the phases. These, in turn, interact with the physical properties of biomaterials included in the phases and affect their partitioning. Specific extractions of biomaterials can be effected by including affinity ligands in the systems. The phase systems can also be used to obtain information on the surface properties of materials partitioned in them; to study interactions between biomaterials; and to concentrate such materials.
| Passive adsorption of human antirrabic immunoglobulin onto a polystyrene surface
Rosado, E., H. Caroll, et al. (2005), J Biomater Sci Polym Ed 16(4): 435-48.
Abstract: The latex agglutination immunoassay technique uses polymer colloids as carriers of adsorbed proteins to enhance the antigen-antibody reaction. The aim of the present work is to study the adsorption of Human Antirrabic Immunoglobulin (HA-IgG) on polystyrene latex (PS). The physical adsorption of HA-IgG on PS latex was investigated as a function of pH at 2 mM ionic strength. The amount of HA-IgG adsorbed onto PS latex greatly depends on pH; its value showed a maximum in the neighborhood of the IEP of HA-IgG. The electrophoretic method was applied to characterize latex particles. The influence of the amount of HA-IgG adsorbed (J(ads)) on the electrophoretic mobility and zeta-potential values was also studied.
| Passive stent coatings in the drug-eluting era
Menown, I., R. Lowe, et al. (2005), J Invasive Cardiol 17(4): 222-8.
Abstract: Advances in coronary stent technology, both in terms of stent design and function, have significantly improved the safety and efficacy of percutaneous coronary intervention, including marked reduction in restenosis. This has led to its use in increasingly challenging clinical and lesional subsets, with potential for increased risk of stent-associated thrombosis. In this article we outline the development of passive stent coatings, and evaluate the ongoing role of such coatings in the contemporary era of antiproliferative drug-eluting stents.
| Patent issue: supplier liability in medical implants and devices: the "Biomaterials Access Assurance Act"
Pabst, P. L. and K. V. Mills (2000), Tissue Eng 6(2): 189-90.
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