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Mechanisms of solute transport in extracorporeal therapies
Ronco, C. and N. W. Levin (2005), Contrib Nephrol 149: 10-7.
Abstract: Diffusion and convection are the main mechanisms involved in the membrane separation processes occurring in extracorporeal hemodialysis. Operational parameters should be optimized in hollow fiber hemodialyzers to achieve the maximal efficiency. The nature of blood which is a non Newtonian fluid, requires specific attention in the design of dialyzers to ensure that the blood compartment operates properly. Similar attention must be placed in the design of the dialysate compartment to ensure a homogeneous distribution of the fluid and to prevent blood to dialysate flow mismatch. Finally, the membrane represents the third component of the hemodialyzer. Membrane performance depends on the used biomaterial, its biocompatibility, the thickness, the hydrophilic-hydrophobic mixture, the hydraulic permeability and the number and diameter of the pores. In this setting, diffusion and convection tend to reciprocally interfere, producing a final result that depends on the prevalence of one or the other mechanism for every specific solute.

Medial-grade calcium sulfate hemihydrate (surgiplaster) in healing of a human extraction socket--histologic observation at 3 months: a case report
Guarnieri, R., N. N. Aldini, et al. (2005), Int J Oral Maxillofac Implants 20(4): 636-41.
Abstract: PURPOSE: Following tooth extraction, wound healing is characterized by remodeling and resorption of the alveolar bone at the extraction site. This produces reduction in ridge volume. Medical-grade calcium sulfate hemihydrate (MGCSH) has been proposed as a graft material for extraction sockets to minimize the reduction in ridge volume. The aim of this study was to investigate the influence of MGCSH on the histopathologic pattern of intrasocket regenerated bone and to evaluate histologically the healed MGCSH-grafted extraction socket site at 3 months postextraction. MATERIALS AND METHODS: MGCSH was grafted in a fresh human extraction socket, and at 3 months a cylindric tissue specimen, 2.5 mm in diameter, was trephined from the previously grafted site and an implant was placed. Non-decalcified specimens were sectioned at a horizontal plane and stained for histologic and histomorphometric evaluation. RESULTS: The mean trabecular area was 58.6% +/- 9.2% in the coronal sections, 58.1% +/- 6.2% in the middle sections, and 58.3% +/- 7.8% in the apical sections. The differences in mean trabecular area between sections were not statistically significant. DISCUSSION: It is significant that the MGCSH underwent complete resorption and replacement by newly formed bone because the most important negative attribute of other graft materials is the resorption time. Moreover, calcium sulfate shows great potential for guided bone regeneration in surgical sites. CONCLUSION: MGCSH seems to be an acceptable graft material for extraction socket bone regeneration because it is completely resorbable and allows new trabecular bone arrangement in a limited 3-month period.

Mediation of biomaterial-cell interactions by adsorbed proteins: a review
Wilson, C. J., R. E. Clegg, et al. (2005), Tissue Eng 11(1-2): 1-18.
Abstract: An appropriate cellular response to implanted surfaces is essential for tissue regeneration and integration. It is well described that implanted materials are immediately coated with proteins from blood and interstitial fluids, and it is through this adsorbed layer that cells sense foreign surfaces. Hence, it is the adsorbed proteins, rather than the surface itself, to which cells initially respond. Diverse studies using a range of materials have demonstrated the pivotal role of extracellular adhesion proteins--fibronectin and vitronectin in particular--in cell adhesion, morphology, and migration. These events underlie the subsequent responses required for tissue repair, with the nature of cell surface interactions contributing to survival, growth, and differentiation. The pattern in which adhesion proteins and other bioactive molecules adsorb thus elicits cellular reactions specific to the underlying physicochemical properties of the material. Accordingly, in vitro studies generally demonstrate favorable cell responses to charged, hydrophilic surfaces, corresponding to superior adsorption and bioactivity of adhesion proteins. This review illustrates the mediation of cell responses to biomaterials by adsorbed proteins, in the context of osteoblasts and selected materials used in orthopedic implants and bone tissue engineering. It is recognized, however, that the periimplant environment in vivo will differ substantially from the cell-biomaterial interface in vitro. Hence, one of the key issues yet to be resolved is that of the interface composition actually encountered by osteoblasts within the sequence of inflammation and bone regeneration.

Medical devices and biomaterials pathology. Primary data for health care technology assessment
Kossovsky, N. and R. Kossowsky (1988), Int J Technol Assess Health Care 4(2): 319-23.
Abstract: Through the postmortem examination, pathologists offer the ultimate clinico-pathologic assessment of the efficacy of medical care. Similarly, pathologists can offer a clinico-pathologic assessment of the efficacy of health care technology. Assessment by pathologists has diagnostic authority because it draws on the resources of the laboratories of surgical and necropsy pathology. In this essay we argue for enhancing the accuracy of medical device and biomaterials technology assessment by systematically collecting pathology-oriented data. We recommend the establishment of a pathology-based medical device registry to assess implantable medical device technology by accumulating reports routinely issued by pathology departments throughout the country. We further suggest that establishment of a university-based, industry-supported Medical Device and Biomaterials Pathology Institute to operate the registry, collect recovered, used health care devices, and generate definitive, pathology-based, primary data for health care technology assessment.

Medium-term results from the clinical and angiographic follow-up of patients after angioplasty and implantation of sirolimus-eluting stents
Dardas, P. S., D. D. Tsikaderis, et al. (2005), Hellenic J Cardiol 46(2): 117-23.
Abstract: INTRODUCTION: The aim of this study was to evaluate the medium-term clinical and angiographic results, as well as the occurrence and treatment of restenosis, following the implantation of sirolimus-eluting stents (SES) in patients undergoing coronary angioplasty. METHODS: All patients who have an SES implanted in our department are entered into a database, with a view to evaluating the use of such stents in everyday clinical practice. This study included patients who consented to repeat angiography 8+/-2.4 months after stent implantation. The study population consisted of 91 patients (63 men, mean age 58+/-8.1 years) with 116 stenoses in all. This represented 17.4% of all patients who had an SES implanted during the study period. All the angiographic examinations were analysed independently using quantitative coronary analysis in order to determine the relationship between clinical and angiographic data and restenosis and late lumen loss. RESULTS: The mean vessel diameter was 2.5+/-0.48 mm and the mean lesion length was 12.61+/-1.54 mm. The late lumen loss was 0.04+/-0.49 mm. Restenosis was seen in 10 patients (12 vessels), of whom 4 were diabetics. The restenosis was in-stent in 7 vessels, in-segment in 5, and was localised (length of restenosis <10 mm) in all patients. After repeat angioplasty and SES implantation all the patients with restenosis remained free of symptoms 8+/-1.5 months later. Diabetes mellitus was the only factor to be correlated with restenosis. CONCLUSIONS: Restenosis following implantation of SES is mainly localised and occurs with about the same frequency within and outside the stent. The incidence of major cardiac events and restenosis following SES implantation is low. However, their long term efficacy in everyday clinical practice must be proved in large randomised studies in order to confirm the results presented here.

Membrane biocompatibility does not affect whole body protein metabolism during dialysis
Veeneman, J. M., H. A. Kingma, et al. (2005), Blood Purif 23(3): 211-8.
Abstract: BACKGROUND: Protein-calorie malnutrition is present in 30-50% of dialysis patients. The lack of biocompatibility of the dialysis membrane, which results in low-grade inflammation, could be responsible for this malnutrition. We investigated whether protein-energy malnutrition could be partly due to incompatibility of the dialyzer during the dialysis session. METHODS: Five patients were dialyzed during 2 periods of 3 weeks (cross-over) with either a single-use low-flux polysulfone or cellulose triacetate (biocompatible) or a single-use cuprophan (bio-incompatible) membrane. As a measure of whole body protein metabolism, a primed constant infusion of L-[1-(13)C]-valine was used during a 4-hour dialysis session. RESULTS: Cuprophan was a more powerful activator of the complement system than other membranes. Protein metabolism parameters during both study protocols were not different and resulted in the same protein balance during polysulfone/cellulose triacetate (-15 +/- 3) and cuprophan (-13 +/- 2 micromol/kg/h) dialysis. CONCLUSION: In stable hemodialysis patients with no apparent complications, protein metabolism during dialysis is not affected by the compatibility of the dialysis membrane.

Membrane for immunoisolation--properties before, and post implantation: preliminary report
Granicka, L. H., A. Werynski, et al. (2004), Artif Cells Blood Substit Immobil Biotechnol 32(4): 539-48.
Abstract: The membranes preventing tissue overgrowth as well as toxic influence on cells encapsulated within can be obtained modifying the polypropylene membranes by silanization. The influence of the silanization with different siloxanes on membrane transport properties was assessed before and post implantation. No change in cut-off values was observed. All of the modified membranes delayed tissue overgrowth of implant in mouse. Spectroscopic evaluation of the membrane material after 4, 7 days, 2 and 4 months of implantation revealed membrane material stability. We concluded that evaluated membranes with cells encapsulated within may be applied as the systems for delivery of biologically active substances.

Meniscal regeneration using tissue engineering with a scaffold derived from a rat meniscus and mesenchymal stromal cells derived from rat bone marrow
Yamasaki, T., M. Deie, et al. (2005), J Biomed Mater Res A 75(1): 23-30.
Abstract: The purpose of this study was to regenerate a meniscus using a scaffold from a normal meniscus and mesenchymal stromal cells derived from bone marrow (BM-MSCs). Thirty Sprague-Dawley rat menisci were excised and freeze-thawed three times with liquid nitrogen to kill the original meniscal cells. Bone marrow was aspirated from enhanced green fluorescent protein transgenic Sprague-Dawley rats. BM-MSCs were isolated, cultured for 2 weeks, and 2 x 10(5) cells were then seeded onto the meniscal scaffolds. Using a fluorescent microscope and immunohistochemical staining, repopulation of enhanced green fluorescent protein positive cells was observed in the superficial zone of the scaffold after 1 week of culture, and then in the deep zone after 2 weeks. At 4 weeks, expression of extracellular matrices was detected histologically and expression of mRNA for aggrecan and type X collagen was detected. Stiffness of the cultured tissue, assessed by the indentation stiffness test, had increased significantly after 2 weeks in culture, and approximated the stiffness of a normal meniscus. From this study, we conclude that a scaffold derived from a normal meniscus seeded with BM-MSCs can form a meniscus approximating a normal meniscus.

Meniscal tissue regeneration using a collagenous biomaterial derived from porcine small intestine submucosa
Gastel, J. A., W. R. Muirhead, et al. (2001), Arthroscopy 17(2): 151-9.
Abstract: PURPOSE: The present investigation is a preliminary study designed to evaluate the use of a collagen-based biomaterial, chemically unaltered porcine small intestine submucosa (SIS), as a scaffold for meniscal tissue regeneration. TYPE OF STUDY: Basic research. METHODS: Surgical defects were created in the lateral menisci of 12 mature New Zealand white rabbits. The defects were repaired with a similarly shaped and sized wedge of a new collagenous biomaterial (SIS) and sutured in place. The opposite knees served as controls by creating a defect in the lateral meniscus without filling with SIS graft. Full cage activity was allowed until the animals were killed at 4, 12, and 24 weeks. RESULTS: At 4 weeks, the graft material retained its physical position and grossly appeared soft and translucent. Histologically, cellular elements had infiltrated between the laminates of the graft. At 12 weeks, the graft grossly appeared more solid and opaque. Histologically, the host meniscal fibrochondrocytes were seen streaming into the peripheral margin of the graft. Early repopulation of the graft with apparently differentiated meniscal tissue was observed. At 24 weeks, the meniscus defect was grossly healed across and looked virtually normal: the normal meniscal shape, contour, consistency, and color had been replicated. Histologically, the healing tissue showed infiltration of what appeared to be meniscal fibrochondrocytes and connective tissue resembling the host meniscal tissue. The graft was nearly totally replaced by host tissue. CONCLUSIONS: This pilot animal study demonstrates that the multilaminated collagenous graft is conducive for cellular repopulation with host meniscal elements, and, by 24 weeks, is capable of supporting complete healing of a large meniscal defect.

Mesenchymal stem cell adhesion and spreading on nanostructured biomaterials
Catledge, S. A., Y. K. Vohra, et al. (2004), J Nanosci Nanotechnol 4(8): 986-9.
Abstract: Bone marrow-derived human mesenchymal stem cells were seeded in serum-free media onto ion beam-deposited nanostructured metalloceramic (Ti-Cr-N) films and plasma-nitrided titanium disks, which were left uncoated as well as precoated with fetal bovine serum. Precoating the disks with serum appears to stimulate cell spreading on both the titanium nitride and metalloceramic materials for as little as 1 hour incubation time. The implication is that both of these materials can adsorb serum proteins in amounts sufficient to influence cell adhesion and spreading for potentially improved in vivo response of orthopedic and dental implants. The materials in this study may prove to exhibit enhanced biological and mechanical properties when compared to conventional micron-scale implant materials such as titanium or cobalt-chrome alloys.

Mesenchymal stem cell-based cartilage tissue engineering: cells, scaffold and biology
Song, L., D. Baksh, et al. (2004), Cytotherapy 6(6): 596-601.
Abstract: Cartilage repair and regeneration by stem cell-based tissue engineering could be of enormous therapeutic and economic potential benefit for an aging population. However, to use stem cells effectively, their natural environment must be understood in order to expand them in vitro without compromising their multilineage potential and their specific differentiation program. Collaboration between diverse academic disciplines and between research and regulatory government agencies and industry is crucial before cell-based cartilage tissue engineering can achieve its full therapeutic potential.

Metabolic studies of hepatocytes cultured on collagen substrata modified to contain glycosaminoglycans
Kataropoulou, M., C. Henderson, et al. (2005), Tissue Eng 11(7-8): 1263-73.
Abstract: Bioartificial liver devices replace the function of the failing liver, using primary hepatocytes cultured in a bioreactor module. Most devices have been based on cartridge designs, but alternative designs using monolayers of cells in a flat plate bioreactor may be more efficacious. Collagen coating improves the maintenance of hepatocytes on polymeric membranes, and in this article the effect of contact with glycosaminoglycans (GAGs) on the function of hepatocytes was assessed. The effect of two different GAGs, chondroitin-6-sulfate and heparin, in the presence and absence of a cross-linking agent (1,6-diaminohexane [DAH]), on the activities of two major metabolic pathways in hepatocytes (cytochrome P-450-dependent monooxygenase activity, assessed by the hydroxylation of testosterone, and UDP-glucuronosyltransferase activity, assessed by the glucuronidation of kaempferol) cultured on collagen gels and films is presented. Testosterone metabolism was more extensive in cells cultured on collagen films than in cells cultured on gels. The addition of heparin and DAH to collagen gels supported the formation of 6beta-hydroxy, 16alpha-hydroxy, and 2alpha-hydroxy testosterone by cells cultured for 48 h. The extent of glucuronidation of kaempferol was not different when comparing cells cultured on films or gels at the various times in culture; however, the ratio of formation of the two glucuronides formed, M1 and M2, was different. The combination of chondroitin- 6-sulfate and DAH increased glucuronidation of cells cultured for 7 days on both collagen films and gels. This approach may increase the expression of hepatocyte-specific functions in monolayers cultured on membranes in flat plate bioreactors.

Metal ion adsorption by Phomopsis sp. biomaterial in laboratory experiments and real wastewater treatments
Saiano, F., M. Ciofalo, et al. (2005), Water Res 39(11): 2273-80.
Abstract: An insoluble material of polysaccharidic nature has been obtained by thermal alkali treatment of the filamentous fungus Phomopsis sp. FT-IR spectrum of the resulting material as well as its nitrogen content suggest that chitosan and glucans are the main components of the biomaterial. Information on Lewis base sites has also been obtained and used as a guideline in the evaluation of the complexing ability against a number of metal ions in aqueous media at pH in the range 4--6. Results indicate that after 24h contact time, up to 870 micromol/g of lead, 390 micromol/g of copper, 230 micromol/g of cadmium, 150 micromol/g of zinc and 110 micromol/g of nickel ions are adsorbed into the material. After approximately 10 min, about 70% of the overall adsorption process has already been completed. Adsorbed metal ions can be recovered by washing with dilute acid. Experiments have been extended to a real wastewater effluent confirming the potential of this biomaterial as a depolluting agent.

Metal release from dental biomaterials
Brune, D. (1986), Biomaterials 7(3): 163-75.
Abstract: Levels of corrosion products released from dental alloys in natural or synthetic saliva, i.e. from amalgams, cobalt, gold, nickel, iron, or titanium based alloys have been surveyed. The amounts of Ag, Au, Cd, Co, Cr, Cu, Hg, Mo, Ti or Ni released from such alloys, either in vitro or in vivo during animal tests or during clinical usage have been compiled. The quantities released have been adapted to a 'standard restored man' with a specified number of restorations or a specified construction with a defined surface area, and compared to man's food and drink intake of similar elements. This was done as one approach to a security analysis of wearing dental alloys. In view of the assessment of extensive corrosion testing using electrochemical methods, rather scarce information seems presently available pertinent to release kinetics of specific elements in various biological environments like saliva or saliva substitutes. Several examinations indicate that mercury released from amalgams could be a substantial part of man's daily intake of this element, e.g. in the initial period following insertion, as well as on a long-term basis. From a copper amalgam cadmium could be released in vitro in amounts close to food and drink intake. The mercury release from the amalgam surface seems to be strongly influenced by the interaction of mechanical forces, e.g. chewing, and seems to be released according to a cyclic pattern. From a base metal alloy with high nickel content nickel could be released in vitro at the same level as from food and drink intake. However, from cobalt based alloys the nickel release seems insignificant in this context. The elemental release from the other alloys seemed to be far below the intake of similar elements from food and drink. Release under static and dynamic conditions has been discussed.

Metal removal in asymptomatic children and adolescents
Stanitski, C. L. (2005), J Pediatr Orthop 25(4): 557.

Metal shafts: designs to meet the required performance
Farrissey, L. (2004), Med Device Technol 15(10): 26-9.
Abstract: When designing shafts for minimally invasive devices such as catheters and guidewires, features that improve one area of performance may hinder performance in another area. This article describes how the traditional limits of metal shafts can be extended to enable their use in a variety of new applications.

Metallic biomaterials TiN-coated: corrosion analysis and biocompatibility
Paschoal, A. L., E. C. Vanancio, et al. (2003), Artif Organs 27(5): 461-4.
Abstract: Corrosion processes due to contact with the physiological environment should be avoided or minimized in orthopedic implants. Four metallic substrates frequently used as biomaterials: pure Ti, Ti-6Al-4V alloy, ASTM F138 stainless steel, and Co-Cr-Mo alloy, were coated with TiN using the physical vapor deposition (PVD) technique. These coatings have been screened by polarization curves in physiological solutions. TiN prepared by PVD is efficient as coating for stainless steel. On titanium and alloy there are no benefits concerning the corrosion resistance compared to the bare Ti-materials. TiN coatings have been screened according to ISO 10993 standard tests for biocompatibility and exhibited no cytotoxicity, dermal irritation, or acute systemic toxicity response.

Metallic implant-associated lymphoma: a distinct subgroup of large B-cell lymphoma related to pyothorax-associated lymphoma?
Cheuk, W., A. C. Chan, et al. (2005), Am J Surg Pathol 29(6): 832-6.
Abstract: Primary non-Hodgkin lymphoma arising at the site of metallic implant is very rare, and the possible carcinogenic effects of the metallic components and wear particles of the implant have not been answered despite many years of investigation. We report a case of large B-cell lymphoma occurring in a 78-year-old man who had a knee prosthesis implant for more than 30 years. The lymphoma was of microscopic size and found incidentally in the wear debris removed at surgical revision of the loosened prosthesis. The lymphoma expressed CD20, showed clonal rearrangements of immunoglobulin gene, and harbored Epstein-Barr virus (EBV). This case, together with previously reported cases, suggests that metallic implant-associated lymphoma is a distinctive subgroup of large B-cell lymphoma that shares many similarities with pyothorax-associated lymphoma and osteomyelitis-associated lymphoma, in that the lymphoma is an EBV-associated large B-cell lymphoma arising in a setting of chronic inflammation or irritation in a confined body space.

Method for quantitative determination of spatial polymer distribution in alginate beads using Raman spectroscopy
Heinemann, M., H. Meinberg, et al. (2005), Appl Spectrosc 59(3): 280-5.
Abstract: A new method based on Raman spectroscopy is presented for non-invasive, quantitative determination of the spatial polymer distribution in alginate beads of approximately 4 mm diameter. With the experimental setup, a two-dimensional image is created along a thin measuring line through the bead comprising one spatial and one spectral dimension. For quantitative analysis of the Raman spectra, the method of indirect hard modeling was applied to make use of the information contained in the entire recorded spectra. For quantification of the alginate signals from within the beads, a calibration curve acquired from sodium alginate solutions was used after it was shown that only negligible differences occur between signals from alginate solutions and alginate gels. The distribution of alginate over the bead gel matrix was acquired with high spatial (51 microm) and time (12 s) resolution. The inhomogeneous distribution obtained using the new measuring technique is qualitatively in excellent agreement with data from the literature. In contrast to known measuring techniques, correct quantitative information about the spatial polymer distribution within the matrix was derived. It gave an alginate mass fraction of approximately 0.045 g/g at the edges and 0.02 g/g in the center of the beads. Next to the determination of mere polymer concentrations, the excellent time resolution of the presented method will enable investigation of the dynamic process of gel formation and it will also serve as a basis for investigation of mass transfer of small diffusing molecules in alginate matrices.

Methodology for rheological testing of engineered biomaterials at low audio frequencies
Titze, I. R., S. A. Klemuk, et al. (2004), J Acoust Soc Am 115(1): 392-401.
Abstract: A commercial rheometer (Bohlin CVO120) was used to mechanically test materials that approximate vocal-fold tissues. Application is to frequencies in the low audio range (20-150 Hz). Because commercial rheometers are not specifically designed for this frequency range, a primary problem is maintaining accuracy up to (and beyond) the mechanical resonance frequency of the rotating shaft assembly. A standard viscoelastic material (NIST SRM 2490) has been used to calibrate the rheometric system for an expanded frequency range. Mathematically predicted response curves are compared to measured response curves, and an error analysis is conducted to determine the accuracy to which the elastic modulus and the shear modulus can be determined in the 20-150-Hz region. Results indicate that the inertia of the rotating assembly and the gap between the plates need to be known (or determined empirically) to a high precision when the measurement frequency exceeds the resonant frequency. In addition, a phase correction is needed to account for the magnetic inertia (inductance) of the drag cup motor. Uncorrected, the measured phase can go below the theoretical limit of -pi. This can produce large errors in the viscous modulus near and above the resonance frequency. With appropriate inertia and phase corrections, +/- 10% accuracy can be obtained up to twice the resonance frequency.

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Last Modified: 8 February 2006