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Record 2701 to 2720

Macro kinetic studies for photocatalytic degradation of benzoic acid in immobilized systems
Mehrotra, K., G. S. Yablonsky, et al. (2005), Chemosphere 60(10): 1427-36.
Abstract: Semiconductor photocatalytic process has been studied extensively in recent years due to its intriguing advantages in environmental remediation. In this study, a two-phase swirl-flow monolithic-type reactor is used to study the kinetics of photocatalytic degradation of benzoic acid in immobilized systems. Transport contributions into the observed degradation rates were determined when catalyst is immobilized. Intrinsic kinetic rate constants and its dependence on light intensity and catalyst layer thickness, values of adsorption equilibrium constant, internal as well as external mass transfer parameters were determined. The simultaneous effect of catalyst loading and light intensity and optimum catalyst layer thickness were also determined experimentally. Reaction rate constants and overall observed degradation rates were compared with slurry systems.

Macrophage adhesion on gelatin-based interpenetrating networks grafted with PEGylated RGD
Phillips, J. M. and W. J. Kao (2005), Tissue Eng 11(5-6): 964-73.
Abstract: Human blood-derived macrophage adhesion on interpenetrating networks (IPNs) composed of PEGylated RGD-modified gelatin and poly(ethylene glycol) diacrylate was studied. The interaction between biomaterial immobilized with biofunctional peptides such as RGD and macrophages is central in the design of tissue-engineering scaffolds. PEGylated RGD-modified gelatin was synthesized via several steps involving PEG derivations and characterized by high-performance liquid chromatography, mass spectroscopy, gel permeation chromatography, and the trinitrobenzenesulfonic acid method. IPNs containing modified or unmodified gelatin were cultured with human macrophages and monitored at 2, 24, 96, and 168 h. At each time point, IPNs containing gelatin modified with PEGylated RGD showed a comparable adherent macrophage density as tissue culture polystyrene and a significantly higher cell density than other IPN formulations containing unmodified gelatin or gelatin modified with PEGylated triglycine. Although surface-immobilized RGD can serve to mediate the adhesion of different cell types on the biomaterial surface, the interaction of RGD with immune/inflammatory cells such as macrophages should also be considered when assessing the potential host response of tissue-engineering scaffolds.

Macrophage subpopulation differentiation by stimulation with biomaterials
Rhodes, N. P., J. A. Hunt, et al. (1997), J Biomed Mater Res 37(4): 481-8.
Abstract: Macrophages were elicited by the subcutaneous implantation of ultra high molecular weight polyethylene (UHMWPE) for periods of 2, 7, and 14 days in rats. Exudates of varying volumes were produced that was comprised of granulocytes, monocytes, immature and mature macrophages, and T-lymphocytes. No B-lymphocytes were observed at any time periods. Cell types were identified by their granularity and positivity to the following antibodies: leucocyte common antigen (LCA, pan leucocyte); CD11b/c (macrophage/monocyte); CD5 (T-lymphocyte); CD45RA (B-lymphocyte); HIS48 (granulocyte); ED2 (mature macrophage); and MCP-1 (monocyte chemoattractant protein 1). Monocytes isolated from control rat blood demonstrated a size slightly larger than that of granulocytes but with less granularity. Their size and granularity were followed over increasing time periods. The macrophages elicited by UHMWPE showed a similar pattern, with the exception of an apparently highly granular subpopulation with volumes similar to that of granulocytes but significantly more granular. The granular macrophage subset had a very high degree of ED2 and MCP-1 positivity, and their proportion, compared with other macrophages, was greatest at 2 days. The high MCP-1 expression was accounted for by MCP-1 molecules bound to the surface of a small proportion of macrophages that were activated. It is postulated that this subpopulation was responsible for the synthesis of the MCP-1 and could indicate a mechanism by which monocytes are attracted to the site of an implanted material.

Macrophage/biomaterial interactions: the stimulation of endothelialization
Greisler, H. P., J. W. Dennis, et al. (1989), J Vasc Surg 9(4): 588-93.
Abstract: This current study analyzed macrophage/biomaterial interactions as modulators of endothelial cell proliferation. Rabbit peritoneal macrophages were harvested and seeded (1 x 10(6) cells/ml) into culture flasks with Dulbecco's modified Eagle medium and 10% platelet-poor, plasma-derived equine serum. Macrophages were identified by morphologic characteristics, nonspecific esterase, and Fc (immunoglobulin G) receptors on the cell membranes. Culture conditions were (1) no prosthetic material, (2) Dacron, or (3) Polyglactin 910 (PG910) (Ethicon, Inc., Somerville, N.J.). Both prosthetic materials were finely shredded into the media. After 5 weeks in culture, PG910 inclusions were seen within macrophage cytoplasm. No intracytoplasmic Dacron was observed. Conditioned media from all three groups were collected weekly from week 5 to week 10, centrifuged, filtered, and added in serial dilutions to cultured quiescent murine capillary lung endothelial cells. Quiescence was achieved by serum deprivation and verified by [3H]thymidine incorporation. Sixteen hours after addition of conditioned media, [3H]thymidine was measured in and expressed as percent increase above quiescent levels. Mitogenic activity in the PG910 group progressively increased from weeks 6 to 10. At week 10, the PG910 group (1:10 dilution) yielded a 620% increase in DNA synthesis. The Dacron group never varied from the control group (no prosthetic). The mean increases in [3H]thymidine incorporations over weeks 7 to 10 were PG910, 540% +/- 65%; Dacron, 323% +/- 65%, and control, 343% +/- 26% (PG910 vs Dacron, p less than or equal to 0.004). These studies suggest macrophage activation by bioresorbable prostheses, yielding growth factor release with subsequent enhanced endothelial cell proliferation.

Macrophage-biomaterial interactions with bioresorbable vascular prostheses
Greisler, H. (1988), ASAIO Trans 34(4): 1051-9.

Macroporous calcium phosphate glass-ceramic prepared by two-step pressing technique and using sucrose as a pore former
Wang, C., T. Kasuga, et al. (2005), J Mater Sci Mater Med 16(8): 739-44.
Abstract: Macroporous calcium phosphate glass-ceramic with an initial glass composition of 60CaO.30P2O5.3TiO2.7Na2O in mol% was successfully prepared by sintering the mixture compact consisting of calcium phosphate glass and sucrose powders, which was formed using a two-step pressing technique. After burning off the sucrose phase, a 3D interconnected macroporous structure was formed in the sintered body, in which the skeleton consisting of the calcium phosphate glass-ceramic (including beta-calcium pyrophosphate and beta-tricalcium phosphate as the crystalline phases) was transformed from the initial glass during the sintering. The macropores with several hundred microns in diameter and the large interconnection size (approximately 100 microm), which result from the controllably large-sized sucrose particles and the hot-pressing at a little higher temperature than the sucrose's melting point, are believed to meet the requirements for cell adhesion and bone tissue regeneration well. Moreover, in vitro dissolution behavior study indicates that the calcium phosphate glass-ceramic is soluble to an acetic acid solution of pH 5-7. These, together with the simplicity and feasibility of the innovative fabrication method itself, show that the formed porous glass-ceramic has a promising potential for application to a scaffold for bone tissue engineering.

Macroporous hydrogels based on 2-hydroxyethyl methacrylate. Part II. Copolymers with positive and negative charges, polyelectrolyte complexes
Pradny, M., P. Lesny, et al. (2005), J Mater Sci Mater Med 16(8): 767-73.
Abstract: Crosslinked macroporous hydrogels based on 2-hydroxyethyl methacrylate (HEMA)-[2-(methacryloyloxy)ethyl]trimethylammonium chloride (MOETACl) copolymer, HEMA-MOETACl-methacrylic acid (MA) terpolymer, and on a polyelectrolyte complex of HEMA-MA copolymer with poly(MOETACl) were prepared. All the hydrogels were prepared in the presence of fractionated sodium chloride particles. The hydrogels were characterized by the number of pores and the total volume of all pores in unit volume, the average volume and the average diameter of single pore. Morphology of the hydrogels was investigated by confocal and scanning electron microscopy. The hydrogels based on polyelectrolyte complexes were also characterized by chemical composition. Homogeneous (non-porous) hydrogels with the same composition as macroporous hydrogels were prepared and characterized by their biocompatibility.

Macroporous hydrogels based on 2-hydroxyethyl methacrylate. Part III. Hydrogels as carriers for immobilization of proteins
Michalek, J., M. Pradny, et al. (2005), J Mater Sci Mater Med 16(8): 783-6.
Abstract: Four series of macroporous hydrogels based on crosslinked copolymers of 2-hydroxyethyl methacrylate (HEMA)-sodium methacrylate (MANa), copolymer HEMA-[2-(methacryloyloxy)ethyl]trimethylammonium chloride (MOETACl), terpolymer HEMA-MANa-MOETACl and on a polyelectrolyte complex were used as carriers for immobilization of proteins, chicken egg white albumin and avidin. The adsorption capacity of the hydrogels for the two proteins, kinetics and pH dependence of albumin adsorption and desorption were studied. The morphology of the hydrogels with and without immobilized albumin was studied by low-vacuum scanning electron microscopy.

Macroporous interconnected dextran scaffolds of controlled porosity for tissue-engineering applications
Levesque, S. G., R. M. Lim, et al. (2005), Biomaterials 26(35): 7436-46.
Abstract: Dextran hydrogels have been studied as drug delivery vehicles but not as scaffolds for tissue-engineering likely because previously synthesized dextran hydrogels had pores too small for cell penetration. Our goal was to create macroporous, interconnected dextran scaffolds. To this end, we took advantage of the liquid-liquid immiscibility of poly(ethylene glycol) and methacrylated dextran during radical crosslinking of the methacrylated moieties. By controlling the degree of methacrylate substitution on dextran, dextran molar mass and PEG concentration, macroporous hydrogels were created. The presence of PEG in solution had a significant effect on the final morphology of the dextran hydrogel leading to the formation of different types of structures, from microporous gel to macroporous gel-wall to a macroporous interconnected-beaded structure. A series of formulation diagrams were prepared which allowed us to determine which conditions led to the formation of macroporous interconnected-beaded scaffolds. Dextran macroporous interconnected-beaded gels had a high water content, between 89% and 94%, a homogeneous morphology, determined by scanning electron microscopy, with interconnected macroporous pores, as determined by protein diffusivity where the effective diffusion coefficients of BSA were calculated to be 3.1 x 10(-7)cm2/s for Dex-MA 40 kDa DS 5 and 1 x 10(-7)cm2/s for Dex-MA 6 kDa DS10, which are similar to that of BSA in water, 5.9 x 10(-7)cm2/s. Mercury intrusion porosimetry showed that the macroporous interconnected-beaded scaffolds had a bimodal distribution of macropores, with a median diameter of 41 microm, interconnected by throats, which had a median diameter of 11 microm. Together, these data suggest that the dextran scaffolds will be advantageous in applications that require an interconnected macroporous geometry, such as those of tissue engineering where cell penetration and nutrient diffusion are necessary for tissue regeneration.

Macro-structural effect of metal surfaces treated using computer-assisted yttrium-aluminum-garnet laser scanning on bone-implant fixation
Hirao, M., K. Sugamoto, et al. (2005), J Biomed Mater Res A 73(2): 213-22.
Abstract: Porous coatings have been applied to the surface of prosthetic devices to foster stable device fixation. The coating serves as a source of mechanical interlocking and may stimulate healthy bone growth through osseointegrated load transfer in cementless arthroplasty. Joint arthroplasty by porous-coated prostheses is one of the most common surgical treatments, and has provided painless and successful joint mobility. However, long-term success is often impaired by the loss of fixation between the prosthesis and bone. Porous-coated prostheses are associated with several disadvantages, including metal debris from porous coatings (third body wear particles) and irregular micro-texture of metal surfaces. Consequently, quantitative histological analysis has been very difficult. These issues arise because the porous coating treatment is based on addition of material and is not precisely controllable. We recently developed a precisely controllable porous texture technique based on material removal by yttrium-aluminum-garnet laser. Free shapes can be applied to complex, three-dimensional hard metal surfaces using this technique. In this study, tartan check shapes made by crossing grooves and dot shapes made by forming holes were produced on titanium (Ti6A14V) or cobalt chrome (CoCr) and evaluated with computer-assisted histological analysis and measurement of bone-metal interface shear strength. Width of grooves or holes ranged from 100 to 800 mum (100, 200, 500, and 800 microm), with a depth of 500 microm. When the cylindrical porous-texture-treated metal samples (diameter, 5 mm; height, 15 mm) were implanted into a rabbit femoral condyle, bone tissue with bone trabeculae formed in the grooves and holes after 2 or 4 weeks, especially in 500-microm-wide grooves. Abundant osteoconduction was consistently observed throughout 500-microm-wide grooves in both Ti6A14V and CoCr. Speed of osteoconduction was faster in Ti6A14V than in CoCr, especially in the tartan check shape made of 500-microm-wide grooves. In pushout testing, the tartan check shape made of 500-microm-wide grooves had significantly higher bone-metal interface shear strength than the dot shape or commercial porous coating. These results indicate that the tartan check shape made of 500-microm-wide grooves on metal surfaces has potential for clinical application in artificial prosthesis design.

Magnesium and its alloys as orthopedic biomaterials: A review
Staiger, M. P., A. M. Pietak, et al. (2006), Biomaterials 27(9): 1728-34.
Abstract: As a lightweight metal with mechanical properties similar to natural bone, a natural ionic presence with significant functional roles in biological systems, and in vivo degradation via corrosion in the electrolytic environment of the body, magnesium-based implants have the potential to serve as biocompatible, osteoconductive, degradable implants for load-bearing applications. This review explores the properties, biological performance, challenges and future directions of magnesium-based biomaterials.

Magnetic field interactions of orthodontic wires during magnetic resonance imaging (MRI) at 1.5 Tesla
Klocke, A., J. Kemper, et al. (2005), J Orofac Orthop 66(4): 279-87.
Abstract: BACKGROUND: Orthodontic appliances pose a potential risk during magnetic resonance imaging (MRI) due to forces on metallic objects within the static magnetic field of MRI systems. The aim of the present investigation was to measure forces on orthodontic wires caused by the static magnetic field of a 1.5-Tesla MRI system, and to assess the safety hazards associated with these forces. MATERIALS AND METHODS: Thirty-two different orthodontic wires (21 arch wires, eight ligature wires and three retainer wires) were investigated in a 1.5-Tesla MRI system (Magnetom Symphony, Siemens Medical Solutions, Erlangen, Germany). The translational forces were measured using the deflection angle test (ASTM F2052-02); rotational forces were assessed on a 5-point qualitative scale. RESULTS AND CONCLUSION: All retainer wires and the steel arch wires (the Noninium arch wire being the exception) were subjected to considerable rotational and translational forces within the MRI system's magnetic field. Translational forces were from 9.1- to 27.6-times as high as gravitational forces on these objects. Steel ligature wires and arch wires made of cobalt chromium, titanium molybdenum, nickel-titanium, and brass alloys showed no or negligible forces within the magnetic field. The translational and rotational forces within the MRI magnetic field should pose no risk to carefully-ligated arch wires. Steel retainer wire bonds should be checked to ensure secure attachment prior to an MRI investigation.

Magnetic nanoparticles: applications beyond data storage
Reiss, G. and A. Hutten (2005), Nat Mater 4(10): 725-6.

Magnetic resonance imaging of self-assembled biomaterial scaffolds
Bull, S. R., M. O. Guler, et al. (2005), Bioconjug Chem 16(6): 1343-8.
Abstract: Current interest in biomaterials for tissue engineering and drug delivery applications have spurred research into self-assembling peptide amphiphiles (PAs). Nanofiber networks formed from self-assembling PAs can be used as biomaterial scaffolds with the advantage of specificity by the incorporation of peptide-epitopes. Imaging the materials noninvasively will give information as to their fate in vivo. We report here the synthesis and in vitro MR images of self-assembling peptide amphiphile contrast agents (PACAs) that form nanofibers. At 400 MHz using a 0.1 mM Gd(III) conjugate of the PA we observed a T(1) three times that of a control gel. The PA derivative was doped into various epitope bearing PA solutions and upon gelling resulted in a homogeneous biomaterial as imaged by MRI.

Magnetically responsive carboxylated magnetite-polydipyrrole/polydicarbazole nanocomposites of core-shell morphology. Preparation, characterization, and use in DNA hybridization
Lellouche, J. P., G. Senthil, et al. (2005), J Am Chem Soc 127(34): 11998-2006.
Abstract: Novel bis-heterocyclic mono- and dicarboxylated dipyrrole and dicarbazole monomers have been synthesized in a modular manner. Their oxidative polymerization around magnetite nanosized particles has been investigated and optimized toward new magnetic magnetite-polydipyrrole/polydicarbazole nanocomposites (NCs) of a core-shell morphology. These NCs were thoroughly characterized by FT-IR, TGA (Thermal Gravimetric Analysis), low- and high-resolution TEM/HR-TEM microscopies, and Mossbauer spectroscopy along with magnetization studies. Exploiting the versatile COOH chemistry (activation by water-soluble diimides) introduced by the polymeric shell, DNA hybridization experiments have been conducted onto NC surfaces using an efficient blue-colored HRP-based enzymatic screening biological system. Highly parallel NC-supported DNA hybridization experimentations revealed that these NCs presented an interesting potential for DNA-based diagnostic applications.

Major mesh-related complications following hernia repair: events reported to the Food and Drug Administration
Robinson, T. N., J. H. Clarke, et al. (2005), Surg Endosc 19(12): 1556-60.
Abstract: Mesh material affects complications following hernia repair. Medical device reports on the use of surgical mesh for hernia repair were reviewed from the Food and Drug Administration's (FDA) Manufacturer User Facility Device Experience Database from January 1996 to September 2004. We analyzed 252 adverse event reports related to the use of surgical mesh for hernia repair. Adverse events included infection (42%, 107 reports), mechanical failure (18%, 46), pain (9%, 23), reaction (8%, 20), intestinal complications (7%, 18), adhesions (6%, 14), seroma (4%, 9), erosion (2%, 6), and other (4%, 9). Compared to all other mesh types, Sepra/polypropylene mesh had more mechanical failures (80 vs 14%, p < 0.05), biomaterial mesh had more reactions (57 vs 7%, p < 0.05), polytetrafluoroethylene (PTFE)/polypropylene mesh had more intestinal complications (14 vs 7%, p < 0.05), and PTFE mesh tended to have more infections (75 vs 41% all other, p = 0.07). Death occurred in 2% (5). We conclude that specific mesh materials are related to specific complications.

Management for postoperative complications of breast augmentation by injected polyacrylamide hydrogel
Qiao, Q., X. Wang, et al. (2005), Aesthetic Plast Surg 29(3): 156-61; discussion 162.
Abstract: Polyacrylamide hydrogel, a new biomaterial, has been used for injected breast augmentation in China since 1997. A series of 30 patients with various complications after injected polyacrylamide hydrogel visited the author's department. Most of these patients had undergone injection of both breasts. The average age of the patients was 27.6 years, and the time of consultation for the complications was from 3 to 36 months postopertively. Nearly all the patients had breast lumps and other common complications including breast pain, disfigurement, and infection. Ultrasound examination showed diffuse, irregular, anechoic zones of mammary tissue. Pathologic results indicated inflammatory cell infiltration and fibrous capsular formation. An open suction technique and partial mastectomies via periareolar incisions were performed for the all patients. Most of their symptoms were relieved after removal of the polyacrylamide hydrogel. Only one patient had undergone immediate breast reconstruction with implants, whereas five patients had received breast implants secondarily via an axillary incision. The authors conclude that polyacrylamide hydrogel should be prohibited for injected breast augmentation before more scientific data are available about the long effect of the gel in breast tissue.

Management of an "Ear Camp" for children in Namibia
Lehnerdt, G., A. van Delden, et al. (2005), Int J Pediatr Otorhinolaryngol 69(5): 663-8.
Abstract: OBJECTIVE: In this publication, we present our experiences with managing an "Ear Camp" in northern Namibia, where the population is predominantly black. Medical coverage for ear problems is poor in this part of the country. METHODS: Within 10 days, 38 children (median age 12 years) were operated mainly for (sub) total defects of the tympanic membrane. In two cases, an open cavity had to be created because of a cholesteatoma. We performed a tympanoplasty type I in 18 cases and a tympanoplasty type III in 20 cases. Additionally, in 8 cases an antrotomy and in another 8 cases a mastoidectomy was performed. The ossicular chain was reconstructed with a titanium-PORP (14 cases), a titanium-TORP, interposition of the head of the malleus or a cartilage columella (one case each) or by placing the reconstructed tympanic membrane directly onto the head of the stapes (three cases). The tympanic membrane was reconstructed by the use of tragal cartilage with overlapping perichondrium in underlay-technique. RESULTS: Thirty-one children could be followed up. A defect of the tympanic membrane was found in five cases because of continuous purulent discharge. The average improvement of air conduction thresholds in the frequencies between 250 and 4000 Hz was 15 dB. CONCLUSIONS: Surgical techniques, antibiotic treatment and perioperative management have to be adapted to limited possibilities of pre-treatment and aftercare. As development aid should support people to look after themselves, we started to instruct local doctors with regard to pre- and postoperative care in ear surgery. Training of the local doctors will be continued in our next "Ear Camp" in 2004.

Management of facial burns with a collagen/glycosaminoglycan skin substitute-prospective experience with 12 consecutive patients with large, deep facial burns
Klein, M. B., L. H. Engrav, et al. (2005), Burns 31(3): 257-61.
Abstract: Management of deep facial burns remains one of the greatest challenges in burn care. We have developed a protocol over the past 20 years for management of facial burns that includes excision and coverage with thick autograft. However, the results were not perfect. Deformities of the eyelids, nose and mouth as well as the prominence of skin graft junctures demonstrated the need to explore novel approaches. Integra has been used with success in the management of burns of the trunk and extremities. The purpose of this study was to prospectively evaluate the aesthetic outcome of the use of Integra for deep facial burns. Twelve consecutive patients underwent excision of large, deep facial burns and placement of Integra. Integra provides excellent color and minimally visible skin graft junctures. The texture is good but not as supple as thick autograft. Integra is not well suited for use in the coverage of eyelid burns due to the need to wait 2 weeks for adequate vascularization. In summary, thick autograft remains the gold standard for deep facial burns. However, for patients with extensive burns and limited donor sites, Integra provides an acceptable alternative.

Management of pellucid marginal degeneration with intracorneal ring segments
Barbara, A., R. Shehadeh-Masha'our, et al. (2005), J Refract Surg 21(3): 296-8.
Abstract: PURPOSE: To present intracorneal ring segments for potential management of pellucid marginal degeneration. METHODS: A 41-year-old man with pellucid marginal degeneration with poor visual acuity due to irregular astigmatism was treated with Intacs microthin insert (KeraVision, Fremont, Calif) in the left eye. RESULTS: Uncorrected visual acuity improved from 2/60 to 6/60 following the procedure. The procedure completely eliminated myopia of -8.00 diopters and improved the irregularity of the astigmatism, although it did not change its magnitude. CONCLUSIONS: Insertion of the intracorneal ring segment improves visual acuity in pellucid marginal degeneration by flattening the central corneal protrusion, thus reducing myopia and improving the astigmatism irregularity.

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