Biomaterials.info - Resources for Engineers

Record 761 to 780

Aqueous dispersions of magnetite nanoparticles with NH3+ surfaces for magnetic manipulations of biomolecules and MRI contrast agents
Shieh, D. B., F. Y. Cheng, et al. (2005), Biomaterials 26(34): 7183-91.
Abstract: In the current study, amine surface modified iron-oxide nanoparticles of 6 nm diameter without polymer coating were fabricated in an aqueous solution by organic acid modification as an adherent following chemical coprecipitation. Structure and the superparamagnetic property of magnetite nanoparticles were characterized by selected area electron diffraction (SAED) and superconducting quantum interference measurement device (SQUID). X-ray photoelectron spectrometer (XPS) and zeta potential measurements revealed cationic surface mostly decorated with terminal -NH(3)(+). This feature enables them to function as a magnetic carrier for nucleotides via electrostatic interaction. In addition, Fe(3)O(4)/trypsin conjugates with well-preserved functional activity was demonstrated. The nanoparticles displayed excellent in vitro biocompatibility. The NMR and the in vitro MRI measurements showed significantly reduced water proton relaxation times of both T(1) and T(2). Significantly reduced T(2) and T(2)*-weighted signal intensity were observed in a 1.5 T clinical MR imager. In vivo imaging contrast effect showed a fast and prolonged inverse contrast effect in the liver that lasted for more than 1 week. In addition, it was found that the spherical Fe(3)O(4) assembled as rod-like configuration through an aging process in aqueous solution at room temperature. Interestingly, TEM observation of the liver tissue revealed the rod-like shape but not the spherical-type nanoparticles being taken up by the Kupffer cells 120 h after tail vein infusion. Combining these results, we have demonstrated the potential applications of the newly synthesized magnetite nanoparticles in a broad spectrum of biomedical applications.

Aqueous dispersions of single-wall and multiwall carbon nanotubes with designed amphiphilic polycations
Sinani, V. A., M. K. Gheith, et al. (2005), J Am Chem Soc 127(10): 3463-72.
Abstract: Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting.

Archaeometallurgy of the Etruscan dental protheses: prestige, magic or biocompatibility?
Baggieri, G., C. Giardino, et al. (2000), Acta Univ Carol [Med] (Praha) 41(1-4): 69-74.

Are scaling laws on strength of solids related to mechanics or to geometry?
Carpinteri, A. and N. Pugno (2005), Nat Mater 4(6): 421-3.
Abstract: One of the largest controversial issues of the materials science community is the interpretation of scaling laws on material strength. In spite of the prevailing view, which considers mechanics as the real cause of such effects, here, we propose a different argument, purely based on geometry. Thus, as happened for relativity, geometry could again hold an unexpected and fundamental role.

Are we doing everything we can to conserve blood during bypass? A national survey
Belway, D., F. D. Rubens, et al. (2005), Perfusion 20(5): 237-41.
Abstract: INTRODUCTION: Despite major advances in biomaterial research and blood conservation, bleeding is still a common complication after cardiopulmonary bypass and cardiac surgery remains a major consumer of blood products. Although the underlying mechanisms for these effects are not fully established, two proposed major etiologies are the hemodilution associated with the use of the heart-lung machine and the impact of reinfusion of shed cardiotomy blood. Therapeutic strategies that primarily encompass the use of devices or technologies to overcome these effects may result in improved clinical outcomes. OBJECTIVE: To determine the extent to which 1) lipid/leukocyte filtration and centrifugal processing of cardiotomy blood, and 2) modified ultrafiltration (MUF) are currently applied in adult cardiac surgery in Canada. METHODS: A questionnaire was mailed to the chief perfusionist at all adult cardiac surgical centers in Canada, addressing details regarding the frequency of use of cardiotomy blood processing and MUF. RESULTS: All questionnaires (36, 100%) were completed and returned. With regards to cardiotomy blood management, in 21 centers (58%), no specific processing steps were utilized exclusive of the integrated cardiotomy reservoir filter. Of the remaining centers, two (6%) reported using lipid/leukocyte filtration and 15 (42%) reported washing their cardiotomy blood. Three centers (8%) reported using MUF at the end of CPB. CONCLUSIONS: Despite growing concern about the potential detrimental effects of cardiotomy blood, few centers in Canada routinely manage this blood with additional filtration and/or centrifugal processing prior to reinfusion. Similarly, MUF, demonstrated to be effective in the pediatric population, has not seen popular application in adult cardiac surgical practice.

Argon microwave plasma treatment and subsequent hydrosilylation grafting as a way to obtain silicone biomaterials with well-defined surface structures
Olander, B., A. Wirsen, et al. (2002), Biomacromolecules 3(3): 505-10.
Abstract: A method of grafting well-defined and hydrolytically stable surface structures onto cross-linked poly(dimethylsiloxane) (PDMS) has been developed. In the first step, argon microwave plasma was used to introduce Si-H groups onto the surface. In the second step, allyltetrafluoroethyl ether was grafted to these Si-H groups using a platinum-catalyzed hydrosilylation reaction. The influences of the plasma parameters of power, pressure, and treatment time on the surface composition, both before and after the hydrosilylation step, were investigated by X-ray photoelectron spectroscopy and contact angle measurements. It was found that the pressure had little influence on the results, whereas the power and treatment time determined the rate of change in surface composition during the plasma treatment. The graft yield reached a plateau value corresponding to about 5% grafted molecules in the analyzed surface region. Hydrosilylation grafting of PDMS is a promising method to obtain biomaterials with hydrolytically stable structures covalently bound to the surface.

Aroma sensing and indoor air monitoring by quartz crystal resonators with sensory films prepared by sputtering of biomaterials and sintered polymers
Seyama, M., I. Sugimoto, et al. (2004), Biosens Bioelectron 20(4): 814-24.
Abstract: Thickness shear mode quartz-crystal resonator coated with plasma polymer films (PPFs) produced by radio-frequency sputtering of biomaterials and synthetic polymers were examined with respect to their abilities to continuously monitor indoor air. We confirmed the sensory capabilities of an array of PPF sensors to aromas emitted from essential oils at concentrations as low as the detection threshold of human olfaction. Changes in humidity induced a drift in the response curves of PPF sensors. On the contrary, volatile compounds exhibited pulse signals. The pulse signals of a D-phenylalanine sensor and a polyethylene sensor were synchronous, but the direction of the peaks was inverted in most cases. Compared with a photo-ionization detector sensor, the PPF sensors were able to detect subtle changes in the concentrations of volatile compounds in indoor air.

Arsenic leachability in water treatment adsorbents
Jing, C., J. S. Liu, et al. (2005), Environ Sci Technol 39(14): 5481-7.
Abstract: Arsenic leachability in water treatment adsorbents was studied using batch leaching tests, surface complexation modeling and extended X-ray absorption fine structure (EXAFS) spectroscopy. Spent adsorbents were collected from five pilot-scale filters that were tested for removal of arsenic from groundwater in Southern New Jersey. The spent media included granular ferric hydroxide (GFH), granular ferric oxide, titanium dioxide, activated alumina, and modified activated alumina. The As leachability determined with the Toxicity Characteristic Leaching Procedure (TCLP, 0.1 M acetate solution) was below 180 microg L(-1) for all spent media. The leachate As concentration in the California Waste Extraction Test (0.2 M citrate solution) was more than 10 times higher than that in the TCLP and reached as high as 6650 microg L(-1) in the spent GFH sample. The EXAFS results indicate that As forms inner-sphere bidentate binuclear surface complexes on all five adsorbent surfaces. The As adsorption/desorption behaviors in each media were described with the charge distribution multisite complexation model. This study improved the understanding of As bonding structures on adsorptive media surfaces and As leaching behavior for different adsorbents.

Arthroplasty implant biomaterial particle associated macrophages differentiate into lacunar bone resorbing cells
Pandey, R., J. Quinn, et al. (1996), Ann Rheum Dis 55(6): 388-95.
Abstract: OBJECTIVE: To study the pathogenesis of aseptic loosening: in particular, to determine whether macrophages responding to particles of biomaterials commonly used in arthroplasty surgery for arthritis are capable of differentiating into osteoclastic bone resorbing cells, and the cellular and hormonal conditions required for this to occur. METHODS: Biomaterial particles (polymethylmethacrylate, high density polyethylene, titanium, chromium-cobalt, stainless steel) were implanted subcutaneously into mice. Macrophages were isolated from the foreign body granulomas that resulted, cultured on bone slices and coverslips, and assessed for both cytochemical and functional evidence of osteoclast differentiation. RESULTS: Tartrate resistant acid phosphatase (TRAP) negative macrophages isolated from granulomas containing particles of all types of biomaterial composition were capable of differentiating into TRAP positive cells capable of extensive lacunar bone resorption (assessed by scanning electron microscopy). The presence of both UMR106 rat osteoblast-like cells and 1,25-dihydroxy vitamin D3 was necessary for this to occur. CONCLUSION: All implant materials produce wear particles that are the focus of a heavy foreign body macrophage response in the fibrous membrane between a loose implant component and the host bone undergoing resorption. These findings underline the importance of biomaterial wear particle generation and the macrophage response to different types of biomaterial wear particles in the pathogenesis of aseptic loosening.

Articular cartilage engineering with Hyalograft C: 3-year clinical results
Marcacci, M., M. Berruto, et al. (2005), Clin Orthop Relat Res(435): 96-105.
Abstract: The use of tissue engineering for cartilage repair has emerged as a potential therapeutic option and has led to the development of Hyalograft C, a tissue-engineered graft composed of autologous chondrocytes grown on a scaffold entirely made of HYAFF 11, an esterified derivative of hyaluronic acid. Here we present the results of an ongoing multicenter clinical study conducted with the primary objective to investigate the subjective symptomatic, functional and health-related quality of life outcomes of patients treated with Hyalograft C. Clinical results on the cohort of 141 patients with followup assessments ranging from 2 to 5 years (average followup time: 38 months), are reported. At followup 91.5% of patients improved according to the International Knee Documentation Committee subjective evaluation; 76% and 88% of patients had no pain and mobility problems respectively assessed by the EuroQol-EQ5D measure. Furthermore, 95.7% of the patients had their treated knee normal or nearly normal as assessed by the surgeon; cartilage repair was graded arthroscopically as normal or nearly normal in 96.4% of the scored knees; the majority of the second-look biopsies of the grafted site histologically were assessed as hyaline-like. Importantly, a very limited complication rate was recorded in this study. The positive clinical results obtained indicate that Hyalograft C is a safe and effective therapeutic option for the treatment of articular cartilage lesions. LEVEL OF EVIDENCE: Therapeutic study, Level III-2 (retrospective cohort study). See the Guidelines for Authors for a complete description of levels of evidence.

Artificial cell-cell communication in yeast Saccharomyces cerevisiae using signaling elements from Arabidopsis thaliana
Chen, M. T. and R. Weiss (2005), Nat Biotechnol 23(12): 1551-5.
Abstract: The construction of synthetic cell-cell communication networks can improve our quantitative understanding of naturally occurring signaling pathways and enhance our capabilities to engineer coordinated cellular behavior in cell populations. Towards accomplishing these goals in eukaryotes, we developed and analyzed two artificial cell-cell communication systems in yeast. We integrated Arabidopsis thaliana signal synthesis and receptor components with yeast endogenous protein phosphorylation elements and new response promoters. In the first system, engineered yeast 'sender' cells synthesize the plant hormone cytokinin, which diffuses into the environment and activates a hybrid exogenous/endogenous phosphorylation signaling pathway in nearby engineered yeast 'receiver' cells. For the second system, the sender network was integrated into the receivers under positive-feedback regulation, resulting in population density-dependent gene expression (that is, quorum sensing). The combined experimental work and mathematical modeling of the systems presented here can benefit various biotechnology applications for yeast and higher level eukaryotes, including fermentation processes, biomaterial fabrication and tissue engineering.

Artificial cells as bioreactive biomaterials
Chang, T. M. (1988), J Biomater Appl 3(1): 116-25.
Abstract: Artificial cells can have the same dimensions as biological cells. They can enclose and retain a large variety of bioreactants. Artificial cell membranes can have the required permeability characteristics to allow the rapid equilibration of external molecules to be acted on by the enclosed bioreactants. Polymer, protein, protein-lipid, polymer-lipid, lipid or other materials can form artificial cell membranes. It is possible to vary the membrane thickness and permeability characteristics over a wide range. Many different forms of bioreactive artificial cells are available. This article contains only a few examples. This includes its applications in (1) red blood cell substitutes; (2) immobilisation of enzymes, multienzymes with cofactor recycling, cell cultures and other biotechnological applications; (3) hemoperfusion in kidney failure, poisoning, removal of aluminum and iron; (4) use in liver failure; (5) other applications in microencapsulation.

Artificial nerve conduits in peripheral-nerve repair
Kannan, R. Y., H. J. Salacinski, et al. (2005), Biotechnol Appl Biochem 41(Pt 3): 193-200.
Abstract: Injuries to the nervous system are the result of mechanical, thermal, chemical or congenital pathologies and, if function is not restored, they lead to loss of muscle function, pain and impaired sensation. Current treatment modalities essentially coapt the two nerves ends together or place a nerve graft between the cut ends. However, clinical results have never been optimal, and therefore a quest for better options has taken place. In this review article we look at the synthetic and biomimetic options currently being tested as potential nerve grafts.

Artificial organs and biomaterials
Courtney, J. M. (1993), J Med Eng Technol 17(5): 188-90; discussion 197-8.

Artificial skin as a valuable adjunct to surgical treatment of a large squamous cell carcinoma in a patient with epidermolysis bullosa
Dagregorio, G. and G. Guillet (2005), Dermatol Surg 31(4): 474-6.
Abstract: BACKGROUND: Among tissue-engineered skins, two bilayered cellular constructs and one cryopreserved dermal substitute have been approved for the treatment of epidermolysis bullosa. Nevertheless, the application of artificial skin technology to surgical treatment of squamous cell carcinomas in a patient with epidermolysis bullosa has never been reported. OBJECTIVE: To reconstruct the large defect remaining after squamous cell carcinoma excision in a patient with dominantly inherited dystrophic epidermolysis bullosa. METHODS: To apply a 10 x 15 cm Integra sheet (Integral Life-sciences Corporation, Plainsboro, NJ, USA) (an acellular collagen matrix coated with a thin polysiloxane elastomer) to the excised area and 3 weeks later to cover the Integra sheet with an ultrathin meshed skin graft. RESULTS: The graft take was complete, and the donor site totally regenerated, except for three small bullae at 7 weeks postoperatively. CONCLUSION: Integra offers the advantage of filling huge defects with its dermal layer of collagen fibers and provides an optimal graft bed. This first step makes it possible to use very thin grafts 3 weeks later.

Aspects of the physical chemistry of polymers, biomaterials and mineralised tissues investigated with atomic force microscopy (AFM)
Jandt, K. D., M. Finke, et al. (2000), Colloids Surf B Biointerfaces 19(4): 301-314.
Abstract: Beyond being merely a tool for measuring surface topography, atomic force microscopy (AFM) has made significant contributions to various scientific areas dealing with physical chemistry processes. This paper presents aspects of the physical chemistry at surfaces and interfaces of polymers, biomaterials and tissues investigated with AFM. Selected examples presented include surface induced self-assembly of polymer blends, copolymer interfacial reinforcement of immiscible homopolymers, protein adsorption on biomaterials and erosion of mineralised human tissues. In these areas, AFM is a useful and versatile tool to study structural or dynamic sample properties including thermodynamically driven surface evolution of polymer surfaces, lateral surface composition of interfaces, adsorption processes, and the metrology of demineralisation phenomena.

Assessing acute platelet adhesion on opaque metallic and polymeric biomaterials with fiber optic microscopy
Schaub, R. D., M. V. Kameneva, et al. (2000), J Biomed Mater Res 49(4): 460-8.
Abstract: The degree of platelet adhesion and subsequent thrombus formation is an important measure of biocompatibility for cardiovascular biomaterials. Traditional methods of quantifying platelet adhesion often are limited by the need for direct optical access, limited spatial resolution, or the lack of temporal resolution. We have developed a new imaging system that utilizes fiber optics and fluorescence microscopy for the quantification of platelet adhesion. This fiber optic remote microscope is capable of imaging individual fluorescently labeled platelets in whole blood on opaque surfaces. Using this method, platelet adhesion was quantified on a series of metallic [low-temperature isotropic carbon (LTIC); titanium alloy (Ti); diamond-like carbon (DLC); oxidized titanium alloy (TiO); and polycrystalline diamond (PCD)] and polymeric [woven Dacron (WD)] collagen-impregnated Dacron (HEM), expanded polytetrafluoroethylene (ePTFE), and denucleated ePTFE (dePTFE)] biomaterials designed for use in cardiovascular applications. These materials were perfused with heparinized whole human blood in an in vitro parallel plate flow chamber. Platelet adhesion after 5 min of perfusion ranged from 3.7 +/- 1.0 (dePTFE) to 16.8 +/- 1.5 (WD) platelets/1000 micrometer. The temporal information revealed by these studies provides a comparative measure of the acute thrombogenicity of these materials as well as some insight into their long-term hemocompatibilities. Also studied here were the effects of wall shear rate and axial position on platelet adhesion. A predicted increase in platelet adhesion with increased wall shear rate and a trend toward a decrease in platelet adhesion with increased axial distance was observed with the fiber optic microscope. Future applications for this imaging technique may include the long-term evaluation of thrombosis in blood-contacting devices in vitro and, in animal models, in vivo.

Assessing the in vitro biocompatibility of a novel carbon device for the treatment of sepsis
Sandeman, S. R., C. A. Howell, et al. (2005), Biomaterials 26(34): 7124-31.
Abstract: The aim of the present study was to conduct a preliminary investigation into the blood biocompatibility of a novel, uncoated carbon for use in a filtration/adsorption device for the treatment of sepsis. Carbon well prototypes were manufactured from phenol-formaldehyde-aniline-based pyrolysed carbons using monolithic polymer technology. Inflammatory blood cell and plasma protein mediation of the inflammatory response were evaluated using the novel carbon prototypes and compared with dialyser membrane and tissue culture plate controls. Assays determining monocyte and granulocyte adhesion, platelet adhesion and activation, granulocyte activation and complement activation were performed. Preliminary findings suggest an adsorptive but passivating carbon surface. Moderate levels of monocyte and granulocytes adhesion were seen in conjunction with adsorption of plasma proteins to the carbon surface. Activation of granulocyte and adherent platelets was not detected and the complement cascade was not activated by the carbons, indicating a surface compatible with blood contact. The results support the further development of the proposed carbon-based device for the treatment of sepsis.

Assessing the in vitro cell based ocular compatibility of contact lens materials
Lloyd, A. W., R. G. Faragher, et al. (2000), Cont Lens Anterior Eye 23(4): 119-23.
Abstract: A series of in vitro assays for determining the biocompatibility of ocular biomaterials have been developed and used to assess the differences in performance of omafilcon A, etafilcon A and nelfilcon A contact lens materials. The assays assessed bacterial attachment, macrophage adhesion, granulocyte adhesion and activation, epithelial cell adhesion and corneal cell contact damage. Overall, omafilcon A was found to be more biocompatible than the other materials although there was no significant difference between the epithelial cell adhesion and granulocyte adhesion and activation on any of the hydrogels. Etailcon A performed less well compared to nelfilcon A and omafilcon A with respect macrophage adhesion and bacterial adhesion. The results indicate that these biological assays can be successfully applied for the testing of contact lens materials and may be particularly useful in the in vitro screening of new extended wear contact lens materials where cell adhesion and activation may have a greater influence on clinical performance.

Assessing the role of the biomaterial Aquavene in patient reactions to Landmark midline catheters
Silverstein, B., K. M. Witkin, et al. (1997), Regul Toxicol Pharmacol 25(1): 60-7.
Abstract: Landmark midline catheters (Menlo Care, Inc., Palo Alto, CA) provide peripheral venous access for the infusion of medications or fluids. They are constructed of an inner layer of polyurethane and an outer layer of the biomaterial Aquavene, a blend of polyurethane and polyethylene oxide to which butylated hyroxyanisole (BHA), butylated hydroxytoluene (BHT), and triallyl-s-triazine trione (TTT) are added. Once inside the vein, the Aquavene material becomes hydrated and the catheter swells resulting in minimal trauma to the vein. It is well recognized that some patients experience reactions to catheterization. Recent reports of hypersensitivity-like reactions in some patients catheterized with Landmark catheters have prompted the manufacturer to reexamine biocompatibility data and clinical data to assess whether Aquavene was the source of the patient responses. None of the biocompatibility studies provided by Menlo Care in support of U.S. registration and marketing of Aquavene-based catheters demonstrated any tendency for Aquavene or material extracted from Aquavene to invoke an immunological or toxicological response. Examination of potential catheter residuals revealed that significant amounts of BHA and BHT were unlikely to be released from the catheters during expected use. The amounts of polyethylene oxide and TTT expected to be released during the first few minutes after catheter insertion (when most of the patient reactions were reported) are almost 92,500 and 270,000 times lower, respectively, than nontoxic animal exposures. These analyses do not support chemically mediated toxicity as an explanation for the adverse events experienced by some patients. A review of the postmarket surveillance data on Aquavene-based catheters revealed that the reported events were not consistent with a hypersensitivity (immunogenic) response to the biomaterial. The rare reported adverse events tend to occur quickly, most often after flushing of the catheter, and resolve quickly, even when the catheter remains in place. Determining the frequency and severity of adverse events reported in association with the use of Landmark catheters will ultimately require a controlled prospective study, preferably one with a concurrent control group using alternative products.

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