Biomaterials.info - Resources for Engineers

Record 741 to 760

Application of a novel phytotoxicity assay for the detection of herbicides in Hervey Bay and the Great Sandy Straits
Bengtson Nash, S. M., K. McMahon, et al. (2005), Mar Pollut Bull 51(1-4): 351-60.
Abstract: A novel phytotoxicity assay was incorporated into an environmental assessment of Hervey Bay and the Great Sandy Straits, to investigate the role of run-off associated herbicides in the deteriorated health of intertidal seagrass meadows. Dose response curves of common herbicides were performed and their toxicity equivalents elucidated to assist in analysis. The results of the assay were reproducible and corresponded strongly with results of chemical analyses. The incorporation of the assay into the assessment of surface waters added an important aspect to the study by allowing investigation of the toxicity of cumulative herbicide concentrations and yielding biologically relevant data. The highest herbicide concentration detected during the study was equivalent to 0.23 microg l(-1) diuron; a concentration known to inhibit photosynthetic efficiency of the assay biomaterial by approximately 3%.

Application of chitosan-based polysaccharide biomaterials in cartilage tissue engineering: a review
Suh, J. K. and H. W. Matthew (2000), Biomaterials 21(24): 2589-98.
Abstract: Once damaged, articular cartilage has very little capacity for spontaneous healing because of the avascular nature of the tissue. Although many repair techniques have been proposed over the past four decades, none has sucessfully regenerated long-lasting hyaline cartilage tissue to replace damaged cartilage. Tissue engineering approaches, such as transplantation of isolated chondrocytes, have recently demonstrated tremendous clinical potential for regeneration of hyaline-like cartilage tissue and treatment of chondral lesions. As such a new approach emerges, new important questions arise. One of such questions is: what kinds of biomaterials can be used with chondrocytes to tissue-engineer articular cartilage? The success of chondrocyte transplantation and/or the quality of neocartilage formation strongly depend on the specific cell-carrier material. The present article reviews some of those biomaterials, which have been suggested to promote chondrogenesis and to have potentials for tissue engineering of articular cartilage. A new biomaterial, a chitosan-based polysaccharide hydrogel, is also introduced and discussed in terms of the biocompatibility with chondrocytes.

Application of immobilized enzymes for biomaterials used in surgery
Watanabe, S., Y. Shimizu, et al. (1988), Methods Enzymol 137: 545-51.

Application of recombinant DNA technology to the production of useful biomaterials
Imanaka, T. (1986), Adv Biochem Eng Biotechnol 33: 1-27.

Application of SPR & FTIR spectroscopy to the study of protein-biomaterial interactions
Heaton, R. J., P. I. Haris, et al. (1995), Biochem Soc Trans 23(4): 502S.

Application of the low vacuum scanning electron microscope to the study of biomaterials and mammalian cells
Sammons, R. and P. Marquis (1997), Biomaterials 18(1): 81-6.
Abstract: The use of the scanning electron microscope (SEM) in 'low' (reduced) vacuum (lvac) mode permits observation of specimens which have not been coated with a conductive material such as gold or carbon. We have evaluated the use of this mode of observation to the study of biomaterials using the bone-substitute material Interpore as an example. On this material, rat bone cells were visible in lvac mode only in cells traversing pores, when they were readily identified by their cell nuclei. Rat calvarial bone examined uncoated in lvac mode showed the bone structure clearly through the overlying layer of osteoblast cells, which were subsequently revealed by gold coating. Immunogold labelling of alkaline phosphatase was imaged in lvac mode, following silver enhancement and carbon coating. These studies demonstrate the complementary use of the lvac and high vacuum (hvac) SEM to study material composition, the behaviour of mammalian cells on biomaterials and the potential use of lvac SEM to study mineralized tissues without removal of overlying soft tissue.

Application of tissue engineering techniques for rotator cuff regeneration using a chitosan-based hyaluronan hybrid fiber scaffold
Funakoshi, T., T. Majima, et al. (2005), Am J Sports Med 33(8): 1193-201.
Abstract: BACKGROUND: The current surgical procedures for irreparable rotator cuff tears have considerable limitations. Tissue engineering techniques using novel scaffold materials offer potential alternatives for managing these conditions. HYPOTHESIS: A chitosan-based hyaluronan hybrid scaffold could enhance type I collagen products with seeded fibroblasts and thereby increase the mechanical strength of regenerated tendon in vivo. STUDY DESIGN: Controlled laboratory study. METHODS: The scaffolds were created from chitosan-based hyaluronan hybrid polymer fibers. Forty-eight rabbit infraspinatus tendons and their humeral insertions were removed to create defects. Each defect was covered with a fibroblast-seeded scaffold (n = 16) or a non-fibroblast-seeded scaffold (n = 16). In the other 16 shoulders, the rotator cuff defect was left free as the control. At 4 and 12 weeks after surgery, the engineered tendons were assessed by histological, immunohistochemical (n = 2), and biomechanical (n = 6) analyses. RESULTS: Type I collagen was only seen in the fibroblast-seeded scaffold and increased in the regenerated tissue. The tensile strength and tangent modulus in the fibroblast-seeded scaffold were significantly improved from 4 to 12 weeks postoperatively. The fibroblast-seeded scaffold had a significantly greater tangent modulus than did the non-fibroblast-seeded scaffold and the control at 12 weeks. CONCLUSION: This scaffold material enhanced the production of type I collagen and led to improved mechanical strength in the regenerated tissues of the rotator cuff in vivo. CLINICAL RELEVANCE: Rotator cuff regeneration is feasible using this tissue engineering technique.

Application of total internal reflection fluorescence microscopy to study cell adhesion to biomaterials
Burmeister, J. S., L. A. Olivier, et al. (1998), Biomaterials 19(4-5): 307-25.
Abstract: Cell adhesion and function depend upon the formation of adhesive contacts between the cell and substrate. Determination of the cell substrate contact area is necessary in order to understand how biomaterial properties influence cell adhesion. In this review we describe the development and application of total internal reflection fluorescence microscopy (TIRFM) to quantify the separation distance of cells from a biomaterial surface. An approximate theory is presented for the straightforward calculation of separation distances when a fluor is placed in the cell membrane. The validity of this approach is discussed. TIRFM is compared to interference reflection microscopy and related techniques that measure cell/substrate separation distances. This approach is then applied to a number of important problems in cell substrate interactions, including changes in contact area and adhesion strength on biomaterial surfaces, analysis of bond strength, and real-time measurement of cell/substrate separation distances following exposure to flow.

Application of X-ray microanalysis to the study of cell physiology in cells attached to biomaterials
Roomans, G. M. (2002), Eur Cell Mater 3: 1-8.
Abstract: X-ray microanalysis is commonly applied in biomaterials research to study changes in biomaterial composition, calcifications, or to identify particulates in tissue that has been in contact with biomaterials. Studies where the effect of biomaterials on the naturally occurring elements in the cells are studied are rare. Exposure to or contact with biomaterials may give rise to several cellular reactions with characteristic changes in elemental patterns. Experimental systems in which cultured cells are exposed to biomaterials, and the resulting changes in elemental content measured by X-ray microanalysis are presented. Proliferation results in an increase in Mg, P and K. Injury and necrosis result in increased Na, Cl and Ca, and decreased K and Mg. The Na/K ratio is a sensitive indicator of cell damage. Apoptosis results in increased Na/K and an increase P/S ratios. Mechanical effects of biomaterials may cause changes in cell-shape or cell volume that may result in volume-regulating ion fluxes, e.g., of chloride, accompanied by efflux of potassium. The multi-element detection capability of X-ray microanalysis makes it particularly suitable to detect these characteristic patterns of changes. The technique can also be used to define sub populations of cells that differ with respect to their reactions to external stimuli.

Applications from bacterial adhesion and biofilm studies in relation to urogenital tissues and biomaterials: a review
Reid, G. (1994), J Ind Microbiol 13(2): 90-6.
Abstract: The urogenital tract, particularly of the adult female, is the habitat for many species of microorganisms. These populations are in a state of flux, are susceptible to disruption by antibiotics and spermicides, and are exposed to many different biomaterial substrata. Infections of the genital area and bladder are common, and are invariably initiated by microbial adhesion to surfaces. This review examines the actual and potential applications to industry and to patients emerging from the study of bacterial adhesion to surfaces.

Applications of biomimetic systems in drug delivery
Venkatesh, S., M. E. Byrne, et al. (2005), Expert Opin Drug Deliv 2(6): 1085-96.
Abstract: This review article highlights recent activities in the field of biomimetic systems and their application in controlled drug delivery. A definition and overview of biomimetic processes is given, with a focus on synthesis and assembly for the creation of novel biomaterials. In particular, systems are classified on the basis of three subsets, which include biological, biohybrid and synthetic structures. Examples focus on the current and proposed clinical significance for systems that mimic processes where the underlying molecular principles are well understood. Biomimetic materials and systems are presented as exceptional candidates for various controlled drug delivery applications and have enormous potential in medicine for the treatment of disease.

Applications of chitin and chitosan for biomaterials
Shigemasa, Y. and S. Minami (1996), Biotechnol Genet Eng Rev 13: 383-420.

Applications of computer modelling for the design of orthopaedic, dental and cardiovascular biomaterials
Vander Sloten, J., M. C. Hobatho, et al. (1998), Proc Inst Mech Eng [H] 212(6): 489-500.
Abstract: Biomaterials do not escape from the general trend present in all contemporary science and technology towards increasing use of computers and information technology. In this paper the use of computer modelling for the design of biomaterials is discussed. The word 'biomaterials' is interpreted in its broadest sense, i.e. referring to any foreign object brought into the body for temporary or permanent use. Computer modelling will first be discussed as a tool to model biological structures (bones, arteries) or to investigate and simulate biological interactions at implant-host interfaces. It will then be illustrated how computer modelling, using insights gained from the modelling of the biological structures themselves, is used in the design process of dental, orthopaedic and cardiovascular prostheses. The area of computer modelling for biomaterials applications has become so vast that an exhaustive overview is impossible in the framework of one paper. Rather, some illustrative case studies will be discussed which are, in the opinion of the authors, representative of general trends in this challenging domain of science on the boundary between engineering and medicine.

Applications of environmental scanning electron microscopy (ESEM) in biomaterials field
Manero, J. M., F. J. Gil, et al. (2003), Microsc Res Tech 61(5): 469-80.
Abstract: Various tasks were undertaken in our laboratory where environmental scanning electron microscopy (ESEM) has been of particular interest within the biomaterials field. The possibility of observing wet samples, as well as the fact that sample preparation is minimal, has improved shorter time scales and lower costs in microscopy. Minimal preparation has also reduced the possibility of introducing artifacts. Examples like cell cultures used for pit resorption assays, calcium phosphate deposition processes, and dissolution of phosphate glasses used as biomaterials are presented. Finally, a servohydraulic testing machine designed for mechanical testing in situ in ESEM has allowed the study of shape memory alloys for orthodontic applications or the behavior of different adhesives used in odontology.

Applications of natural silk protein sericin in biomaterials
Zhang, Y. Q. (2002), Biotechnol Adv 20(2): 91-100.
Abstract: Silk sericin is a natural macromolecular protein derived from silkworm Bombyx mori. During the various stages of producing raw silk and textile, sericin can be recovered for other uses. Also, sericin recovery reduces the environmental impact of silk manufacture. Sericin protein is useful because of its properties. The protein resists oxidation, is antibacterial, UV resistant, and absorbs and releases moisture easily. Sericin protein can be cross-linked, copolymerized, and blended with other macromolecular materials, especially artificial polymers, to produce materials with improved properties. The protein is also used as an improving reagent or a coating material for natural and artificial fibers, fabrics, and articles. The materials modified with sericin and sericin composites are useful as degradable biomaterials, biomedical materials, polymers for forming articles, functional membranes, fibers, and fabrics.

Applications of polymer nanofibers in biomedicine and biotechnology
Venugopal, J. and S. Ramakrishna (2005), Appl Biochem Biotechnol 125(3): 147-58.
Abstract: Recent advancements in the electrospinning method enable the production of ultrafine solid and continuous fibers with diameters ranging from a few nanometers to a few hundred nanometers with controlled surface and internal molecular structures. A wide range of biodegradable biopolymers can be electrospun into mats with specific fiber arrangement and structural integrity. Through secondary processing, the nanofiber surface can be functionalized to display specific biochemical characteristics. It is hypothesized that the large surface area of nanofibers with specific surface chemistry facilitates attachment of cells and control of their cellular functions. These features of nanofiber mats are morphologically and chemically similar to the extracellular matrix of natural tissue, which is characterized by a wide range of pore diameter distribution, high porosity, effective mechanical properties, and specific biochemical properties. The current emphasis of research is on exploiting such properties and focusing on determining appropriate conditions for electrospinning various polymers and biopolymers for eventual applications including multifunctional membranes, biomedical structural elements (scaffolds used in tissue engineering, wound dressing, drug delivery, artificial organs, vascular grafts), protective shields in specialty fabrics, and filter media for submicron particles in the separation industry. This has resulted in the recent applications for polymer nanofibers in the field of biomedicine and biotechnology.

Applications of X-ray powder diffraction in materials chemistry
Skakle, J. (2005), Chem Rec 5(5): 252-62.
Abstract: X-ray powder diffraction is a standard technique in materials chemistry, yet it is often still used in the laboratory as a "one-hit" technique, e.g. for fingerprinting and following the progress of reactions. It is important, however, that the wealth of information available from powder data is not overlooked. While it is only possible here to scratch the surface of possibilities, a range of examples from our research is used to emphasize some of the more accessible techniques and to highlight successes as well as potential problems. The first example is the study of solid solution formation in the oxide systems Ba(3-3x)La(2x)V2O8 and Sr(4-x)Ba(x)Mn3O10 and in the silicate-hydroxyapatite bioceramic, Ca10(PO4)6-x(SiO4)x(OH)2-x. Database mining is also explored, using three phases within the pseudobinary phase diagram Li3SbO4-CuO as examples. All three phases presented different challenges: the structure of Li3SbO4 had been previously reported in higher symmetry than was actually the case, Li3Cu2SbO6 was found to be isostructural with Li2TiO3 but the cation ordering had to be rationalized, and Li3CuSbO5 was believed to be triclinic, presenting challenges in indexing the powder pattern. Quantitative phase analysis is briefly discussed, with the emphasis both on success (determination of amorphous phase content in a novel cadmium arsenate phase) and on possible failure (compositional analysis in bone mineral); the reasons for the problems in the latter are also explored. Finally, the use of an area detector system has been shown to be of value in the study of orientational effects (or lack of them) in non- and partially-ordered biomaterials, including p-HEMA, annulus fibrosis of lumbar discs, and keratin in the horn of cow's hooves.

Applied biomaterials standards report
Daniels, A. U. (1987), J Biomed Mater Res 21(A3 Suppl): 247-50.

Applied biomaterials standards report
Daniels, A. U. (1989), J Biomed Mater Res 23(A1 Suppl): 9-11.
Abstract: The purpose of my column is to provide readers with current information on biomaterials-related standards produced by both private groups and government agencies, and standards-related activities. Standards are descriptive documents given official status by their producers and, in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials. Please consider this column not only a place to obtain biomaterials standards information but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to all members of any and all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows. And last, a caveat--since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in January, 1989.

Aptamer-based capture molecules as a novel coating strategy to promote cell adhesion
Guo, K., H. P. Wendel, et al. (2005), J Cell Mol Med 9(3): 731-6.
Abstract: The improvement of the cytocompatibility of medical implants is a major goal in biomaterials research. During the last years many researchers worked on the fascinating approach to seed the respective cell types on various artificial substrates before implantation. For instance, cell-seeded implants are supposed to be better candidates for transplantable bone substitutes than conventional artificial bone grafts. To improve cell seeding efficiency and cytocompatibility, we designed a new coating material for medical implants. We used aptamers, highly specific cell binding nucleic acids generated by combinatorial chemistry with an in vitro selection called systematic evolution of exponential enrichment (SELEX). Aptamers do have high binding affinity and selectivity to their target. In our study, human osteoblasts from osteosarcoma tissue were used as a target to create the aptamer. Single aptamer mediated cell sorting assays showed the binding affinity with osteoblasts. Additionally, the aptamers immobilized on tissue culture plates could capture osteoblasts directly and rapidly from the cell solution. This model proves that aptamer coated artificial surfaces can greatly enhance cell adhesion. We assume that this strategy is capable to improve the clinical application of tissue engineered implants.

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