Biomaterials.info - Resources for Engineers

Record 1081 to 1100

Biomaterials: applications----innovations----principles: the contributions of C. William Hall
Andrade, J. D. (1985), J Biomed Mater Res 19(9): 981-6.
Abstract: Bill Hall has always had practical goals and objectives, be it an artificial heart, a cardiac assist device, a percutaneous lead, an artificial skin, or a direct skeletal attachment endoprosthesis. Always a careful analysis of the problem, with a keen understanding and appreciation of the biologic and physiologic nature and properties of the tissues with which he was working and must interface, led to innovative approaches which permitted him to work with, rather than against, natural biologic forces and processes. Bill Hall's understanding and practical successes have led to a set of principles that will help guide the education and development of future generations of biomaterial scientists and engineers, and through them and their medical coworkers, the development and application of devices and methods for patient treatment.

Biomaterials: everything old is new again
Asa, R. (1993), CDS Rev 86(4): 8-12.

Biomaterials: selection and complications
Vitale, T. D. and L. M. Fallat (1988), J Foot Surg 27(6): 533-40.
Abstract: Basic concepts of bioengineering and biomechanics are presented. The application of these various terms explain the mechanical and physical properties of biomaterials widely used in implanted devices. An explanation and literature review explains the possible biocompatibility reactions to these implants.

Biomaterials: silk's secrets
Atkins, E. (2003), Nature 424(6952): 1010.

Biomaterials: Stable antifouling surfaces
Nuzzo, R. G. (2003), Nat Mater 2(4): 207-8.

Biomaterials: taming the beast
Spector, M. (1992), J Biomed Mater Res 26(1): 1-5.

Biomaterials: the new frontiers in spine surgery
Gunzburg, R., M. Szpalski, et al. (2001), Eur Spine J 10 Suppl 2: S85.

Biomaterials: thwarting thrombus
Keefer, L. K. (2003), Nat Mater 2(6): 357-8.

Biomaterials: where we have been and where we are going
Ratner, B. D. and S. J. Bryant (2004), Annu Rev Biomed Eng 6: 41-75.
Abstract: Since its inception just over a half century ago, the field of biomaterials has seen a consistent growth with a steady introduction of new ideas and productive branches. This review describes where we have been, the state of the art today, and where we might be in 10 or 20 years. Herein, we highlight some of the latest advancements in biomaterials that aim to control biological responses and ultimately heal. This new generation of biomaterials includes surface modification of materials to overcome nonspecific protein adsorption in vivo, precision immobilization of signaling groups on surfaces, development of synthetic materials with controlled properties for drug and cell carriers, biologically inspired materials that mimic natural processes, and design of sophisticated three-dimensional (3-D) architectures to produce well-defined patterns for diagnostics, e.g., biological microelectromechanical systems (bioMEMs), and tissue engineering.

Biomaterials-related programs and initiatives at the National Heart, Lung, and Blood Institute
Didisheim, P. (1991), J Vasc Surg 13(5): 729.

Biomechanical and allergological characteristics of a biodegradable poly(D,L-lactic acid) coating for orthopaedic implants
Gollwitzer, H., P. Thomas, et al. (2005), J Orthop Res 23(4): 802-9.
Abstract: A poly(D,L-lactic acid) surface coating (PDLLA) has been developed to optimize interactions at the implant-tissue interface. Mechanical and allergological characteristics were evaluated in the present study to elucidate possible indications and limitations prior to clinical application. Implants of stainless steel and Ti-6Al-4V and Co-Cr-Mo alloys were coated with PDLLA, and mechanical stability was studied during intramedullary implantation into rat and human cadaver bones and during dilation of coronary artery stents. Elongation resistance was examined on AlMgSi alloy specimens. Furthermore, proliferation of peripheral blood mononuclear cells of nickel-allergic donors and controls and interleukin-4 and interferon-gamma levels were measured in the presence of coated/uncoated implants and after stimulation with phytohemagglutinin or NiSO4. PDLLA remained stable on the implants with a minimum of 96% of the original coating mass and tolerated lengthening of at least 8%. Further lengthening was followed by microcracking and cohesive failure within the coating. PDLLA exerted no suppressive effect upon spontaneous and pan-T-cell mitogen inducible T-cell proliferation. Furthermore, specific proliferation to nickel in cells of nickel-allergic blood donors and production of interleukin-4 and IFN-gamma were not influenced by the coating. PDLLA coating proved high mechanical stability on different orthopaedic implants and did not influence in vitro T-cell reactivity towards specific biomaterials.

Biomechanical and biomaterial considerations of natural teeth, tooth replacements, and skeletal fixation
Buch, J. D., J. G. Crose, et al. (1974), Biomater Med Devices Artif Organs 2(1): 171-86.

Biomechanical research on junction system of bone with biomaterials
Nishihara, K. and S. Nakagiri (1994), Biomed Mater Eng 4(3): 151-9.
Abstract: Regarding the junction of bioceramics with original bone, which have quite different material constants of Young's modulus and Poisson's ratio from each other, synostosis (ankylosis) cannot be obtained under severe loading conditions. Therefore, it is necessary to introduce a new junction system for the interface between the biomaterial mechanical organ and original bone. The jointing system of dental root to jawbone reflects on the function against mastication. The interface between different mechanical organs with different materials necessitates a specific juncture system under severe loading because of the disparity of material constants. The authors already reported the result of studies on the shape effect of artificial roots in functioning jawbone by means of finite element analysis. Studies on the functional effect of artificial roots in undulated shape were carried out biomechanically by means of finite element analysis using models to investigate an effective juncture system between bone and biomaterials. The results of finite element analysis were compared with the findings obtained from histological specimens. To observe the juncture state of bioceramics with tubular bone cortex, tubular apatite artificial bone was implanted in the femur of a dog. From these studies, the following results and conclusions were obtained: (a) The fibrous juncture system around bioceramics has an important role, after which the principal stress trajectories are converted; and (b) optimal undulated morphology compatible to the artificial bone's juncture system by means of fibrous ligament is essential for remodeling of the bone around the artificial skeletal bone.

Biomedical coatings to improve the tissue-biomaterial interface
Rizzi, G., A. Scrivani, et al. (2004), Int J Artif Organs 27(8): 649-57.
Abstract: One of the most important factors determining the degree of tissue interaction of an implanted device is the property of its surface. Thus, great importance is given to chemical and morphological characteristics of biomaterial surfaces to improve biocompatibility, cell migration, proliferation and differentiation, mechanical stability and endogenous tissue ingrowth. In order to obtain new and healing stimulating properties, it is possible to apply a coating or more generally a surface treatment to the surface of a prosthetic device. One of the most versatile methods for coating is thermal spray technology. This paper considers the principle of thermal spray processes and their application in the biomedical field, namely the coatings used for orthopedic prostheses and dental implants. Among thermal spray processes, plasma spray as well as High Velocity Oxygen Fuel (HVOF) processes will be particularly considered and their most important aspects will be illustrated.

Biomembranes, ion channels and new biomaterials
Chapman, D. and P. I. Haris (1996), Biochem Soc Trans 24(2): 329-40.

Biometric surfactant polymers designed for shear-stable endothelialization on biomaterials
Sagnella, S., F. Kligman, et al. (2003), J Biomed Mater Res A 67(3): 689-701.
Abstract: We have developed a series of extracellular matrix (ECM)-like biomimetic surfactant polymers to improve endothelial cell adhesion and growth on vascular biomaterials. These polymers provide a single-step procedure for modifying the surface of existing biomaterials and consist of a poly(vinyl amine) (PVAm) backbone with varying ratios of cell-binding peptide (RGD) to carbohydrate (maltose), ranging from 100% RGD:0% maltose to 50% RGD:50% maltose. Three biomimetic surfaces, as well as a fibronectin (FN)-coated glass surface were seeded at confluence with human pulmonary artery endothelial cells (HPAECs) and exposed to shear stresses ranging from 0-40.6 dyn/cm2 for periods of 2 h and 6 h. Surfaces were examined for HPAEC coverage and cytoskeletal arrangement as a function of time and shear stress. In general, after 6 h of shear exposure, EC retention on 100% RGD > FN > 75% RGD > 50% RGD. The 100% RGD surface maintained more than 50% of its initial EC monolayer at low to moderate shear stresses whereas all other surfaces dropped to approximately 40% or less in the same shear stress range. The most stable surface, 100% RGD, showed a significant increase in cytoskeletal organization at all shear stresses greater than 2.5 dyn/cm2. In contrast, there was no real change in cytoskeletal organization on the FN surface, and there was a decrease on the 75% RGD surface over time. These results indicate that increasing surface peptide density can control EC shear stability. Furthermore, improved shear stability increases with increasing peptide density and is related to the EC's ability to reorganize its cytoskeleton.

Biomimetic deposition of apatite coating on surface-modified NiTi alloy
Gu, Y. W., B. Y. Tay, et al. (2005), Biomaterials 26(34): 6916-23.
Abstract: TiO(2) coatings were prepared on NiTi alloy by heat treatment in air at 300, 400, 600 and 800 degrees C. The heat-treated NiTi alloy was subsequently immersed in a simulated body fluid for the biomimetic deposition of the apatite layer onto the surface of TiO(2) coating. The apatite coatings as well as the surface oxide layer on NiTi alloy were characterized using scanning electron microscopy equipped with energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. Results showed the samples heat-treated at 600 degrees C produced a layer of anatase and rutile TiO(2) on the surface of NiTi. No TiO(2) was detected on the surface of NiTi after heat treatment at 300 and 400 degrees C by X-ray diffraction, while rutile was formed on the surface of the 800 degrees C heat-treated sample. It was found that the 600 degrees C heat-treated NiTi induced a layer consisted of microcrystalline carbonate containing hydroxyapatite on its surface most effectively, while 300 and 400 degrees C heat-treated NiTi did not form apatite. This was due to the presence of anatase and/or rutile in the 600 and 800 degrees C heat-treated NiTi which could provide atomic arrangements in their crystal structures suitable for the epitaxy of apatite crystals, and anatase had better apatite-forming ability than rutile. XPS and Raman results revealed that this apatite layer was a carbonated and non-stoichiometric apatite with Ca/P ratio of 1.53, which was similar to the human bone. The formation of apatite on 600 degrees C heat-treated NiTi following immersion in SBF for 3 days indicated that the surface modified NiTi possessed excellent bioactivity.

Biomimetic peptide-amphiphiles for functional biomaterials: the role of GRGDSP and PHSRN
Mardilovich, A. and E. Kokkoli (2004), Biomacromolecules 5(3): 950-7.
Abstract: The study we present involves the use of a biomimetic system that allows us to study specific interactions in the alpha(5)beta(1) receptor-GRGDSP ligand system with an atomic force microscope (AFM). Bioartificial membranes that mimic the adhesion domain of the extracellular matrix protein fibronectin are constructed from peptide-amphiphiles. A novel peptide-amphiphile is designed that contains both GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro, the primary recognition site for alpha(5)beta(1)) and PHSRN (Pro-His-Ser-Arg-Asn, the synergy binding site for alpha(5)beta(1)) sequences in a single peptide formulation, separated by a spacer. Two different antibodies are used to immobilize and activate isolated alpha(5)beta(1) integrins on the AFM tip. The interaction measured between immobilized alpha(5)beta(1) integrins and peptide-amphiphiles is specific for integrin-peptide binding and is affected by divalent cations in a way that accurately mimics the adhesion function of the alpha(5)beta(1) receptor. The strength of the PHSRN synergistic effect depends on the accessibility of this sequence to alpha(5)beta(1) integrins. An increase in adhesion is observed compared to surfaces displaying only GRGDSP peptides when the new biomimetic peptide-amphiphiles are diluted with lipidated poly(ethylene glycol), which provides more space for the peptide headgroups to bend and expose more of the PHSRN at the interface.

Biomimetism and bioinspiration as tools for the design of innovative materials and systems
Sanchez, C., H. Arribart, et al. (2005), Nat Mater 4(4): 277-88.
Abstract: Materials found in nature combine many inspiring properties such as sophistication, miniaturization, hierarchical organizations, hybridation, resistance and adaptability. Elucidating the basic components and building principles selected by evolution to propose more reliable, efficient and environment-respecting materials requires a multidisciplinary approach.

Biomodels of bone: a review
Lohfeld, S., V. Barron, et al. (2005), Ann Biomed Eng 33(10): 1295-311.
Abstract: In this paper, a definition of a biomodel is presented, based on which different specific types of biomodels are identified, viz., virtual biomodels, computational biomodels, and physical biomodels. The paper then focuses on both physical and virtual biomodels of bone, and presents a review of model generation methodologies, giving examples of typical biomodel applications. The use of macroscale biomodels for such issues as the design and preclinical testing of surgical implants and preoperative planning is discussed. At the microscale, biomodels of trabecular bone are examined and the link with scaffolds for tissue engineering is established. Conclusions are drawn on the state of the art, and the major developments necessary for the continued expansion of the field are identified. Finally, arguments are given on the benefits of integrating the use of the different types of biomodels reviewed in this paper, for the benefit of future research in biomechanics and biomaterials.

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