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At least 145 records · Page 8Linked to original sources

PubMed1986

Biocompatibility: bioengineering aspects.

Bioengineers have contributed to biocompatibility research. Many materials have been designed, synthesized, and characterized by use of various analytical instruments. The blood compatibility of materials has been studied by focusing on the blood-material interfacial reactions. Although much information has been accumulated regarding such local reactions, understanding of biocompatibility is still limited. A more global approach to study is needed. A new approach to understanding biocompatibility is proposed and discussed. Three points are stressed: interaction within body's defense system and its effect on blood-material reactions; induction of a systemic reaction by a local reaction, which then affects the blood-material interaction; the time sequence of such interactions between local and systemic reactions. To establish a logical approach to study biocompatibility is most important at this moment for the future progress in biocompatibility research.

Biocompatible Materials↗

PubMed1992

Molecular bioengineering of biomaterials in the 1990s and beyond: a growing liaison of polymers with molecular biology.

An important trend in biomaterials research and development is the synthesis of polymers that combine capabilities of biologic recognition (biomimetic) with special physicochemical properties of the synthetic polymer system. Another important trend in such "molecular bioengineering" is to develop, perhaps via computer-aided molecular design, new artificial biomimetic systems by exact placement of functional groups on rigid polymer backbones, cross-linked structures, or macromolecular assemblies. In this way, biocatalytic functioning or biorecognition similar to enzymes and antibodies can be achieved without the inherent instability often encountered with the native biomolecules or assemblies. Perhaps the most exciting trend in biomaterials research and development is the availability of new biomolecules, e.g., via protein engineering and of hardy cells with specific biofunctions and bioresponses that can be tailored to specific medical or biotechnological needs. The wide variety of ways that such biomolecules and cells can be combined with polymeric biomaterials provides tremendously exciting opportunities for the biomaterials scientists and engineers. In addition to these synthetic approaches, new and exciting analytical tools, such as the scanning tunneling microscope and the atomic force microscope, are permitting study on a molecular scale of individual and small clusters of proteins and other biomolecular assemblies on surfaces. Cell attachments and spreading may also be visualized at various depths within the cell using the confocal laser microscope. Such analytical techniques can lead to important new knowledge about biologic interactions with biomaterials and, therefore, to development of even more biocompatible implants and devices. This paper overviews the present state of polymeric biomaterials and highlights the important and exciting opportunities generated by the liaison of these materials with molecular biology.

Biocompatible Materials↗

PubMed1987

Cardiac valve prostheses: pathological and bioengineering considerations.

Cardiac valve replacement with mechanical prosthetic or bioprosthetic devices enhances patient survival and quality of life. Nevertheless, prosthesis-associated complications are frequent and contribute significantly to outcome. Thromboembolic complications are the most important problems in patients with mechanical valves, necessitating chronic anticoagulation in all patients receiving them. In contrast, patients with bioprosthetic valves, composed of chemically treated animal tissues, generally do not require anticoagulants. However, bioprostheses fail frequently by degeneration, especially that involving cuspal calcification. This paper reviews the pathological and bioengineering considerations in the selection of cardiac prosthetic valves and the management of patients who have received these devices. The significance, morphology, and pathogenesis of the observed major complications and other alterations during function are described in detail. Contemporary investigative trends are summarized, including studies of inhibition of mineralization and other degenerative changes in bioprostheses, improved design rigid mechanical valves with pyrolytic carbon occluders and the development of central-flow, flexible polymeric leaflet valves.

Biomedical Engineering↗

PubMed1988

Bioengineering and the patch test.

Several non-invasive techniques based on different physical principles have been developed to investigate skin function and have been used for patch test assessment. In the present paper, the advantages and the defects of these methods are described in the light of the more recent data available in literature. Meanwhile, the eye and the fingers still remain the simplest method to assess skin irritancy. Bioengineering techniques could provide efficient recording systems for monitoring skin color, skin blood flow and barrier function damage, useful to the investigator rather than to the clinician.

Colorimetry↗

PubMed1999

Intra-and inter-individual variations in transepidermal water loss on the face: facial locations for bioengineering studies.

The volar forearm is the favored location for bioengineering studies. However, transepidermal water loss (TEWL), which is an important indicator of the function of the epidermal barrier, shows regional variations, and for the evaluation of cosmetic formulations, facial skin would be more suitable. In this study, we have compared 10 facial locations with 1 test site on the volar forearm for absolute TEWL values, reproducibility, and correlation. Measurements were performed over 3 consecutive days. The TEWL values of the facial test sites were higher compared to forearm values and did not correlate with the forearm. On the face, there was a good correlation between the values of the right compared to the left side of the face. The sites superior to the nervus supraorbitalis, the medial borders of the musculus masseter, and the center of the chin proved to be locations with relatively stable TEWL values. There was a greater variability at the center of the forehead and at the center of the cheeks. It is recommended that TEWL measurements on facial locations with stable TEWL values are used for the evaluation of cosmetic formulations.

Adult↗

PubMed2005

Bioengineered tissues: the science, the technology, and the industry.

OBJECTIVE: The bioengineering of tissues and organs, sometimes called tissue engineering and at other times regenerative medicine, is emerging as a science, as a technology, and as an industry. The goal is the repair, replacement, and/or the regeneration of tissues and organs. The objective of this paper is to identify and discuss the major issues that have become apparent. RESULTS: One of the critical issues is that of cell source, i.e. what will be the source of the cells to be employed? Another critical issue is the development of approaches for the fabrication of substitute tissues/organs and/or vehicles for the delivery of biological active molecules for use in the repair/regeneration of tissues. A third critical issue, one very much related to cell source, is that of immune acceptance. In addition, there are technological hurdles; there are additional issues such as the scale-up of manufacturing processes and the preservation of living-cell products for off-the-shelf availability. Although the initial products have been superficially applied skin substitutes, as this fledgling industry continues to evolve, it is beginning to focus on a wider range of more invasive and complicated products. From a public health perspective, the real opportunity may be in addressing chronic diseases, as well as the transplantation crisis (i.e. the tremendous disparity between patient need for vital organs and donor availability) and, equally important is the challenge of neural repair. CONCLUSION: These are the grand challenges, and the scientific community, business/private sector, and federal government must mobilize itself together in this emerging area to translate the benchtop science to the patient bedside.

Biocompatible Materials↗

PubMed2000

Genetic technologies. Bioengineered food--safety and labeling.

The safety and labeling of genetically engineered foods are two areas that have elicited considerable public concern and debate. This Policy Forum provides a legal analysis of these issues in the context of two bills that have been recently proposed in The U.S. Congress, the Genetically Engineered Food Safety Act and the Genetically Engineered Food Right to Know Act. Most transgenic components of foods currently on the market are plant-incorporated protectants or their inert ingredients. Therefore, they have been evaluated for safety by the Environmental Protection Agency (as well as the Food and Drug Administration), and their disclosure in labeling should not be required. If plant-incorporated protectants are considered safer than chemical pesticides, and chemical pesticides do not have to be disclosed in labels, then bioengineered foods should not be subject to stricter regulation, nor should they be required to be labeled. The two bills are inconsistent, in many respects, with well-established principles of food regulation.

Animals↗

PubMed1997

Bioengineering of emulsifier structure: emulsan analogs.

Strategies were investigated to modulate the side chain structure of emulsans formed by Acinetobacter calcoaceticus RAG-1. Analysis of emulsan fatty acid side chain groups by gas chromatography--mass spectrometry (GC-MS) revealed that by provoking the exogenous n-alkanoic fatty acids 15:0, 16:0, and 17:0, emulsan analogs were formed with 53, 46, and 44 mol%, respectively, of fatty acid substituents with chain lengths equal to that of the carbon source. In contrast, the increase in emulsan fatty acids of chain lengths less than 15 or greater than 17 by providing corresponding shorter and longer chain length fatty acids as carbon sources was not substantial. When [1-13C]-labeled (99% enriched) palmitic acid was used as a carbon source along with acetate, analysis of M/z 75/74 and 87/88 isotopomer ratios by GC-MS indicated that 84 and 86% of the 16:0 (9-cis) side groups, respectively, were incorporated intact from the 16:0 carbon source. The percentage of 14- 15-, 16-, 17-, and 18-carbon chain length fatty acid esters that were monounsaturated were 11, 26, 50, 70, and 85% respectively. Based on the observed percentage of unsaturated chain length dependence and almost identical enrichment at C-1 of 16:0 and 16:1 (9-cis) side groups from [1-13 C]-labeled experiments, it was concluded that desaturation of preformed n-alkanoic acids was the predominant mechanism of their formation. Further work established correlations between side chain structure and product emulsification specificity/activity, so that bioengineered emulsans with improved selectivity can now be formed.

Acinetobacter calcoaceticus↗

PubMed1999

Is occupational irritant contact dermatitis predictable by cutaneous bioengineering methods? Results of the Swiss Metalworkers' Eczema Study (PROMETES).

BACKGROUND: Since identification of subjects with high eczema risk by screening tests is desirable, different skin bioengineering methods were studied for their validity as predictive measures for the development of hand eczema. METHODS: 205 metalworker trainees were followed up over 2.5 years from the beginning of their apprenticeship to observe the occurrence of hand eczema. Within the first weeks of their training they underwent a number of noninvasive biophysical tests. Transepidermal water loss, skin moisture and skin roughness were measured, and irritation tests with dimethyl sulfoxide (DMSO), sodium hydroxide (NaOH) and sodium lauryl sulfate were conducted. Sensitivity, specificity and predictive values of the performed tests and test combinations were calculated. RESULTS: None of the observed single biophysical methods can be considered a valid screening test. CONCLUSION: A combination of short irritation tests (DMSO and NaOH tests) and the measurement of skin moisture, however, allows to identify individuals at high risk for hand dermatitis with a high sensitivity, though low specificity.

Adult↗

PubMed1985

Bioengineering changes in spastic cerebral palsy groups following cerebellar stimulation.

Quantitative bioengineering tests were performed on 30 spastic cerebral palsy (CP) patients who underwent chronic cerebellar stimulation (CCS) using the fully implantable pulse generator (Neurolith 601, 1.1-1.8 microC/cm2/phase). Using respiratory inductive plethysmography to measure 8 patients with paroxysmal and/or ataxic breathing patterns, 5 were shown to revert to normal with 3 others markedly improved within 5 months of CCS. Compliance testing of the ankle was performed on 4 patients who showed improvement in 9 of the 16 tests performed. Motor performance ability was evaluated with 9 comprehensive tests in 17 patients. Following 1-2 weeks of CCS, 52% showed performance increases greater than 10%, increasing to 62% during the first year.

Cerebellum↗

PubMed1991

Skin bioengineering in the noninvasive assessment of cutaneous aging.

Cutaneous changes induced by aging can be quantified and monitored noninvasively by means of bioengineering tools. Skin elasticity, hydration, skin blood flow and skin surface pattern show age-related changes reflecting the damage of cutaneous structures involved. Impairment and degeneration of elastic and collagen networks are responsible for the progressive decrease in skin elasticity recorded during aging. Reduction in blood flow and water supply with probably defective stratum corneum binding result in reduced stratum corneum water content and transepidermal water loss. Morphological changes such as increased skin roughness, pigmentation and alteration of skin surface pattern appearing from the age of 30 years onwards may be investigated at a subclinical level allowing the detection of early signs of aging.

Biomechanical Phenomena↗

PubMed2000

Bioengineered cardiac grafts: A new approach to repair the infarcted myocardium?

BACKGROUND: The myocardium is unable to regenerate because cardiomyocytes cannot replicate after injury. The heart is therefore an attractive target for tissue engineering to replace infarcted myocardium and enhance cardiac function. We tested the feasibility of bioengineering cardiac tissue within novel 3-dimensional (3D) scaffolds. METHODS AND RESULTS: We isolated and grew fetal cardiac cells within 3D porous alginate scaffolds. The cell constructs were cultured for 4 days to evaluate viability and morphology before implantation. Light microscopy revealed that within 2 to 3 days in culture, the dissociated cardiac cells form distinctive, multicellular contracting aggregates within the scaffold pores. Seven days after myocardial infarction, rats were randomized to biograft implantation (n=6) or sham-operation (n=6) into the myocardial scar. Echocardiography study was performed before and 65+/-5 days after implantation to assess left ventricular (LV) remodeling and function. Hearts were harvested 9 weeks after implantation. Visual examination of the biograft revealed intensive neovascularization from the neighboring coronary network. Histological examination revealed the presence of myofibers embedded in collagen fibers and a large number of blood vessels. The specimens showed almost complete disappearance of the scaffold and good integration into the host. Although control animals developed significant LV dilatation accompanied by progressive deterioration in LV contractility, in the biograft-treated rats, attenuation of LV dilatation and no change in LV contractility were observed. CONCLUSIONS: Alginate scaffolds provide a conducive environment to facilitate the 3D culturing of cardiac cells. After implantation into the infarcted myocardium, the biografts stimulated intense neovascularization and attenuated LV dilatation and failure in experimental rats compared with controls. This strategy can be used for regeneration and healing of the infarcted myocardium.

Alginates↗

PubMed2005

Use of telomerase to create bioengineered tissues.

Telomeres are repetitive DNA (TTAGGG) elements at the ends of chromosomes. Telomerase is a ribonucleoprotein complex that catalyzes the addition of telomeric sequences to the ends of chromosomes. The catalytic protein component of telomerase (hTERT) is expressed only in specific germ line cells, proliferative stem cells of renewal tissues, and cancer cells. The expression of hTERT in normal cells reconstitutes telomerase activity and circumvents the induction of senescence. Telomeres shorten with each cell division, eventually leading to senescence (aging), due to incomplete lagging DNA strand synthesis and end-processing events, and because telomerase activity is not detected in most somatic tissues. There are specific tissues and locations in which replicative senescence likely contributes to the decline in human physiological function with increased age and with chronic illnesses. While expressing hTERT in cells results in the maintenance of telomere length and greatly extended life span, blocking replicative aging systemically would be predicted to increase the potential for tumor formation. However, there are many situations in which the transient rejuvenation of cells could be beneficial. Ectopic expression of hTERT has been shown to immortalize human skin keratinocytes, dermal fibroblasts, muscle satellite (stem), and vascular endothelial, myometrial, retinal-pigmented, and breast epithelial cells. In addition, human bronchial, corneal and skin cells expressing hTERT can be used to form organotypic (3D) cultures (bioengineered tissues) that express differentiation-specific proteins, demonstrating that hTERT by itself does not alter normal physiology. The production of hTERT-engineered tissues offers the possibility of producing tissues to treat a variety of chronic diseases and age-related medical conditions that are due to telomere-based replicative senescence.

Aging↗

PubMed1991

Bioengineering in the Department of Mechanical Engineering at the University of Western Australia.

Although bioengineering is not formally taught in the Department of Mechanical Engineering, University of Western Australia, undergraduate and postgraduate projects in this area are very popular among the students. Meetings of the research staff and students working in this area and in tribology in general are organized once a week where the research progress is reported and problems encountered are discussed. Very good collaboration has been established with the Royal Perth Hospital and the Departments of Anatomy and Pathology, University of Western Australia. The Department of Mechanical Engineering, University of Western Australia, has been most helpful over the years in meeting financial needs. The Department has also received over the years some support from the West Australian Arthritic Research Foundation.

Biomechanical Phenomena↗

PubMed2006

Application of bioinformatics for DNA microarray data to bioscience, bioengineering and medical fields.

In the 1990s, DNA microarray or DNA chip as a novel biological experimental technology was developed, which enables the comprehensive measurement of the expression levels of hundreds of genes, simultaneously. Using this technique, a comprehensive understanding of the cell can be achieved. However, because even simple life forms, such as microorganisms, have more than a thousand kinds of genes, the data from a DNA chip cannot be analyzed without statistical and informational technology. Bioinformatics is the interdisciplinary research field integrating molecular biology with informatics, and it is expected to have a huge impact on the bioscientific, bioengineering and medical fields. There are many techniques in bioinformatics for the analysis of DNA microarray data; however, these are mainly divided into fold-change analysis, clustering, classification, genetic network analysis, and simulation. In this review, these techniques are briefly explained by using some examples.

Animals↗

PubMed2000

Multistep production of bioengineered skin substitutes: sequential modulation of culture conditions.

Many studies are being conducted to define the role of growth factors in cutaneous physiology in order to add cytokines in a timely fashion for optimal tissue engineering of skin. This study is aimed at developing a multistep approach for the production of bioengineered skin substitutes, taking into account the effects of various growth factors according to the culture time. The use of a serum-supplemented medium throughout the whole culture period of skin substitutes was compared to the sequential use of specific additives at defined culture steps. Histological analysis revealed that serum was necessary for keratinocyte proliferation and migration on dermal substitutes during the first 2 d after their seeding. However, the serum-free medium presented some advantages when supplemented with different additives at specific culture steps. Interestingly, ascorbic acid added to the dermal substitutes before and after keratinocyte seeding maintained their cuboidal morphology in the basal epidermal layer. In the absence of serum, collagen matrix degradation slowed down, and a better multilayered epidermal organization was obtained, notably with retinoic acid. Stratum corneum formation was also enhanced by fatty acids. Thus, sequential addition of exogenous factors to the medium used to produce skin substitutes can improve their structural features and functional properties in vitro.

Animals↗

PubMed2005

Development of a bioengineered tissue model and its application in the investigation of the depth selectivity of polarization gating.

Understanding the propagation of polarized light in tissue is crucial for a number of biomedical optics applications. Here we report the development of a bioengineered connective tissue model fabricated by the combination of scaffolding and cross-linking techniques to study light transport in biological tissue. It demonstrates great similarity to real connective tissue in its optical properties as well as microarchitecture. Moreover, the optical properties of the model can be reproducibly controlled. As an example, we report the utilization of this model to study the effect of epithelium and the underlying connective tissue on the depth selectivity of polarization gating.

Animals↗

PubMed2004

Dermagraft, a bioengineered human dermal equivalent for the treatment of chronic nonhealing diabetic foot ulcer.

Chronic nonhealing diabetic foot ulcers are a common medical problem that may precede severe complications such as infection, sepsis and limb loss. Current standard methods of treatment are aimed at removing necrotic debris, controlling infection, and relieving chronic pressure on the wound. Unfortunately, healing rates are poor with standard treatment, averaging 12-20 weeks in clinical trials. A new strategy for the treatment of diabetic foot ulcers has been developed through tissue engineering, allowing the application of healthy living skin cells to assist in the healing process. It is hoped that the living tissue will release appropriate quantities of growth factors, cytokines and other proteins to stimulate the chronic wound bed and accelerate healing. Dermagraft (Smith & Nephew) is a neonatal-derived bioengineered tissue comprised of dermal fibroblasts. In this article, the structure and behavior of this tissue will be examined, focusing particularly on the randomized clinical trials performed to justify its use in diabetic foot ulcers.

Bioprosthesis↗