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At least 343 records · Page 19Linked to original sources
PubMed1978

Bioengineering aspects of the artificial pancreas.

In this paper, results of work aimed at the development of artificial beta-cells are presented. An electrolytically driven pump is considered to be a proper device for insulin injection. The transient characteristics of the simplified version of such a pump make it suitable for application in open-loop devices. Methods for electrical control of the injection rate of this pump for application in closed-loop artificial beta-cells are given. An essential component of a closed-loop artificial beta-cell is a glucose sensor. A modified version of the glucose sensor has been developed and its performance is described. Considerations of some control problems related to the artificial pancreas are briefly discussed.

Animals↗
PubMed1986

Immunomodulation: bioengineering aspects.

Plasmapheresis is generally recognized as a "black box" therapy. Factors effecting the immunomodulating influence of plasmapheresis and their impact on the clinical results include the disease state and stage, associated drug and medical therapies, and the methodology of plasmapheresis. The immunomodulating influence of the methodology of plasmapheresis, including duration of treatment, frequency of treatment, equipment type, materials choice, anticoagulant choice, and volume replacement versus selective removal, has a profound impact on the clinical results. Limitations in the design of controlled trials emphasize the importance of assessing the events occurring within and as a result of the individual black box utilized in plasmapheresis therapy. The analysis and understanding of the immunomodulating influences of the "black box" will prove to be very valuable in the development of better technologies for patient care.

Biocompatible Materials↗
PubMed1992

Monitoring of skin response to sodium lauryl sulphate: clinical scores versus bioengineering methods.

The present trial was designed to evaluate clinical scores (single observer) of sodium lauryl sulphate (SLS)-induced skin irritation in a group of subjects (n = 10) over a 10-day period along with various skin function parameters. In order to avoid significant variations due to secondary phenomena, the following parameters were recorded with non-invasive instruments in this order: skin capacitance (C1; arbitrary units; CM420 Corneometer), transepidermal water loss (TEWL; g/m2.h; Evaporimeter) and laser Doppler flowmetry (CBFV: cutaneous blood flow values; Periflux). All examinations were performed during winter on reclined relaxed subjects present for at least 10 min in a test room with controlled temperature and relative humidity (t degrees: 19.5-20.7 degrees C and RH: 47.3-60.3%). The analysis of differential data (delta = value at tx-value before test; 2-way ANOVA) was made on single parameters as a function of site (volar forearm versus neck) and time (from 24 h after 48-h occlusion with 5% SLS up to 10 days later). The profile of erythema scores over time differed between neck and forearm, but the delta CBFV readings with the laser Doppler instrument did not detect significant site-time interactions. Roughness (blind evaluation with palpating finger) and capacitance readings (delta C1) showed significant differences between sites, but the profile over time was similar in both locations. delta TEWL did not differ according to anatomical location. The reason for different erythema scores on neck and forearm might be related to inherent regional variation of optical properties of the skin or to a substantial contribution of SLS-induced roughness to the readings of erythema.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Skin irritation in man: a comparative bioengineering study using improved reflectance spectroscopy.

Variable types of skin irritation were induced in 8 human female volunteers, ranging from subclinical to visible erythema with slight oedema. Skin reactions were graded clinically and objectively using transepidermal water loss (TEWL), laser Doppler flowmetry (LDF) and improved reflectance spectroscopy. This last technique enables separation of in vivo erythemas into relatively deoxygenated (venous--deoxy hem) and oxygenated (arterial--oxy hem) haemoglobin components. Compared to uninvolved skin, an empty patch increased oxy hem by 197% +/- 121% (p < 0.05). Exposure to vehicles also changes skin biophysics. At sodium lauryl sulfate (SLS) and hydrochloric acid (HCl) exposed sites, a linear correlation between concentration and oxy hem, LDF and TEWL was found. These chemicals predominantly increased TEWL values. Nonanoic acid (NON) and imipramine (IMI) also raised oxy hem, LDF and TEWL values linearly at increasing concentrations. Although IMI 2.5% clinically was graded as a type ++ response, no significant increase in TEWL was found. The improved reflectance spectroscopic technique proved valid in skin irritation studies, with a higher sensitivity than laser Doppler flowmetry, and allowed irritant vascular reactions to be discriminated into arterial and venous components. Furthermore, our observations clearly demonstrate that clinically indistinguishable skin irritation reactions induce significantly different changes in barrier function (disruption) and vascular status.

Adult↗
PubMed1997

The efficacy of different moisturizers on barrier recovery in hairless mice evaluated by non-invasive bioengineering methods. A model to select the potentially most effective product.

Moisturizers (emollients) are used frequently on normal and diseased skin. However, only few studies have examined their effects in dynamic situations and in more clinically relevant settings. We evaluated the effect of 4 commonly used products in a hairless mice model after acute skin barrier perturbation with acetone. The efficacy was evaluated by measurement of the transepidermal water loss (TEWL) and electrical conductance at various time intervals during barrier repair. The test products were compared with acetone-treated air-exposed controls allowed to recover otherwise normally and with a known irritant product, chlorhexidine cream 1%. Locobase was the most effective product in correcting barrier function and significantly improved barrier function during early stages of barrier recovery (< 6 h) without interfering with late stages of barrier recovery (> 6 h). The irritant control product, chlorhexidine cream 1%, delayed barrier recovery in the late stages. The model makes it possible to evaluate the combined effects of exogenous and endogenous components on barrier repair and to select the potentially most effective products before performing more cumbersome and time-consuming field studies.

Acetone↗
PubMed2005

Actively regulating bioengineered tissue and organ formation.

OBJECTIVES: Describe current and future approaches to tissue engineering, specifically in the area of bone regeneration. These approaches will allow one to actively regulate the cellular populations participating in this process. DESIGN: Many approaches to actively regulate cellular phenotype are under exploration, and these typically exploit known signal transduction pathways via presentation of specific receptor-binding ligands, and may also deliver mechanical information via the physical bridge formed by the receptor-ligand interactions. Cellular gene expression may also be directly modulated utilizing gene therapy approaches to control tissue regeneration. CONCLUSIONS: Significant progress has been made to date in bone regeneration using inductive molecules and transplanted cells, and FDA approved therapies have resulted. While approaches to date have focused on delivery of single stimuli (e.g. one growth factor), future efforts will likely attempt to more closely mimic developmental processes by the delivery of multiple inputs to the cells in spatially and temporally regulated fashions.

Biocompatible Materials↗
PubMed2005

Current concepts in periodontal bioengineering.

Repair of tooth supporting alveolar bone defects caused by periodontal and peri-implant tissue destruction is a major goal of reconstructive therapy. Oral and craniofacial tissue engineering has been achieved with limited success by the utilization of a variety of approaches such as cell-occlusive barrier membranes, bone substitutes and autogenous block grafting techniques. Signaling molecules such as growth factors have been used to restore lost tooth support because of damage by periodontal disease or trauma. This paper will review emerging periodontal therapies in the areas of materials science, growth factor biology and cell/gene therapy. Several different polymer delivery systems that aid in the targeting of proteins, genes and cells to periodontal and peri-implant defects will be highlighted. Results from preclinical and clinical trials will be reviewed using the topical application of bone morphogenetic proteins (BMP-2 and BMP-7) and platelet-derived growth factor-BB (PDGF) for periodontal and peri-implant regeneration. The paper concludes with recent research on the use of ex vivo and in vivo gene delivery strategies via gene therapy vectors encoding growth promoting and inhibiting molecules (PDGF, BMP, noggin and others) to regenerate periodontal structures including bone, periodontal ligament and cementum.

Animals↗
PubMed2001

The role of a bioengineered artificial kidney in renal failure.

Renal failure continues to carry substantial burden of morbidity and mortality in both acute and chronic forms, despite advances in transplantation and dialysis. There is evidence to suggest that the kidney has metabolic, endocrine, and immune effects transcending its filtration functions, even beyond secretion of renin and erythropoietin. Our laboratory has developed experience in the tissue culture of renal parenchymal cells, and has now been able to demonstrate the metabolic activity of these cells in an extracorporeal circuit recapitulating glomerulotubular anatomy. We have observed active transport of sodium, glucose, and glutathione. We describe the design and initial preclinical testing of the bioartificial kidney, as well as future directions of our research.

Animals↗
PubMed2002

Molecular signaling in bioengineered tissue microenvironments.

Biological tissues and organs consist of specialized living cells arrayed within a complex structural and functional framework known generally as the extracellular matrix (ECM). The great diversity observed in the morphology and composition of the ECM contributes enormously to the properties and function of each organ and tissue. For example, the ECM contributes to the rigidity and tensile strength of bone, the resilience of cartilage, the flexibility and hydrostatic strength of blood vessels, and the elasticity of skin. The ECM is also important during growth, development, and wound repair: its own dynamic composition acts as a reservoir for soluble signaling molecules and mediates signals from other sources to migrating, proliferating, and differentiating cells. Artificial three-dimensional substitutes for ECM, called tissue scaffolds, may consist of natural or synthetic polymers or a combination of both. Scaffolds have been used successfully alone and in combination with cells and soluble factors to induce tissue formation or promote tissue repair. Appropriate numbers of properly functioning living cells are central to many tissue-engineering strategies, and significant efforts have been made to identify and propagate pluripotent stem cells and lineage-restricted progenitor cells. The study of these and other living cells in artificial microenvironments, in turn, has led to the identification of signaling events important for their controlled proliferation, proper differentiation, and optimal function.

Animals↗