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At least 649 records · Page 36Linked to original sources
PubMed2005

[Tissue engineering of dentin-pulp complex-like structures by human dental mesenchymal cells].

OBJECTIVE: To establish three-dimensional culture model of human dental mesenchymal cells and bioengineer in vivo with ceramic bovine bone (CBB) and Collagraft as scaffolds. METHODS: Human dental mesenchymal cells induced upon stimulation of bFGF and IGF-1 or TGF-beta(1) were implanted onto CBB and Collagraft containing the same kinds of growth factors respectively. Then cell/scaffold constructs were transplanted into nude mice to establish in vivo culture model of dental mesenchymal cells. Control groups were set up at the same time. After 4 weeks or 10 weeks, the implants were taken out for histological and immunohistochemical analysis. RESULTS: Within 10-week implant tissues, typical dentin-pulp complex-like structures were generated in scaffolds containing growth factors. Human dentin sialoprotein (DSP) was expressed in the newly formed dentin. This phenomenon wasn't observed in control groups and 4-week implants. CONCLUSIONS: Dentin-pulp complex-like structures could be bioengineered successfully with human dental mesenchymal cells and CBB or Collagrafts containing growth factors in nude mice.

Animals↗
PubMedDate not supplied

[Progresses and perspectives in cybersurgery].

Aim of this paper is to describe the last progress of surgical robotics owing to the more precise and more reliable instrumentations The surgical robotic applications supported by these technological developments and by the new applications allowed by the outstanding contribution of Electronic Bioengineering Had the possibility to utilise more powerful Telecommunications Networks, essential tool for the data transmission, having an impact in several areas like Telemedicine, Diagnosis and Medical and Surgical Therapy of the patient. The data transmission in real time, that of course is not influenced by the distance, allows a new virtual contact (Map-Volume) and a Clinical three-dimensional Anatomical Space (3D) operative between the surgeon and the complex robotical system. Formed by the Monitor/Controller/Robot Surgeon/patients and distant neighbours. The use of Robotic Surgery, more and more involved in Telemedicine and in the complex system of teleassistance inside the Emergency Centres for all type of catastrophe, will be essential and decisive in the nearer future. In conclusion, many new scenarios with various applications have be opened us for Telerobotic Surgery. Innovations, applications, developments of new systems will involve a greater and greater number of technicians, Doctors, Bioengineers, Clinical Engineers, Informatic Staff in all Telemedicine sectors..

Equipment Design↗
PubMed1989

Neural integration in ocular motility.

The NI is an important part of the ocular motor system; one that determines both normal and certain pathological eye movements. As this chapter has chronicled, bioengineers have played the major role in developing this concept. Early models predicted its use by the ocular motor system for accuracy and stability. Required velocity-to-position signal conversions (i.e., mathematical integration) necessitated its existence in the brain stem. Each type of conjugate eye movement used integration to convert premotor velocity commands into the required position commands. Successful synergistic operation of all subsystems was best served by one common NI but the flexibility and observed independence of certain functions suggested a local NI for the PG. The very nature of integration resulted in the realization that one neuron could not perform this mathematical operation and therefore, the NI was likely to be distributed in several brain stem locations. Finally, the creation of neural network models that accomplish the task of mathematical integration demonstrated the need for reciprocal inhibition. Although the theoretical grounds for some of the hypotheses of bioengineers were not always based in neurophysiology, many of the resulting conclusions are supported by later neurophysiological evidence.

Brain Stem↗
PubMed1989

[Ways of developing the first and second generation biocatalysts for antibiotic production].

Methods for development of bioengineering systems of different types useful in synthesis and transformation of antibiotics are discussed. It was shown that in development of monoenzymatic biocatalysts on the basis of immobilized cells and in preparation of immobilized cultures producing secondary metabolites with enzymological engineering directed action on the cells could be provided which made it possible to establish highly efficient bioengineering systems. Various means for providing the directed action and method for estimation of the carrier-culture interation are proposed. The prospects of using the second generation biocatalysts in improvement of the processes for production of antibiotics are described.

Catalysis↗
PubMed1989

Clinical utilization of the artificial heart.

During the past 30 years the artificial heart has evolved from a bioengineering concept to clinical reality. To date four patients have had an artificial heart implanted as a permanent device, while over 150 artificial hearts have been utilized temporarily as a bridge to cardiac transplantation. Increased use of this device requires that a number of issues be critically addressed: (1) criteria for patient selection; (2) operative techniques for implantation including size of device and its position in the mediastinum; and (3) management of the patient in the intensive care unit (ICU), in particular, regimens of anticoagulation, assessment of adequacy of organ perfusion, and prevention of sepsis. This chapter is a discussion of these bioengineering and clinical concerns with respect to the Jarvik total artificial heart (TAH). Clinical data are presented which highlight the current problems with these devices and the areas of future research that need to be undertaken.

Heart Transplantation↗
PubMedDate not supplied

[An experimental biotechnical system for determining an index of toxicity].

The system of bioengineering for determination of toxicity index with bovine spermatozoal suspension as a primary transducer was developed. The toxicity index is determined according to a change in spermatozoal suspension mobility defined with the help of an optoelectronic device. The system of bioengineering is used for determination of toxicity index of polymers for medical applications.

Animals↗
PubMed1984

Science and standards. RF-hazards and standards: an historical perspective.

The following topics are discussed: Standard of safety considerations. Early efforts in bioengineering and biophysics before and after World War II, Work after World War II (1950s), Early interest in hazards, Soviet work and The Tri-Service area and ANSI. The author concludes that the historical development of biophysics and bioengineering, both as a whole and in the specialty area of nonionizing radiation, proceeded in a fairly rational fashion. Formulation of exposure standards in the West was based on the biophysical approach, which prevails in the interdisciplinary sciences involving biomedical and engineering disciplines. No pressure by an "industrial-military establishment" was evident in the quest for standards, and the Soviet approach and work were under surveillance from the late 1950's. A continuous interest in athermal effects has persisted since the 1930's. Historical accounts are based on personal experience and study of the literature. They are therefore limited to the extent that such experience and study is incomplete. The author had the good fortune to participate over a professional lifetime in the development of biophysical and biomedical engineering sciences, including those that address nonionizing radiation and Western standards of safety.

Biomedical Engineering↗
PubMedDate not supplied

[Control and diagnosis in the biotechnical systems of artificial clearance].

Controlling and diagnostic processes in the bioengineering artificial clearance systems despite of the procedures applied, their functional use and design seem to occur in the artificial organs, each of them consists of controlling and actuating processors ensuring their homogeneous (material, energy-producing, informational) or combined interaction with the patient's body. Centralized control over artificial clearance is proposed by using universal controlling processes which are informationally connected with the operator, the central computer and other controlling processes of the bioengineering system.

Artificial Organs↗
PubMedDate not supplied

Studies on the scale-up of microfiltration membrane devices.

This paper addresses the prediction and modeling of fouling in microfiltration (MF) membrane devices during the filtration of biological solutions. The membrane-fouling model described can be used by bioengineers to characterize a solution's filterability when using a specific microfiltration product line. This allows bioengineers to predict the scale up of filtration from laboratory through clinical production to full marketing production. The model used to correlate filtration results contains two parameters (initial flux and membrane plugging constant) that must be determined experimentally. Once these parameters are known, it is possible to predict the performance (fouling and throughput) of larger membrane devices as a function of operating pressure, processing time, and membrane area. This allows users of MF devices to perform laboratory tests of their solution at relatively small scale, and based on these tests determine the performance of larger-scale MF devices for filtration of the same solution.

Animals↗
PubMed2021

Novel human liver-tropic AAV variants define transferable domains that markedly enhance the human tropism of AAV7 and AAV8.

Recent clinical successes have intensified interest in using adeno-associated virus (AAV) vectors for therapeutic gene delivery. The liver is a key clinical target, given its critical physiological functions and involvement in a wide range of genetic diseases. Here, we report the bioengineering of a set of next-generation AAV vectors, named AAV-SYDs (where "SYD" stands for Sydney, Australia), with increased human hepato-tropism in a liver xenograft mouse model repopulated with primary human hepatocytes. We followed a two-step process that staggered directed evolution and domain-swapping approaches. Using DNA-family shuffling, we first mapped key AAV capsid regions responsible for efficient human hepatocyte transduction in vivo. Focusing on these regions, we next applied domain-swapping strategies to identify and study key capsid residues that enhance primary human hepatocyte uptake and transgene expression. Our findings underscore the potential of AAV-SYDs as liver gene therapy vectors and provide insights into the mechanism responsible for their enhanced transduction profile.

AAV↗
PubMed2003

Treatment of chronic wounds with bone marrow-derived cells.

BACKGROUND: Recent evidence indicates that bone marrow contains stem cells with the potential for differentiation into a variety of tissues, including endothelium, liver, muscle, bone, and skin. It may thus be plausible that bone marrow-derived cells can provide progenitor and/or stem cells to wounds during healing. Our objective in this study was to establish proof of principle that bone marrow-derived cells applied to chronic wounds can lead to closure of nonhealing wounds. We applied autologous bone marrow cells to chronic wounds in 3 patients with wounds of more than 1-year duration. These patients had not previously responded to standard and advanced therapies, including bioengineered skin application and grafting with autologous skin. OBSERVATIONS: Complete closure and evidence of dermal rebuilding was observed in all patients. Findings suggesting engraftment of applied cells was observed in biopsy specimens of treated wounds. Clinical and histologic evidence of reduced scarring was also observed. CONCLUSION: Directly applied bone marrow-derived cells can lead to dermal rebuilding and closure of nonhealing chronic wounds.

Abdominal Wall↗
PubMed2002

Human limbal progenitor cells expanded on intact amniotic membrane ex vivo.

BACKGROUND: The transplantation of human limbal epithelium on amniotic membrane as a substrate is a new treatment for limbal stem cell deficiency. Limbal epithelial stem cells are characterized by a slow cell cycle and the lack of K3 keratin and connexin 43 (Cx43), a gap junction protein. We investigated Cx43 expression, gap junction intercellular communication (GJIC), and proliferative activity of limbal epithelium expanded on amniotic membrane. METHODS: Connexin 43 expression and bromodeoxyuridine (BrdU) incorporation were determined by immunohistology. The GJIC was investigated by a scrape-loading dye transfer assay. Expression of Cx43 and K3 keratin as well as BrdU-retaining nuclei were also analyzed after xenotransplantation in nude mice. RESULTS: Limbal epithelium showed mean +/- SD 12.4% +/- 14.5% positive units of Cx43 expression and a low BrdU labeling index of 2.4% +/- 0.9% (n = 5), of which the latter was due to slow cycling, as proved by its increase to 62.0% +/- 9.5% after continuous BrdU labeling for 5 days. Most of the expanded epithelium did not show GJIC (83%), significantly more than that grown on plastic (6%; P<.002). Basal cells of the stratified epithelium after xenotransplantation did not express Cx43 and K3 keratin, but their nuclei retained BrdU. CONCLUSION: These results support the hypothesis that intact amniotic membrane preferentially preserves and expands Cx43-negative, keratin K3-negative, and GJIC-deficient limbal epithelium, a phenotype resembling that of stem cell-containing limbal basal epithelial cells in vivo. CLINICAL RELEVANCE: Intact amniotic membrane is a suitable substrate for bioengineering limbal epithelia for ocular surface reconstruction.

Amnion↗
PubMed2006

Autologous serum-derived cultivated oral epithelial transplants for severe ocular surface disease.

OBJECTIVE: To evaluate the use of autologous serum (AS)-derived cultivated oral epithelial transplants for the treatment of severe ocular surface disease. METHODS: We used AS from 10 patients with severe ocular surface disease and total limbal stem cell deficiency to develop autologous cultivated oral epithelial equivalents. These were compared with epithelial equivalents derived from conventional fetal bovine serum-supplemented medium. Surgery involved removal of the corneal pannus and surrounding diseased tissue and transplantation of the AS-derived epithelial equivalents. The oral equivalents were analyzed by review of histologic and immunohistochemical findings. RESULTS: Oral epithelial sheets cultivated in AS- and fetal bovine serum-supplemented media were similar in morphology, and both formed basement membrane assembly proteins important for maintaining graft integrity. Complete corneal epithelialization was achieved within 2 to 5 days postoperatively. The ocular surface remained stable without major complications in all eyes during a mean +/- SD follow-up of 12.6 +/- 3.9 months. The visual acuity improved by more than 2 lines in 9 of 10 eyes, with transplanted oral epithelium surviving up to 19 months. CONCLUSION: The successful use of an AS-derived oral epithelial equivalent to treat severe ocular surface disease represents an important advance in the pursuit of completely autologous xenobiotic-free bioengineered ocular equivalents for clinical transplantation.

Adult↗
PubMed1996

Tracheal autograft prefabrication using microfibrillar collagen and bone morphogenetic protein.

OBJECTIVE: To investigate the feasibility of prefabricating a tracheal autograft capable of microvascular free tissue transfer using microfibrillar collagen (Avitene) as a carrier for bone morphogenetic protein (BMP). METHODS AND DESIGN: Using heterotopic bone induction and soft tissue molding, an attempt was made to prefabricate a homologous tracheal autograft in a rodent free flap model. In 12 male Sprague-Dawley rats, linear troughs were dissected along the length of the gracillis muscle, filled with BMP-saturated microfibrillar collagen, molded around a silicone tracheal stent, and left pedicled on the femoral vessels. Untreated microfibrillar collagen was buried in muscle at a distant control site in 3 animals. Autografts were susequently evaluated for lumen integrity, vascular patency, and bone induction at 3 weeks. RESULTS: With the exception of 2 nonviable grafts, rings of heterotopic bone were created in all 10 animals. Rings spanning at least one third of the tracheal circumference maintained a noncollapsible lumen. Microfibrillar collagen was replaced by cancellous bone that reproduced the exact shape and volume of the collagen carrier. The lumen was lined by smooth fibroplasia, and there was no significant inflammatory response, bone exposure, or overgrowth. Soft tissue between rings allowed longitudinal flexibility, homologous to the native trachea. Bone induction did not occur in any of the control sites. CONCLUSIONS: Microfibrillar collagen is an effective carrier for BMP and may serve as the ideal substrate for tracheal reconstruction without the need for stenting. The potential use of BMP to bioengineer microvascular free flaps with intrinsic skeletal support has an unlimited potential and will add a new dimension to head and neck reconstruction.

Animals↗
PubMed2001

Advances in biomedical engineering.

The most visible contributions of biomedical engineering to clinical practice involve instrumentation for diagnosis, therapy, and rehabilitation. Cell and tissue engineering also have emerged as clinical realities. In the next 25 years, advances in electronics, optics, materials, and miniaturization will accelerate development of more sophisticated devices for diagnosis and therapy, such as imaging and virtual surgery. The emerging new field of bioengineering-engineering based in the science of molecular cell biology-will greatly expand the scope of biomedical engineering to tackle challenges in molecular and genomic medicine.

Biocompatible Materials↗
PubMed1998

Deconstructing (and reconstructing) cell migration.

An overriding objective in cell biology is to be able to relate properties of particular molecular components to cell behavioral functions and even physiology. In the "traditional" mode of molecular cell biology, this objective has been tackled on a molecule-by-molecule basis, and in the "future" mode sometimes termed "functional genomics," it might be attacked in a high-throughput, parallel manner. Regardless of the manner of approach, the relationship between molecular-level properties and cell-level function is exceedingly difficult to elucidate because of the large number of relevant components involved, their high degree of interconnectedness, and the inescapable fact that they operate as physico-chemical entities-according to the laws of kinetics and mechanics-in space and time within the cell. Cell migration is a prominent representative example of such a cell behavioral function that requires increased understanding for both scientific and technological advance. This article presents a framework, derived from an engineering perspective regarding complex systems, intended to aid in developing improved understanding of how properties of molecular components influence the function of cell migration. That is, cell population migration behavior can be deconstructed as follows: first in terms of a mathematical model comprising cell population parameters (random motility, chemotaxis/haptotaxis, and chemokinesis/haptokinesis coefficients), which in turn depend on characteristics of individual cell paths that can be analyzed in terms of a mathematical model comprising individual cell parameters (translocation speed, directional persistence time, chemotactic/haptotactic index), which in turn depend on cell-level physical processes underlying motility (membrane extension and retraction, cell/substratum adhesion, cell contractile force, front-vs.-rear asymmetry), which in turn depend on molecular-level properties of the plethora of components involved in governance and regulation of these processes. Hence, the influence of any molecular component on cell population migration can be understood by reconstructing these relationships from the molecular level to the physical process level to the individual cell path level to the cell population distribution level. This approach requires combining experimental, theoretical, and computational methodologies from molecular biology, biochemistry, biophysics, and bioengineering.

Cell Count↗
PubMed1993

Surgical management of pelvic and extremity osteosarcoma.

Between 60-80% of all patients with osteosarcomas of the pelvis and the extremities can now be safely treated with limb-sparing surgery. Results (as defined by rates of local recurrence, overall survival, and function) are equal to or better than those associated with amputation. Successful use of limb-sparing procedures, however, depends on a well-developed surgical plan. An understanding of the biologic behavior and growth patterns of these lesions is fundamental. Staging of the primary tumor must involve a full complement of imaging modalities, including plain radiography, bone scintigraphy, computerized axial tomography (CAT), magnetic resonance imaging (MRI), and angiography. The biopsy must be well placed to reduce the possibility of tissue contamination, which is a common reason for amputation. Restaging is necessary before surgery for patients who have undergone neoadjuvant therapy; there is recent evidence that preoperative therapy may make limb-sparing surgery possible in more than 50% of patients who otherwise would have required amputation. Relative contraindications to limb-sparing surgery include major involvement of the neurovascular bundle, pathologic fracture, inappropriate biopsy site, infection, immature skeletal age, and extensive muscle involvement. Each of these factors is relative, and patient selection decisions must be made on an individual basis. Limb-sparing surgery consists of the following three phases: tumor resection, skeletal reconstruction, and soft tissue and muscle transfers. The range of reconstruction techniques has been broadened by developments in bioengineering. Among the more commonly used techniques are custom endoprostheses and allograft replacements. Future progress in induction regimens and reconstructive techniques will undoubtedly enable limb-sparing surgery to be a satisfactory alternative to amputation in even more patients.

Amputation, Surgical↗
PubMed2000

Semi-interpenetrating polymer networks composed of biocompatible phospholipid polymer and segmented polyurethane.

2-Methacryloyloxyethyl phosphorylcholine (MPC) polymers, which have excellent biocompatibility, have been receiving increasing attention in biomedical and bioengineering fields; however, the mechanical strength of the hydrated MPC polymers is not sufficient for use in these fields as a bulk material. Therefore, we hypothesized that a novel material might be realized by reinforcing the MPC polymer network with segmented polyurethane (SPU). Semi-interpenetrating polymer networks (IPNs) composed of crosslinked MPC polymer and SPU were prepared. The mechanical properties of the IPN membrane were significantly improved compared with those of the MPC polymer membrane. Three-dimensional polymer networks of the MPC polymer in the IPNs were observed after solvent extraction of SPU. An X-ray photoelectron spectrum analysis revealed that the MPC units were exposed on the IPN surface. When the IPN was alternately soaked in water and ethanol, the swelling ratio was found to be completely reversible and no disintegration of the network structure was observed. The permeation coefficient of 1, 4-di(2-hydroxyethoxy)benzene through the IPN membrane was 1.11 x 10(-7) cm(-2)s(-1). The amount of adsorbed protein and the number of adherent platelets on the IPN membrane were effectively reduced compared with those on SPU. We concluded that IPNs composed of the MPC polymer and SPU are a new bulk biomaterial, which possesses both blood compatibility and good mechanical properties.

Absorption↗