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PubMed2006

Sintering and robocasting of beta-tricalcium phosphate scaffolds for orthopaedic applications.

beta-Tricalcium phosphate (beta-TCP) scaffolds with designed, three-dimensional (3-D) geometry and mesoscale porosity have been fabricated by direct-write assembly (robocasting) techniques. Concentrated beta-TCP inks with suitable viscoelastic properties were developed to enable the fabrication of the complex 3-D structures. A comprehensive study of the sintering behavior of TCP as a function of the calcium content in the starting powder was also carried out, and the optimal heat treatment for fabricating scaffolds with dense beta-TCP rods has been determined. Such analysis provides clues to controlling the microstructure of the fabricated structures and, therefore, enabling the fabrication by robocasting of TCP scaffolds with tailored performance for bone tissue engineering applications.

Biocompatible Materials↗
PubMed2006

Engineered riboswitches as novel tools in molecular biology.

During the last years the great importance of RNA for regulating gene expression in all organisms has become obvious. Consequently, several recent approaches aim to utilize the outstanding chemical properties of RNA to develop artificial RNA regulators for conditional gene expression systems. A combination of rational design, in vitro selection and in vivo screening systems has been used to create a versatile set of RNA based molecular switches. These tools rely on diverse mechanisms and exhibit activity in several organisms. In this review, we summarize recent developments in the application of engineered riboswitches for gene regulation in vivo.

Aptamers, Nucleotide↗
PubMed2001

Extensive in vivo angiogenesis following controlled release of human vascular endothelial cell growth factor: implications for tissue engineering and wound healing.

Vascular endothelial cell growth factor (VEGF) has strong stimulating effects on vascularization. Though very potent, VEGF is rapidly degraded due to its short half-life and when administrated by uncontrolled and nonspecific methods; however, its systemic administration in large doses can cause harmful side effects. Controlled release technology would allow delivering desired levels of bioactive VEGF within extended periods and permit examination of the in vivo effects of the compound in a broader way. The objective of this study was to determine the in vitro release behavior of VEGF from calcium alginate microspheres and the potency of this controlled release system in promoting localized neovascularization at the subcutaneous site of the rat model. In vitro release of human VEGF165 (2 and 4 microg/cm3 microsphere) was studied for 3 weeks under static conditions at 25 degrees C, and daily hormone release was measured using a competitive enzyme immunoassay. Following an uncontrolled release within the first 4 days, a quite constant zero-order VEGF release of 50 to 90 and 70 to 120 ng/day was achieved from 2 and 4 microg/cm3 polymer loaded microspheres respectively. In vivo angiogenesis was studied for a period of 8 weeks and evaluated using immunoperoidase staining and histopathological measurements. In vivo studies with rats (n = 24) showed a considerable level of capillary network formation at the epigastric groin fascia of VEGF microsphere-implanted rats starting from the first week. The most extensive neovascularization was observed in the group with 3 week postimplanted 4 microg VEGF containing microspheres; this level of vascularization was quite similar after 8 weeks. While the control group showed no evidence of angiogenesis, the difference in VEGF-induced neovascularization is statistically significant (p < 0.03). Immunostaining of the specimens showed a strong relationship between the release of human VEGF and neovascularization. The controlled VEGF release system described here promotes vigorous angiogenesis and has applicability for tissue engineering and wound healing studies.

Animals↗
PubMed2001

Biomechanics of cardiovascular development.

It long has been known that mechanical forces play a role in the development of the cardiovascular system, but only recently have biomechanical engineers begun to explore this field. This paper reviews some of this work. First, an overview of the relevant biology is discussed. Next, a mechanical theory is presented that can be used to model developmental processes. The theory includes the effects of finite volumetric growth and active contractile forces. Finally, applications of this and other theories to problems of cardiovascular development are discussed, and some future directions are suggested. The intent is to stimulate further interest among engineers in this important area of research.

Animals↗
PubMed2000

Cytokine delivery and tissue engineering.

Tissue engineering has been applied to various tissues, and particularly significant progress has been made in the areas of skin, cartilage, and bone regeneration. Inclusion of bioactive factors into the synthetic scaffolds has been suggested as one of the possible tissue engineering strategies. The growth factors are polypeptides that transmit signals to modulate cellular activities. They have short half-lives, for example, platelet-derived growth factor (PDGF), isolated from platelets, has a half life of less than 2 minutes when injected intravenously. Extended biological activity and the controlled release of growth factor are achieved by incorporating growth factor into the polymeric device. This review will focus on growth factor delivery for tissue engineering. Particular examples will be given whereby growth factors are delivered from a tissue-engineered device to facilitate wound healing and tissue repair.

Animals↗
PubMed2001

New experimental and theoretical tools for metabolic engineering of micro-organisms.

Presently an increasing gap is developing between our experimental capabilities in metabolic engineering of microbial metabolism and our quantitative theoretical understanding of the kinetic interaction between primary metabolism and product pathways. Such theoretical understanding is absolutely needed for a rational design of said metabolic engineering experiments and targets. To obtain such understanding in-vivo kinetic experiments and in-vivo kinetic models are needed. To this end the following new methods for in-vivo kinetic studies of Saccharomyces cerevisiae have recently been developed. The Bioscope device allows the reliable and repeated perturbation (e.g. glucose pulse, or inhibitor etc.) of steady state biomass outside the fermentor and subsequent sampling and quenching to measure glycolytical intermediates and nucleotides in a time frame of 0-70 seconds. Dynamic modelling of fermentor off-gas O2/CO2-measurements allows to calculate O2 uptake and CO2 production rates in such a perturbation experiment (0-70 seconds time windows). A new LC-MSMS based method has been developed to measure large sets of intracellular metabolites in said in-vivo kinetic experiments. It has been shown for the first time that in long chemostat cultivation (up to 800 hrs.) intracellular metabolites levels drop, showing absence of a real steady state. A new kinetic format, lin log kinetics, has been developed for describing the intracellular kinetic behavior of metabolic networks. This format allows general analytical solutions of networks flux, metabolic levels. From simulation studies it appears that this approach is remarkable accurate in describing intracellular metabolite dynamics and in metabolic design questions of where to change enzyme levels and how much to achieve a desired change in fluxes and metabolite levels. At this moment these tools are being applied in metabolic engineering studies of Saccharomyces cerevisiae and Penicillin chrysogenum.

Adenosine Triphosphate↗
PubMed1998

Tissue engineering: the first decade and beyond.

This article reviews the important developments in the field of tissue engineering over the last 10 years. Research in the area of biomaterials is examined from the perspective of providing the foundation for the development of tissue engineering. Early efforts combining cells with biocompatible materials are described and applications of this technology presented, with particular focus on uses in orthopaedics and maxillofacial surgery. The basic principles of tissue engineering and state-of-the-art technology in cell biology and materials science as used currently in the field are presented. Finally, futures challenges are outlined from the perspective of integrating technologies from medicine, biology, and engineering, in hopes of translating tissue engineering to clinical applications.

Animals↗
PubMed1995

Clinical engineering helps reduce equipment costs.

Clinical engineering involves, among other activities, managing equipment repair and maintenance activities, assessing technology needs and potential equipment acquisitions, training users, negotiating service contracts, and optimizing patient-care equipment utilization. Effective clinical engineering programs can help healthcare organizations reduce the high cost of acquiring and maintaining patient care equipment.

Biomedical Engineering↗
PubMed2006

The state of the art of nanobioscience in Japan.

This paper reviews a part of the state of the art of nanobioscience in Japan. The importance of combination and integration of interdisciplinary principles is emphasized for the development of nanobioscience. Biomagnetics, biomechanics, nanomachining, self-replicating cell model, neuronal network, drug delivery system, and tissue engineering are discussed.

Biological Science Disciplines↗
PubMed2000

Matrices for tissue engineering-scaffold structure for a bioartificial liver support system.

This study proposes a new composite scaffold system. A woven polyethylenterephtalate (PET) fabric was coated on one side with a biodegradable PLGA film, in order to obtain a geometrically polarized scaffold structure for an bioartificial liver support system. The composite structure ensures the stability of the membrane during degradation of the membrane polymer. The mesh size of the composite does not significantly influence the degradation behavior. Hepatocyte culturing studies reveal that the formation of aggregates depends on the mesh size and on the pretreatment: The largest aggregates could be observed after 48 h when PVLA coating, large mesh size and EGF were combined. Thus, the combination of a geometrically structured, partially degradable scaffold with receptor-mediated cell attachment sites offers promising possibilities in liver tissue engineering.

Animals↗