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At least 793 records · Page 44Linked to original sources
PubMed2004

Contractile cardiac grafts using a novel nanofibrous mesh.

Cardiomyoctes are terminally differentiated cells and therefore unable to regenerate after infarction. The use of autologous bioengineered cardiac grafts has been suggested to replace infarcted myocardium and enhance cardiac function. Here we report the development of an in vitro system for engineered myocardium. Cardiac nanofibrous meshes (CNM) were developed by culturing cardiomyocytes from neonatal Lewis rats on electrospun, nanofibrous polycaprolactone (PCL) meshes. The mesh had an ECM-like topography and was suspended across a wire ring that acted as a passive load to contracting cardiomyocytes. The cardiomyocytes started beating after 3 days and were cultured in vitro for 14 days. The cardiomyocytes attached well on the PCL meshes and expressed cardiac-specific proteins such as alpha-myosin heavy chain, connexin43 and cardiac troponin I. The results demonstrate the formation of contractile cardiac grafts in vitro. Using this technique, cardiac grafts can be matured in vitro to obtain sufficient function prior to implantation. It is conjectured that cardiac grafts with clinically relevant dimensions can be obtained by stacking CNMs and inducing vascularization with angiogenic factors.

Animals↗
PubMed2004

Synthesis and characterization of partially biodegradable, temperature and pH sensitive Dex-MA/PNIPAAm hydrogels.

The objective of the study is to impart temperature and pH-sensitive capabilities to polysaccharide-based hydrogels, so that they can change their swelling property upon external stimulation like temperature or/and pH. Dextran was chosen as the model polysaccharide compound for such a demonstration. A novel class of dextran-maleic anhydride (Dex-MA)/poly(N-isopropylacrylamide) hybrid hydrogels was designed and synthesized by UV photocrosslinking. The dextran-based precursor (Dex-MA) was prepared by substituting the hydroxyl groups in Dex by MA. This Dex-MA precursor was then photocrosslinked with a known temperature sensitive precursor (N-isopropylacrylamide, NIPAAm) to form hybrid hydrogels having a wide range of composition ratio of Dex-MA to NIPAAm precursors. Due to the biodegradable nature of dextran, these Dex-MA/PNIPAAm hybrid hydrogels are partially biodegradable. These smart hybrid hydrogels were characterized by Fourier transform infrared spectroscopy for structural determination, differential scanning calorimertry for thermal property, maximum swelling ratio, swelling kinetics, temperature response kinetics, and effect of pH. The data obtained clearly show that these new smart hybrid hydrogels were responsive to the external changes of temperature as well as pH. The magnitude of smart and hydrogel properties of these hybrid hydrogels were found to depend on the feed composition ratio of the two precursors. By changing the composition ratio of these two precursors, the phase transition temperature (lower critical solution temperature) of the hybrid hydrogels could also be adjusted to be or near the body temperature for the potential applications in bioengineering and biotechnology fields.

Absorption↗
PubMed2004

Synthetic elastin hydrogels derived from massive elastic assemblies of self-organized human protein monomers.

A key objective of bioengineering is the development of new scaffolding biomaterials with appropriate mechanical and biological properties such as strength, elasticity and biocompatibility that mimic the native host connective tissue. Here we describe the production and properties of massive synthetic elastin assemblies formed by chemically cross-linking recombinant human tropoelastin with bis(sulfosuccinimidyl) suberate, permitting the construction of elastic sponges, sheets and tubes. The innate characteristics of synthetic elastin constructs are common with those of native elastin. The Young's Modulus ranged from 220 to 280 kPa with linearity of extension to at least 150%. Synthetic elastin was extensible by 200-370%. The constructs behaved as hydrogels and displayed stimuli-responsive characteristics towards temperature and salt concentrations. Intrinsic fluorescence spectroscopy demonstrated that the elastin fluorophore is a feature of the polypeptide. Scanning electron microscopy allowed us to construct a model of elastin assembly that was driven by the lateral association of small twisted rope-like fibrils. FT-Raman spectra at 100% strain gave amide I and III peaks that correlated with a stretch-dependent increase in alpha-helical content. Growth and proliferation of cells were supported in vitro while in vivo implants were well tolerated. We conclude that synthetic elastin has potential as a novel biomaterial that can be easily molded into a variety of shaped tissue substrates and has a range of properties that are required for elastic, cell-interacting and compliant applications. Furthermore, its in vitro construction provides a powerful tool to probe the early stages of elastin assembly and the molecular basis for its elasticity.

Animals↗
PubMed2005

Size control of calcium alginate beads containing living cells using micro-nozzle array.

Size-controlled small (i.e. less than 300 microm) polyelectrolyte complex gel beads are urgently desired for wide-spread application, including use in medical, pharmaceutical, and bioengineering fields. However, it was impossible to obtain smaller beads less than 300 microm with conventional apparatuses. We developed a novel microfluidics device that utilizes silicon micro-nozzle (MN) array, enabling to produce 50-200 microm calcium alginate beads with a narrow size distribution. Alginate aqueous solution was extruded through a precisely fabricated thin (30 microm x 30 microm) and short (500 microm) MN and was sheared by the viscous drag force of oil flow to form alginate droplets. Alginate droplets were immediately reacted with CaCl2 droplets at the downstream of oil flow to form calcium alginate gel beads. This device enabled us to successfully encapsulate living cells into 162 microm calcium alginate beads with maintaining viability, which was confirmed by the expression of marker protein.

Alginates↗
PubMed2005

The effect of bioactive glasses on bone marrow stromal cells differentiation.

Bone marrow is a mixture of hematopoietic, vascular, stromal and mesenchymal cells capable of skeletal repair/regeneration thanks to the ability of bone marrow cells to differentiate into osteoblasts and osteoclasts. This ability is important in tissue regeneration during fracture healing, or for successful osteointegration of implanted prostheses, and in bone remodelling. Therefore, bone marrow cell culture systems seem to be useful and relatively close to in vivo conditions models to study interactions occurring at the cell-material interface of implants directed to hard tissue engineering. The purpose of this study was to investigate the ability of three bioactive glasses (45S, 58S and 77S) to induce osteogenic differentiation and cell mineralisation. A significant effect of the 45S and 77S bioactive materials was seen on early differentiation of the marrow stromal cells into osteoblast-like cells. 45S bioglass evidenced also the highest effect on cell mineralisation at the same level as cells treated with dexametasone, used as positive control. 77S treated cells evidenced also a significant inhibition in the number of multinucleated TRAP-positive cells (ostoclast-like cells) in comparison with the control untreated cells and in marrow cells treated with 45S and 58S bioactive glasses. These findings have potential implications and applications for tissue engineering where three-dimensional bioactive glass substrates could be used as scaffolds for in vitro production of bioengineered bone.

Animals↗
PubMed2005

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications.

Superparamagnetic iron oxide nanoparticles (SPION) with appropriate surface chemistry have been widely used experimentally for numerous in vivo applications such as magnetic resonance imaging contrast enhancement, tissue repair, immunoassay, detoxification of biological fluids, hyperthermia, drug delivery and in cell separation, etc. All these biomedical and bioengineering applications require that these nanoparticles have high magnetization values and size smaller than 100 nm with overall narrow particle size distribution, so that the particles have uniform physical and chemical properties. In addition, these applications need special surface coating of the magnetic particles, which has to be not only non-toxic and biocompatible but also allow a targetable delivery with particle localization in a specific area. To this end, most work in this field has been done in improving the biocompatibility of the materials, but only a few scientific investigations and developments have been carried out in improving the quality of magnetic particles, their size distribution, their shape and surface in addition to characterizing them to get a protocol for the quality control of these particles. Nature of surface coatings and their subsequent geometric arrangement on the nanoparticles determine not only the overall size of the colloid but also play a significant role in biokinetics and biodistribution of nanoparticles in the body. The types of specific coating, or derivatization, for these nanoparticles depend on the end application and should be chosen by keeping a particular application in mind, whether it be aimed at inflammation response or anti-cancer agents. Magnetic nanoparticles can bind to drugs, proteins, enzymes, antibodies, or nucleotides and can be directed to an organ, tissue, or tumour using an external magnetic field or can be heated in alternating magnetic fields for use in hyperthermia. This review discusses the synthetic chemistry, fluid stabilization and surface modification of superparamagnetic iron oxide nanoparticles, as well as their use for above biomedical applications.

Animals↗
PubMed2005

Polyurethane films seeded with embryonic stem cell-derived cardiomyocytes for use in cardiac tissue engineering applications.

Cardiomyocytes are terminally differentiated cells and therefore unable to regenerate heart tissue after infarction. The successful engraftment of various cell types resulting in improved cardiac function has been reported, however methods for improving the delivery of donor cells to the infarct site still need to be developed. The use of bioengineered cardiac grafts has been suggested to replace infarcted myocardium and enhance cardiac function. In this study, we cultured embryonic stem (ES) cell-derived cardiomyocytes on thin polyurethane (PU) films. The films were coated with gelatin, laminin or collagen IV in order to encourage cell adhesion. Constructs were examined for 30 days after seeding. Cells cultured on laminin and collagen IV, exhibited preferential attachment, as assessed by cellular counts, and viability assays. These surfaces also resulted in a greater number of contracting films compared to controls. A degradable elastomer seeded with embryonic stem cell-derived cardiomyocytes may hold potential for the repair of damaged heart tissue.

Bioprosthesis↗
PubMed2006

Micromolding of photocrosslinkable chitosan hydrogel for spheroid microarray and co-cultures.

Bioengineering approaches, such as co-cultures of multiple cell types, that aim to mimic the physiological microenvironment may be beneficial for optimizing cell function and for engineering tissues in vitro. This study describes a novel method for preparing a spheroid microarray on microfabricated hydrogels, alone or in co-cultures. Photocrosslinkable chitosan was synthesized and utilized for fabricating hydrogel microstructures through a micromolding process. The chitosan surface was initially cell repellent but became increasingly cell adhesive over time. By using this unique property of chitosan hydrogels, it was possible to generate patterned co-cultures of spheroids and support cells. In this scheme, cells were initially microarrayed within low shear stress regions of microwells. Human hepatoblastoma cells, Hep G2, seeded in these wells formed spheroids with controlled sizes and shapes and stably secreted albumin during the culture period. The change of cell adhesive properties in the chitosan surface facilitated the adhesion and growth of a second cell type, NIH-3T3 fibroblast, and therefore enabled co-cultures of hepatocyte spheroids and fibroblast monolayers. This co-culture system could be a useful platform for studying heterotypic cell-cell interactions, for drug screening, and for developing implantable bioartificial organs.

Animals↗
PubMed2006

Micro-finite element models of bone tissue-engineering scaffolds.

Tissue engineering is an emerging area in bioengineering at the frontiers between biomaterials, biology and biomechanics. The basic knowledge of the interactions between mechanical stimuli, cells and biomaterials is growing but the quantitative effect of mechanical stimuli on cells attached to biomaterials is still unknown. The objective of this study was to develop finite element models of various bone scaffolds based on calcium phosphate in order to calculate the load transfer from the biomaterial structure to the biological entities. Samples of porous calcium phosphate bone cement and biodegradable glass were scanned using micro-CT to determine the overall macroporosity, architecture and to develop finite element models of such materials. Compressive loads were applied on the models to simulate the in vitro environment of a bioreactor and stress and strain distributions were calculated. It was found that the effective Young's modulus was linearly related to the sample macroporosity. Results suggest that a 0.5% overall compressive strain can produce internal strain of the same order of magnitude as found in previous in vitro mechanically cell-strained studies or in mechanoregulation studies. Stress and strain concentrations due to the porous structures are possible candidate for favouring cell differentiation. Although strain distributions were similar between bone cement and porous glass, the stress distribution is clearly different. Future in vitro results could correlate the results obtained with such finite element study to explain the influence of mechanical stimuli on cell behaviour.

Bone Cements↗
PubMed2004

Characterization of two polyketide synthase genes in Exophiala lecanii-corni, a melanized fungus with bioremediation potential.

Exophiala lecanii-corni has significant bioremediation potential because it can degrade a wide range of volatile organic compounds. In order to identify sites for the insertion of genes that might enhance this potential, a genetic analysis of E. lecanii-corni was undertaken. Two polyketide synthase genes, ElPKS1 and ElPKS2, have now been discovered by a PCR-based strategy. ElPKS1 was isolated by a marker rescue technique. The nucleotide sequence of ElPKS1 consists of a 6576-bp open reading frame encoding a protein with 2192 amino acids, which was interrupted by a 60-bp intron near the 5' end and a 54-bp intron near the 3' end. Sequence analysis, results from disruption experiments, and physiological tests showed that ElPKS1 encoded a polyketide synthase required for melanin biosynthesis. Since ElPKS1 is non-essential, it is a desirable bioengineering target site for the insertion of native and foreign genes. The successful expression of these genes could enhance the bioremediation capability of the organism. ElPKS2 was cloned by colony hybridization screening of a partial genomic library with an ElPKS2 PCR product. ElPKS2 had a 6465-bp open reading frame that encoded 2155 amino acids and had introns of 56, 67, 54, and 71 bp. Although sequence analysis of the derived protein of ElPKS2 confirmed the polyketide synthase nature of its protein product, the function of that product remains unclear.

Amino Acid Sequence↗
PubMed2005

Biodiesel production from heterotrophic microalgal oil.

The present study introduced an integrated method for the production of biodiesel from microalgal oil. Heterotrophic growth of Chlorella protothecoides resulted in the accumulation of high lipid content (55%) in cells. Large amount of microalgal oil was efficiently extracted from these heterotrophic cells by using n-hexane. Biodiesel comparable to conventional diesel was obtained from heterotrophic microalgal oil by acidic transesterification. The best process combination was 100% catalyst quantity (based on oil weight) with 56:1 molar ratio of methanol to oil at temperature of 30 degrees C, which reduced product specific gravity from an initial value of 0.912 to a final value of 0.8637 in about 4h of reaction time. The results suggested that the new process, which combined bioengineering and transesterification, was a feasible and effective method for the production of high quality biodiesel from microalgal oil.

Biotechnology↗
PubMed2004

Oligonucleotide-modified screen-printed gold electrodes for enzyme-amplified sensing of nucleic acids.

An electrochemical genosensor for the detection of specific sequences of DNA has been developed using disposable screen-printed gold electrodes. Screen-printed gold electrodes were firstly modified with a mixed monolayer of a 25-mer thiol-tethered DNA probe and a spacer thiol, 6-mercapto-1-hexanol (MCH). The DNA probe sequence was internal to the sequence of the 35S promoter, which sequence is inserted in the genome of GMOs regulating the transgene expression. An enzyme-amplified detection scheme, based on the coupling of a streptavidin-alkaline phosphatase conjugate and biotinylated target sequences was then applied. The enzyme catalysed the hydrolysis of the electroinactive alpha-naphthyl phosphate to alpha-naphthol; this product is electroactive and has been detected by means of differential pulse voltammetry. The assay was, firstly, characterised using synthetic oligonucleotides. Relevant parameters, such as the probe concentration and the immobilisation time, the use of the MCH and different enzymatic conjugates, were investigated and optimised. The genosensor response was found to be linearly related to the target concentration between 0 and 25 nmol/L; the detection limit was 0.25 nmol/L. The analytical procedure was then applied for the detection of the 35S promoter sequence, which was amplified from the pBI121 plasmid by polymerase chain reaction (PCR). Hybridisation conditions (i.e., hybridisation buffer and hybridisation time) were further optimised. The selectivity of the assay was confirmed using biotinylated non-complementary amplicons and PCR blanks. The results showed that the genosensor enabled sensitive (detection limit: 1 nmol/L) and specific detection of GMO-related sequences, thus providing a useful tool for the screening analysis of bioengineered food samples.

Alkaline Phosphatase↗
PubMed2005

Sonochemically fabricated acetylcholinesterase micro-electrode arrays within a flow injection analyser for the determination of organophosphate pesticides.

This report describes the development of novel sonochemically fabricated, bioengineered acetylcholinesterase and polyaniline carbon/cobalt phthalocyanine biosensors for the ultra-sensitive determination of a number of different pesticides. Arrays of this type typically have population micro-electrode densities of up to approximately 2 x 10(5) cm(-2); these represent the highest micro-electrode population densities reported to date by any fabrication means. The enzymatic response of the sensors is inhibited upon incubation with the pesticide, and we have shown that Dichlorvos, Parathion and Azinphos may be determined down to concentrations of approximately 1 x 10(-17) M, approximately 1 x 10(-16) M and approximately 1 x 10(-16) M, respectively. These lower limits of detection are lower than otherwise achievable by any other analytical approach. Measurements were performed within a custom built flow injection system that operates at a constant flow of 1 ml min(-1). Sensor stability studies were also performed whereby a stabilizer mixture of sucrose and polygalacturonic acid was added to the immobilised enzyme matrix at the working electrode and left to dry. Sixty-five percent of the initial enzyme activity was found to remain after a period of 92 days to allow storage of these electrodes and facilitating transportation if required.

Acetylcholinesterase↗
PubMed2005

Design and fabrication of a largely deformable sensorized polymer actuator.

Polypyrrole (PPy), with its biomimetic properties such as high power density, large strain, and biocompatibility, is an excellent candidate for a biomimetic microactuator in microrobotics and bioengineering. A polyvinylidene fluorid (PVDF) sensor is also biocompatible, flexible, and chemically stable. Therefore, a PPy actuator is integrated with a PVDF sensor to realize a sensorized polymer actuator. A novel sensorized polymer actuator can accurately measure its bending motion precisely with real time. Experimental results demonstrate the feasibility of the sensorized polymer actuator. The polymer actuator can be actuated while it senses signals induced from the bending motion. In addition, the position of the sensorized polymer actuator can be controlled and adjusted precisely with feedback signals from its embedded sensor at the time of operation. If this system becomes more robust and reliable, its applications are promising and can be realized in cell handling, microrobotics, and microsurgery with the integration of standard microfabrication techniques.

Biocompatible Materials↗
PubMed2003

Intelligent infrastructure for sustainable potable water: a roundtable for emerging transnational research and technology development needs.

PROBLEM STATEMENT: Recent commercial and residential development have substantially impacted the fluxes and quality of water that recharge the aquifers and discharges to streams, lakes and wetlands and, ultimately, is recycled for potable use. Whereas the contaminant sources may be varied in scope and composition, these issues of urban water sustainability are of public health concern at all levels of economic development worldwide, and require cheap and innovative environmental sensing capabilities and interactive monitoring networks, as well as tailored distributed water treatment technologies. To address this need, a roundtable was organized to explore the potential role of advances in biotechnology and bioengineering to aid in developing causative relationships between spatial and temporal changes in urbanization patterns and groundwater and surface water quality parameters, and to address aspects of socioeconomic constraints in implementing sustainable exploitation of water resources. WORKSHOP OUTCOMES: An interactive framework for quantitative analysis of the coupling between human and natural systems requires integrating information derived from online and offline point measurements with Geographic Information Systems (GIS)-based remote sensing imagery analysis, groundwater-surface water hydrologic fluxes and water quality data to assess the vulnerability of potable water supplies. Spatially referenced data to inform uncertainty-based dynamic models can be used to rank watershed-specific stressors and receptors to guide researchers and policymakers in the development of targeted sensing and monitoring technologies, as well as tailored control measures for risk mitigation of potable water from microbial and chemical environmental contamination. The enabling technologies encompass: (i) distributed sensing approaches for microbial and chemical contamination (e.g. pathogens, endocrine disruptors); (ii) distributed application-specific, and infrastructure-adaptive water treatment systems; (iii) geostatistical integration of monitoring data and GIS layers; and (iv) systems analysis of microbial and chemical proliferation in distribution systems. IMPACT: This operational framework is aimed at technology implementation while maximizing economic and public health benefits. The outcomes of the roundtable will further research agendas in information technology-based monitoring infrastructure development, integration of processes and spatial analysis, as well as in new educational and training platforms for students, practitioners and regulators. The potential for technology diffusion to emerging economies with limited financial resources is substantial.

Conservation of Natural Resources↗
PubMed2005

Enzymatic modification of phospholipids for functional applications and human nutrition.

Rapid progress in biochemistry of phospholipids and evolution of modern bioengineering has brought forth a number of novel concepts and technical advancements in the modification of phospholipids for industrial applications and human nutrition. Highlights cover preparation of novel phospholipid analogs based on the latest understanding of pivotal role of phospholipids in manifold biological processes, exploration of remarkable application potentials of phospholipids in meliorating human health, as well as development of new chemical and biotechnological approaches applied to the modification of phospholipids. This work reviews the natural occurrence and structural characteristics of phospholipids, their updated knowledge on manifold biological and nutritional functions, traditional and novel physical and chemical approaches to modify phospholipids as well as their applications to obtain novel phospholipids, and brief introduction of the efforts focusing on de novo syntheses of phospholipids. Special attention is given to the summary of molecular structural characteristics and catalytic properties of multiple phospholipases, which helps to interpret experimental phenomena and to improve reaction design. This will of course provide fundamental bases also for the development of enzymatic technology to produce structured or modified phospholipids.

Food Analysis↗
PubMed2004

The buccal fad pad lined with a metabolic active dermal replacement (Dermagraft) for treatment of defects of the buccal plane.

The buccal fad pad flap (BFPF) is an easy to raise pedicled flap for closure of intraoral defects with barely any donor defect. The major disadvantage of the BFPF is the missing epithelial lining, which can induce fibrous tissue formation with resulting functional impairment. To overcome this problem we lined the BFPF with a dermal replacement (Dermagraft) consisting of living metabolic active fibroblasts. In six patients, defects resulting from tumour removal were reconstructed with a combination of the BFPF and Dermagraft and followed up for at least 2 years. In all patients a defect closure was achieved with no functional impairment. The clinical character which was achieved was more a type of defect regeneration than a flap closure. The availability of bioengineered metabolic active tissue can overcome the major problem of the BFPF as an option for defect closure of the buccal side. Furthermore the regeneration of the defects optimises clinical tumour monitoring.

Aged↗
PubMed2006

An experimental study on the repair of full skin loss of nude mice with composite graft of epidermal stem cells.

This study is to constitute a composite skin substitute with epidermal stem cells (ESCs) and fibroblasts on collagen sponge. ESCs were selected by rapid attachment to collagen IV for 10 min. Collagen was extracted from rat's tail. The matrix lattice was fabricated by freeze-dryer and cross-linked with glutaraldehyde. Fibroblasts were inoculated on collagen sponge and cultured for 1 week prior to inoculation of ESCs. Having cultured for 2 weeks in submerged culture, the bioengineered tissue was raised to the air-liquid interface and cultured for 2 weeks. The artificial skin was then grafted onto full skin loss wounds of nude mice. Collagen sponge membrane lacking cell inoculation and an artificial skin with epidermal cells (ECs) and fibroblasts were used as controls. The wounds were observed daily. Tissue samples were harvested and examined by means of histology, immunohistochemistry and electron microscopy. The wounds in the test group healed at a significantly faster rate than controls, with good skin appearance and minimal scar formation. The control group showed delayed wound healing and intensive wound contraction as compared to the test group. Thus the skin substitute with ESCs seemed to be a good equivalent.

Animals↗