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Physiological Environment (physiological + environment)
Selected AbstractsThe Prospects of Carrying and Releasing Drugs Via Biodegradable Magnesium Foam,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Eli Aghion Abstract Powder metallurgy technology was used to produce magnesium foams in order to evaluate their ability to perform as a solid biodegradable platform for drug delivery. The amount and delivery time of the released drug (gentamicin) was controlled by the level of space-holding particles (spacer) that was mixed with the magnesium powder prior to the sintering process. Metallurgical examination of the magnesium foams was carried out using optical and scanning electron microscopy (SEM) and X-ray diffraction analysis. Microtomography CT analysis was used to evaluate the structural characteristics of the magnesium foams and their internal interconnected porosity configuration. The corrosion behavior of the magnesium foams was evaluated by immersion test in a simulated physiological environment (PBS solution). The absorption of gentamicin was obtained by immersing magnesium foams in concentrated gentamicin solutions within a vacuum chamber, followed by water evaporation. The detection of gentamicin in PBS solution was carried out using a Fluorescence Polarimetry analyzer. The results show that the release profile of gentamicin from magnesium foam with 10 and 25% spacer in PBS solution was in accord with common dissolution kinetics of an active ingredient from polymeric drug delivery systems. [source] Fabrication of Galactosylated Polyethylenimine and Plasmid DNA Multilayers on poly (D,L -lactic acid) Films for in situ Targeted Gene Transfection,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Yan Hu This study presents surface-mediated targeted in situ gene delivery from gene-tagged poly(D,L -lactic acid) (PDLLA) films, which were fabricated via a layer-by-layer (LbL) assembly technique with galactosylated polyethylenimine (GP) and plasmid DNA (pDNA, pSV-,-galactosidase). A linear growth of GP/pDNA multilayered films was observed. The pDNA was continuously released from multilayered films for over 32,h. The multilayered structure degraded and simultaneously formed GP/pDNA complexes in situ when exposing to a physiological environment. The pDNA was well protected by GP against DNase I digestion within formed GP/pDNA complexes. Our results demonstrated that GP contributes to receptor-mediated targeting for cell uptake and in situ gene transfection. The results reported here are potentially important for gene therapy, surface engineering of biomaterials, tissue engineering and implant technology. [source] Controlling the biodegradation rate of magnesium using biomimetic apatite coatingJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Yajing Zhang Abstract Magnesium is light, biocompatible and has similar mechanical properties to natural bone, so it has the potential to be used as a biodegradable material for orthopedic applications. However, pure magnesium severely corrodes in a physiological environment, which may result in fracture prior to substantial tissue healing. Hydroxyapatite (HA) is the main composition of natural bone. It has excellent bioactivity and osteoconductivity. In this study, HA coating with two different thicknesses was applied onto the surface of pure magnesium substrates using a biomimetic technique. The corrosion rate of the surface-treated substrates was tested. It was found that both types of coatings substantially slowed down the corrosion of the substrate, and the dual coating was more effective than the single coating in hindering the degradation of the substrate. Thus, the corrosion rate of magnesium implants can be closely tailored by adjusting apatite coating thickness and thereby monitoring the release of magnesium ions into the body. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Whole-blood aggregometry: are there any limits with regard to platelet counts?ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2009A. M. MENGISTU Background: Whole-blood aggregometry (WBA) is a promising tool to assess platelet function in its physiological environment. Dilution of whole blood in WBA disregards platelet concentrations that may impact the results, especially in the case of low platelet counts. In a blinded, prospective in vitro study, the influence of platelet concentrations on WBA was assessed. Methods: Aggregation studies were carried out using whole blood from 10 healthy volunteers adjusted to platelet concentrations of 150, 100, 75, 50 and 25/nl using a plasma-balanced crystalloid solution. Platelet aggregation was measured by a new near-side whole blood aggregometer, activated by adenosin-diphosphate, collagen and thrombin-receptor activating protein. Three different approaches were applied: P1: whole blood diluted by an isotonic saline solution before activation, P2: undiluted whole blood with the single and P3: with the twofold concentration of the stimulating agent. Results: Aggregometry in diluted whole blood (P1) decreased significantly from a platelet concentration of 100/nl (P<0.01). In undiluted whole blood, aggregation declined significantly from concentrations of 75 and 50/nl for P2 and P3 (P<0.01). No correlation to platelet count occurred in the undiluted approaches until a platelet concentration of 75/nl, whereas correlation in the diluted test run was detected starting from 100/nl. Conclusions: This study demonstrates that WBA depends on the platelet count and sensitivity towards low platelet concentrations may be improved by abdication of further dilution and the use of undiluted whole blood. [source] Alternative drug delivery approaches for the therapy of inflammatory bowel diseaseJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2008Yvette Meissner Abstract This article shall give an overview on drug delivery systems for new therapeutic strategies in the treatment of inflammatory bowel disease. The various features of the different approaches allowing locally restricted drug delivery to the inflamed colon are discussed including the main physiological and pathophysiological limitations for the different systems. Conventional drug delivery systems are tightly adapted from developments for colonic delivery by oral administration triggered by release mechanisms owing to the physiological environment that these systems encounter in the colonic region. The newer developments in this context aim for an increased selectivity of drug delivery by targeting mechanisms which have a closer relation to pathophysiological particularities of the disease. Therefore, we were focused especially on new strategies for such treatment including liposomal formulations, cyclodextrins, micro- or nanoparticles, viral gene therapy approaches, and others. Effective and selective delivery even of an otherwise nonspecifically acting drug could provide new therapeutic pathways in the treatment of inflammatory bowel disease. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 2878,2891, 2008 [source] In-vitro evaluation of khaya and albizia gums as compression coatings for drug targeting to the colonJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2005Oluwatoyin A. Odeku Khaya and albizia gums were evaluated as compression coatings for target drug delivery to the colon using indometacin (a water insoluble drug) and paracetamol (a water soluble drug) as model drugs. The core tablets were compression-coated with 300 and 400mg of 100% khaya gum, 100% albizia gum and a mixture of khaya and albizia gum (1:1). Drug release studies were carried out in 0.1M HCI (pH 1.2) for 2h, Sorensen's buffer (pH 7.4) for 3 h and then in phosphate-buffered saline (pH 6.8) or in simulated colonic fluid for the rest of the experiment to mimic the physiological conditions from the mouth to colon. The results indicated that khaya and albizia gums were capable of protecting the core tablet in the physiological environment of the stomach and small intestine, with albizia gum showing greater ability than khaya gum. The release from tablets coated with the mixture of khaya and albizia gums was midway between the two individual gums, indicating that there was no interaction between the gums. Studies carried out using rat caecal matter in phosphate-buffered saline at pH 6.8 (simulated colonic fluid) showed that the gums were susceptible to degradation by the colonic bacterial enzymes, leading to release of the drug. The results demonstrate that khaya gum and albizia gum have potential for drug targeting to the colon. [source] Corrosion aspects of metallic implants , An overviewMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2008A. Balamurugan Abstract The ability to replace or augment diseased body parts totally or partially has improved both the quality and life span of human population. The decline in surgical risks during recent decades has encouraged the development of more complex procedures for prosthetic implantation. Additionally, a variety of extracorporeal devices, such as the heart, lung and blood dialysis machines are used routinely, but these prosthetic elements have several limitations. Hence, research projects are currently underway to overcome the limitations of synthetic materials by developing formulations with varying properties, such as asymptomatic, long-term function in the human physiological environment, etc., to meet the needs of biomedical surgeons. This review focuses on the several biomaterials corrosion and its measures to prevent corrosion. [source] Visualization of protein interactions in living plant cells using bimolecular fluorescence complementationTHE PLANT JOURNAL, Issue 3 2004Michael Walter Summary Dynamic networks of protein,protein interactions regulate numerous cellular processes and determine the ability to respond appropriately to environmental stimuli. However, the investigation of protein complex formation in living plant cells by methods such as fluorescence resonance energy transfer has remained experimentally difficult, time consuming and requires sophisticated technical equipment. Here, we report the implementation of a bimolecular fluorescence complementation (BiFC) technique for visualization of protein,protein interactions in plant cells. This approach relies on the formation of a fluorescent complex by two non-fluorescent fragments of the yellow fluorescent protein brought together by association of interacting proteins fused to these fragments (Hu et al., 2002). To enable BiFC analyses in plant cells, we generated different complementary sets of expression vectors, which enable protein interaction studies in transiently or stably transformed cells. These vectors were used to investigate and visualize homodimerization of the basic leucine zipper (bZIP) transcription factor bZIP63 and the zinc finger protein lesion simulating disease 1 (LSD1) from Arabidopsis as well as the dimer formation of the tobacco 14-3-3 protein T14-3c. The interaction analyses of these model proteins established the feasibility of BiFC analyses for efficient visualization of structurally distinct proteins in different cellular compartments. Our investigations revealed a remarkable signal fluorescence intensity of interacting protein complexes as well as a high reproducibility and technical simplicity of the method in different plant systems. Consequently, the BiFC approach should significantly facilitate the visualization of the subcellular sites of protein interactions under conditions that closely reflect the normal physiological environment. [source] Formulation and evaluation of chitosan microspheres of aceclofenac for colon-targeted drug deliveryBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 7 2010S. K. Umadevi Abstract The objective of this investigation was to develop novel colon specific drug delivery. Aceclofenac, a NSAID, was successfully encapsulated into chitosan microspheres. Various formulations were prepared by varying the ratio of chitosan, span-85 and stirring speed and the amount of glutaraldehyde. The SEM study showed that microspheres have smooth surfaces. Microspheres were characterised by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) to confirm the absence of chemical interactions between drug and polymer and to know the formation of microspheres structure. The microspheres were evaluated for particle size, encapsulation efficiency, drug loading capacity, mucoadhesion studies, stability studies, in vitro and in vivo drug release studies. Particle sizes, as measured by the laser light scattering technique, were of an average size in the range 41,80,µm. The swelling index was in the range 0.37,0.82 and the entrapment efficiency range was 51,75% for all the formulations. The optimised batch ACM13 released 83.6% at 8,h and 104% at 24,h in SCF containing rat caecal content. Eudragit coated chitosan microspheres prevented the release of the aceclofenac in the physiological environment of the stomach and small intestine and released 95.9±0.34% in the colon. With regard to release kinetics, the data were best fitted with the Higuchi model and showed zero order release with non-Fickian diffusion mechanism. The in vivo findings suggest that aceclofenac microspheres exhibit a prolonged effect of aceclofenac in rats and produce a significant anti-inflammatory effect. The findings of the present study conclusively state that chitosan microspheres are promising for colon targeting of aceclofenac to synchronise with chronobiological symptoms of rheumatoid arthritis. Copyright © 2010 John Wiley & Sons, Ltd. [source] ,-Zein secondary structure in solution by circular dichroismBIOPOLYMERS, Issue 3 2008Tatiana C. Bicudo Abstract The proline-rich N-terminal domain of ,-zein has been reported in relevant processes, which include its ability to cross the cell membranes. Evidences indicate that synthetic hexapeptide (PPPVHL), naturally found in N-terminal portion of ,-zein, can adopt the polyproline II (PPII) conformation in aqueous solution. The secondary structure of ,-zein in maize protein bodies had been analyzed by solid state Fourier transform infrared and nuclear magnetic resonance spectroscopies. However, it was not possible to measure PPII content in physiological environment since the ,-sheet and PPII signals overlap in both solid state techniques. Here, the secondary structure of ,-zein has been analyzed by circular dichroism in SDS aqueous solution with and without ditiothreitol (DTT), and in 60% of 2-propanol and water with DTT. The results show that ,-zein has high helical content in all solutions. The PPII conformation was present at about 7% only in water/DTT solution. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 175,178, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley. com [source] Windows of operation for bioreactor design for the controlled formation of tissue-engineered arteriesBIOTECHNOLOGY PROGRESS, Issue 3 2009Spyridon Gerontas Abstract The availability of large numbers of units of artificial arteries would offer significant benefits to the clinical management of bypass surgery. Tissue engineering offers the potential of providing vessels that can mimic the morphology, function, and physiological environment of native vessels. Ideally this would involve culturing stem cells in vitro within a biodegradable tubular scaffold so as to construct tissue for implantation. Essential to establishing a robust process for the production of tissue-engineered arteries is the understanding of the impact of changes in the operating conditions and bioreactor design on the construct formation. In this article, models of transport phenomena were developed to predict the critical flow rates and mass transfer requirements of a prototype bioreactor for the formation of tissue-engineered arteries. The impact of the cell concentration, tube geometry, oxygen effective diffusivity in alginate, substrate and metabolite concentration levels, feed rate, and recycle rate on the design of the bioreactor was visualized using windows of operation and contour plots. The result of this analysis determined the best configuration of the bioreactor that meets the cellular transport requirements as well as being reliable in performance while seeking to reduce the amount of nutrients to be used. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Effects of Oxygen Transport on 3-D Human Mesenchymal Stem Cell Metabolic Activity in Perfusion and Static Cultures: Experiments and Mathematical ModelBIOTECHNOLOGY PROGRESS, Issue 4 2005Feng Zhao Human mesenchymal stem cells (hMSCs) have unique potential to develop into functional tissue constructs to replace a wide range of tissues damaged by disease or injury. While recent studies have highlighted the necessity for 3-D culture systems to facilitate the proper biological, physiological, and developmental processes of the cells, the effects of the physiological environment on the intrinsic tissue development characteristics in the 3-D scaffolds have not been fully investigated. In this study, experimental results from a 3-D perfusion bioreactor system and the static culture are combined with a mathematical model to assess the effects of oxygen transport on hMSC metabolism and proliferation in 3-D constructs grown in static and perfusion conditions. Cells grown in the perfusion culture had order of magnitude higher metabolic rates, and the perfusion culture supports higher cell density at the end of cultivation. The specific oxygen consumption rate for the constructs in the perfusion bioreactor was found to decrease from 0.012 to 0.0017 ,mol/106 cells/h as cell density increases, suggesting intrinsic physiological change at high cell density. BrdU staining revealed the noneven spatial distribution of the proliferating cells in the constructs grown under static culture conditions compared to the cells that were grown in the perfusion system. The hypothesis that the constructs in static culture grow under oxygen limitation is supported by higher YL/G in static culture. Modeling results show that the oxygen tension in the static culture is lower than that of the perfusion unit, where the cell density was 4 times higher. The experimental and modeling results show the dependence of cell metabolism and spatial growth patterns on the culture environment and highlight the need to optimize the culture parameters in hMSC tissue engineering [source] Immuno-Carbon Nanotubes and Recognition of PathogensCHEMBIOCHEM, Issue 4 2005Tara Elkin Tubular warning bells. Water-soluble, protein-functionalized, single-walled carbon nanotubes (immuno-SWNTs) have been prepared that can recognize and capture pathogenic E. coli cells selectively by antibody,antigen conjugation in a physiological environment, as shown in the scanning electron microscopy image. [source] | |||||||||||||||||||