|Articles about Biomaterials|
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| Morphological and phenotypical characterization of human endothelial progenitor cells in an early stage of differentiation
Bellik, L., F. Ledda, et al. (2005), FEBS Lett 579(12): 2731-6.
Abstract: The exact phenotype and lineage of endothelial progenitor cells (EPCs) are still a matter of debate and different expansion protocols are used to obtain them. In this study, EPC expansion from peripheral blood mononuclear cells was analyzed within the first week of culture. Both the adherent and suspended cells, of which the latter usually discarded, were considered. We provide, for the first time, a systematic study of EPC phenotype and functional features within the first 3 days of culture. Moreover, within the 2nd day, both cellular fractions displayed a significant increase in endothelial marker expression which correlated with EPC properties.
| Morphological and topographic effects on calcification tendency of pHEMA hydrogels
Lou, X., S. Vijayasekaran, et al. (2005), Biomaterials 26(29): 5808-17.
Abstract: Poly(2-hydroxyethyl methacrylate) hydrogels were prepared in the presence of varying concentrations of water, or a co-monomer ethoxyethyl methacrylate at different strengths of crosslinking agent ethylene glycol dimethacrylate. Calcification tendency and its correlation with monomer mixture composition, topography and porosity of these materials were investigated. Scanning (SEM) and transmission electron microscopy (TEM) was used to study topography and porosity respectively. Calcification and calcium diffusion ability in to the hydrogels were investigated by light microscopy, SEM and energy dispersive analysis of X-rays (EDAX) after incubation of the materials in a metastable calcifying solution for 48 days. Polymer and solvent volume fractions were also studied to determine if a correlation existed between porosity and calcification. Most of the series of hydrogels showed surface irregularities. Internal structure showed evidence of a porous structure in one of the series. Calcification studies indicated diffusion of calcium ions in some of the series. The diffusion of calcium is limited to 30-40 microm in most calcified specimens. For hydrogels that exhibited substantial surface irregularities and micro channels, the infiltration of calcium up to 200 microm was observed. Attempts to detect porosity by electron microscopy failed in some of the hydrogels due to difficulty in sample processing and sectioning. However, collaboration of the results with different techniques used, indicated that surface defects are the major contributors to calcium deposition. Decrease in porosity reduces the amount of calcium deposits and infiltration with decreasing solvent volume fraction which is associated with crosslinking concentration and initial water content of the polymer.
| Morphological changes occurring during thrombogenesis and embolization on biomaterials in a canine ex-vivo series shunt
Lelah, M. D., C. A. Jordan, et al. (1983), Scan Electron Microsc(Pt 4): 1983-94.
Abstract: An acute canine ex-vivo femoral A-V shunt technique was used to study thrombus formation and embolization on a number of porous and non-porous polymer surfaces over a one-hour blood contact period. The technique allows for simultaneous exposure of all the surfaces under similar physiological and hematological conditions. This makes comparisons between surfaces more reliable. SEM was used to study changes in the morphology of platelets and thrombi present on the polymer surfaces. Quantitative information was obtained using radiolabeled platelets. In general, platelet deposition, activation, and aggregation was followed by thrombus formation which peaked at about 15-30 minutes of blood contact. Thrombi were composed mainly of platelets with few leukocytes present. Embolization was observed on Silastic (SIL), polyvinylchoride (PVC), polyethylene (PE), and oxidized polyethylene (OX-PE) surfaces between 20 and 60 minutes of blood contact. The mechanism for embolization involved clot retraction under the influence of a shear field. Leukocytes did not appear to be necessary for the initiation of embolization but were present during the embolization phase on OX-PE, possibly due to chemotactic factors. Although extensive thrombus formation was observed on the porous PTFE materials (GORE-TEX and IMPRA), the thrombi formed were flat and did not significantly block the lumen. By 60 minutes of blood contact, only minimal embolization had occurred on the PTFE surfaces. SEM examination of the sequence of thrombus formation and embolization was found to correlate well with trends in platelet deposition measured using radiolabeling techniques.
| Morphological characterization and in vitro biocompatibility of a porous nickel-titanium alloy
Prymak, O., D. Bogdanski, et al. (2005), Biomaterials 26(29): 5801-7.
Abstract: Disks consisting of macroporous nickel-titanium alloy (NiTi, Nitinol, Actipore) are used as implants in clinical surgery, e.g. for fixation of spinal dysfunctions. The morphological properties were studied by scanning electron microscopy (SEM) and by synchrotron radiation-based microtomography (SRmuCT). The composition was studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and energy-dispersive X-ray spectroscopy (EDX). The mechanical properties were studied with temperature-dependent dynamical mechanical analysis (DMA). Studies on the biocompatibility were performed by co-incubation of porous NiTi samples with isolated peripheral blood leukocyte fractions (polymorphonuclear neutrophil granulocytes, PMN; peripheral blood mononuclear leukocytes, PBMC) in comparison with control cultures without NiTi samples. The cell adherence to the NiTi surface was analyzed by fluorescence microscopy and scanning electron microscopy. The activation of adherent leukocytes was analyzed by measurement of the released cytokines using enzyme-linked immunosorbent assay (ELISA). The cytokine response of PMN (analyzed by the release of IL-1ra and IL-8) was not significantly different between cell cultures with or without NiTi. There was a significant increase in the release of IL-1ra (p<0.001), IL-6 (p<0.05), and IL-8 (p<0.05) from PBMC in the presence of NiTi samples. In contrast, the release of TNF-alpha by PBMC was not significantly elevated in the presence of NiTi. IL-2 was released from PBMC only in the range of the lower detection limit in all cell cultures. The material, clearly macroporous with an interconnecting porosity, consists of NiTi (martensite; monoclinic, and austenite; cubic) with small impurities of NiTi2 and possibly NiC(x). The material is not superelastic upon manual compression and shows a good biocompatibility.
| Morphological response of the peritoneum and spleen to intraperitoneal biomaterials
Guo, W., R. Willen, et al. (1993), Int J Artif Organs 16(5): 276-84.
Abstract: The present study was performed to evaluate the morphological response of the peritoneum and spleen to biomaterials. Silicone elastomer, knitted dacron or rubber was implanted, respectively, into a rat's peritoneal cavity and the morphology of the peritoneum and spleen was studied at 4 hours and on the 1st, 4th, 7th and 21st day after surgery. The morphological changes were identical among groups with different implanted materials. After intraperitoneal implantation of biomaterials from 4 hours and on, an infiltration of inflammatory cells was found in the slackened edematous superficial part of the peritoneum. Also noted in the spleen were stasis, vessel dilatation and fibrin deposition. With the help of scanning electron microscopy, a marked denudation and separation of the mesothelial cells, with infiltration of inflammatory cells, were observed. Peripheral leucocytes significantly increased in number one day after intraperitoneal implantation. Three weeks after intraperitoneal implantation, the materials were completely encapsulated and the morphological aberration of the peritoneum and spleen disappeared. The findings reveal the consequence and the resolution of the host-biomaterial interaction, which could contribute to the explanation of various pathophysiological alterations, including the translocation of enteric bacteria and the development of infectious complications after intraperitoneal biomaterial implantation.
| Morphological studies of oligodeoxyribonucleotides probes covalently immobilized at polystyrene modified surfaces
Munoz-Serrano, L., A. R. Guadalupe, et al. (2005), J Biotechnol 118(3): 233-45.
Abstract: The immobilization of short ss-DNA (18- and 36-mer) and their hybridization were studied at gold and glassy carbon substrates modified with low molecular weight (approximately 12, 18 and 24 kg/mol) polystyrene thin films. Amino-modified DNA was attached to the surface by reaction with succinimide ester groups bound to the polystyrenes. A ferrocene modified DNA target was used to confirm the probe-target hybridization. Atomic force microscopy studies showed significant morphological changes after probe immobilization and hybridization compared to the featureless structure of the polystyrene film. Single-stranded DNA samples had a globular morphology with an average density of 3.8 and 2.2 (x 10(11)) globules/cm2 for the 18- and 36-mer, respectively. The formation of a porous structure with a 2.0 and 1.0 (x10(11)) average pore density corresponding to the 18- and 36-mer was observed after hybridization. A surface composition analysis was done by X-ray photoelectron spectroscopy to confirm and support the images interpretation. Ferrocene oxidation (+323 mV/18-mer, +367 mV/36-mer, versus Ag/AgCl) proved the presence of ds-DNA at the modified surfaces.
| Morphology and gelation of thermosensitive chitosan hydrogels
Crompton, K. E., R. J. Prankerd, et al. (2005), Biophys Chem 117(1): 47-53.
Abstract: The morphology of physical hydrogels is often difficult to examine due to the delicate nature of the system and therefore has not been studied in detail. Chitosan/GP (glycerophosphate salt) is a significant hydrogel in the biomedical and cosmetic fields as it is thermosensitive and contains less than 5% polysaccharide. The morphology of this system was examined with laser scanning confocal microscopy (LSCM) to image the gel morphology. The images indicate that the gel is quite heterogeneous, and power spectra reveal a fractal-like morphology. A study of composition found that increasing chitosan concentration increased the amount of polymer-rich phase present in the gel, and that the smallest aggregates decreased in size.
| Morphology and growth of murine cell lines on model biomaterials
Godek, M. L., N. L. Duchsherer, et al. (2004), Biomed Sci Instrum 40: 7-12.
Abstract: All biomaterial implants are assaulted by the host "foreign body" immune response. Understanding the complex, dynamic relationship between cells, biomaterials and milieu is an important first step towards controlling this reaction. Material surface chemistry dictates protein adsorption, and thus subsequent cell interactions. The cell-implant is a microenvironment involving 1) proteins that coat the surface and 2) cells that interact with these proteins. Macrophages and fibroblasts are two cell types that interact with proteins on biomaterials surfaces and play different related, but equally important, roles in biomaterials rejection and implant failure. Growth characteristics of four murine cell lines on model biomaterials surfaces were examined. Murine monocyte-macrophages (RAW 264.7 and J774A.1), murine macrophage (IC-21) and murine fibroblast (NIH 3T3) cell lines were tested to determine whether differences exist in adhesion, proliferation, differentiation, spreading, and fusion (macrophage lineages only) on these surfaces. Differences were observed in the ability of cells to adhere to and subsequently proliferate on polymer surfaces. (Monocyte-) macrophages grew well on all surfaces tested and growth rates were measured on three representative polymer biomaterials surfaces: tissue culture polystyrene (TCPS), polystyrene, and Teflon-AF. J774A.1 cultures grown on TCPS and treated with exogenous cytokines IL-4 and GM-CSF were observed to contain multinucleate cells with unusual morphologies. Thus, (monocyte-) macrophage cell lines were found to effectively attach to and interrogate each surface presented, with evidence of extensive spreading on Teflon-AF surfaces, particularly in the IC-21 cultures. The J774A.1 line was able to proliferate and/or differentiate to more specialized cell types (multinucleate/dendritic-like cells) in the presence of soluble chemokine cues.
| Morphology and metabolism of Ba-alginate encapsulated hepatocytes with galactosylated poly(allyl amine) and poly(vinyl alcohol) as extracellular matrices
Kang, I. K., J. S. Moon, et al. (2005), J Mater Sci Mater Med 16(6): 533-9.
Abstract: Lactobionic acid, bearing a beta -galactose group, was coupled with poly(allyl amine) to provide synthetic extracellular matrices together with poly(vinyl alcohol) (PVA). The hepatocytes were encapsulated in Ba-alginate capsules with galactosylated poly(allyl amine) (GA) and PVA as extracellular matrices. From microscopic observation, it was revealed that the microcapsule prepared has a highly porous structure with interconnected pores and pore sizes ranging between 50-150 nm on both the surface and the cross-section. It was found, from the permeability experiment of microcapsules using FITC-dextrans with different molecular weights, that the capsule has a molecular weight cut off (MWCO) of 120 kDa, showing the potential that it can function as an immunoprotecting wall. The hepatocytes, cultured with GA and PVA in the core of the microcapsule, rapidly aggregated within a day, thus resulting in good metabolic functions such as albumin synthesis and ammonia removal.
| Morphology and metabolism of hepatocytes microencapsulated with acrylic terpolymer-alginate using gelatin and poly(vinyl alcohol) as extracellular matrices
Moon, J. S., H. M. Jeon, et al. (2005), J Biomater Sci Polym Ed 16(10): 1245-59.
Abstract: Microcapsules with good mechanical stability were prepared using an appropriate mixture of alginate and acrylic terpolymer. It was found from the microscopic observation that the microcapsules had a porous structure with interconnected pores, with a size of 50-150 nm. The results of the permeability experiment of microcapsules using FITC-dextrans showed that the capsule had a molecular mass cut-off of 120 kDa. The hepatocytes encapsulated in both alginate and acrylic terpolymer with gelatin and PVA rapidly aggregated in the core. The aggregated cells showed high albumin synthesis and ammonia removal, suggesting good metabolic function.
| Motility and fertility of alginate encapsulated boar spermatozoa
Huang, S. Y., C. F. Tu, et al. (2005), Anim Reprod Sci 87(1-2): 111-20.
Abstract: Ejaculated boar spermatozoa are vulnerable to cold shock. Prolonged storage of boar spermatozoa at low temperatures reduces survival rate, resulting in a bottleneck for the extension of artificial insemination in pig husbandry. This study evaluated whether alginate microencapsulization processing can improve the longevity of boar spermatozoa stored at 5 degrees C and the fertility of microencapsulated spermatozoa in vivo. Sperm-rich fraction semen from three purebred boars were concentrated and microencapsulated using alginate at 16-18 degrees C, and then were stored at 5 degrees C. Following storage for 1, 3 and 7 days, the microcapsule was taken out to assess sperm release under 37 degrees C incubation with or without 110 rpm stirring. The percentage of sperm released from microcapsules with 110 rpm stirring was higher than without stirring (81 versus 60%) after 24h of incubation. In another experiment, semen was also microencapsulated to evaluate the sperm motility. The motility of spermatozoa was assessed at 10 min, 8, 24, 32, 48, 56 and 72 h following incubation at 37 degrees C for nine consecutive days. The fertility of the free and microencapsulated semen was assessed by inseminating sows, and the reproductive traits (conception rate, farrowing rate, and litter size) were recorded. The motility of encapsulated spermatozoa was significantly higher than that of free semen after 8h incubation at 37 degrees C after storing for over three days (P<0.05). No significant difference existed in conception rate, farrowing rate, and litter size between the microencapsulated and non-encapsulated semen after four days of storage. In conclusion, microencapsulation can increase the longevity of boar spermatozoa and may sustain in vivo ova fertilization ability.
| Moving beyond the cost per quality-adjusted life year: modelling the budgetary impact and clinical outcomes associated with the use of sirolimus-eluting stents
Shrive, F. M., W. A. Ghali, et al. (2005), Can J Cardiol 21(9): 783-7.
Abstract: Restenosis is a major limitation to the long-term success of percutaneous coronary intervention. Drug-eluting stents are the most recent technological advance in restenosis prevention. While they are effective, their use is associated with a significant incremental cost, and a recent economic evaluation performed by the authors suggested that their use is associated with a cost per quality-adjusted life year of $58,721. How should decision-makers react to this value, particularly given that the use of sirolimus-eluting stents appears more attractive in certain patient subgroups, such as those with complex coronary lesions? In the present paper, the authors explore an alternative method of presenting the results of their economic evaluation, rather than the usual cost per quality-adjusted life year rubric, in an attempt to assist decision-makers in deciding whether, and for whom, to fund sirolimus-eluting stents. Several issues that decision-makers and providers may wish to consider when making such funding decisions are discussed.
| Mucoadhesive microspheres for nasal administration of an antiemetic drug, metoclopramide: in-vitro/ex-vivo studies
Gavini, E., G. Rassu, et al. (2005), J Pharm Pharmacol 57(3): 287-94.
Abstract: Microparticulate delivery systems designed for the nasal administration of an antiemetic drug, metoclopramide hydrochloride, were prepared. Microspheres composed of sodium alginate, chitosan hydrochloride, or both, were obtained using a spray-drying method; some batches of drug-free microparticles were prepared as a comparison. The morphology, in-vitro swelling behaviour, mucoadhesive properties and drug release from microparticles were evaluated. Ex-vivo drug permeation tests were carried out using sheep nasal mucosa; permeation test of the drug solution was performed as comparison. During ex-vivo permeation tests, transmission electron microscopy (TEM) analyses were carried out on the nasal mucosa to study the morphological changes of epithelial cells and tight junctions, while the change in microsphere morphology was examined using photostereo microscopy (PM). Spray-dried microparticles had a mean diameter (d(vs)) in the range of about 3-10 microm. They showed good in-vitro mucoadhesive properties. In-vitro release profiles and swelling behaviour depended on their composition: the drug release occurred in 1-3 h. Ex-vivo studies showed that drug permeation through the mucosa from microparticles based on chitosan was higher than from those consisting of alginate alone. This can be related to the penetration enhancing properties of chitosan. Complexation of chitosan with alginate led to a control of the drug release. Microscopy observation of microspheres during the permeation tests revealed that microparticles swelled and gelled, maintaining their shape. TEM analyses of the mucosa after exposure to the microparticles consisting of alginate/chitosan showed opened tight junctions. This preliminary study shows that alginate/chitosan spray-dried microspheres have promising properties for use as mucoadhesive nasal carriers of an antiemetic drug.
| Mucosal targeting of allergen-loaded microspheres by Aleuria aurantia lectin
Roth-Walter, F., I. Scholl, et al. (2005), Vaccine 23(21): 2703-10.
Abstract: Murine intestinal M-cells express alpha-L-fucose residues. We constructed alpha-L-fucose-targeting particles for oral immunotherapy of IgE-mediated allergy. Poly(D,L-lactic-co-glycolic acid)-microspheres were loaded with birch pollen allergens, and functionalised with the alpha-L-fucose specific Aleuria aurantia lectin (AAL). The AAL-microspheres had a size of 1-3 microm, protected the entrapped allergens from gastric degradation and released 46.6+/-1.3% allergen over 21 days in vitro. Oral gavages of AAL-particles to naive BALB/c mice induced birch pollen-specific IgG2a, but not IgG1 antibodies. We conclude that targeting allergens to alpha-L-fucose-receptor bearing cells using AAL-microspheres induces specific Th1-antibody responses possibly counteracting Th2-dominated allergy, and therefore provides a potentially useful formulation for oral immunotherapy.
| Multiblock copolyesters as biomaterials: in vitro biocompatibility testing
Saad, B., O. M. Keiser, et al. (1997), J Mater Sci Mater Med 8(8): 497-505.
Abstract: Cell adhesion, cell growth and cell activities of macrophages and fibroblasts, cultured on newly developed degradable multiblock-copolyesters were studied to examine the biocompatibility and the possible use of these polymers for medical applications. The biocompatibility and the biodegradability of the polymers were confirmed by subcutaneous implantation of polymer foils in rats.The newly developed polymers, two polyesters (DegraPol/bsc43 and DegraPol/bsd43) and a polyesterether (DegraPol/bst41), were found to exhibit good cell compatibility; the cell-to-substrate interactions induced neither cytotoxic effects nor activation of macrophages.The adhesion and growth of fibroblasts and macrophages were different among the substrate. Fibroblasts adhered on the polyesters to about 60% of control cell cultured on tissue culture polystyrene (TCPS) and proliferated in the same doubling time as on TCPS. On the polyetherester cells exhibited weak adhesion; however, they proliferated up to day 4 after plating at the same doubling time as on TCPS (of about 42 h), and then decreased their doubling time to 27 h. Macrophages attached to the polyesters to about 40-60% of TCPS but no significant change was seen in the doubling time of cells cultured on TCPS and the polyesters. Again on the polyetherester, macrophages exhibited relatively low adhesion (25% of TCPS) and high doubling time (about 100 h).Fibroblasts produced high amounts (up to 500% of control cells) of collagen type I and type IV, and fibronectin. Macrophages responded to lipopolysaccharide treatment by the production of nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha), indicating that the cell-to-polymer interactions allow fibroblasts and macrophages to maintain their phenotype.All three test polymers exhibit favourable tissue compatibility. The formed capsule was just a few cell layers thick (<30 microm). After 2 months implanted subcutaneously in rats, the molecular weight of the test polymers was reduced by >20% depending on their chemical structure.Taken collectively, the present data demonstrate that the newly developed multiblock copolyesters are biocompatible and biodegradable.
| Multielectrode arrays with elastomeric microstructured overlays for extracellular recordings from patterned neurons
Claverol-Tinture, E., M. Ghirardi, et al. (2005), J Neural Eng 2(2): L1-7.
Abstract: Multielectrode array technology constitutes a promising approach for the characterization of the activity-dependent neuronal plasticity underlying information processing in the nervous system. For this purpose, long-term monitoring and stimulation of cultured neuronal networks with one-to-one neuron-sensor interfacing is advantageous. Existing neurochips that meet these specifications have made use of custom 3D structures requiring clean-room intensive microfabrication techniques. Low-cost fabrication procedures with potential for mass production would facilitate progress in the area. To this end, we have developed a sandwich structure comprising an elastomeric film, microstructured by replica moulding and microhole punching, for neuronal patterning, and a standard planar microelectrode array (MEA), for stimulation and recording. The elastomeric film includes microwells for cell body confinement, and microchannels capable of guiding neurites for network topology specification. The device is formed by overlaying the elastomeric structures on planar arrays. The combination of replica moulding, rapid prototyping and planar MEAs results in low-cost neurochips accessible to most neurophysiology labs. Single neuron patterning and recordings of extracellular potentials are demonstrated.
| Multielectrode microprobes for deep-brain stimulation fabricated with a customizable 3-D electroplating process
Motta, P. S. and J. W. Judy (2005), IEEE Trans Biomed Eng 52(5): 923-33.
Abstract: Although deep-brain stimulation (DBS) can be used to improve some of the severe symptoms of Parkinson's disease (e.g., Bradykinesia, rigidity, and tremors), the mechanisms by which the symptoms are eliminated are not well understood. Moreover, DBS does not prevent neurodegeneration that leads to dementia or death. In order to fully investigate DBS and to optimize its use, a comprehensive long-term stimulation study in an animal model is needed. However, since the brain region that must be stimulated, known as the subthalamic nucleus (STN), is extremely small (500 microm x 500 microm x 1 mm) and deep within the rat brain (10 mm), the stimulating probe must have geometric and mechanical properties that allow accurate positioning in the brain, while minimizing tissue damage. We have designed, fabricated, and tested a novel micromachined probe that is able to accurately stimulate the STN. The probe is designed to minimize damage to the surrounding tissue. The probe shank is coated with gold and the electrode interconnects are insulated with silicon nitride for biocompatibility. The probe has four platinum electrodes to provide a variety of spatially distributed stimuli, and is formed in a novel 3-D plating process that results in a microwire like geometry (i.e., smoothly tapering diameter) with a corresponding mechanically stable shank.
| Multilayer nanocapsules of polysaccharide chitosan and alginate through layer-by-layer assembly directly on PS nanoparticles for release
Ye, S., C. Wang, et al. (2005), J Biomater Sci Polym Ed 16(7): 909-23.
Abstract: Polysaccharide multilayer nanocapsules have been fabricated in aqueous media by the layer-by-layer self-assembly of chitosan (CHI) and sodium alginate (ALG) on monodisperse polystyrene (PS) nanoparticles with a diameter of 180 nm as template, followed by removal of the templates through dissolving in THF. The pH and added salt concentration of the polyelectrolyte deposition solutions were optimized to ensure the alternating deposition. Consequently, the most suitable pH values were found to be 6.0-8.0 for ALG and 3.5 for CHI and were used in the deposition. The concentration of added NaCl used in the adsorption solutions was 0.5 M, which led to an average thickness of about 13 nm for 5 bilayers of CHI/ALG shell-wall. zeta-potential indicated the stepwise and alternating adsorption of CHI and ALG to form multilayer film on the PS nanoparticles. The characteristic bands of PS residue almost disappeared in the IR spectrum of the nanocapsule after dipped in THF, confirming thorough removal of PS templates from the core-shell particles. TEM, SEM and AFM were utilized to observe the nanocapsules of about 225 nm in diameter (by TEM). A hydrophilic drug model, acridine hydrochloride (AH), was chosen to investigate the loading and release properties of the nanocapsules. The positively charged AH spontaneously deposited into the capsule due to the electrostatic interaction with the negatively charged styrene sulfonate residues from the PS template inside the capsule. The rate of AH release became slightly slower when the capsule wall was cross-linked with glutaraldehyde, but the accumulative released amount for the cross-linked capsule was obviously reduced. These nanocapsules made from nature polysaccharides have a potential application in controlled drug release.
| Multilayers of a globular protein and a weak polyacid: role of polyacid ionization in growth and decomposition in salt solutions
Izumrudov, V. A., E. Kharlampieva, et al. (2005), Biomacromolecules 6(3): 1782-8.
Abstract: Thin films obtained from a layer-by-layer deposition of a weak polycarboxylic acid and a positively charged globular protein were studied by in situ ATR-FTIR. The system was chicken egg lysozyme (Lys), bovine pancrease ribonuclease A (RNase), or bovine gamma-globulin (IgG) self-assembled with polycarboxylic acids. When the pH value was lowered below a critical point, the growth of films and their tolerance to decomposition by added sodium chloride improved dramatically. Stabilization of protein/polyacid films in salt solutions at lower pH values occurred due to the onset of nonelectrostatic interactions to intermolecular binding within protein/polyacid multilayers and was controlled by polyacid ionization within the film rather than the pH of the external solution. A fractional ionization of polyacid in the pH-stabilization region was lower with protein-containing films than for polyacid/linear polycation films, reflecting hindrance of the inter-association of protonated carboxylic groups by protein globules. Practical ramifications of the pH-stabilization effect might extend to areas of biotechnology and biomaterials.
| Multilineage differentiation of human mesenchymal stem cells in a three-dimensional nanofibrous scaffold
Li, W. J., R. Tuli, et al. (2005), Biomaterials 26(25): 5158-66.
Abstract: Functional engineering of musculoskeletal tissues generally involves the use of differentiated or progenitor cells seeded with specific growth factors in biomaterial scaffolds. Ideally, the scaffold should be a functional and structural biomimetic of the native extracellular matrix and support multiple tissue morphogenesis. We have previously shown that electrospun, three-dimensional nanofibrous scaffolds that morphologically resemble collagen fibrils are capable of promoting favorable biological responses from seeded cells, indicative of their potential application for tissue engineering. In this study, we tested a three-dimensional nanofibrous scaffold fabricated from poly(epsilon-caprolactone) (PCL) for its ability to support and maintain multilineage differentiation of bone marrow-derived human mesenchymal stem cells (hMSCs) in vitro. hMSCs were seeded onto pre-fabricated nanofibrous scaffolds, and were induced to differentiate along adipogenic, chondrogenic, or osteogenic lineages by culturing in specific differentiation media. Histological and scanning electron microscopy observations, gene expression analysis, and immunohistochemical detection of lineage-specific marker molecules confirmed the formation of three-dimensional constructs containing cells differentiated into the specified cell types. These results suggest that the PCL-based nanofibrous scaffold is a promising candidate scaffold for cell-based, multiphasic tissue engineering.
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