UMLS:C0432222 - FACTA Search

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Query: UMLS:C0432222 (SEM)
47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reconstitution of fibrillar collagen and its assemblies with heparin and hyaluronic acid was studied in vitro. Fibril formation kinetics were analyzed by turbidity and depletion measurements in solutions containing varied concentrations of collagen and glycosaminoglycans. Fibril-forming collagen solutions were further applied for the coating of planar substrates which had been modified with alternating maleic anhydride copolymer films before. The immobilized collagen assemblies were characterized with respect to the deposited amount of protein using ellipsometry and acidic hydrolysis/HPLC-based amino acid analysis, respectively. AFM, SEM, and cLSM were utilized to gain information on structural features and patterns formed by surface-attached fibrils depending on the initial solution concentrations of collagen. The results revealed that the addition of heparin and hyaluronic acid affected both the fibril dimensions and the meshwork characteristics of the surface-bound fibrils.
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PMID:In vitro reconstitution of fibrillar collagen type I assemblies at reactive polymer surfaces. 1524 49

Poly(vinyl alcohol) hydrogels prepared by freeze-thawing procedure represent synthetic systems widely investigated as non-biodegradable scaffolds for tissue regeneration. In order to improve the biocompatibility properties of pure poly(vinyl alcohol) (PVA) hydrogels, blends of PVA with different biological macromolecules, such hyaluronic acid, dextran, and gelatin were prepared and used to produce "bioartificial hydrogels". The porosity characteristics of these hydrogels were investigated by scanning electron microscopy and mercury intrusion porosimetry. The morphology of bioartificial hydrogels was evaluated and compared with that of pure PVA hydrogels. In particular the effect exerted by each biological component on pore size and distribution was investigated. The obtained results indicate that when a natural macromolecule is added to PVA the internal structure of the material changes. A small amount of biopolymer induces the structural elements of PVA matrix to take on a well evident lamellar appearance and an apparent preferential orientation. Comparing the results of SEM and mercury intrusion porosimetry it was concluded that hydrogels containing 20% of biological component have the most regular structure and at the same time the lowest total porosity. On the contrary samples with the highest content of natural polymer (40%) show the less regular structure and the highest total porosity.
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PMID:Morphological evaluation of bioartificial hydrogels as potential tissue engineering scaffolds. 1574 83

Characterization of the extracellular matrix of the temporomandibular joint (TMJ) disc is crucial to advancing efforts in tissue engineering the disc. However, the current literature is incomplete and often contradictory in its attempts to describe the nature of the TMJ disc matrix. The aim of this study was to identify the variation of key matrix components along the three axes of the porcine disc using ELISAs to quantify these matrix components, immunohistochemistry to identify their regional distribution, and SEM to examine collagen fiber diameter and orientation. The overall GAG content of the TMJ disc (including the dermatan sulfate proteoglycans) was 5.3+/-1.2% of the dry weight. Chondroitin sulfate, which comprised 74% of this total GAG content, was 4.4, 8.2, and 164 times more abundant than dermatan sulfate proteoglycan, keratan sulfate, and hyaluronic acid, respectively. In general, these GAGs were most concentrated in the intermediate zone of the TMJ disc, appearing in dense clusters, and least concentrated in the posterior band. Additionally, chondroitin sulfate was more abundant medially than laterally. Collagen II was discovered in trace amounts, with higher relative amounts in the intermediate zone. Collagen fibers were observed to run primarily in a ring-like fashion around the periphery of the disc and anteroposteriorly through the intermediate zone, with a mean fiber diameter of 18+/-9 mum. Characterization studies of the TMJ disc, including prior biomechanical and cell studies along with the current study of the extracellular matrix, collectively reveal a distinct character of the intermediate zone of the disc compared to its anterior and posterior bands.
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PMID:Quantitative analysis and comparative regional investigation of the extracellular matrix of the porcine temporomandibular joint disc. 1574 1

The effect of fibronectin protein (Fn) coating onto polysaccharide layers of hyaluronic acid (Hyal) and its sulfated derivative (HyalS) on fibroblast cell adhesion was analyzed. The Hyal or HyalS were coated and grafted on the glass substrate by a photolithographic method. The Fn coating was achieved by two different routes: the immobilization of Fn by covalent bond to the polysaccharide layers and the simple adsorption of Fn onto Hyal and HyalS surfaces. AFM, SEM, and ATR-FTIR techniques were used for the chemical and topographical characterization of the surfaces. According to AFM and SEM data, the surface topography was dependent on the method used to cover the polysaccharide layers with the protein. ATR-FTIR analysis supplied information about the rearrangement of Fn after the interaction (adsorption or binding) with the Hyal and the HyalS. The conformational changes of the Fn were minimal when it was simply adsorbed on HyalS surfaces and larger once bound, whereas on the Hyal layer the protein underwent a bigger conformational change once adsorbed and covalently grafted. Then, the biological characterization was carried out by analyzing the human diploid skin fibroblasts adhesion on these surfaces. The morphology of fibroblasts was evaluated by SEM, whereas the dynamics of fibroblasts movement were recorded by a time-lapse system. Cell variations in area, perimeter, and length were analyzed at 2, 4, and 6 h. It was found that the addition of Fn (covalently bound or merely adsorbed) was fundamental in the promotion of fibroblasts adhesion and spreading. The greatest adhesion occurred onto HyalS layers covered by the adsorbed Fn.
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PMID:Fibroblast cell behavior on bound and adsorbed fibronectin onto hyaluronan and sulfated hyaluronan substrates. 1576 24

Fibrillar collagen was reconstituted from mixtures of monomeric tropocollagen and heparin or hyaluronic acid, respectively. Turbidity measurements were utilized to follow the fibrillar assembly and demonstrated the influence of the concentration of the glycosaminoglycan on the maximum optical densities. Thin film coatings of maleic anhydride copolymers were utilized for the covalent immobilization of the fibrillar assemblies to solid supports. Quantification of surface-bound collagen was accomplished by ellipsometry and HPLC-based amino acid analysis indicating that less collagen was immobilized in the presence of the glycosaminoglycans. SEM and AFM revealed various sizes and shapes of the immobilized fibrillar assemblies if collagen fibrils were prepared in the presence of heparin or hyaluronic acid. Human hematopoietic stem cells (HSCs) were cultivated on the surface-bound collagen fibrils and the migration of adherent cells was studied by time-lapse microscopy. Migration rates on fibrillar structures were significantly lower then on tropocollagen indicating a more intimate contact of HSCs to the fibrillar substrates.
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PMID:Fibrillar collagen assembled in the presence of glycosaminoglycans to constitute bioartificial stem cell niches in vitro. 1592 75

The hyaluronic acid (HA) hydrogels modified with laminin were used for implantation in rat brain in present study, in order to investigate its effects in reparation of injury in the CNS. Cross-linked HA hydrogels were synthesized and their characteristics were analyzed. Laminin, an extracellular matrix protein, which participates in neuronal development and survival, was immobilized on the backbone of the hydrogels. Hydrogels unmodified and modified with laminin were implanted into cortical defects mechanically created in rats and their ability to improve tissue reconstruction was then evaluated. After 6 and 12 weeks of implantation, sections of brains were processed with Nissl and Glees staining for revealing neural cell bodies and fibers, with DAB histochemistry for detecting the blood vessels, as well as with immunocytochemistry for recognizing GFAP. The sections were also taken to SEM and TEM for ultrastructral examination. The results showed that the HA hydrogels synthesized had mechanical properties and rheological behavior similar to the brain tissue. After being implanted into the lesion of the cortex, the porous hydrogels created a scaffold, which could support cell infiltration and angiogenesis, and simultaneously inhibit the formation of glial scar. In addition, HA hydrogels modified with laminin could promote neurite extension. It seems possible that the tissue engineering technique may pave the way to repair injury in the CNS as suggested by the results in present study.
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PMID:The repair of brain lesion by implantation of hyaluronic acid hydrogels modified with laminin. 1597 68

Recent studies pointed out advantages of high-molecular hyaluronic acid (HA) application into dialysis fluids. This molecule is an essential component of peritoneal extracellular matrix. The compound shows antiadhesive properties and participates in restoring of peritoneal integrality and remodeling of peritoneum, which have been changed by prolonged peritoneal dialysis and returning incidents of peritonitis. Influence of HA on transperitoneal transport of large and small molecules is recognized in a little range. The aim of presented studies in vitro was qualification of hyaluronan influence on transport dynamics of the selected macromolecules (albumin 1 g/dL, icodextrin 7.5 g/dL and insulin 0.1 g/dL). Values of the transfer, directed from the interstitial to the mesothelial side of membrane (I-->M) and in the opposite direction (M-->I) were expressed as coefficient of diffusive permeability P [cm/s]. In the case of each macromolecule, two separate research series of the experiments were done. In the first one transperitoneal transport in the control conditions (120 min) was analyzed, and in the secondtransfer parameters before (15-60 min) and after hyaluronan (0.04 g/dL) application on the mesothelial side of peritoneal membrane (75-120 min) were examined. Stability of albumin and insulin transport (in the case of the both transfer directions) and icodextin passage (only M-->I direction) was observed in the presented studies when we compare the first and the second hours of the experiments. In the opposite direction (I-->M) it was showed an increase of its transport with time by about 50%. The mean values of P +/- SEM amounted to 0,271 +/- 0,056 [x10(-4); cm/s] and 0,315 +/- 0,057 [x10(-4); cm/s] for albumin and 0,145 +/- 0,033 [x10(-4); cm/s] and 0,146 +/- 0,022 [x10(-4); cm/s] for insulin, respectively in the case of I-->M and M-->I directions and 0,194 +/- 0,035 [x10(-4); cm/s] for icodextrin transfer directed from the mesothelial to the interstitial side of membrane. In the opposite direction (I-->M) values of P coefficient amounted to: 0,280 +/- 0,038 [x10(-4); cm/s] in the first experimental hour, and 0,394 +/- 0,046 [x10(-4); cm/s] in the second one. It was observed also asymmetry of glucose polymer passage with I-->M transfer domination. Hyaluronan eliminated this asymmetry. After use this compound the transport parameters of icodextrin were stable for the both I-->M and M-->I directions. Hyaluronan did not change values of diffusive permeability coefficients P in the case of bidirectional transfer of albumin and insulin. The obtained results show, that values of macromolecules transfer across peritoneum in vitro don't depend on their molecular weight and isoelectric points. Dynamics of albumin and insulin transperitoneal passage is stable. Icodextrin transport, directed from the interstitial to the mesothelial side of membrane, predominates transfer in the opposite direction. Hyaluronan modifies dynamics of transperitoneal icodextrin passage, but doesn't influence on permeability of the membrane in the case of albumin and insulin.
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PMID:[Influence of hyaluronan on peritoneal permeability for macromolecules in vitro]. 1678 85

In this paper, hyaluronic acid hydrogels with open porous structure have been developed for scaffold of brain tissue engineering. A short peptide sequence of arginine-glycine-aspartic acid (RGD) was immobilized on the backbone of the hydrogels. Both unmodified hydrogels and those modified with RGD were implanted into the defects of cortex in rats and evaluated for their ability to improve tissue reconstruction. After 6 and 12 weeks, sections of brains were processed for DAB and Glees staining. They were also labeled with GFAP and ED1 antibodies, and observed under the SEM for ultrastructral examination. After implanting into the lesion of cortex, the porous hydrogels functioned as a scaffold to support cells infiltration and angiogenesis, simultaneously inhibiting the formation of glial scar. In addition, HA hydrogels modified with RGD were able to promote neurites extension. Our experiments showed that the hyaluronic acid-RGD hydrogel provided a structural, three-dimensional continuity across the defect and favoured reorganization of local wound-repair cells, angiogenesis and axonal growth into the hydrogel scaffold, while there was little evidence of axons regeneration in unmodified hydrogel.
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PMID:Hyaluronic acid hydrogel immobilized with RGD peptides for brain tissue engineering. 1714 72

Hydrogels composed of collagen and hyaluronic acid are types of crosslinked water-swellable polymers and possess vast potential for applications in the medical industry. Collagen (Co) is the major structural protein of connective tissues such as skin, tendon and cartilage. Hyaluronic acid (HA) is a non-immunogenic, non-adhesive glycosaminoglycan that has a high water absorption property and plays significant roles in several cellular processes. The purpose of this study is to prepare a collagen (Co)-modified hyaluronic acid (MHA) hydrogel and investigate its potential utility for biomedical products such as wound dressing materials. Collagen (Co, type I) was obtained from pig skin and mucopolysaccharide-HA was modified by a poly (ethylene glycol) diglycidyl ether (PEGDGE) crosslinker. Thermal stability, swelling behavior, and mechanical strength of Co-MHA hydrogel according to different mass ratios of Co and MHA in hydrogel networks were investigated. The physical properties of the hydrogel were measured by SEM, Differential Scanning Calorimetry (DSC), Thermal Gravity Analysis (TGA), and a Universal Testing Machine (UTM). The cell viability of Co-MHA hydrogel was also evaluated using an in vitro MTT assay.
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PMID:Preparation and properties of collagen/modified hyaluronic acid hydrogel for biomedical application. 1804 73

We have combined the therapeutic potential of nanoparticles systems with the ease of manipulation of microparticles by developing a hybrid vector named Trojan particles. We aim to use this new delivery vehicle for intravitreal administration of dexamethasone. Initialy, dexamethasone acetate (DXA) encapsulation into biodegradable poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles was optimized. Then, Trojan particles were formulated by spray drying 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC), hyaluronic acid (HA) and different concentrations of nanoparticle suspensions. The effect of nanoparticles concentration on Trojan particle physical characteristics was investigated as well as the effect of the spray drying process on nanoparticles size. Finally, DXA in vitro release from nanoparticles and Trojan particles was evaluated under sink condition. SEM and confocal microscopy show that most of Trojan particles are spherical, hollow and possess an irregular surface due to the presence of nanoparticles. Neither Trojan particle tap density nor size distribution are significantly modified as a function of nanoparticles concentration. The mean nanoparticles size increase significantly after spray drying. Finally, the in vitro release of DXA shows that the excipient matrix provides protection to encapsulated nanoparticles by slowing drug release.
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PMID:Dexamethasone acetate encapsulation into Trojan particles. 1837 42

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