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The development of suitable three-dimensional matrices for the maintenance of cellular viability and differentiation is critical for applications in tissue engineering and cell biology. To this end, gel matrices of different proportions of alginate/elastin/polyethylene glycol (Alg/Ela/PEG) were prepared and examined. The composite matrix membranes were evaluated for their porous scaffold using SEM, enzymatic degradation and water content. An equal blend of Alg/Ela with a ratio of Alg/Ela: PEG (7:3) was selected for fabricating Alg/Ela/PEG scaffolds for this study. The Alg/Ela/PEG membranes fabricated at 20 degrees C and - 20 degrees C had a mean surface pore size of 35-45 microm. However, their ultrastructures had shown bigger pore structures (60-75 microm) compared to their surface. It is interesting to note that the membranes of Alg/Ela/PEG prepared at 20 degrees C had larger ultrastructural pores than that of membranes prepared at -20 degrees C. Further, the SEM studies revealed that in the absence of PEG the composite membranes of Alg/Ela formed with less porous structures. The water content of membranes prepared at 20 degrees C was higher with Alg/Ela/PEG (61.6 +/- 4.8%), compared to Alg/Ela (49.9 +/- 0.3%). The enzymatic degradation and water content studies also revealed that the membranes fabricated at - 20 degrees C had high water uptake and low enzymatic degradation, as that of the membranes prepared at 20 degreees C. In other words the larger pore structured membranes had less water content and high degradation profile. This study proposes that this novel composite matrix produces a hierarchical structure that is useful for generating tissue scaffolds for repairing the failing cardiac muscles. However, more detailed investigations with cytocompatibility studies are needed to find applications.
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PMID:The development of porous alginate/elastin/PEG composite matrix for cardiovascular engineering. 1279 21

The micro- and nanoarchitectures of water-swollen hydrogels were routinely analyzed in three dimensions at very high resolution by two cryopreparation methods that provide stable low-temperature specimens for in-lens high magnification recordings. Gemini surfactants (gS), poly-N-isopropylacrylamides (p-NIP Am), and elastin-mimetic di- (db-E) and triblock (tb-E) copolymer proteins that form hydrogels have been routinely analyzed to the sub-10-nm level in a single day. After they were quench or high pressure frozen, samples in bulk planchets were subsequently chromium coated and observed at low temperature in an in-lens field emission SEM. Pre-equilibrated planchets (4-40 degrees C) that hold 5-10 microl of hydrogel facilitate dynamic morphological studies above and below their transition temperatures. Rapidly frozen samples were fractured under liquid nitrogen, low-temperature metal coated, and observed in-lens to assess the dispersion characteristics of micelles and fragile colloidal assemblies within bulk frozen water. Utilizing the same planchet freezing system, the cryoetch-HRSEM technique removed bulk frozen water from the hydrogel matrix by low-temperature, high-vacuum sublimation. The remaining frozen solid-state sample faithfully represented the hydrogel matrix. Cryo- and cryoetch-HRSEM provided vast vistas of hydrogels at low and intermediate magnifications whereas high magnification recordings and anaglyphs (stereo images) provided a three-dimensional prospective and measurements on a molecular level.
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PMID:In-lens cryo-high resolution scanning electron microscopy: methodologies for molecular imaging of self-assembled organic hydrogels. 1290 63

A new protein engineering strategy was utilized to synthesize an elastin-mimetic polypeptide. The primary structure represents an elastic motif composed of thirty amino acids with one lysine and one glutamic acid per repeat unit EMM = (VPGVG VPGKG VGPVG VPGVG VPGEG VPGIG). The gene was constructed using a Seamless Cloning method by generating three DNA cassettes which all encoded the EMM repeat unit, but with different flanking restriction recognition sites. The DNA cassettes were assembled to yield a gene that could be directly cloned into the multiple cloning site of pBluescript II SK+. The resulting gene (EMM)(7) with approximately 650 base pairs in length was further cloned into the expression vector pET-28b. Protein biosynthesis in E. coli strain BLR(DE3) resulted in the 21.5 kDa repeating polypeptide His(6)-(EMM)(7) yielding up to 50 mg . L(-1) of cell culture. Secondary structure analysis by far UV circular dichroism revealed a minimum at 197 nm and a shoulder at 218 nm indicative for a random coil with some type II beta-turn conformation content. Lower critical solution temperature (LCST) behavior strongly depends on salt and polypeptide concentration. Importantly, first cross-linking experiments indicate successful hydrogel formation with a surface structure reminiscent to natural elastin as visualized by SEM micrographs.
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PMID:Biosynthesis of an elastin-mimetic polypeptide with two different chemical functional groups within the repetitive elastin fragment. 1594 26

Meshes of collagen and/or elastin were successfully prepared by means of electrospinning from aqueous solutions. Flow rate, applied electric field, collecting distance and composition of the starting solutions determined the morphology of the obtained fibres. Addition of PEO (M(w)=8 x 10(6)) and NaCl was always necessary to spin continuous and homogeneous fibres. Spinning a mixture of collagen and elastin resulted in fibres in which the single components could not be distinguished by SEM. Increasing the elastin content determined an increase in fibres diameters from 220 to 600 nm. The voltage necessary for a continuous production of fibres was dependent on the composition of the starting solution, but always between 10 and 25 kV. Under these conditions, non-woven meshes could be formed and a partial orientation of the fibres constituting the mesh was obtained by using a rotating tubular mandrel as collector. Collagen/elastin (1:1) meshes were stabilized by crosslinking with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). This treatment afforded materials with a high thermal stability (T(d)=79 degrees C) without altering their original morphology. Upon crosslinking PEO and NaCl were fully leached out. Smooth muscle cells grew as a confluent layer on top of the crosslinked meshes after 14 d of culture.
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PMID:Electrospinning of collagen and elastin for tissue engineering applications. 1611 44

Our prior studies demonstrated that exogenous supplements of pure hyaluronan (HA) tetramers (HA4) dramatically upregulate elastin matrix synthesis by adult vascular smooth muscle cells (SMCs). Some studies suggest that exogenous HA likely only transiently contacts and signals cells, and may elicit different cell responses when presented on a substrate (e.g., scaffold surface). To clarify such differences, we used a carbodiimide-based chemistry to tether HA4 onto glass, and compared elastin matrix synthesis by SMCs cultured on these substrates, with those cultured with equivalent amounts of exogenous HA4. Tethered HA4-layers were first characterized for homogeneity, topography, and hydrolytic stability using SEM, XPS, AFM, and FACE. In general, mode of HA4 presentation did not influence its impact on SMC proliferation, or cell synthesis of tropoelastin and matrix elastin, relative to non-HA controls; however, surface-tethered HA4 stimulated SMCs to generate significantly greater amounts of elastin-stabilizing desmosine crosslinks, which partially accounts for the greater resistance to enzymatic breakdown of elastin derived from these cultures. Elastin derived from both sets of cultures contained peptide masses that correspond to the predominant peptides present in rat aortic elastin. SEM and TEM showed that HA4-stimulated fibrillin-mediated elastin matrix deposition, and organization into fibrils. Surface-immobilized HA4 was particularly conducive to organization of elastin into aggregating fibrils, and their networking to form closely woven sheets of elastin fibers, as seen in cardiovascular tissues. The results suggest that incorporation of elastogenic HA4 mers onto cell culture substrates or scaffolds is a better approach than exogenous supplementation for in vitro or in vivo regeneration of architecturally and compositionally faithful-, and more stable mimics of native vascular elastin matrices.
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PMID:Impact of delivery mode of hyaluronan oligomers on elastogenic responses of adult vascular smooth muscle cells. 1757 66

Loss of skin elasticity is one of the main problems of ageing. This is a mechanical property influenced by elastin, a protein in the dermis which, together with collagen and glycosaminoglycans, makes up the connective tissue. This tissue is affected by a large number of events (such as cutaneous ageing, pregnancy, slimming processes and cellulitis) which eventually cause it to change. At the same time, the metabolism of the proteins of the connective tissue decreases and there is an ever greater presence of enzymes, principally elastases and collagenases, which are responsible for breaking down the elastin and the collagen. One way to prevent such a loss of elasticity is to use active ingredients that are able to inhibit elastase enzymes. A plant complex was prepared using the following plants: lady's thistle (Silybum marianum GAERTN), alchemilla or yarrow (Alchemilla vulgaris L.), horsetail (Equisetum arvense L.) as well as germinated seeds (Glycine soja Siebold and Zucc., Triticum vulgare Vilars, Medicago sativa L., Raphanus sativus L.). The complex was standardized to give the corresponding active principles, silybin, tannins, silicon and peptides, respectively, and in vitro enzymatic tests were carried out to establish its ability to inhibit elastase. The study of enzymatic inhibition was carried out using two enzymes: (1) porcine pancreatic elastase (PPE), and (2) human leukocyte elastase (HLE). The results showed that the plant complex presents non-competitive inhibition in the order of 41.0% against PPE and 50.0% against HLE. An in vivo test was made alongside the in vitro test using an SEM 474 Cutometer (Courage & Khazaka) to study the elasticity of the skin, and positive effects were obtained when applying a cosmetic formulation containing 5% of the plant complex. Image analysis of duplicates of the cutaneous surface, before and after treatment began with a product containing 5% of plant complex and showed that wrinkles were decreased by 36.7%.
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PMID:Study of the refirming effect of a plant complex. 1850 6

In order to evaluate the possibility for making artificial blood vessels, a series of microbial copolyesters poly(3-hydroxybutyrate-co-4-hydroxybutyrate)s (P3HB4HB)s containing 0-40 mol% 4-hydroxybutyrate (4HB) were studied for growth and formation of elastin of rabbit blood vessel smooth muscle cells (RaSMCs) incubated on the solvent-casting polyester films. Porous scaffolds of all P3HB4HBs except P(HB-40 mol% 4HB) were used to compare their potentials as materials for tissue engineering blood vessel (TEBV). The polyesters were studied using static contact angles, differential scanning calorimetry (DSC), cell count kit-8 (CCK-8) and Fastin elastin assays. Simultaneously, SEM, H&E and DAPI staining were employed to study cell morphology and cell growth in the polyester scaffolds. Viability of rabbit blood vessel smooth muscle cells (RaSMCs) grown on P(HB-7 mol% 4HB) films was the strongest among all other tested polyester films during the whole growth process. H&E and DAPI staining clearly suggested good cells' growth and even confluent growth in the P3HB4HB scaffolds. Fastin elastin assay demonstrated that 4HB component in the P3HB4HB copolymer benefited the elastin formation and accumulation. P(HB-20 mol% 4HB) showed a 160% more elastin production compared with that on the well-studied poly(3-hydroxybutyrate-co-12 mol% 3-hydroxyhexanoate) (PHBHHx) incubated under the same conditions. Since the P3HB4HB has adjustable elasticity and strength, combined with its ability to induce elastin formation, it can be regarded as a useful material for developing into a material for artificial blood vessels.
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PMID:The expression of cross-linked elastin by rabbit blood vessel smooth muscle cells cultured in polyhydroxyalkanoate scaffolds. 1868 1

Electrospun polyglyconate (Maxon) and its blends with proteins such as gelatin and elastin, with a spatially designed layer structure, were prepared as potential scaffolds for vascular tissue engineering. In vitro biodegradation of the electrospun tubular protein/Maxon scaffolds in phosphate buffered saline (pH = 7.3) was studied for the first time. The biodegradation is manifested by uptake of the PBS medium by the hydrophilic proteins and also by the mass loss due to the removal of degraded fragments and uncrosslinked proteins from the matrices. The effect of degradation on the structure-property relations was evaluated by IR, XRD, and DSC analyses of the aged scaffolds. The degradation of amorphous phase of Maxon in the early stages of aging has resulted in an increase in the crystallinity of the polymer. SEM analysis indicated a significant change in nanofiber morphology and fiber-breaking. The mass loss and fiber breaking have negatively impacted the mechanical properties and the effect was maximum at 15-20 days of aging. The scaffold containing low molecular weight buffer soluble elastin revealed relatively better degradation properties compared to that containing high molecular weight buffer insoluble elastin.
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PMID:In vitro biodegradation of designed tubular scaffolds of electrospun protein/polyglyconate blend fibers. 1878 Mar 60

The aim of this study was to investigate the effect of high pressure CO(2) on the crosslinking of elastin-based polymers and the characteristics of the fabricated hydrogels. A hydrogel was fabricated by chemically crosslinking alpha-elastin with glutaraldehyde at high pressure CO(2). The effects of pressure, reaction time, and crosslinker concentration on the characteristics of the fabricated hydrogels were determined. The reaction time had negligible effect on either the swelling ratio or the pore size of the fabricated hydrogels. Increasing the processing pressure from 30bar to 150bar resulted in a 60% increase in the hydrogel swelling ratio. The crosslinked hydrogels displayed stimuli-responsive characteristics towards temperature and salt concentration. The dense gas process facilitated coacervation, expedited the crosslinking reaction, and dramatically affected the micro- and macrostructures of pores within the sample. The results of micro-CT scan and SEM images demonstrated that pore interconnectivity was substantially enhanced for alpha-elastin hydrogels fabricated using high pressure CO(2). Dense gas CO(2) reduced the wall thickness and size of the pores and importantly induced channels within the structure of the alpha-elastin hydrogels. In vitro cell culture studies demonstrated that the channels facilitated fibroblast penetration and proliferation within alpha-elastin structures.
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PMID:The fabrication of elastin-based hydrogels using high pressure CO(2). 1884 97

A recombinant silk-elastin-like protein copolymer SELP-47K containing tandemly repeated amino acid sequence blocks from silk, GAGAGS, and elastin, GVGVP, was fabricated into microdiameter fibers using a wet-spinning technique. Raman spectral analysis revealed the formation of antiparallel beta-sheet crystals of the silk-like blocks. Dry SELP-47K fibers display the dependence of mechanical properties such as Young's modulus on fiber diameter, suggesting more oriented and crystallized molecular chains in small-diameter fibers. Additionally, a brittle fracture mode was identified for dry fibers by SEM analysis of fracture surfaces. Hydration dramatically influenced the mechanical behavior of SELP-47K fibers. In contrast to the high tensile strength and limited strains to failure of dry fibers, fully hydrated SELP-47K fibers possessed strains to failure as high as 700%. Furthermore, upon chemical cross-linking, a tensile mechanical strength up to 20 MPa was achieved in hydrated fibers without compromising their high deformability. By combing the silk- and elastin-derived sequences into a single SELP-47K protein polymer, we demonstrated that protein fibers with high tensile strength and high deformability can be fabricated.
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PMID:Wet-spinning of recombinant silk-elastin-like protein polymer fibers with high tensile strength and high deformability. 1918 50


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