Development of a Collagen/Clay Nanocomposite Biomaterial

2012 ◽  
Vol 706-709 ◽  
pp. 461-466 ◽  
Author(s):  
Alejandra Reyna-Valencia ◽  
P. Chevallier ◽  
D. Mantovani
Keyword(s):  
Mechanical Properties ◽  
Aqueous Media ◽  
Three Dimensional ◽  
Clay Particles ◽  
Network Characteristics ◽  
Polymer Molecules ◽  
Nanocomposite Hydrogels ◽  
Clay Concentration ◽  
Dimensional Network ◽  
Collagen Hydrogels

Collagen hydrogels are widely used as three-dimensional scaffolds for cells and tissue in culture environments. These materials, which consist of crosslinked biopolymer (protein-based) networks in aqueous media, are particularly suitable for recreating part of the extra-cellular matrix, but their poor mechanical properties represent a major limitation. One strategy to enhance the strength of this kind of hydrogels might be to incorporate clay nanoscopic particles. In fact, it has been observed that the charged surface of clay nanosheets can interact with certain functional groups belonging to polymer molecules, yielding stronger networks. Moreover, clay particles are recognized to be biocompatible. In the present work, the gelation process and the resulting morphological and mechanical properties of collagen/laponite clay nanocomposite hydrogels were invastigated. Upon gelation, the biopolymer molecules assemble into nanoscale fibrils, which bundle into fibers and entangle into a three-dimensional network. The network characteristics depend on tunable parameters such as pH and clay concentration.

Mechanochemical Devulcanization of Vulcanized Gum Natural Rubber

2005 ◽  
Vol 21 (3) ◽  
pp. 183-199
Author(s):  
G.K. Jana ◽  
C.K. Das
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Three Dimensional ◽  
Elongation At Break ◽  
Tear Strength ◽  
Vulcanized Rubber ◽  
Dimensional Network ◽  
Polymeric Chains ◽  
Cure Time

De-vulcanization of vulcanized elastomers represents a great challenge because of their three-dimensional network structure. Sulfur-cured gum natural rubbers containing three different sulfur/accelerator ratios were de-vulcanized by thio-acids. The process was carried out at 90 °C for 10 minutes in an open two-roll cracker-cum-mixing mill. Two concentrations of de-vulcanizing agent were tried in order to study the cleavage of the sulfidic bonds. The mechanical properties of the re-vulcanized rubber (like tensile strength, modulus, tear strength and elongation at break) were improved with increasing concentrations of de-vulcanizing agent, because the crosslink density increased. A decrease in scorch time and in optimum cure time and an increase in the state of cure were observed when vulcanized rubber was treated with high amounts of de-vulcanizing agent. The temperature of onset of degradation was also increased with increasing concentration of thio-acid. DMA analysis revealed that the storage modulus increased on re-vulcanization. From IR spectroscopy it was observed that oxidation of the main polymeric chains did not occur at the time of high temperature milling. Over 80% retention of the original mechanical properties (like tensile strength, modulus, tear strength and elongation at break) of the vulcanized natural rubber was achieved by this mechanochemical process.

Proanthocyanidin as a crosslinking agent for fibrin, collagen hydrogels and their composites with decellularized Wharton’s-jelly-extract for tissue engineering applications

2020 ◽  
Vol 35 (6) ◽  
pp. 554-571
Author(s):  
Elham Hasanzadeh ◽  
Narges Mahmoodi ◽  
Arefeh Basiri ◽  
Faezeh Esmaeili Ranjbar ◽  
Zahra Hassannejad ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Biomedical Application ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Wharton’S Jelly ◽  
The Body ◽  
Grape Seeds ◽  
Wharton's Jelly ◽  
Collagen Hydrogels

In tissue engineering, natural hydrogel scaffolds gained considerable attention due to their biocompatibility and similarity to macromolecular-based components in the body. However, their low mechanical strength and high degradation degree limit their biomedical application. By varying the composition of hydrogels, their biochemical and mechanical properties can be improved. In this study, the stability of fibrin and collagen hydrogels and their composites with decellularized Wharton’s jelly extract (DEWJ) was improved using proanthocyanidin (PA) as a cross-linker, extracted from grape seeds. The cytocompatibility, physicochemical and mechanical properties of the hydrogels were evaluated. Human endometrial stem cells (hEnSCs) were seeded on the hydrogels and their attachment, morphology, and proliferation were investigated using a scanning electron and optical microscopy. Our results showed that hydrogels containing DEWJ along with PA enhance cell proliferation and showed higher mechanical properties compared with the fibrin and collagen hydrogel. The results present the potential utility of these hydrogels in tissue engineering and for application in three-dimensional culture.

Thermodynamics of rubber elasticity

1976 ◽  
Vol 351 (1666) ◽  
pp. 331-350 ◽  
Keyword(s):  
Three Dimensional ◽  
Rubber Elasticity ◽  
Simple Extension ◽  
Molecular Processes ◽  
Polymer Molecules ◽  
Dimensional Network ◽  
Thermodynamic Measurements ◽  
Elastomeric Materials ◽  
Adequate Representation ◽  
Gaussian Theory

The process of vulcanization, which links the polymer molecules into a three dimensional network, enables reversible thermodynamic measurements to be made on elastomeric materials from which the entropy and energy contributions to the free energy of deformation can be determined. The molecular processes responsible for rubber elasticity are most readily interpreted in terms of the constant volume coefficients (∂ U /∂ L ) V, T and (∂ S /∂ L ) V, T . Taken as a whole the results from thermodynamic studies on lightly cross-linked rubbery polymers support the view that the retractive force is primarily intramolecular in origin. The results also show that in general the retractive force contains a significant energetic contribution. The Gaussian theory of rubber elasticity as reformulated by Flory is able to account satisfactorily for the temperature dependence of the force, but it does not lead to an adequate representation of the pressure depen­dence of the force and hence of the strain induced dilation. Several pheno­menological equations which have been proposed for predicting the dilation behaviour for the case of simple extension are considered.

New Developments in Dynamically Cured PP—EPDM Blends

2001 ◽  
Vol 74 (2) ◽  
pp. 211-220 ◽  
Author(s):  
Miguel A. López-Manchado ◽  
Miguel Arroyo ◽  
José M. Kenny
Keyword(s):  
Mechanical Properties ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Dynamic Vulcanization ◽  
New Developments ◽  
Dimensional Network ◽  
Polymeric Chains ◽  
Ethylene Propylene Diene Terpolymer ◽  
Vulcanization Process

Abstract Different procedures for preparing thermoplastic vulcanizates (TPVs), based on isotactic polypropylene (iPP) and ethylene—propylene—diene terpolymer rubber (EPDM), are used and analyzed in this work. In order to determine the effect of the vulcanization method on material properties, a rheological study, dynamic-mechanical analysis, mechanical properties and morphological study have been carried out. In all cases, the sulfur is used as crosslinking agent of the elastomeric phase. It has been shown that the dynamically cured blends (referred in the work as V2 and V3) present better properties in relation to those statically cured (V1) and uncrosslinked (V). Thus, the elastic ability, mechanical properties and rheological characteristics of these systems sensibly increase when the samples are dynamically vulcanized. Morphological analysis performed by scanning electron microscopy (SEM) is clearly in agreement with the analyzed properties, showing a better dispersion between both polymeric chains, when the blends are dynamically cured. These results seem to indicate that the dynamic vulcanization process gives rise to the formation of a thermally stable three-dimensional network, and as a consequence of it, a sensible increase of the properties is obtained.

Glucose-Responsive Hydrogels Based on Phenylboronic Acid

2018 ◽  
Vol 913 ◽  
pp. 714-721 ◽  
Author(s):  
Yuan Yuan Ma ◽  
Han Ting Liu ◽  
Jing Hong Ma ◽  
Jing Hua Gong
Keyword(s):  
Phenylboronic Acid ◽  
Aqueous Media ◽  
Three Dimensional ◽  
Immune Rejection ◽  
Key Factors ◽  
Dimensional Network ◽  
Controlled Drug Delivery System ◽  
Potential Applications ◽  
Low Toxicity ◽  
Responsive Hydrogels

Glucose-sensitive hydrogels that have three-dimensional network structure can respond to the glucose, which arouses great interest in biochemistry and biomedical. As a glucose sensitive group, Benzene boric acid has the advantages of good stability, low toxicity and no immune rejection. In this study, synthetic 3-acrylamidophenylboronic acid (AAPBA) with N-isopropylacrylamide (NIPAM) were used to fabricate glucose-responsive hydrogels via free radical polymerization in aqueous media. Several key factors such as polymer compositions and polymer concentrations have been investigated to sensitivity of the hydrogels. These polymers can respond in the presence of glucose, and the monomer ratio has a significant influence on the response behavior of hydrogels. Therefore, it has potential applications in the field of insulin-controlled drug delivery system and biosensor.

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