Saloplastic Macroporous Polyelectrolyte Complexes: Cartilage Mimics

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Abstract

Complexes of sodium poly(4-styrenesulfonate) (NaPSS) and poly(diallyldimethylammonium chloride) (PDADMAC) were formed on mixing equimolar solutions in high salt concentration. Under ultracentrifugal fields, the complex precipitates were transformed into compact polyelectrolyte complexes (CoPECs), which showed extensive porosity. The mechanical properties of CoPECS make them attractive for bioimplants and tissue engineering applications. Free NaPSS chains in the closed pores of CoPECs create excess osmotic pressure, which controls the pore size and contributes to the mechanical resistance of the material. The mechanical properties of CoPECs, modulated by the ionic strength of the doping medium, were studied by uniaxial tensile testing and the stress−strain data were fit to a three-element Maxwell model which revealed at least two regimes of stress relaxation.

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Comparison of the equilibrium response of articular cartilage in unconfined compression, confined compression and indentation.

R.K. Korhonen, M.S Laasanen, J. Töyräs … (2002)

At mechanical equilibrium, articular cartilage is usually characterized as an isotropic elastic material with no interstitial fluid flow. In this study, the equilibrium properties (Young's modulus, aggregate modulus and Poisson's ratio) of bovine humeral, patellar and femoral cartilage specimens (n=26) were investigated using unconfined compression, confined compression, and indentation tests. Optical measurements of the Poisson's ratio of cartilage were also carried out. Mean values of the Young's modulus (assessed from the unconfined compression test) were 0.80+/-0.33, 0.57+/-0.17 and 0.31+/-0.18MPa and of the Poisson's ratio (assessed from the optical test) 0.15+/-0.06, 0.16+/-0.05 and 0.21+/-0.05 for humeral, patellar, and femoral cartilages, respectively. The indentation tests showed 30-79% (p<0.01) higher Young's modulus values than the unconfined compression tests. In indentation, values of the Young's modulus were independent of the indenter diameter only in the humeral cartilage. The mean values of the Poisson's ratio, obtained indirectly using the mathematical relation between the Young's modulus and the aggregate modulus in isotropic material, were 0.16+/-0.06, 0.21+/-0.05, and 0.26+/-0.08 for humeral, patellar, and femoral cartilages, respectively. We conclude that the values of the elastic parameters of the cartilage are dependent on the measurement technique in use. Based on the similar values of Poisson's ratios, as determined directly or indirectly, the equilibrium response of articular cartilage under unconfined and confined compression is satisfactorily described by the isotropic elastic model. However, values of the isotropic Young's modulus obtained from the in situ indentation tests are higher than those obtained from the in vitro unconfined or confined compression tests and may depend on the indenter size in use.

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Optical and mechanical determination of Poisson's ratio of adult bovine humeral articular cartilage.

J.S. Jurvelin, M.D. Buschmann, E.B. Hunziker … (1997)

The equilibrium stiffness of articular cartilage is controlled by flow-independent elastic properties (Young's modulus, ES, and Poisson's ratio, v(s)) of the hydrated tissue matrix. In the current study, an optical (microscopic) method has been developed for the visualization of boundaries of cylindrical bovine humeral head articular cartilage disks (n = 9), immersed in physiological solution, and compressed in unconfined geometry. This method allowed a direct, model-independent estimation of Poisson's ratio of the tissue at equilibrium, as well as characterization of the shape changes of the sample during the nonequilibrium dynamic phase. In addition to optical analyses, the equilibrium behavior of cartilage disks in unconfined and confined ramp-stress relaxation tests provided a direct estimation of the aggregate modulus, H(a) and Young's modulus and, indirectly, Poisson's ratio for the articular cartilage. The mean value for Poisson's ratio obtained from the optical analysis was 0.185 +/- 0.065 (mean +/- S.D., n = 9). Values of elastic parameters obtained from the mechanical tests were 0.754 +/- 0.198 MPa, 0.677 +/- 0.223 MPa, and 0.174 +/- 0.106 for H(a), ES, and v(s), respectively (mean +/- S.D., n = 7). The similar v(s)-values obtained with optical and mechanical techniques imply that, at equilibrium for these two tests, the isotropic model is acceptable for mechanical analysis. However, the microscopic technique revealed that the lateral expansion, especially during the initial phase of relaxation, was inhomogeneous through the tissue depth. The superficial cartilage zone expanded less than the radial zone. The zonal differences in expansion were attributed to the known zonal differences in the fibrillar collagen architecture and proteoglycan concentration.

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In Situ Infrared Study of Water−Sulfate Coadsorption on Gold(111) in Sulfuric Acid Solutions

Ken-ichi Ataka, Masatoshi Osawa (1998)

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Journal

Journal ID (nlm-ta): Macromolecules

Journal ID (iso-abbrev): Macromolecules

Journal ID (publisher-id): ma

Journal ID (coden): mamobx

Title: Macromolecules

Publisher: American Chemical Society

ISSN (Print): 0024-9297

ISSN (Electronic): 1520-5835

Publication date PMC-release: 22 September 2011

Publication date (Electronic): 22 September 2010

Publication date (Print): 26 October 2010

Volume: 43

Issue: 20

Pages: 8656-8663

Affiliations

Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306

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[* ]Corresponding author. E-mail: schlen@ 123456chem.fsu.edu .

Article

DOI: 10.1021/ma1012978

PMC ID: 2994323

PubMed ID: 21132107

SO-VID: 506f3a44-37bd-4c69-a7ad-dc0258ff2d1b

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This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

History

Date received : 10 June 2010

Date revision received : 31 August 2010

Funding

National Institutes of Health, United States

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document-id-new-14 ma-2010-012978

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ScienceOpen disciplines: Polymer chemistry

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ScienceOpen disciplines: Polymer chemistry

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Saloplastic Macroporous Polyelectrolyte Complexes: Cartilage Mimics

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Abstract

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Trace Elements and Electrolytes

Most cited references 19

Comparison of the equilibrium response of articular cartilage in unconfined compression, confined compression and indentation.

Optical and mechanical determination of Poisson's ratio of adult bovine humeral articular cartilage.

In Situ Infrared Study of Water−Sulfate Coadsorption on Gold(111) in Sulfuric Acid Solutions

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