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Issue 18, 2010
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Nanoscopic mechanical anisotropy in hydrogel surfaces

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The bulk mechanical properties of soft materials have been studied widely, but it is unclear to what extent macroscopic behavior is reflected in nanomechanics. Using an atomic force microscopy (AFM) imaging method called force spectroscopy mapping (FSM), it is possible to map the nanoscopic spatial distribution of Young's modulus, i.e. “stiffness,” and determine if soft or stiff polymer domains exist to correlate nano- and macro-mechanics. Two model hydrogel systems typically used in cell culture and polymerized by a free radical polymerization process, i.e. poly (vinyl pyrrolidone) (PVP) and poly(acrylamide) (PAam) hydrogels, were found to have significantly different nanomechanical behavior despite relatively similar bulk stiffness and roughness. PVP gels contained a large number of soft and stiff nanodomains, and their size was inversely related to crosslinking density and changes in crosslinking efficiency within the hydrogel. In contrast, PAam gels displayed small nanodomains occuring at low frequency, indicating relatively uniform polymerization. Given the responsiveness of cells to changes in gel stiffness, inhomogeneities found in the PVP network indicate that careful nanomechanical characterization of polymer substrates is necessary to appreciate complex cell behavior.

Graphical abstract: Nanoscopic mechanical anisotropy in hydrogel surfaces

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The article was received on 07 May 2010, accepted on 24 Jun 2010 and first published on 09 Aug 2010

Article type: Paper
DOI: 10.1039/C0SM00339E
Citation: Soft Matter, 2010,6, 4466-4470
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    Nanoscopic mechanical anisotropy in hydrogel surfaces

    M. V. Flores-Merino, S. Chirasatitsin, C. LoPresti, G. C. Reilly, G. Battaglia and A. J. Engler, Soft Matter, 2010, 6, 4466
    DOI: 10.1039/C0SM00339E

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