Model-free Rheo-AFM probes the viscoelasticity of tunable DNA soft colloids

Moreno-Guerra, J. A., Romero-Sánchez, I. C., Martinez-Borquez, A., Tassieri, M. , Stiakakis, E. and Laurati, M. (2019) Model-free Rheo-AFM probes the viscoelasticity of tunable DNA soft colloids. Small, 15(42), 1904136. (doi: 10.1002/smll.201904136) (PMID:31460707)

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Atomic force microscopy rheological measurements (Rheo‐AFM) of the linear viscoelastic properties of single, charged colloids having a star‐like architecture with a hard core and an extended, deformable double‐stranded DNA (dsDNA) corona dispersed in aqueous saline solutions are reported. This is achieved by analyzing indentation and relaxation experiments performed on individual colloidal particles by means of a novel model‐free Fourier transform method that allows a direct evaluation of the frequency‐dependent linear viscoelastic moduli of the system under investigation. The method provides results that are consistent with those obtained via a conventional fitting procedure of the force‐relaxation curves based on a modified Maxwell model. The outcomes show a pronounced softening of the dsDNA colloids, which is described by an exponential decay of both the Young's and the storage modulus as a function of the salt concentration within the dispersing medium. The strong softening is related to a critical reduction of the size of the dsDNA corona, down to ≈70% of its size in a salt‐free solution. This can be correlated to significant topological changes of the dense star‐like polyelectrolyte forming the corona, which are induced by variations in the density profile of the counterions. Similarly, a significant reduction of the stiffness is obtained by increasing the length of the dsDNA chains, which we attribute to a reduction of the DNA density in the outer region of the corona.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Tassieri, Dr Manlio
Authors: Moreno-Guerra, J. A., Romero-Sánchez, I. C., Martinez-Borquez, A., Tassieri, M., Stiakakis, E., and Laurati, M.
College/School:College of Science and Engineering > School of Engineering > Biomedical Engineering
Journal Name:Small
ISSN (Online):1613-6829
Published Online:28 August 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Small 15(42):1904136
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
3014410Experiencing the micro-world - a cell's perspectiveManlio TassieriEngineering and Physical Sciences Research Council (EPSRC)EP/R035067/1ENG - Biomedical Engineering