Issue 8, 2017

Probing the surface chemistry of self-assembled peptide hydrogels using solution-state NMR spectroscopy

Abstract

The surface chemistry of self-assembled hydrogel fibres – their charge, hydrophobicity and ion-binding dynamics – is recognised to play an important role in determining how the gels develop as well as their suitability for different applications. However, to date there are no established methodologies for the study of this surface chemistry. Here, we demonstrate how solution-state NMR spectroscopy can be employed to measure the surface chemical properties of the fibres in a range of hydrogels formed from N-functionalised dipeptides, an effective and versatile class of gelator that has attracted much attention. By studying the interactions with the gel fibres of a diverse range of probe molecules and ions, we can simultaneously study a number of surface chemical properties of the NMR invisible fibres in an essentially non-invasive manner. Our results yield fresh insights into the materials. Most notably, gel fibres assembled using different tiggering methods bear differing amounts of negative charge as a result of a partial deprotonation of the carboxylic acid groups of the gelators. We also demonstrate how chemical shift imaging (CSI) techniques can be applied to follow the formation of hydrogels along chemical gradients. We apply CSI to study the binding of Ca2+ and subsequent gelation of peptide assemblies at alkaline pH. Using metal ion-binding molecules as probes, we are able to detect the presence of bound Ca2+ ions on the surface of the gel fibres. We briefly explore how knowledge of the surface chemical properties of hydrogels could be used to inform their practical application in fields such as drug delivery and environmental remediation.

Graphical abstract: Probing the surface chemistry of self-assembled peptide hydrogels using solution-state NMR spectroscopy

Supplementary files

Article information

Article type
Paper
Submitted
24 Oct 2016
Accepted
31 Jan 2017
First published
31 Jan 2017
This article is Open Access
Creative Commons BY license

Soft Matter, 2017,13, 1716-1727

Probing the surface chemistry of self-assembled peptide hydrogels using solution-state NMR spectroscopy

M. Wallace, J. A. Iggo and D. J. Adams, Soft Matter, 2017, 13, 1716 DOI: 10.1039/C6SM02404A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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