Issue 45, 2022

Observation of dissipating solvated protons upon hydrogel formation

Abstract

Aqueous hyaluronan solutions form an elastic hydrogel within a narrow pH range, around pH 2.4, making this a model system to study the conformational changes of the hydrogen bond network upon gelation. This pH-dependent behavior allows us to probe water surrounding a biologically relevant molecule in different environments (liquid versus elastic state) which change due to an environmental stimulus. Here, we use Terahertz (THz) reflection absorption spectroscopy in attenuated total reflection (ATR) geometry as a tool to study gelation. THz spectroscopy is sensitive to changes in the hydrogen-bonded water network, and here we show that we can correlate changes in macroscopic properties to changes in the solvation of hyaluronan. Above and below the gelation pH, solvated protons are present in the solutions, however, this spectral signature is completely absent between pH 2.4–2.8, which is the pH at which hyaluronan forms a hydrogel. We propose that solvated protons are forming ion pairs with hyaluronan in this pH range. Adding urea or glucose to hyaluronan solutions changes their elasticity, in which an increase or decrease in elasticity can be linked to the formation and destruction of these ion pairs, respectively.

Graphical abstract: Observation of dissipating solvated protons upon hydrogel formation

Supplementary files

Article information

Article type
Paper
Submitted
28 Apr 2022
Accepted
15 Oct 2022
First published
17 Oct 2022

Phys. Chem. Chem. Phys., 2022,24, 27893-27899

Observation of dissipating solvated protons upon hydrogel formation

E. P. van Dam, B. König, S. Ramos, E. M. Adams, G. Schwaab and M. Havenith, Phys. Chem. Chem. Phys., 2022, 24, 27893 DOI: 10.1039/D2CP01949C

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