Water and Polymer Mobility in Hydrogel Biomaterials Quantified by ¹H NMR: A Simple Model Describing Both <i>T</i>₁ and <i>T</i>₂ Relaxation

Abstract

1H NMR T1 relaxation has been measured in a series of commercially available contact lens hydrogels of varying composition and equilibrium water content (EWC). Using previously published T2 relaxation data for the same materials, the data were analyzed using a relatively simple model incorporating magnetization transfer between water and polymer protons. It was found that both data sets were generally well described using common fit parameters. Analysis of the fitted parameters suggests that the average water mobility in these materials is largely governed by the EWC, although at a given EWC, slightly increased mobility (decreased average binding) was found in the IGEL materials that possess no exchangeable protons on the polymer chains. The combination of T1 and T2 measurements in a single model allows more accurate quantification of water and polymer mobility and binding in these hydrogels. The methodology outlined in this study should also be applicable to other hydrogel systems.