Using Magnetic Resonance Imaging to Study Enzymatic
Hydrogelation
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Abstract
Herein, we report, for the first
time, the use of MRI methods to
study enzymatic hydrogelation. Supramolecular hydrogels have been
exploited as biomaterials for many applications. However, behaviors
of the water molecules encapsulated in hydrogels have not been fully
understood. In this work, we designed a precursor <b>1</b> which
could self-assemble into nanofibers and form hydrogel <b>I</b> (gel <b>I</b>) upon the catalysis of phosphatase. The differences
of mechanic property, pore size, water diffusion rate, and magnetic
resonance relaxation times <i>T</i><sub>1</sub> and <i>T</i><sub>2</sub> of gel <b>I</b> containing different
concentrations of <b>1</b> were systematically studied and analyzed. <i>T</i><sub>1</sub>, <i>T</i><sub>2</sub>, and diffusion-weighted <sup>1</sup>H MR images from gel <b>I</b> phantoms were obtained
at 9.4 T. Analyses of the MRI data uncovered how the density of the
nanofiber networks affects the relaxation behaviors of the water protons
encapsulated in such hydrogels. Rheological analyses and cryo-TEM
observations showed increased gel elasticities with increased concentrations
of <b>1</b> while the pore sizes of gel <b>I</b> decreased.
This also resulted in an increase in the proton relaxation rate (i.e.,
shortened <i>T</i><sub>1</sub>, <i>T</i><sub>2</sub>, and apparent diffusion coefficient (ADC)) for the water encapsulated
in the hydrogel. With MRI, our study provides a new in vitro method
to potentially mimic and study in vivo diseases that involve fibrous
aggregates