In-Situ Exploration of Phytic Acid-Mediated Supramolecular Self-Assembly and Gelation

TL;DR

This study uses Raman spectroscopy to explore how phytic acid helps form hydrogels from G-quadruplexes, revealing new structural and mechanical insights.

Contribution

A noninvasive method using Raman spectroscopy to study phytic acid-mediated hydrogel self-assembly and its mechanical properties.

Findings

A previously unidentified Raman peak (∼96–110 cm–1) suggests lattice packing of G-tetrads in the hydrogel.

Phytic acid acts as a cross-linker at low concentrations and forms clusters at higher concentrations to enhance mechanical strength.

Raman monitoring of P–OH stretching and water hydrogen bonding reveals structural changes in the hydrogel.

Abstract

Molecular gels emerge
as a promising type of material
owing to
their high tunability for versatile applications. However, there are
still gaps in our mechanistic understanding of the molecular assembly
and its consequent physicochemical properties. Additionally, most
of the methods for hydrogel characterization require pretreatment,
which makes it difficult to verify the exact fibril structures of
the hydrogels and the intermolecular interactions involved. Herein,
we employed Raman spectroscopy, a technique frequently used to verify
intermolecular forces, to revisit the dynamic molecular self-assembly
of guanosine monophosphate in the acidic milieu. In addition to the
confirmed presence of G-quadruplexes in the hydrogel, a previously
unidentified peak was discovered in the low wavenumber region (∼96–110
cm–1), potentially referring to the lattice packing
of G-tetrads. The phytic acid (PA)-mediated formation of G-quadruplex-based
hydrogels consisted of a bifibre-bundle structure, resulting in higher
mechanical strength. Furthermore, we found that monitoring the P–OH
stretching mode (850–860 cm–1) and the water-associated
hydrogen bonding in the high wavenumber region (>2000 cm–1) revealed that, at low PA concentrations, PA molecules mainly act
as cross-linkers between G-quadruplex fibrils. When the concentration
increases, the aggregation of excess PA may form clusters to support
the gel void, providing extra mechanical strength. This study establishes
a methodology to noninvasively resolve the supramolecular hydrogel
self-assembly.

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