Probing assembly/disassembly of ordered molecular hydrogels

Area of Science:

• Supramolecular chemistry
• Materials science
• Biomedical engineering

Background:

• Supramolecular hydrogels are vital in biomedical applications, including tissue engineering and drug delivery.
• L-Phenylalanine (Phe) self-assembles into fibrous networks, with modifications influencing gelation.
• Controlling multi-component gel systems offers advantages for tuning material properties.

Purpose of the Study:

• To investigate the structural and dynamic properties of multi-component hydrogels formed by Phe and amino-L-phenylalanine (NH2-Phe).
• To explore the patterns of ordered/disordered domains within gel fibers and their interfaces.
• To elucidate the general trends of intermolecular interactions in these complex hydrogel systems.

Main Methods:

• Utilized multicomponent gels based on Phe and NH2-Phe.
• Employed NMR crystallography (combining solid- and solution-state NMR) for structural and dynamic insights.
• Supported findings with experimental (diffraction, rheology, microscopy, thermal analysis) and computational methods.

Main Results:

• Phe and NH2-Phe self-assemble into crystalline hydrogels in water.
• NH2-Phe exhibited faster exchange dynamics than Phe, correlating with weaker intermolecular interactions.
• Low NH2-Phe concentrations disrupted the network by interfering with Phe's electrostatic interactions; high concentrations formed novel multi-gelator hydrogels.

Conclusions:

• The head groups of amino acids play a crucial role in dictating the strength of intermolecular interactions in hydrogels.
• Structural and dynamic heterogeneities in hydrogels can be effectively probed using advanced NMR techniques.
• Multi-component hydrogel systems provide a versatile platform for tailoring material properties for specific applications.