Gel properties and network structure of the hydrogel constructed by iota-carrageenan and Ala-Lys dipeptide

Gel properties of hydrogel-forming by Ala-Lys dipeptide (AK) and iota-carrageenan (iota-C) were investigated by rheological behavior, fourier transform infrared analysis, cryo-scanning electron microscopy, low field-NMR relaxometry and magnetic resonance imaging. Iota-carrageenan was changed from a liquid to a gel with the addition of AK, and the existence of AK significantly increased the storagemodulus (G') of iota-C from 590.4 to 1077.8 Pa. In the iota-C/AK gel, the blue-shift of O-H stretching and water deformation were observed, meanwhile, the presence of amide I band at 1682 cm(-1) was observed. The network of iota-C/AK gel showed a dense honeycomb structure with flocculating continuous phase and rough entanglement morphology. After adding AK, the water free in the pores of iota-C entered the iota-C/AK gel matrix, and the binding capacity of bound water was enhanced. These scenarios proved that the AK as the cationic dipeptide could control the conversion of negatively charged iota-C from an original random structure to a helical structure due to electrostatic interactions and hydrogen bonds. This study provides a new opportunity for the peptides into carbohydrate-based gel matrices, which could provide insights for the further application of iota-C/AK gels in the fields of food industry, tissue engineering and drug delivery. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The gel properties of hydrogel formed by Ala-Lys dipeptide and iota-carrageenan were investigated in this study. Addition of Ala-Lys dipeptide transformed iota-carrageenan from liquid to gel state and increased the storage modulus significantly. The study provided insights into the potential applications of this new gel in the fields of food industry, tissue engineering, and drug delivery.