# Starch Hydrogel Films with Dual Cross-Linking: Structural and Functional Characterization

## TL;DR

This paper explores using dual cross-linking methods to improve starch hydrogel films for biomedical applications.

## Contribution

The study introduces a dual cross-linking approach combining chemical and physical methods for starch hydrogels.

## Key findings

- Chemical cross-linking with citric acid significantly stabilizes the hydrogel matrix.
- Dual cross-linking reduces water uptake and improves barrier properties.
- The combination method allows customization of hydrogel properties for biomedical use.

## Abstract

Hydrogels consist of three-dimensional polymeric networks
with
hydrophilic functional groups. This study evaluated the influence
of chemical cross-linking (Cc) using citric acid (CA) and physical
cross-linking (Pc) based on cooling and heating cycles as an eco-friendly
alternative to conventional cross-linking techniques for starch hydrogel
films. The samples were subjected to both methods to assess the potential
synergistic effects of a dual cross-linking approach. Cc hydrogel
films were produced using 0, 0.5, 1.5, 2.5% CA concentrations and
subjected to two Pc cycles. Structural, mechanical, thermal, and morphological
analyses were performed while also assessing hydration and barrier
properties. Results indicated that Cc promoted the formation of cross-links
and significantly stabilized the matrix. At a 0.5% CA concentration,
chemical cross-linking was more effective than cooling and heating
cycles, reducing solubility by up to 11% when compared to Pc sample.
Kinetic swelling studies conducted for 24 h showed that CA at 2.5%
achieved a stable equilibrium with a significant decrease in water
uptake compared to the control, also showing a denser and more rigid
network. The 1.5% CA decreased the water vapor transmission rate by
approximately 190% compared to the control group in both treatments
(Cc and Pc). These findings highlight that the combination cross-linking
has the potential to customize the physicochemical properties of starch/xanthan
hydrogels for biomedical and controlled-release applications.