Exploring citric acid cross-linking: achieving optimal properties in cellulose–gelatin films for antimicrobial biopolymer applications

This study investigates the cross-linking mechanism’s ability to modify and enhance material properties, particularly in biopolymer applications. Although cross-linking offers numerous advantages, precise control over the cross-linking level is essential for achieving optimal properties and reducing undesirable effects. We explored the multifunctional effects of citric acid (CA) as a cross-linking agent in cellulose–gelatin films, assessing its impact at various concentrations. Our findings reveal that excessive cross-linking does not always improve film properties. Notably, cellulose–gelatin films containing 10% (wt) CA exhibited a smooth surface and favorable characteristics, achieving a percent elongation of 77.44%, tensile strength of 0.09 MPa, and Young modulus of 1.21. The films also exhibit a high swelling ratio, indicating their excellent swelling ability in aqueous environments. Furthermore, in vitro evaluations indicated that CA significantly enhances the antibacterial activity of films against Escherichia coli and Staphylococcus aureus. These results demonstrate the potential of CA cross-linked cellulose–gelatin films in medical and healthcare applications, particularly as wound dressings that deliver durable antimicrobial efficacy.