The aim of this research was the modification of fish collagen films with various amounts of dialdehyde starch (DAS). Film properties were examined before and after the cross-linking process by DAS. Prepared biopolymer materials were characterized by Fourier Transform Infrared Spectroscopy and Atomic Force Microscopy. Moreover, the mechanical, thermal and swelling properties of the films were evaluated and the contact angle was measured. Research has shown that dialdehyde starch applied as a cross-linking agent influences collagen film properties. Mechanical testing indicated a decrease in Young's Modulus and an increase in breaking force, elongation at break, and tensile strength parameters. Results for contact angle were significantly higher for collagen films cross-linked with DAS; thus, the hydrophilicity of samples decreased. Modified samples presented a lower swelling degree in PBS than native collagen films. However, the highest values for the degree of swelling among the modified specimens were obtained from the 1% DAS samples, which were 717% and 702% for 1% and 2% collagen, respectively. Based on AFM images and roughness values, it was noticed that DAS influenced collagen film surface morphology. The lowest value of Rq was observed for 2%Coll_2%DAS and was approximately 10 nm. Analyzing thermograms for collagen samples, it was observed that pure collagen samples were less thermally stable than cross-linked ones. Dialdehyde starch is a promising cross-linking agent for collagen extracted from fish skin and may increase its applicability.
Keywords: biopolymer film; collagen; cross-linking; dialdehyde starch.