Engineering properties of composite film from chitosan–alginate–carrageenan as antibacterial material

Chitosan–alginate–carrageenan composite films were synthesized through processes such as dissolution, mixing to form precipitation, filtration, and precipitation casting. In this process, chitosan was dissolved in an acetic acid solution at pH 3, carrageenan was dissolved in double-distilled water, and sodium alginate was dissolved in a sodium carbonate solution at pH 9. These three solutions were then mixed, reacted to form polymer precipitation due to the presence of CaCl₂. The precipitation was formed until the solution becomes transparent, after which the mixture was filtered and poured into a petri dish, and dried to form the chitosan–alginate–carrageenan composite film. The engineering properties of the chitosan–alginate–carrageenan composite films were tested and evaluated, including swelling capacity, mechanical properties, electrical conductivity, and solubility. Antibacterial activity was assessed on the chitosan–alginate–carrageenan composite films using the diffusion method. The results show that the films had a tensile strength ranging from 3.6 to 5.2 MPa, a swelling ratio of up to 1347%, and electrical conductivity from 216 to 306 µS/cm. The solubility test confirmed that the chitosan–alginate–carrageenan composite films swelled but did not dissolve in distilled water (pH 7). Notably, the chitosan–alginate–carrageenan composite films exhibited high antibacterial activity against Escherichia coli (E. coli) ATCC 25922 and Staphylococcus aureus (S. aureus) ATCC 25923.