Modified Ca‐Alginate Films: Synthesis, Characterization, Antibacterial and Antioxidant Activity

ABSTRACT Alginate‐based biopolymers have gained significant attention due to their biocompatibility, biodegradability and ease of functionalisation, making them ideal candidates for biomedical and packaging applications. However, enhancing their antimicrobial and antioxidant capabilities remains a key research focus for expanding their practical utility. This study aimed to develop and evaluate functional Ca‐alginate films enhanced with bioactive agents for antimicrobial and antioxidant applications. Calcium alginate (Ca‐alginate) films were synthesized and modified using ampicillin (AMP), tannic acid (TA) and silver nitrate (AgNO₃). Antimicrobial activity was tested against Escherichia coli , Pseudomonas aeruginosa , Staphylococcus aureus and Bacillus subtilis , while antioxidant activity was assessed via DPPH radical scavenging and total phenol content. The design of multifunctional biopolymer films with dual antioxidant and antimicrobial activities is of great importance for applications in food preservation and wound healing. In this study, Ca‐alginate films were functionalised with tannic acid, ampicillin and silver nanoparticles to enhance their bioactivity. The functionalised films exhibited remarkable antioxidant performance, achieving a DPPH radical inhibition of 60.84% and a total phenolic content of 53.16 mg/mL. Furthermore, the Ca‐alginate–AMP films showed strong antimicrobial activity, with inhibition zones of 29.33 ± 1.15 mm against S. aureus , 20.66 ± 3.78 mm against B. subtilis , and 15.33 ± 1.52 mm against E. coli . The enhanced activities can be attributed to the synergistic effects of tannic acid's phenolic groups, the antibiotic properties of ampicillin and the antimicrobial activity of silver ions within the alginate matrix. These findings highlight the novelty of integrating multiple agents into Ca‐alginate films to achieve combined functionality, underscoring their strong potential as sustainable materials for active food packaging and biomedical wound dressing applications.