# Sodium Alginate/Cuprous Oxide Composite Materials with Antibacterial Properties: A Preliminary Study Revealing the Counteracting Effects of Oligosaccharides in the Matrix

## TL;DR

This study explores how adding oligosaccharides to sodium alginate and cuprous oxide composites affects their antibacterial properties, finding that oligosaccharides can reduce effectiveness by acting as food for bacteria.

## Contribution

The study reveals the counteracting effects of chitin and chitosan oligosaccharides on the antibacterial performance of sodium alginate/cuprous oxide composites.

## Key findings

- SA-Cu2O composites showed significant antibacterial activity against Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa.
- Incorporation of NACOS and COS reduced antibacterial efficacy by serving as carbon sources for bacteria.
- Antimicrobial effectiveness was not influenced by surface hydrophilicity, as shown by swelling and contact angle measurements.

## Abstract

The integration of biopolymers with antimicrobial inorganic materials has emerged as a promising strategy for developing eco-friendly and biocompatible functional materials for food packaging and biomedical applications. However, the impact of biopolymer matrix composition on the antimicrobial efficacy of inorganic fillers remains underexplored. This study addresses this critical gap by investigating the effects of chitin or chitosan oligosaccharides (NACOS or COS) on the antimicrobial properties of sodium alginate (SA)/cuprous oxide (Cu2O) composite gels. The composite gels were synthesized through a physical blending of the components, followed by calcium-induced crosslinking of SA. Characterization using UV-vis, FTIR, and EDX confirmed the successful incorporation of Cu2O, while a SEM analysis revealed its uniform dispersion. Antibacterial assays demonstrated that SA-Cu2O exhibited the highest inhibition rates, with a 67.4 ± 11.9% growth suppression of Staphylococcus aureus (MRSA), 33.7 ± 5.1% against Escherichia coli, and 39.1 ± 14.8% against Pseudomonas aeruginosa. However, incorporating NACOS and COS reduced inhibition, as oligosaccharides served as bacterial carbon sources. Swelling and contact angle measurements indicate that antimicrobial effectiveness was independent of surface hydrophilicity. These findings underscore the importance of rational composite design to balance bioactivity and material stability for antimicrobial applications.