κ−Carrageenan−Based flexible antibacterial and pH−Sensitive hydrogels with phenanthroline covalent conjugation groups

Development of antibacterial materials are essential for many fields. In this paper, κ−carrageenan−based flexible antibacterial and pH−sensitive hydrogels with phenanthroline covalent conjugation groups were prepared. The swelling behavior demonstrated the hydrogels were with fairly good resistance to aqueous with pH values of 3–8. The bend, twist and compressing test revealed the hydrogels had fairly good flexibility and mechanical performance. The hydrogels were pH−sensitive because they can change color visible by the naked eye with the variation of pH values in the range of 3–5 and 9−13. The antibacterial performance against natural miscellaneous bacteria, S. aureus, E. coli and M. albican was investigated in detail. OD600 measurement, bacterial suspensions, antibacterial ring assay and morphology for the S. aureus, E. coli and M. albican showed that the hydrogels exhibited quite high antibacterial activity against both S. aureus and E. coli. The antibacterial rates against S. aureus and E. coli can reach 99% and 98% after 9 h incubation, respectively. The experiments for application in monitoring beef freshness demonstrated that the hydogels are potential materials for real–time monitoring the freshness of high protein food such as the beef.