Green synthesis of κ-carrageenan@Ag submicron-particles with high aqueous stability, robust antibacterial activity and low cytotoxicity.

Silver nanoparticles (AgNPs) are effective antimicrobial reagent, especially for the treatment of multidrug-resistant microorganisms. However, it is difficult to remove the residual harmful reducing agents in AgNPs synthesized by the traditional chemical reduction method. In addition, AgNPs exhibit cytotoxicity when exposed directly to cells for biomedical applications and will rapidly aggregate in aqueous environment. Herein, we develop a new route to synthesize submicron-particles containing AgNPs (κC@Ag MPs) with high aqueous stability, robust antibacterial activity and low cytotoxicity. AgNPs were firstly greenly synthesized using κ-carrageenan as environmental friendly reducing and stabilizing agent under heating in aqueous solution. Then the AgNPs were immobilized in the net of κ-carrageenan by adding KCl to obtain κC@Ag MPs. The results indicated that κC@Ag MPs were quite stable without any agglomeration and precipitation in aqueous solution for more than three months. κC@Ag MPs exhibited robust antibacterial activity against Gram-positive and Gram-negative bacteria, even better than that of pure AgNPs. Notably, κC@Ag MPs maintained the long-lasting retention of antibacterial activity. In addition, κC@Ag MPs possessed well cytocompatibility towards the L02 and L929 cells. Overall, κC@Ag MPs may have prospective application as effective and sustainable antibacterial agent in biomedical fields.