Carboxymethyl Chitosan-Functionalized Magnetic Nanoparticles for Disruption of Biofilms of Staphylococcus aureus and Escherichia coli

Bacteria in biofilms are much more resistant to antibiotics and microbicides as compared to their planktonic stage. Thus, to achieve the same antibacterial efficacy, a much higher dose of antibiotics is required for biofilm bacteria. However, the widespread use of antibiotics has been recognized as the main cause for the emergence of antibiotic-resistant microbial species, which has now become a major public health crisis globally. In this work, we present an efficient nonantibiotic-based strategy for disrupting biofilms using carboxymethyl chitosan (CMCS) coated on magnetic iron oxide nanoparticles (CMCS-MNPs). CMCS-MNPs demonstrate strong bactericidal activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) planktonic cells. More than 99% S. aureus and E. coli planktonic cells were killed after incubation with CMCS-MNPs for 10 and 5 h, respectively. In the presence of a magnetic field (MF), CMCS-MNPs can effectively penetrate into both S. aureus and E. coli biofilms, resulting in a reduction of viable cells counts by 84% and 95%, respectively, after 48 h incubation, as compared to the control experiment without CMCS-MNPs or CMCS. CMCS-MNPs are noncytotoxic toward mammalian cells and can potentially be a useful antimicrobial agent to eliminate both planktonic and biofilm bacteria.