Metal-Enzyme Nanoaggregates Eradicate Both Gram-Positive and Gram-Negative Bacteria and Their Biofilms

To palliate the appearance of antimicrobial resistance (AMR), the use of bactericidal agents acting differently than conventional antibiotics and the elimination of bacterial biofilm, are the two most promising strategies. Here, we integrated these two complementary strategies into new antimicrobial metal-enzyme nanoaggregates (NAs) of α-amylase and silver (αAgNAs) that are able to eliminate bacteria and their biofilm. The nanoparticle (NP) synthesis approach applied protein desolvation and laccase-mediated NP stabilization to innovatively produce catalytically active α-amylase nanoparticles (αNPs) for the elimination of the bacterial biofilm. At the same time, αNPs efficiently reduced silver for the incorporation of bactericidal Ag⁰ and formation of the αAgNAs. The bactericidal and antibiofilm efficacies of αAgNAs were demonstrated by 5.4 and 6.1 log reduction of Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, respectively, and more than 80% removal of their biofilms, coupled with high biocompatibility. The biofilm-αAgNA interaction was assessed by quartz crystal microbalance and atomic force microscopy revealing how the degradation of a settled biofilm by αAgNAs caused an increase of the biofilm water content, thus weakening the biofilm surface attachment and facilitating its removal. With the present work, we not only provide a new efficient antimicrobial material to face the AMR threat, but we also envisage that the newly established method for the synthesis of metal-enzyme NAs is potentially transferable to other biocatalysts to expand the enzyme NP toolbox.