Bactericidal Effect of Gold–Chitosan Nanocomposites in Coculture Models of Pathogenic Bacteria and Human Macrophages

The ability of pathogenic bacteria to develop resistance mechanisms to avoid the antimicrobial potential of antibiotics has become an increasing problem for the healthcare system. The search for more effective and selective antimicrobial materials, though not harmful to mammalian cells, seems imperative. Herein we propose the use of gold–chitosan nanocomposites as effective bactericidal materials avoiding damage to human cells. Nanocomposites were obtained by taking advantage of the reductive and stabilizing action of chitosan solutions on two different gold precursor concentrations. The resulting nanocomposites were added at different final concentrations to a coculture model formed by Gram-positive (Staphylococcus aureus) or Gram-negative (Escherichia coli) bacteria and human macrophages. Gold–chitosan colloids exhibited superior bactericidal ability against both bacterial models without showing cytotoxicity on human cells at the concentrations tested. Morphological and in vitro viability studies suppor...