N-Doped Carbon Nanoparticles as Antibacterial Agents on Escherichia coli: The Role of the Size and Chemical Composition of Nanoparticles

In the last years N-doped carbon nanoparticles have been shown to have improved antibacterial activity over the undoped nanomaterial, but it is difficult to find correlations between the structure of the nanoparticle and its antibacterial activity. This prevents us from proposing a clear antibacterial mechanism and makes it difficult to select materials with the best physical and chemical properties for use as antibacterial agents. With this purpose, here, we analyze the effect of, the size and the surface chemical composition of four N-doped carbon nanoparticles on the growth of Escherichia coli bacteria, used in this work as a model of Gram-negative bacteria. Our results indicated great antibacterial activity as the concentration of the carbon nanoparticles increased. The IC50 values obtained ranged between 23 and 34 μg/mL, the lowest values found in the literature for CNPs in the absence of metals. The reduction rate was analyzed using a Ligand-Substrate model based on Monod’s equation, which allows us to interpret the dependence of the nanoparticle-bacteria affinity with the nanomaterial structure. The results of the model indicate the contribution of two mechanisms, oxidative stress and the nanoknife in the antibacterial process on Escherichia coli bacteria.