Superparamagnetic Nanoparticles coupled with silver and copper: growth inhibition of bacterial pathogens

Magnetite nanoparticles are extensively applied in different fields thanks to their properties conferred by the nanoscale size. The purpose of this work is to test Biomimetic Magnetic nanoparticles and Magnetic nanoparticles, both coupled with silver or copper, against different bacterial pathogens; they were tested both against gram-positive and gram-negative bacteria. The physico-chemical characterization of the samples is obtained by Dynamic Light Scattering and ICP mass spectroscopy for both immobilized ions on both types of nanoparticles to confirm the presence of the cations, previously assessed through indirect quantitative analysis performed during the immobilization. The workflow to test the inhibition activity is reported below: the concentration of different ions was tested using soft agar plates to confirm growth inhibition and we were able to verify the formation of a distinctive halo around sample spots, confirming the exclusive inhibitory activity of our nanoassemblies when compared with superparamagnetic nanoparticles not treated with the cations. A growth curve for both pathogens was determined, and a Colony Forming Unit test was done to quantify the grown cells; Minimum Concentration Inhibitory (MIC) tests have been also performed overtime. Biomimetic nanoparticles and Magnetic nanoparticles coupled with silver or copper have different behavior depending on which bacteria is under test. Anyway, an inhibitory activity was found for both bacteria strains in presence of both ions immobilized on the nanoparticles and this will open a new antibiotic-free approach to counteract the proliferation of antibiotic-resistant bacteria.