Effect of colloidal silver and copper nanoparticles on generation of radical oxygen species (ROS) in human neutrophils

Introduction: Silver and copper nanoparticles (AgNPs, CuNPs) applied as hydronanocolloids are known to produce strong antibacterial and antifungal activities. They are extensively used in a number of applications including pharmacy, medicine and cosmetology (especially for surface-applied treatment of skin lesions) as well as agriculture, industry (paint, construction, etc.) and home or office (mainly disinfection applications). Moreover, there is a promising perspective of an intra-systemic NP use, especially to optimize targeted drug delivery. For the above reasons NPs cause risk of penetrating human body and exerting toxic effects and/or stress reactions. This issue has inspired the authors to launch studies on the influence of colloidal AgNPs and CuNPs on physiological potential of neutrophils, blood-cells acting as the first line of immunological defense. Methods: Physiological activity of neutrophils was evaluated by measuring their ability to generate oxygen radicals (radical oxygen species, ROS) due to the respiratory (oxidative) burst mechanism. Human, peripheral blood-isolated neutrophils were stimulated with a standard activating agent (polystyrene latex particles) to develop high physiological potential revealed by enhanced ability to produce oxygen radicals. The cells were treated with silver and copper hydronanocolloids (each applied at concentrations ranging from 0.4 to 50 mg/kg) alternatively: in the absence and presence of the mentioned activator. The level of generated ROS upon oxidative burst was monitored chemiluminometrically. Results: The tested Ag and Cu-nanocolloids were not toxic against neutrophils although they hampered mitochondrial dehydrogenase activities when applied at higher levels. At lower concentrations they tended to stimulate ROS generation; however the treatment did not launch the oxidative burst. In the case of the latex-stimulated neutrophils, both types of nanoparticles in all experimental variants did not influence the levels of produced ROS. Conclusions: The obtained results indicate that the exposure of human neutrophils to colloidal AgNPs and CuNPs does not lead to an enhanced ROS generation, which may enable direct intra-blood application of the tested nanostructures, provided further necessary toxicological studies are carried out.