In vitro cytokine modulation by cobalt nano- and microparticles and solutions.

The use of particles from micro to nanoscale provides benefits to diverse scientific fields, but because a large percentage of their atoms lie on the surface, nanomaterials could be highly reactive and can pose potential risks to humans. Due to their wide range of application, Cobalt nano-particles are of a great interest both in industry and in life-science. To date, there are few studies on Co nano-particles toxicology. In this respect, the study aims at evaluating in vitro the potential interference of Co nano-particles on the production of several cytokines (IL-2, IL-4, IL-6, IL-10, IFNγ and TNFα) by PBMCs, comparing their effects to those of Co micro-particles and Co solution (CoCl2). Cells were cultured in Opticell flasks with escalating concentrations (10-5, 10-6 and 10-7 M), of Co nano- and micro-particles and CoCl2 or without metal. Cytokines were quantified in the supernatants using a human Th1/Th2 cytokine cytometric bead array. Co micro-particles showed a greater inhibitory effect as compared to other Co forms. Its inhibitory activity was detected at all concentrations and towards all cytokines, whereas Co solutions selectively inhibited IL-2, IL-10 and TNF-α at maximal concentration. Co nano-particles induced an increase of TNF-α and IFN-γ release and an inhibition of IL-10 and IL-2: a cytokine pattern similar to that detected in the experimental and clinical autoimmunity. On the basis of the obtained data, immune endpoints should be sought in the next series of studies both in vitro and in vivo in subjects exposed to cobalt nano-particles.