Abstract
Platinum nanoparticles (PtNPs) attract great attention due to their efficient catalysis and good degree of cytocompatibility, but information about their effects on the human immune system is still missing. Monocytes are key cells of the innate immune system and the understanding of their reactions to PtNPs is crucial in view of any feasible application to human pathologies. Here, we evaluate the internalization of citrate-coated PtNPs into THP-1 monocytes and its consequences on immune cell responses. We found that the presence of intracellular PtNPs efficiently reduce reactive oxygen species (ROS) without affecting cell viability. The physiological expression of the immune receptors Cluster of Differentiation 14 (CD14), CD11b, CC-Chemokine Receptor 2 (CCR2) and CCR5 and the expression of cytokines and chemokines are not compromised by the presence of PtNPs within THP-1 cells. On the other hand, the treatment with PtNPs modulates the transcription of sixty genes, some of them involved in lipopolysaccharide (LPS) signaling in different cells. However, the treatment with PtNPs of monocytes does not compromise the LPS-induced increase of cytokines in THP-1 monocytes in vitro. Our results demonstrate that citrate-coated PtNPs are non-toxic, perform efficient intracellular reactive oxygen species (ROS) scavenging activity and possess good immune-compatibility, suggesting them as feasible synthetic enzymes for applications in nanomedicine.
Highlights
The intrinsic catalytic activity of platinum nanoparticles (PtNPs), as well as other nanomaterials such as fullerenes, palladium and cerium-oxide nanoparticles (NPs), allows efficient reactive oxygen species (ROS) removing inside cells [1,2,3]
The administration of PtNPs to THP-1 monocytes cultured in complete RPMI medium resulted in 3c.e1l.lCinytteorcnomalpizaatitbioilnityofotfhPetNPs,waisthdeTmHoPn-s1trMatoendocbyyteTsEM (Figure 2A,B)
Apoptotic and total dead cells were evaluated by flow cytometry using the Annexin V/Propidium Iodide (PI) assay; (D) Cell metabolic activity of THP-1 cells after 2, 6 and 24 h exposure to increasing doses of PtNPs evaluated by WST-8 assay. 10% DMSO was used as positive control in all the experiments
Summary
The intrinsic catalytic activity of platinum nanoparticles (PtNPs), as well as other nanomaterials such as fullerenes, palladium and cerium-oxide nanoparticles (NPs), allows efficient reactive oxygen species (ROS) removing inside cells [1,2,3]. The absence of contaminants (e.g., endotoxin, Pt precursors, toxic unreacted reagents, organic solvents, etc.) during their synthesis process is a crucial point to produce biocompatible colloidal suspensions for medical aims [16]. All these parameters influence the NP delivery and its toxicological profile, often triggering unexpected immune reactions and, increasing the contradiction of some results. Blood circulating monocytes, which are the precursors of tissue patrolling macrophages, are key cells of the innate immune system able to discriminate between “self” and “non-self” molecules [18], and aberrantly activated in acute and chronic inflammatory pathologies [19]. We demonstrated very low impact of PtNPs on the immune-physiological response and following LPS-mediated monocyte activation
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