Background Nanotechnology has developed into a key technology of the 21st century. Over the recent years, the number of nanotechnical products has received an enormous boost. Furthermore, nanotechnology in medical applications provides new opportunities for diagnostic and therapeutic interventions in a variety of human diseases. Especially in rheumatoid arthritis (RA) an early diagnosis is still missing, although the treatment is most effective when started early. However, safety aspects still represent crucial problems for the further development of nanotechnology based products. Therefore, the focus of our work here was to identify putative effects of amino-PVA-coated super paramagnetic iron oxide nanoparticles (SPION) on human immune cell functions.
Objectives We analysed the effects of various concentrations of PVA coated SPION on cell viability and cell activation with regard to cytokine secretion in a whole blood assay.
Methods Venous blood, obtained from 18 healthy donors (HD) or 19 patients suffering from RA was collected. Whole blood was diluted 1:1 with RPMI 1640 culture medium in deep-well-plates, and cells were stimulated with LPS (1μg/ml), PHA (5μg/ml), PVA-SPION (1μg/ml, 10μg/ml, 100μg/ml, 1000μg/ml) or left untreated for 20h at 37°C. Cells were analysed for viability by flow cytometry, and supernatants were collected for quantification of cytokines via Bio-Plex® suspension array system. Cell viability was analysed by a combined staining for cell specific surface markers (CD3; CD14; CD15; CD19) and apoptotic and dead cells using Annexin V and 7AAD. As a second approach, intracellular IL1β was analysed to identify the main producers of IL1β. Therefore, cellular transport was blocked by adding Brefeldin A to the whole blood 3h prior to analysis.
Results For both HD and RA, we did not find any significant influence on cell viability as induced by PVA-SPION at concentrations <1000μg/ml. However, when analysing the impact of PVA-SPION on cytokine secretion, we demonstrated a significant dose dependent increase of several secreted cytokines in the cell culture supernatant (such as IL1β, IL4, IL6, IL8 or MIP1b for both HD and RA samples). When analysing IL1β secretion in more detail, we found a PVA-SPION concentration dependent increase in the percentage of IL1β positive cells. Furthermore, we observed that the major cell populations producing IL1β after incubation with PVA-SPION are CD15 positive granulocytes as well as CD14 positive monocytes.
Conclusions PVA-SPION at concentrations up to 1000μg/ml do not increase the frequencies of apoptotic or dead human immune cells but do induce a PVA-SPION dose dependent cytokine secretion. We conclude that PVA-SPION represent a promising diagnostic and possibly also a therapeutic tool in rheumatic diseases, but prior to clinical use the impact of PVA-SPION on other human immune cells and the induction of cytokine secretion has to be further evaluated.
Disclosure of Interest : None declared
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