P0025 The effect of very small superparamagnetic nanoparticles on human blood cells as a diagnostic tool in Inflammatory Bowel Disease

Abstract Background The field of application of organic or inorganic nanoparticles (1-100 nm size) is extensive and involves their use in medicine. This includes using nanoparticles in human beings or animals (life-stock) which holds advantages but also bears risks. Therefore, nanoparticles used in diagnostics and therapy should be inert not affecting tissues or immune cells. Additionally, nanoparticles should not aggregate to form clusters exceeding the size of 100 nm or accumulate in sensitive structures like bone marrow or brain for long-term deposition. We developed in-house very small superparamagnetic iron oxide nanoparticles (VSOP) with a size of 7 nm that were successfully used in preclinical magnetic resonance imaging (MRI) for the detection of intestinal inflammation and sclerosis. This study elucidates the effect of nanoparticles on human blood cells, including monocytes as well as monocyte-derived macrophages, in vitro as a first step toward clinical application in inflammatory bowel disease (IBD). Methods Whole blood of healthy donors and patients suffering from IBD as well as monocytes and monocyte-derived macrophages were treated with VSOP in vitro and analysed for changes in their transcriptome, phenotype and function. For transcriptome analysis, RNA sequencing was performed. Cell abundance, activation and proliferation were measured by mass cytometry. Migratory behavior of monocytes was analyzed by live microscopy. Cell metabolism was detected by Seahorse assay. Results RNA sequencing of monocytes showed that the most significantly regulated gene is encoding for the transferrin receptor (Tcfr). As a response to VSOP treatment and VSOP uptake thereby increasing the levels of intracellular iron, Tcfr is probably downregulated to restrict further iron uptake. While RNA sequencing of whole blood showed only significant differences in non-coding genes (C3orf86P, ENSG00000278996, ENSG00000259002), CyTOF analyses revealed that VSOP-treated monocytes are neither activated nor showing increased proliferation. Also, the migratory behavior is not influenced by VSOP uptake. Additionally, VSOP uptake resulted in an enhanced oxygen consumption rate and extracellular acidification rate. In comparison to the uptake of Latex beads, these increased rates are rather attributed to phagocytosis. Conclusion Analyses of our data with PBMC, monocytes and monocyte-derived macrophages suggest, that treatment with VSOP has no major affect on phenotype and function of immune cells. Therefore, VSOP are a promising tool for the early detection of IBD through MRI.