<p>Functionalization Of T Lymphocytes With Citrate-Coated Superparamagnetic Iron Oxide Nanoparticles For Magnetically Controlled Immune Therapy</p>

Abstract

PurposeImmune activation with T cell tumor infiltration is beneficial for the prognosis of patients suffering from solid cancer. Depending on their immune status, solid tumors can be immunologically classified into three groups: “hot” tumors are infiltrated with T lymphocytes, “cold” tumors are not infiltrated and “immune excluded” tumors are only infiltrated in the peripheral tumor tissue. Checkpoint inhibitors provide new therapeutic options for “hot” tumors by triggering the immune response of T cells. In order to enable this for cold tumors as well, T cells must be enriched in the tumor. Therefore, we use the principle of magnetic targeting to guide T cells loaded with citrate-coated superparamagnetic iron oxide nanoparticles (SPIONCitrate) to the tumor by an externally applied magnetic field.MethodsSPIONCitrate were produced by alkaline coprecipitation of iron(II) and iron(III) chloride and in situ coating with sodium citrate. The concentration-dependent cytocompatibility of the particles was determined by flow cytometry and blood stability assays. Atomic emission spectroscopy was used for the quantification of the particle uptake into T lymphocytes. The attractability of the loaded cells was observed by live-cell imaging in the presence of an externally applied magnetic field.ResultsSPIONCitrate displayed good cytocompatibility to T cells and did not show any sign of aggregation in blood. Finally, SPIONCitrate-loaded T cells were strongly attracted by a small external magnet.ConclusionT cells can be “magnetized” by incorporation of SPIONCitrate for magnetic targeting. The production of the particle-cell hybrid system is straightforward, as the loading process only requires basic laboratory devices and the loading efficiency is sufficient for cells being magnetically controllable. For these reasons, SPIONCitrate are potential suitable candidates for magnetic T cell targeting.

Loading of Primary Human T Lymphocytes with Citrate-Coated Superparamagnetic Iron Oxide Nanoparticles Does Not Impair Their Activation after Polyclonal Stimulation

“…The results of the viability staining with AxV and PI for one representative donor are shown in Figure 1. As previously observed for the murine T cell line EL4, SPION Citrate particle loading influenced the viability of primary human T cells as well [26]. Starting with an average cell viability of 94.4% ± 0.9% for all three donors, the loading of the T cells for 24 h decreased the proportion of viable cells from 90.2% ± 1.6% (control cells) to 75.9% ± 3.5% at an iron concentration of 100 µ g/mL.…”

“…As recently published, SPION Citrate were synthesized according to a modified protocol of Elbialy et al [26,27]. Briefly, under a protective argon atmosphere, iron(II) chloride and iron(III) chloride in a ratio of 1:2 were dissolved in water and stirred.…”

“…As previously described, sterile filtered SPION Citrate were characterized with regard to hydrodynamic diameter, zeta potential, magnetic susceptibility and blood stability [26].…”

“…The toxicity of SPION Citrate had previously been tested up to an iron concentration of 100 µg/mL using the murine T cell line EL4 (ATCC TIB-39), showing a good biocompatibility [26]. To analyze the magnetic labelling of human primary T cells, we isolated CD3 + T cells from human whole blood (Supplementary Table S1, Figure S1).…”

“…Also, Sanz-Ortega et al recently demonstrated the possibility of magnetically enriching T cells loaded with variously coated SPIONs [25]. Due to their low cytotoxicity, citrate-coated SPIONs (SPION Citrate ) have proven to be suitable for this application [26].…”