Protein corona composition of superparamagnetic iron oxide nanoparticles with various physico-chemical properties and coatings.

Because of their biocompatibility and unique magnetic properties, superparamagnetic iron oxide nanoparticles NPs (SPIONs) are recognized as some of the most prominent agents for theranostic applications. Thus, understanding the interaction of SPIONs with biological systems is important for their safe design and efficient applications. In this study, SPIONs were coated with 2 different polymers: polyvinyl alcohol polymer (PVA) and dextran. The obtained NPs with different surface charges (positive, neutral, and negative) were used as a model study of the effect of surface charges and surface polymer materials on protein adsorption using a magnetic separator. We found that the PVA-coated SPIONs with negative and neutral surface charge adsorbed more serum proteins than the dextran-coated SPIONs, which resulted in higher blood circulation time for PVA-coated NPs than the dextran-coated ones. Highly abundant proteins such as serum albumin, serotransferrin, prothrombin, alpha-fetoprotein, and kininogen-1 were commonly found on both PVA- and dextran-coated SPIONs. By increasing the ionic strength, soft- and hard-corona proteins were observed on 3 types of PVA-SPIONs. However, the tightly bound proteins were observed only on negatively charged PVA-coated SPIONs after the strong protein elution.

Biomedical nanoparticles modulate specific CD4+ T cell stimulation by inhibition of antigen processing in dendritic cells.

Understanding how nanoparticles may affect immune responses is an essential prerequisite to developing novel clinical applications. To investigate nanoparticle-dependent outcomes on immune responses, dendritic cells (DCs) were treated with model biomedical poly(vinylalcohol)-coated super-paramagnetic iron oxide nanoparticles (PVA-SPIONs). PVA-SPIONs uptake by human monocyte-derived DCs (MDDCs) was analyzed by flow cytometry (FACS) and advanced imaging techniques. Viability, activation, function, and stimulatory capacity of MDDCs were assessed by FACS and an in vitro CD4+ T cell assay. PVA-SPION uptake was dose-dependent, decreased by lipopolysaccharide (LPS)-induced MDDC maturation at higher particle concentrations, and was inhibited by cytochalasin D pre-treatment. PVA-SPIONs did not alter surface marker expression (CD80, CD83, CD86, myeloid/plasmacytoid DC markers) or antigen-uptake, but decreased the capacity of MDDCs to process antigen, stimulate CD4+ T cells, and induce cytokines. The decreased antigen processing and CD4+ T cell stimulation capability of MDDCs following PVA-SPION treatment suggests that MDDCs may revert to a more functionally immature state following particle exposure.

Effect of cell media on polymer coated superparamagnetic iron oxide nanoparticles (SPIONs): colloidal stability, cytotoxicity, and cellular uptake studies.

The influence of the composition of the polymer coated polyvinyl alcohol (PVA), vinyl alcohol/vinyl amine copolymer (A-PVA) and polyethylenimine (PEI) coated superparamagnetic iron oxide nanoparticles (SPIONs) on the colloidal stability, cytotoxicity and cellular uptake of these particles in different cell media is reported in this paper. Although all examined polymer coated SPIONs were stable in water and PBS buffer these colloidal systems had different stabilities in DMEM or RPMI media without and supplemented with fetal calf serum (FCS). We found that A-PVA coating onto the surface of the SPIONs decreased the cytotoxicity of the polymer compared to the same concentration of A-PVA alone. As well, polyplexes of PEI-SPIONs with DNA in concentration used for transfection experiments showed no cytotoxicity compared to PEI and PEI-SPIONs. Our data show that the choice of medium largely influences the uptake of these particles by HeLa cells. The optimal medium is different for the different examined polymer coated SPIONs and it should be determined in each case, individually.

Fixed bed reactor for solid-phase surface derivatization of superparamagnetic nanoparticles.

The functionalization of nanoparticles is conditio sine qua non in studies of specific interaction with a biological target. Often, their biological functionality is achieved by covalent binding of bioactive molecules on a preexisting single surface coating. The yield and quality of the resulting coated and functionalized superparamagnetic iron oxide nanoparticles (SPIONs) can be significantly improved and reaction times reduced by using solid-phase synthesis strategies. In this study, a fixed bed reactor with a quadrupole repulsive arrangement of permanent magnets was assayed for SPION surface derivatization. The magnet array around the fixed bed reactor creates very high magnetic field gradients that enables the immobilization of SPIONs with a diameter as low as 9 nm. The functionalization on the surface of immobilized 25 nm 3-(aminopropyl)trimethoxysilane-coated SPIONs (APS-SPIONs) was performed using fluorescein-isothiocyanate directly, and by the SV40 large T-antigen nuclear localization signal peptide (PKKKRKVGC) conjugated to acryloylpoly(ethylene glycol)-N-hydroxysuccinimide, where the PEG reagent is conjugated first to create a functionalized nanoparticle and the peptide is added to the acryloyl group. We show that the yield of reactant grafted on the surface of the APS-coated SPIONs was higher in solid-phase within the fixed bed reactor compared to conventional liquid-phase chemistry. In summary, the functionalization of SPIONs using a magnetically fixed bed reactor was superior to the liquid-phase reaction in terms of the yield, reaction times required for derivatization, size distribution, and scalability.

Lectin-affinity chromatography for downstream processing of MDCK cell culture derived human influenza A viruses.

The presented study aims on the development of a capture step for the purification of cell culture derived influenza viruses using lectin affinity chromatography. Human influenza A/Puerto Rico/8/34 virus produced in Madin Darby canine kidney cells have been chosen as a model. The influenza A virus envelop possesses two viral glycoproteins: hemagglutinin and neuraminidase. Oligosaccharides of theses glycoproteins can be targeted as affinity ligands using specific lectins. First, lectins have been screened via lectin blots and spin columns. Adequate lectins have been chosen based on published glycan structures of hemagglutinin. The most specific binding was achieved via the galactose specific Erythrina cristagalli and Euonymus europaeus lectins. Second, the chromatographic separations characteristics of these lectins have been further determined via FPLC. These experiments revealed that the rate of hemagglutinin glycan binding to the ligands was higher with the E. europaeus compared to the E. cristagalli lectin. Third, viral recoveries in addition to the total protein and host cell DNA have been balanced in a series of E. europaeus lectin chromatography runs. The total protein and dsDNA content in the product fraction of the affinity chromatography was reduced from the starting conditions to 21% and 0.1%, respectively. The average viral recovery in the product fraction was 97%. SDS-PAGE analysis indicated that the majority of the eluted proteins were of viral origin. The reproducibility and column stability was confirmed in up to 25 runs applying six different virus product batches.