Immunological effects of iron oxide nanoparticles and iron-based complex drug formulations: Therapeutic benefits, toxicity, mechanistic insights, and translational considerations

Nanotechnology offers several advantages for drug delivery. However, there is the need for addressing potential safety concerns regarding the adverse health effects of these unique materials. Some such effects may occur due to undesirable interactions between nanoparticles and the immune system, and they may include hypersensitivity reactions, immunosuppression, and immunostimulation. While strategies, models, and approaches for studying the immunological safety of various engineered nanoparticles, including metal oxides, have been covered in the current literature, little attention has been given to the interactions between iron oxide-based nanomaterials and various components of the immune system. Here we provide a comprehensive review of studies investigating the effects of iron oxides and iron-based nanoparticles on various types of immune cells, highlight current gaps in the understanding of the structure-activity relationships of these materials, and propose a framework for capturing their immunotoxicity to streamline comparative studies between various types of iron-based formulations.

High-relaxivity superparamagnetic iron oxide nanoworms with decreased immune recognition and long-circulating properties

One of the core issues of nanotechnology involves masking the foreignness of nanomaterials to enable in vivo longevity and long-term immune evasion. Dextran-coated superparamagnetic iron oxide nanoparticles are very effective magnetic resonance imaging (MRI) contrast agents, and strategies to prevent immune recognition are critical for their clinical translation. Here we prepared 20 kDa dextran-coated SPIO nanoworms (NWs) of 250 nm diameter and a high molar transverse relaxivity rate R2 (∼400 mM(-1) s(-1)) to study the effect of cross-linking-hydrogelation with 1-chloro-2,3-epoxypropane (epichlorohydrin) on the immune evasion both in vitro and in vivo. Cross-linking was performed in the presence of different concentrations of NaOH (0.5 to 10 N) and different temperatures (23 and 37 °C). Increasing NaOH concentration and temperature significantly decrease the binding of anti-dextran antibody and dextran-binding lectin conconavalin A to the NWs. The decrease in dextran immunoreactivity correlated with the decrease in opsonization by complement component 3 (C3) and with the decrease in the binding of the lectin pathway factor MASP-2 in mouse serum, suggesting that cross-linking blocks the lectin pathway of complement. The decrease in C3 opsonization correlated with the decrease in NW uptake by murine peritoneal macrophages. Optimized NWs demonstrated up to 10 h circulation half-life in mice and minimal uptake by the liver, while maintaining the large 250 nm size in the blood. We demonstrate that immune recognition of large iron oxide nanoparticles can be efficiently blocked by chemical cross-linking-hydrogelation, which is a promising strategy to improve safety and bioinertness of MRI contrast agents.

Nanoparticle-induced exosomes target antigen-presenting cells to initiate Th1-type immune activation

The mechanisms associated with the induction of systemic immune responses by nanoparticles are not fully understood, but their elucidation is critical to address safety issues associated with the broader medical application of nanotechnology. In this study, a key role of nanoparticle-induced exosomes (extracellularly secreted membrane vesicles) as signaling mediators in the induction of T helper cell type 1 (Th1) immune activation is demonstrated. In vivo exposure to magnetic iron oxide nanoparticles (MIONs) results in significant exosome generation in the alveolar region of Balb/c mice. These act as a source of nanoparticle-induced, membrane-bound antigen/signaling cargo, which transfer their components to antigen-presenting cells (APCs) in the reticuloendothelial system. Through exosome-initiated signals, immature dendritic cells (iDCs) undergo maturation and differentiation to the DC1 subtype, while macrophages go through classical activation and differentiation to the M1 subtype. Simultaneously, iDCs and macrophages release various Th1 cytokines (including interleukin-12 and tumor necrosis factor α) driving T-cell activation and differentiation. Activated APCs (especially DC1 and M1 subtypes) consequently prime T-cell differentiation towards a Th1 subtype, thereby resulting in an orchestrated Th1-type immune response. Th1-polarized immune activation is associated with delayed-type hypersensitivity, which might underlie the long-term inflammatory effects frequently associated with nanoparticle exposure. These studies suggest that nanoparticle-induced exosomes provoke the immune activation and inflammatory responses that can accompany nanoparticle exposure.

Targeted iron oxide particles for in vivo magnetic resonance detection of atherosclerotic lesions with antibodies directed to oxidation-specific epitopes

OBJECTIVES

The aim of this study was to determine whether iron oxide particles targeted to oxidation-specific epitopes image atherosclerotic lesions.

BACKGROUND

Oxidized low-density lipoprotein plays a major role in atherosclerotic plaque progression and destabilization. Prior studies indicate that gadolinium micelles labeled with oxidation-specific antibodies allow for in vivo detection of vulnerable plaques with magnetic resonance imaging (MRI). However, issues related to biotransformation/retention of gadolinium might limit clinical translation. Iron oxides are recognized as safe and effective contrast agents for MRI. Because the efficacy of passively targeted iron particles remains variable, it was hypothesized that iron particles targeted to oxidation-specific epitopes might increase the utility of this platform.

METHODS

Lipid-coated ultra-small superparamagnetic iron particles (LUSPIOs) (<20 nm) and superparamagnetic iron particles (<40 nm) were conjugated with antibodies targeted to either malondialdehyde-lysine or oxidized phospholipid epitopes. All formulations were characterized, and their in vivo efficacy evaluated in apolipoprotein E deficient mice 24 h after bolus administration of a 3.9-mg Fe/kg dose with MRI. In vivo imaging data were correlated with the presence of oxidation-specific epitopes with immunohistochemistry.

RESULTS

MRI of atherosclerotic lesions, as manifested by signal loss, was observed after administration of targeted LUSPIOs. Immunohistochemistry confirmed the presence of malondialdehyde-epitopes and iron particles. Limited signal attenuation was observed for untargeted LUSPIOs. Additionally, no significant arterial wall uptake was observed for targeted or untargeted lipid-coated superparamagnetic iron oxide particles, due to their limited ability to penetrate the vessel wall.

CONCLUSIONS

This study demonstrates that LUSPIOs targeted to oxidation-specific epitopes image atherosclerotic lesions and suggests a clinically translatable platform for the detection of atherosclerotic plaque.

The immunotherapeutic effect of Fe3O4 nanoparticles as adjuvants on mice H22 live cancer

The aim of this paper is to prepare Fe3O4 nanoparticles and study its immunotherapeutic effect as adjuvants on mice H22 live cancer. The Fe3O4 nanoparticles were prepared by chemical coprecipitation route. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Energy Dispersive Analysis (EDS) were used to characterize Fe3O4 nanoparticles. The Fe3O4 nanoparticles were compared with the common alum adjuvants for its ability to induce immunity to inhibit tumor growth rate by prophylactic and therapeutic studies. Results indicated that Fe3O4 nanopaticles adsorbed autovaccine took great advantages over the common alum adjuvants after subcutaneous injection, raised the mass inhibitory rate of tumor, boosted the activity of cytotoxicity and enhanced the level of IFN-gamma cytokine. Thus, we concluded that Fe3O4 nanoparticles as adjuvants had great potential for enhancing anti-tumor immune response.

Sodium ferric gluconate complex in hemodialysis patients. II. Adverse reactions in iron dextran-sensitive and dextran-tolerant patients

BACKGROUND

Iron dextran administration is associated with a high incidence of adverse reactions including anaphylaxis and death. Although dextran, rather than iron, is believed to be the cause of these reactions, it is not known whether iron dextran-sensitive patients can be safely administered another form of parenteral iron, sodium ferric gluconate in sucrose (SFGC).

METHODS

In a 69 center, prospective, double-blind, controlled trial of safety and tolerability of SFGC, the rate of reactions to SFGC and placebo in 144 iron dextran-sensitive patients was compared with 2194 patients who were previously tolerant to iron dextran preparations. Serum tryptase levels, a marker of mast cell degranulation, also were measured.

RESULTS

Among 143 iron dextran-sensitive patients exposed to SFGC, three (2.1%) were intolerant. All three had suspected allergic events to SFGC, including one patient with a serious reaction (0.7%). One dextran-sensitive patient (0.7%) had a suspected allergic reaction after placebo. In contrast, among 2194 iron dextran-tolerant patients, reactions to SFGC were significantly less common, with SFGC intolerance seen in seven patients (0.3%; P = 0.020), including five (0.2%) who had suspected allergic events (P = 0.010), but none who had serious events (0.0%; P = 0.061). Two iron dextran-tolerant patients (0.09%) had allergic-like reactions following placebo injections. Two of the three suspected allergic events in the iron dextran-sensitive group were confirmed as mast cell dependent by a 100% increase in serum tryptase, while there were no confirmed allergic events in the iron dextran-tolerant group. Long-term exposure to SFGC in iron dextran-sensitive patients resulted in intolerance in only one additional patient and no serious adverse events.

CONCLUSIONS

Patients with a history of iron dextran sensitivity had approximately sevenfold higher rates of reaction to both placebo and SFGC compared to iron dextran tolerant patients. However, logistic regression analysis, performed to account for the higher reaction rate to placebo, suggests that this increased reactivity was not drug-specific nor immunologically mediated, but represented host idiosyncrasy. These results support the conclusions that reactions to SFGC can be attributed to pseudoallergy, and that SFGC is not a true allergen.

Specific inhibition of Escherichia coli ferrienterochelin uptake by a normal human serum immunoglobulin

Normal human serum contains an enterochelin-specific antibody which presumably acts with transferrin to hinder iron assimilation by enterochelin-producing pathogens. This antibody can be isolated from serum by sodium sulfate fractionation or affinity chromatography by employing an enterochelin-derived ligand (2,3-dihydroxy-N-benzoyl-L-serine) attached to aminohexyl Sepharose 4B. In assays of iron uptake by whole cells, the antibody inhibited enterochelin-directed uptake but not that mediated by citrate or ferrichrome. Also, the growth stimulatory effect of enterochelin on an Ent- strain of Escherichia coli was blocked by the immunoglobulin. This antibody has a high affinity for enterochelin; various elution procedures employing high salt concentrations and low pH failed to remove it from affinity columns. Elution with 3 M sodium thiocyanate or 13 mM 2,3-dihydroxybenzoic acid proved successful. Two pieces of evidence indicate the enterochelin-specific antibody is primarily of the immunoglobulin A (IgA) isotype. It could be removed from serum with goat antihuman IgA and was present only in sodium sulfate fractions of serum known to contain IgA.