Succinylated ferritin as a novel nanocage-like vehicle of polyphenol: Structure, stability, and absorption analysis.

Ferritin, a protein with an 8-nm cage structure, can encapsulate and deliver bioactive molecules. In this study, succinylation was adopted to modify plant ferritin to fabricate succinylated red been ferritin (SRBF) at pH 8.0. The SRBF was retained as a cage-like shape (12 nm diameter), while its secondary structure was altered, rendering higher negative charge accompanies by decreased surface hydrophobicity. The SRBF also demonstrated favorable property of reversible assembly regulated by pH-transitions (pH 2.0/7.0), thus enabled successful encapsulation of epigallocatechin gallate (EGCG) for fabrication of EGCG-loaded SRBF complexes with a diameter of ~12 nm. Succinylation enhanced the thermal stabilities of ferritin and the embedded EGCG. Moreover, SRBF markedly improved the transport efficiency of EGCG in Caco-2 monolayers relative to EGCG and that encapsulated in unmodified ferritin. These findings have extended the succinylation reaction for the cage-like protein modification, and facilitated the usage of ferritin variant in delivery of bioactive molecules.

Comparative Evaluation of Intestinal Absorption and Functional Value of Iron Dietary Supplements and Drug with Different Delivery Systems.

Iron is a fundament micronutrient, whose homeostasis is strictly regulated. Iron deficiency anemia is among the most widespread nutritional deficiencies and its therapy, based on dietary supplement and drugs, may lead to severe side effects. With the aim of improving iron bioavailability while reducing iron oral therapy side effects, novel dietary supplements based on innovative technologies-microencapsulation, liposomes, sucrosomes-have been produced and marketed. In the present work, six iron dietary supplements for different therapeutic targets were compared in terms of bioaccessibility, bioavailability, and safety by using an integrated in vitro approach. For general-purpose iron supplements, ME + VitC (microencapsulated) showed a fast, burst intestinal iron absorption kinetic, which maintained iron bioavailability and ferritin expression constant over time. SS + VitC (sucrosomes), on the other side, showed a slower, time-dependent iron absorption and ferritin expression trend. ME + Folate (microencapsulated) showed a behavior similar to that of ME + VitC, albeit with a lower bioavailability. Among pediatric iron supplements, a time-dependent bioavailability increase was observed for LS (liposome), while PIC (polydextrose-iron complex) bioavailability is severely limited by its poor bioaccessibility. Finally, except for SS + VitC, no adverse effects on intestinal mucosa vitality and barrier integrity were observed. Considering obtained results and the different therapeutic targets, microencapsulation-based formulations are endowed with better performance compared to the other formulations. Furthermore, performances of microencapsulated products were obtained with a lower iron daily dose, limiting the potential onset of side effects.

Fabrication, structure, and function evaluation of the ferritin based nano-carrier for food bioactive compounds.

The low solubility, instability, and low bioavailability of food bioactive compounds such as polyphenols and flavonoids, restrict their applications in the fields of food science and nutrition. Ferritin protein has received more and more attention in encapsulation and delivery of the bioactive compounds due to its nanosized shell-like structure and its reversible self-assembly character. After encapsulation, bioactive compounds can be functionalized by the ferritin vehicle to achieve stabilization, solubilization, and targeted delivery. In addition, the outer interfaces and the porous structure of ferritin are also artfully harnessed for encapsulation. This review focuses on the newest advances in the fabrication, characterization, and application of ferritin-based nano-carriers for bioactive compounds by the reversible self-assembly, outer-interface decoration methods, and the channel-directed approach. The functional improvements of food bioactive compounds, including their solubility, stability, and cellular uptake, are emphasized. The limitations that affect ferritin encapsulation are also examined.

Positive magnetic resonance angiography using ultrafine ferritin-based iron oxide nanoparticles.

Iron oxide nanoparticles with good biocompatibility can serve as safe magnetic resonance imaging contrast agents. Herein, we report that ultrafine ferritin-based iron oxide (hematite/maghemite) nanoparticles synthesized by controlled biomimetic mineralization using genetically recombinant human H chain ferritin can be used as a positive contrast agent in magnetic resonance angiography. The synthesized magnetoferritin with an averaged core size of 2.2 ± 0.7 nm (hereafter named M-HFn-2.2) shows a r1 value of 0.86 mM-1 s-1 and a r2/r1 ratio of 25.1 at a 7 T magnetic field. Blood pool imaging on mice using the M-HFn-2.2 nanoparticles that were injected through a tail vein by single injection at a dose of 0.54 mM Fe per kg mouse body weight enabled detecting detailed vascular nets at 3 minutes post-injection; the MR signal intensity continuously enhanced up to 2 hours post-injection, which is much longer than that of the commercial magnevist (Gd-DTPA) contrast. Moreover, biodistribution examination indicates that organs such as liver, spleen and kidney safely cleared the injected nanoparticles within one day after the injection, demonstrating no risk of iron overload in test mice. Therefore, this study sheds light on developing high-performance gadolinium free positive magnetic resonance contrast agents for biomedical applications.

Pea Ferritin Stability under Gastric pH Conditions Determines the Mechanism of Iron Uptake in Caco-2 Cells.

Background: Iron deficiency is an enduring global health problem that requires new remedial approaches. Iron absorption from soybean-derived ferritin, an ∼550-kDa iron storage protein, is comparable to bioavailable ferrous sulfate (FeSO4). However, the absorption of ferritin is reported to involve an endocytic mechanism, independent of divalent metal ion transporter 1 (DMT-1), the transporter for nonheme iron. Objective: Our overall aim was to examine the potential of purified ferritin from peas (Pisum sativum) as a food supplement by measuring its stability under gastric pH treatment and the mechanisms of iron uptake into Caco-2 cells. Methods: Caco-2 cells were treated with native or gastric pH-treated pea ferritin in combination with dietary modulators of nonheme iron uptake, small interfering RNA targeting DMT-1, or chemical inhibitors of endocytosis. Cellular ferritin formation, a surrogate measure of iron uptake, and internalization of pea ferritin with the use of specific antibodies were measured. The production of reactive oxygen species (ROS) in response to equimolar concentrations of native pea ferritin and FeSO4 was also compared. Results: Pea ferritin exposed to gastric pH treatment was degraded, and the released iron was transported into Caco-2 cells by DMT-1. Inhibitors of DMT-1 and nonheme iron absorption reduced iron uptake by 26-40%. Conversely, in the absence of gastric pH treatment, the iron uptake of native pea ferritin was unaffected by inhibitors of nonheme iron absorption, and the protein was observed to be internalized in Caco-2 cells. Chlorpromazine (clathrin-mediated endocytosis inhibitor) reduced the native pea ferritin content within cells by ∼30%, which confirmed that the native pea ferritin was transported into cells via a clathrin-mediated endocytic pathway. In addition, 60% less ROS production resulted from native pea ferritin in comparison to FeSO4. Conclusion: With consideration that nonheme dietary inhibitors display no effect on iron uptake and the low oxidative potential relative to FeSO4, intact pea ferritin appears to be a promising iron supplement.

Ferritin Nanocarrier Traverses the Blood Brain Barrier and Kills Glioma.

Over the last decades, considerable efforts have been put into developing active nanocarrier systems that cross the blood brain barrier (BBB) to treat brain-related diseases such as glioma tumors. However, to date none have been approved for clinical usage. Here, we show that a human H-ferritin (HFn) nanocarrier both successfully crosses the BBB and kills glioma tumor cells. Its principle point of entry is the HFn receptor (transferrin receptor 1), which is overexpressed in both BBB endothelial cells (ECs) and glioma cells. Importantly, we found that HFn enters and exits the BBB via the endosome compartment. In contrast, upon specifically targeting and entering glioma cells, nearly all of the HFn accumulated in the lysosomal compartment, resulting in the killing of glioma tumor cells, with no HFn accumulation in the surrounding healthy brain tissue. Thus, HFn is an ideal nanocarrier for glioma therapy and possesses the potential to serve as a therapeutic approach against a broad range of central nervous system diseases.

Extending Half Life of H-Ferritin Nanoparticle by Fusing Albumin Binding Domain for Doxorubicin Encapsulation.

Nanoparticles based on the heavy chain of the human ferritin (HFn) are arousing growing interest in the field of drug delivery due to their exceptional characteristics. However, the unsatisfied plasma half life of HFn substantially limits its application as a delivery platform for antitumor agents. Herein we fused an albumin binding domain (ABD) variant that basically derives from the streptococcal protein G and possesses a long-acting characteristic in serum albumin to the N-terminus of the HFn for the aim of half-life extension. This ABD-HFn construct was highly expressed and fully self-assembled into symmetrical and spherical structure in E. coli bacteria. The purified ABD-HFn showed a similar particle size with wild-type HFn and also exhibited an extremely high binding affinity with human serum albumin. To evaluate the therapeutic potential of this ABD-HFn construct in terms of half-life extension, we encapsulated a model antitumor agent doxorubicin (DOX) into the ABD-HFn. Significantly outstanding loading efficacy of above 60 molecules doxorubicin for each ABD-HFn cage was achieved. The doxorubicin-loaded ABD-HFn nanoparticle was characterized and further compared with the recombinant HFn counterpart. The ABD-HFn/DOX nanoparticle showed dramatically improved stability and comparable cell uptake rate when compared with HFn/DOX counterpart. Pharmacokinetics study in Sprague-Dawley rats showed that ABD-HFn/DOX nanoparticle possessed significantly prolonged plasma half life of ∼17.2 h, exhibiting nearly 19 times longer than that of free doxorubicin and 12 times for HFn/DOX. These optimal results indicated that fusion with ABD will be a promising strategy to extend the half life for protein-based nanoparticles.

Ferritin nanocage with intrinsically disordered proteins and affibody: A platform for tumor targeting with extended pharmacokinetics.

Ferritin nanocages are of particular interest as a novel platform for drug and vaccine delivery, diagnosis, biomineralization scaffold and more, due to their perfect and complex symmetry, ideal physical properties, high biocompatibility, low toxicity profiles as well as easy manipulation by genetic or chemical strategies. However, a short half-life is still a hurdle for the translation of ferritin-based nanomedicines into the clinic. Here, we developed a series of rationally designed long circulating ferritin nanocages (LCFNs) with 'Intrinsically Disordered Proteins (IDP)' as a stealth layer for extending the half-life of ferritin nanocages. Through predictions with 3D modelling, the LCFNs were designed, generated and their pharmacokinetic parameters including half-life, clearance rate, mean residence time, and more, were evaluated by qualitative and quantitative analysis. LCFNs have a tenfold increased half-life and overall improved pharmacokinetic parameters compared to wild-type ferritin nanocages (wtFN), corresponding to the low binding against bone marrow-derived macrophages (BMDMs) and endothelial cells. Subsequently, a tumor targeting moiety, epidermal growth factor receptor (EGFR)-targeting affibody peptide, was fused to LCFNs for evaluating their potential as a theragnostic platform. The tumor targeting-LCFNs successfully accumulated to the tumor tissue, by efficient targeting via active and passive properties, and also the shielding effect of IDP in vivo. This strategy can be applied to other protein-based nanocages for further progressing their use in the field of nanomedicine.

Ferritin glycosylated by chitosan as a novel EGCG nano-carrier: Structure, stability, and absorption analysis.

Ferritin is a shell-like carrier protein with an 8nm diameter cavity which endows a natural space to encapsulate food and drug components. In this work, phytoferritin was unprecedentedly glycosylated by chitosan to fabricate ferritin-chitosan Maillard reaction products (FCMPs) (grafting degree of 26.17%, 24h, 55°C). Results indicated that the amide I and II bands of ferritin were altered due to the chitosan grafting, whereas the ferritin spherical structure were retained. Simulated digestion analysis showed that the FCMPs were more resistant to pepsin and trypsin digestion as compared with ferritin alone. Furthermore, FCMPs were employed as carrier to encapsulate epigallocatechin gallate (EGCG) molecules with an encapsulation ratio of 12.87% (w/w), and the resulting FCMPs-EGCG complexes showed a slow release of EGCG in simulated gastrointestinal tract. Interestingly, different types of food components displayed different effects in EGCG release behavior from the FCMPs, wherein proanthocyanidin, milk and soy protein inhibited the EGCG release. In addition, the absorption of EGCG encapsulated in FCMPs in Caco-2 monolayer model was significantly improved as compared with free EGCG. This work provides a novel nano-vehicle for fabricating core-shell systems in food and drug delivery domain.

Protein cage nanostructure as drug delivery system: magnifying glass on apoferritin.

INTRODUCTION: New frontiers in nanomedicine are moving towards the research of new biomaterials. Apoferritin (APO), is a uniform regular self-assemblies nano-sized protein with excellent biocompatibility and a unique structure that affords it the ability to stabilize small active molecules in its inner core. Areas covered: APO can be loaded by applying a passive process (mainly used for ions and metals) or by a unique formulative approach based on disassemby/reassembly process. In this article, we aim to organize the experimental evidence provided by a number of studies on the loading, release and targeting. Attention is initially focused on the most investigated antineoplastic drug and contrast agents up to the most recent application in gene therapy. Expert opinion: Various preclinical studies have demonstrated that APO improved the potency and selectivity of some chemotherapeutics. However, in order to translate the use of APO into therapy, some issues must be solved, especially regarding the reproducibility of the loading protocol used, the optimization of nanocarrier characterization, detailed understanding of the final structure of loaded APO, and the real mechanism and timing of drug release.

Engineered Human Ferritin Nanoparticles for Direct Delivery of Tumor Antigens to Lymph Node and Cancer Immunotherapy.

Efficient delivery of tumor-specific antigens (TSAs) to lymph nodes (LNs) is essential to eliciting robust immune response for cancer immunotherapy but still remains unsolved. Herein, we evaluated the direct LN-targeting performance of four different protein nanoparticles with different size, shape, and origin [Escherichia coli DNA binding protein (DPS), Thermoplasma acidophilum proteasome (PTS), hepatitis B virus capsid (HBVC), and human ferritin heavy chain (hFTN)] in live mice, using an optical fluorescence imaging system. Based on the imaging results, hFTN that shows rapid LN targeting and prolonged retention in LNs was chosen as a carrier of the model TSA [red fluorescence protein (RFP)], and the flexible surface architecture of hFTN was engineered to densely present RFPs on the hFTN surface through genetic modification of subunit protein of hFTN. The RFP-modified hFTN rapidly targeted LNs, sufficiently exposed RFPs to LN immune cells during prolonged period of retention in LNs, induced strong RFP-specific cytotoxic CD8+ T cell response, and notably inhibited RFP-expressing melanoma tumor growth in live mice. This suggests that the strategy using protein nanoparticles as both TSA-carrying scaffold and anti-cancer vaccine holds promise for clinically effective immunotherapy of cancer.

Epigallocatechin Gallate (EGCG) Decorating Soybean Seed Ferritin as a Rutin Nanocarrier with Prolonged Release Property in the Gastrointestinal Tract.

The instability and low bioavailability of polyphenols limit their applications in food industries. In this study, epigallocatechin gallate (EGCG) and soybean seed ferritin deprived of iron (apoSSF) were fabricated as a combined double shell material to encapsulate rutin flavonoid molecules. Firstly, due to the reversible assembly characteristics of phytoferritin, rutin was successfully encapsulated within apoSSF to form a ferritin-rutin complex (FR) with an average molar ratio of 28.2: 1 (rutin/ferritin). The encapsulation efficiency and loading capacity of rutin were 18.80 and 2.98 %, respectively. EGCG was then bound to FR to form FR-EGCG composites (FRE), and the binding number of EGCG was 27.30 ± 0.68 with a binding constant K of (2.65 ± 0.11) × 10(4) M(-1). Furthermore, FRE exhibited improved rutin stability, and displayed prolonged release of rutin in simulated gastrointestinal tract fluid, which may be attributed to the external attachment of EGCG to the ferritin cage potentially reducing enzymolysis in GI fluid. In summary, this work demonstrates a novel nanocarrier for stabilization and sustained release of bioactive polyphenols.

Targeted tumor delivery and controlled release of neuronal drugs with ferritin nanoparticles to regulate pancreatic cancer progression.

Pancreatic cancer is a lethal malignancy whose progression is highly dependent on the nervous microenvironment. This study develops neural drug-loaded ferritin nanoparticles (Ft NPs) to regulate the nervous microenvironment, in order to control the pancreatic cancer progression. The drug-loaded Ft NPs can target pancreatic tumors via passive targeting of EPR effects of tumors and active targeting via transferrin receptor 1 (TfR1) binding on cancer cells, with a triggered drug release in acidic tumor environment. Two drugs, one activates neural activity (carbachol), the other impairs neural activity (atropine), are encapsulated into the Ft NPs to form two kinds of nano drugs, Nano-Cab NPs and Nano-Ato NPs, respectively. The activation of the nervous microenvironment by Nano-Cab NPs significantly promotes the pancreatic tumor progression, whereas the blockage of neural niche by Nano-Ato NPs remarkably impairs the neurogenesis in tumors and the progression of pancreatic cancer. The Ft-based nanoparticles thus comprise an effective and safe route of delivery of neural drugs for novel anti-cancer therapy.

Ferritin has an important immune function in the ark shell Scapharca broughtonii.

Ferritin, the principle cytosolic iron storage protein in the majority of living organisms, has important roles during immune process in invertebrates. Detailed information about ferritin in the ark shell Scapharca broughtonii, however, has been very limited. In this study, full-length ferritin (termed SbFer) was cloned by the rapid amplication of cDNA ends (RACE) method based upon the sequence from the transcriptome library. The cDNA contained a 182 bp 5'-untranslated region, a 519 bp open reading frame encoding a polypeptide of 172 amino acids, a 229 bp 3'-untranslated region, and three introns (902, 373 and 402 bp) embedded in four exons. There was an iron response element (IRE) in the 5'-untranslated region. The deduced amino acid sequence of SbFer possessed many characteristics of vertebrate H type ferritin, shared 63%-91% identity with mollusks and greater identity with vertebrate H type ferritin compared to the L type. The SbFer gene expression pattern examined by quantitative real-time PCR showed ferritin mRNA was expressed in all ark shell tissues examined. The highest levels of expression were found in hemocytes with decreasing levels of expression in foot, mantle, gill, adductor muscle and hepatopancreas. A challenge with Vibrio anguillarum resulted in time-dependent significant upregulation of SbFer mRNA, indicating SbFer participated actively in the bacterial defense process. Further analysis of the antibacterial activity indicated recombinant SbFer could function as an immune antibacterial agent to both Gram-positive and Gram-negative bacteria. Taken together, these results suggested strongly that ferritin of the ark shell is involved in immune defense against microbial infection and it is a constitutive and inducible acute-phase protein.

Folic acid conjugated ferritins as photosensitizer carriers for photodynamic therapy.

We coupled folic acid as a tumour targeting ligand to the surface of ferritins and loaded them with ZnF16Pc. The resulting nanoconjugates can efficiently hone in on 4T1 tumours in vivo, and, with photoirradiation, leading to suppressed tumour growth and tumour metastasis.

A nanoparticulate ferritin-core mimetic is well taken up by HuTu 80 duodenal cells and its absorption in mice is regulated by body iron.

BACKGROUND: Iron (Fe) deficiency anemia remains the largest nutritional deficiency disorder worldwide. How the gut acquires iron from nano Fe(III), especially at the apical surface, is incompletely understood. OBJECTIVE: We developed a novel Fe supplement consisting of nanoparticulate tartrate-modified Fe(III) poly oxo-hydroxide [here termed nano Fe(III)], which mimics the Fe oxide core of ferritin and effectively treats iron deficiency anemia in rats. METHODS: We determined transfer to the systemic circulation of nano Fe(III) in iron-deficient and iron-sufficient outbread Swiss mouse strain (CD1) mice with use of (59)Fe-labeled material. Iron deficiency was induced before starting the Fe-supplementation period through reduction of Fe concentrations in the rodent diet. A control group of iron-sufficient mice were fed a diet with adequate Fe concentrations throughout the study. Furthermore, we conducted a hemoglobin repletion study in which iron-deficient CD1 mice were fed for 7 d a diet supplemented with ferrous sulfate (FeSO4) or nano Fe(III). Finally, we further probed the mechanism of cellular acquisition of nano Fe(III) by assessing ferritin formation, as a measure of Fe uptake and utilization, in HuTu 80 duodenal cancer cells with targeted inhibition of divalent metal transporter 1 (DMT1) and duodenal cytochrome b (DCYTB) before exposure to the supplemented iron sources. Differences in gene expression were assessed by quantitative polymerase chain reaction. RESULTS: Absorption (means ± SEMs) of nano Fe(III) was significantly increased in iron-deficient mice (58 ± 19%) compared to iron-sufficient mice (18 ± 17%) (P = 0.0001). Supplementation of the diet with nano Fe(III) or FeSO4 significantly increased hemoglobin concentrations in iron-deficient mice (170 ± 20 g/L, P = 0.01 and 180 ± 20 g/L, P = 0.002, respectively). Hepatic hepcidin mRNA expression reflected the nonheme-iron concentrations of the liver and was also comparable for both nano Fe(III)- and FeSO4-supplemented groups, as were iron concentrations in the spleen and duodenum. Silencing of the solute carrier family 11 (proton-coupled divalent metal ion transporter), member 2 (Slc11a2) gene (DMT1) significantly inhibited ferritin formation from FeSO4 (P = 0.005) but had no effect on uptake and utilization of nano Fe(III). Inhibiting DCYTB with an antibody also had no effect on uptake and utilization of nano Fe(III) but significantly inhibited ferritin formation from ferric nitrilotriacetate chelate (Fe-NTA) (P = 0.04). Similarly, cellular ferritin formation from nano Fe(III) was unaffected by the Fe(II) chelator ferrozine, which significantly inhibited uptake and utilization from FeSO4 (P = 0.009) and Fe-NTA (P = 0.005). CONCLUSIONS: Our data strongly support direct nano Fe(III) uptake by enterocytes as an efficient mechanism of dietary iron acquisition, which may complement the known Fe(II)/DMT1 uptake pathway.

Effect of iron status in rats on the absorption of metal ions from plant ferritin.

An isolate of lead-ferritin obtained from soybean seeds sprouted in 25 mM of PbNO3 was introduced into the diet of both iron-deficient and iron non-deficient male rats. After a 21-day administration period, statistical differences in the lead accumulation in the femurs of the rats were noted. Iron-deficient rats accumulated more than four times the amount of lead in their bones than rats without iron-deficiency. No further decrease was observed in haemoglobin concentrations in the groups of animals fed with lead isolates, either iron-deficient or iron non-deficient. Also, no differences in the mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV) were observed at the end of the experiment in the group of iron non-deficient rats fed with lead-ferritin isolate compared to the control group of iron non-deficient rats. In the iron-deficient group fed with lead-ferritin isolate, a small increase in haemoglobin concentrations, MCH, MCV and mean corpuscular haemoglobin concentrations (MCHC) was recorded. The results presented in this paper confirm that lead from the tested preparation-lead ferritin isolate-was better absorbed by those rats with induced iron deficiency anaemia. Additionally, we may also suspect based on the obtained results that absorption of ferritin-iron depends on iron status in the body.

Toxicity, biodistribution, and ex vivo MRI detection of intravenously injected cationized ferritin.

The goal of the work was to establish the toxicity and biodistribution of the superparamagnetic protein cationized ferritin (CF) after intravenous injection. Intravenously injected CF has been used to target the extracellular matrix with high specificity in the kidney glomerulus, allowing measurements of individual glomeruli using T2*-weighted MRI. For the routine use of CF as an extracellular matrix-specific tracer, it is important to determine whether CF is toxic. In this work, we investigated the renal and hepatic toxicity, leukocyte count, and clearance of intravenously injected CF. Furthermore, we studied CF labeling in several organs using MRI and immunohistochemistry. Serum measurements of biomarkers suggest that intravenous injection of CF is neither nephrotoxic nor hepatotoxic and does not increase leukocyte counts in healthy rats at a dose of 5.75 mg/100 g. In addition to known glomerular labeling, confocal and MRI suggest that intravenously injected CF labels the extracellular matrix of the hepatic sinusoid, extracellular glycocalyx of alveolar endothelial cells, and macrophages in the spleen. Liver T2* values suggest that CF is cleared by 7 days after injection. These results suggest that CF may serve as a useful contrast agent for detection of a number of structures and functions with minimal toxicity.

Absorption of iron from ferritin is independent of heme iron and ferrous salts in women and rat intestinal segments.

Ferritin iron from food is readily bioavailable to humans and has the potential for treating iron deficiency. Whether ferritin iron absorption is mechanistically different from iron absorption from small iron complexes/salts remains controversial. Here, we studied iron absorption (RBC (59)Fe) from radiolabeled ferritin iron (0.5 mg) in healthy women with or without non-ferritin iron competitors, ferrous sulfate, or hemoglobin. A 9-fold excess of non-ferritin iron competitor had no significant effect on ferritin iron absorption. Larger amounts of iron (50 mg and a 99-fold excess of either competitor) inhibited iron absorption. To measure transport rates of iron that was absorbed inside ferritin, rat intestinal segments ex vivo were perfused with radiolabeled ferritin and compared to perfusion with ferric nitrilotriacetic (Fe-NTA), a well-studied form of chelated iron. Intestinal transport of iron absorbed inside exogenous ferritin was 14.8% of the rate measured for iron absorbed from chelated iron. In the steady state, endogenous enterocyte ferritin contained >90% of the iron absorbed from Fe-NTA or ferritin. We found that ferritin is a slow release source of iron, readily available to humans or animals, based on RBC iron incorporation. Ferritin iron is absorbed by a different mechanism than iron salts/chelates or heme iron. Recognition of a second, nonheme iron absorption process, ferritin endocytosis, emphasizes the need for more mechanistic studies on ferritin iron absorption and highlights the potential of ferritin present in foods such as legumes to contribute to solutions for global iron deficiency.

In vivo magnetic resonance imaging of ferritin-based reporter visualizes native neuroblast migration.

Adult neurogenesis research in mammals presents a challenge as most stem cells and progenitors are located deep in opaque brain tissues. Here, we describe an efficient ferritin-based magnetic resonance imaging (MRI) reporter and its use to label mouse subventricular zone progenitors, enabling in vivo visualization of endogenous neuroblast migration toward the olfactory bulb. We quantify the effect of the ferritin transgene expression on cellular iron transport proteins such as transferrin receptor, divalent metal transporter and STEAP reductase. Based on these data, we elucidate key aspects of the cellular pathways that the reporter utilizes to load iron and form its superparamagnetic core. This MRI reporter gene platform can facilitate the non-invasive study of native or transplanted stem cell migration and associated neurogenic or therapeutic molecular events in live animals.