title: Mechanisms of Iron Uptake from Ferric Phosphate Nanoparticles in Human Intestinal Caco-2 Cells.
abstract: Food fortification programs to reduce iron deficiency anemia require bioavailable forms of iron that do not cause adverse organoleptic effects. Rodent studies show that nano-sized ferric phosphate (NP-FePO4) is as bioavailable as ferrous sulfate, but there is controversy over the mechanism of absorption. We undertook in vitro studies to examine this using a Caco-2 cell model and simulated gastrointestinal (GI) digestion. Supernatant iron concentrations increased inversely with pH, and iron uptake into Caco-2 cells was 2-3 fold higher when NP-FePO4 was digested at pH 1 compared to pH 2. The size and distribution of NP-FePO4 particles during GI digestion was examined using transmission electron microscopy. The d50 of the particle distribution was 413 nm. Using disc centrifugal sedimentation, a high degree of agglomeration in NP-FePO4 following simulated GI digestion was observed, with only 20% of the particles ≤1000 nm. In Caco-2 cells, divalent metal transporter-1 (DMT1) and endocytosis inhibitors demonstrated that NP-FePO4 was mainly absorbed via DMT1. Small particles may be absorbed by clathrin-mediated endocytosis and micropinocytosis. These findings should be considered when assessing the potential of iron nanoparticles for food fortification.
authors.affiliation: 1Norwich Medical School, University of East Anglia, Norwich, Norfolk NR4 7UQ, UK; a.perfecto@uea.ac.uk2School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; c.n.elgy@bham.ac.uk (C.E.); e.valsamijones@bham.ac.uk (E.V.-J.)3Diabetes and Nutritional Sciences Division, King's College London, London SE1 9NH, UK; paul.a.sharp@kcl.ac.uk4Institute of Food, Nutrition, and Health, ETH, Schmelzbergstrasse 9, 8092 Zürich, Switzerland; florentine.hilty@gmail.com. a.perfecto@uea.ac.uk.
authors.forename: Antonio
authors.initials: A
authors.lastname: Perfecto
authors.affiliation: 1Norwich Medical School, University of East Anglia, Norwich, Norfolk NR4 7UQ, UK; a.perfecto@uea.ac.uk2School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; c.n.elgy@bham.ac.uk (C.E.); e.valsamijones@bham.ac.uk (E.V.-J.)3Diabetes and Nutritional Sciences Division, King's College London, London SE1 9NH, UK; paul.a.sharp@kcl.ac.uk4Institute of Food, Nutrition, and Health, ETH, Schmelzbergstrasse 9, 8092 Zürich, Switzerland; florentine.hilty@gmail.com. c.n.elgy@bham.ac.uk.
authors.forename: Christine
authors.initials: C
authors.lastname: Elgy
authors.affiliation: 1Norwich Medical School, University of East Anglia, Norwich, Norfolk NR4 7UQ, UK; a.perfecto@uea.ac.uk2School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; c.n.elgy@bham.ac.uk (C.E.); e.valsamijones@bham.ac.uk (E.V.-J.)3Diabetes and Nutritional Sciences Division, King's College London, London SE1 9NH, UK; paul.a.sharp@kcl.ac.uk4Institute of Food, Nutrition, and Health, ETH, Schmelzbergstrasse 9, 8092 Zürich, Switzerland; florentine.hilty@gmail.com. e.valsamijones@bham.ac.uk.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Valsami-Jones
authors.affiliation: 1Norwich Medical School, University of East Anglia, Norwich, Norfolk NR4 7UQ, UK; a.perfecto@uea.ac.uk2School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; c.n.elgy@bham.ac.uk (C.E.); e.valsamijones@bham.ac.uk (E.V.-J.)3Diabetes and Nutritional Sciences Division, King's College London, London SE1 9NH, UK; paul.a.sharp@kcl.ac.uk4Institute of Food, Nutrition, and Health, ETH, Schmelzbergstrasse 9, 8092 Zürich, Switzerland; florentine.hilty@gmail.com. paul.a.sharp@kcl.ac.uk.
authors.forename: Paul
authors.initials: P
authors.lastname: Sharp
authors.affiliation: 1Norwich Medical School, University of East Anglia, Norwich, Norfolk NR4 7UQ, UK; a.perfecto@uea.ac.uk2School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; c.n.elgy@bham.ac.uk (C.E.); e.valsamijones@bham.ac.uk (E.V.-J.)3Diabetes and Nutritional Sciences Division, King's College London, London SE1 9NH, UK; paul.a.sharp@kcl.ac.uk4Institute of Food, Nutrition, and Health, ETH, Schmelzbergstrasse 9, 8092 Zürich, Switzerland; florentine.hilty@gmail.com. florentine.hilty@gmail.com.
authors.forename: Florentine
authors.initials: F
authors.lastname: Hilty
authors.affiliation: 1Norwich Medical School, University of East Anglia, Norwich, Norfolk NR4 7UQ, UK; a.perfecto@uea.ac.uk2School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; c.n.elgy@bham.ac.uk (C.E.); e.valsamijones@bham.ac.uk (E.V.-J.)3Diabetes and Nutritional Sciences Division, King's College London, London SE1 9NH, UK; paul.a.sharp@kcl.ac.uk4Institute of Food, Nutrition, and Health, ETH, Schmelzbergstrasse 9, 8092 Zürich, Switzerland; florentine.hilty@gmail.com. s.fairweather-tait@uea.ac.uk.
authors.forename: Susan
authors.initials: S
authors.lastname: Fairweather-Tait
mesh_terms: D018938:Caco-2 Cells; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D004063:Digestion; D004705:Endocytosis / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005290:Ferric Compounds / Q000737:chemistry / Q000493:pharmacokinetics*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007422:Intestines / Q000166:cytology / Q000187:drug effects; D007501:Iron / Q000493:pharmacokinetics*; D053768:Metal Nanoparticles / Q000737:chemistry; D010316:Particle Size; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D027682:Cation Transport Proteins; D005290:Ferric Compounds; D007501:Iron; D034741:RNA, Small Interfering; D000099236:Solute Carrier Family 11, Member 2; C035885:ferric phosphate
keywords: Caco-2 cells; DMT1; NP-FePO4; bioavailability; endocytosis; nano iron; simulated gastrointestinal digestion