title: Transferrin receptor-1 iron-acquisition pathway - synthesis, kinetics, thermodynamics and rapid cellular internalization of a holotransferrin-maghemite nanoparticle construct.
abstract: BACKGROUND
  Targeting nanoobjects via the iron-acquisition pathway is always reported slower than the transferrin/receptor endocytosis. Is there a remedy?
  
  
  METHODS
  Maghemite superparamagnetic and theragnostic nanoparticles (diameter 8.6nm) were synthesized, coated with 3-aminopropyltriethoxysilane (NP) and coupled to four holotransferrin (TFe2) by amide bonds (TFe2-NP). The constructs were characterized by X-ray diffraction, transmission electron microscopy, FTIR, X-ray Electron Spectroscopy, Inductively Coupled Plasma with Atomic Emission Spectrometry. The in-vitro protein/protein interaction of TFe2-NP with transferrin receptor-1 (R1) and endocytosis in HeLa cells were investigated spectrophotometrically, by fast T-jump kinetics and confocal microscopy.
  
  
  RESULTS
  In-vitro, R1 interacts with TFe2-NP with an overall dissociation constant KD=11nM. This interaction occurs in two steps: in the first, the C-lobe of the TFe2-NP interacts with R1 in 50μs: second-order rate constant, k1=6×10(10)M(-1)s(-1); first-order rate constant, k-1=9×10(4)s(-1); dissociation constant, K1d=1.5μM. In the second step, the protein/protein adduct undergoes a slow (10,000s) change in conformation to reach equilibrium. This mechanism is identical to that occurring with the free TFe2. In HeLa cells, TFe2-NP is internalized in the cytosol in less than 15min.
  
  
  CONCLUSIONS
  This is the first time that a nanoparticle-transferrin construct is shown to interact with R1 and is internalized in time scales similar to those of the free holotransferrin.
  
  
  CONCLUSIONS
  TFe2-NP behaves as free TFe2 and constitutes a model for rapidly targeting theragnostic devices via the main iron-acquisition pathway.
authors: Université Paris Diderot Sorbonne Paris Cité - CNRS UMR, Paris Cedex, France.
authors: Hélène
authors: H
authors: Piraux
authors: Jun
authors: J
authors: Hai
authors: Philippe
authors: P
authors: Verbeke
authors: Nawal
authors: N
authors: Serradji
authors: Souad
authors: S
authors: Ammar
authors: Rémi
authors: R
authors: Losno
authors: Nguyêt-Thanh
authors: NT
authors: Ha-Duong
authors: Miryana
authors: M
authors: Hémadi
authors: Jean-Michel
authors: JM
authors: El Hage Chahine
mesh_terms: D015703:Antigens, CD / Q000502:physiology*; D005290:Ferric Compounds / Q000008:administration & dosage / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism*; D018613:Microscopy, Confocal; D053758:Nanoparticles; D011990:Receptors, Transferrin / Q000502:physiology*; D013816:Thermodynamics; D014168:Transferrin / Q000008:administration & dosage / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D015703:Antigens, CD; C068126:CD71 antigen; D005290:Ferric Compounds; D011990:Receptors, Transferrin; D014168:Transferrin; C110714:holotransferrin; C000499:ferric oxide; D007501:Iron