title: In vivoevaluation of riboflavin receptor targeted fluorescent USPIO in mice with prostate cancer xenografts.
abstract: Riboflavin (Rf) receptors bind and translocate Rf and its phosphorylated forms (e.g. flavin mononucleotide, FMN) into cells where they mediate various cellular metabolic pathways. Previously, we showed that FMN-coated ultrasmall superparamagnetic iron oxide (FLUSPIO) nanoparticles are suitable for labeling metabolically active cancer and endothelial cellsin vitro. In this study, we focused on thein vivoapplication of FLUSPIO using prostate cancer xenografts. Size, charge, and chemical composition of FLUSPIO were evaluated. We explored thein vitrospecificity of FLUSPIO for its cellular receptors using magnetic resonance imaging (MRI) and Prussian blue staining. Competitive binding experiments were performedin vivoby injecting free FMN in excess. Bio-distribution of FLUSPIO was determined by estimating iron content in organs and tumors using a colorimetric assay. AFM analysis and zeta potential measurements revealed a particulate morphology approximately 20-40 nm in size and a negative zeta potential (-24.23 ± 0.15 mV) in water. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry data confirmed FMN present on the USPIO nanoparticle surface. FLUSPIO uptake in prostate cancer cells and human umbilical vein endothelial cells was significantly higher than that of control USPIO, while addition of excess of free FMN reduced accumulation. Similarly,in vivoMRI and histology showed specific FLUSPIO uptake by prostate cancer cells, tumor endothelial cells, and tumor-associated macrophages. Besides prominent tumor accumulation, FLUSPIO accumulated in the liver, spleen, lung, and skin. Hence, our data strengthen our hypothesis that targeting riboflavin receptors is an efficient approach to accumulate nanomedicines in tumors opening perspectives for the development of diagnostic and therapeutic systems.
  
  
  BACKGROUND
  Supplementary material is available for this article at 10.1007/s12274-016-1028-7 and is accessible for authorized users.
authors.affiliation: Institute for Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 30, Aachen, 52074 Germany ; Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, Heidelberg, 69120 Germany ; Molecular Imaging Group, Department of Structural Biology, Leibniz Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, Berlin, 13125 Germany.
authors.forename: Jabadurai
authors.initials: J
authors.lastname: Jayapaul
authors.affiliation: Institute for Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 30, Aachen, 52074 Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Arns
authors.affiliation: AstraZeneca, Pharmaceutical Development, Charter Way, Macclesfield, Cheshire, SK10 2NA UK ; Molecular Profiles Ltd., 8 Orchard Place, Nottingham Business Park, Nottingham, NG8 6PX UK.
authors.forename: Matt
authors.initials: M
authors.lastname: Bunker
authors.affiliation: Institute for Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 30, Aachen, 52074 Germany.
authors.forename: Marek
authors.initials: M
authors.lastname: Weiler
authors.affiliation: Molecular Profiles Ltd., 8 Orchard Place, Nottingham Business Park, Nottingham, NG8 6PX UK.
authors.forename: Sandra
authors.initials: S
authors.lastname: Rutherford
authors.affiliation: Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, Heidelberg, 69120 Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Comba
authors.affiliation: Institute for Experimental Molecular Imaging, RWTH Aachen University, Pauwelsstrasse 30, Aachen, 52074 Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Kiessling
keywords: flavin mononucleotide; iron oxide nanoparticles; magnetic resonance imaging; molecular imaging; riboflavin carrier protein; riboflavin transporters