1 Effect of Surface Chemistry and Associated Protein Corona on the Long-Term Biodegradation of Iron Oxide Nanoparticles In Vivo Grazyna Stepien, 1, ‡ María Moros, 1,2, ‡ ,* Marta Pérez-Hernández, 1,3 Marta Monge, 4,5 Lucía Gutiérrez, 1 Raluca M. Fratila, 6 Marcelo de las Heras, 7 Sebastián Menao Guillén, 8 Juan José Puente Lanzarote, 8 Conxita Solans, 4 Julián Pardo, 1,3,9 and Jesús Martínez de la Fuente. 6,10,* 1-Institute of Nanoscience of Aragon (INA), University of Zaragoza, 50018 Zaragoza, Spain 2- Institute of Applied Sciences and Intelligent Systems-CNR, Via Campi Flegrei, 34, 80078, Pozzuoli, Italy 3- Aragón Health Research Institute (IIS Aragón), Biomedical Research Centre of Aragón (CIBA), 50009 Zaragoza, Spain 4- Institute of Advanced Chemistry of Catalonia (IQAC-CSIC) and CIBER in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Jordi Girona 18-26, Barcelona 08034 5- Department of Pharmacy and Pharmaceutical Technology and Physical Chemistry, University of Barcelona, Av/Joan XXIII s/n, 08028 Barcelona, Spain Page 1 of 44 ACS Paragon Plus Environment ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60