title: Magnetic and relaxation properties of multifunctional polymer-based nanostructured bioferrofluids as MRI contrast agents.
abstract: A series of maghemite/polymer composite ferrofluids with variable magnetic core size, which show a good efficiency as MRI contrast agents, are presented. These ferrofluids are biocompatible and can be proposed as possible platforms for multifunctional biomedical applications, as they contain anchoring groups for biofunctionalization, can incorporate fluorescent dyes, and have shown low cellular toxicity. The magnetic properties of the ferrofluids have been determined by means of magnetization and ac susceptibility measurements as a function of temperature and frequency. The NMR dispersion profiles show that the low frequency behavior of the longitudinal relaxivity r(1) is well described by the heuristic model of (1)H nuclear relaxation induced by superparamagnetic nanoparticles proposed by Roch and co-workers. The contrast efficiency parameter, i.e., the nuclear transverse relaxivity r(2), for samples with d > 10 nm assumes values comparable with or better than the ones of commercial samples, the best results obtained in particles with the biggest magnetic core, d = 15 nm. The contrast efficiency results are confirmed by in vitro MRI experiments at ν = 8.5 MHz, thus allowing us to propose a set of optimal microstructural parameters for multifunctional ferrofluids to be used in MRI medical diagnosis.
authors.affiliation: Dipartimento di Scienze Molecolari Applicate ai Biosistemi, Università degli studi di Milano, Milano, Italy.
authors.forename: Houshang
authors.initials: H
authors.lastname: Amiri
authors.forename: Rodney
authors.initials: R
authors.lastname: Bustamante
authors.forename: Angel
authors.initials: A
authors.lastname: Millán
authors.forename: Nuno J O
authors.initials: NJ
authors.lastname: Silva
authors.forename: Rafael
authors.initials: R
authors.lastname: Piñol
authors.forename: Lierni
authors.initials: L
authors.lastname: Gabilondo
authors.forename: Fernando
authors.initials: F
authors.lastname: Palacio
authors.forename: Paolo
authors.initials: P
authors.lastname: Arosio
authors.forename: Maurizio
authors.initials: M
authors.lastname: Corti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Lascialfari
mesh_terms: D003287:Contrast Media / Q000737:chemistry*; D004553:Electric Conductivity; D005290:Ferric Compounds / Q000737:chemistry*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; D011108:Polymers; C000499:ferric oxide