A fistful of chemico-physical parameters crucial for 1H-NMR relaxation : the effect of size, shape and coating in iron oxides core-shell nanoparticles

An increasing awareness about novel medical applications of smaller, inorganic-based nanoparticles, possessing unique properties at the nanoscale, has led to a burst of research activities in the development of “nanoprobes” for diagnostic medicine and agents for novel, externally activated, therapies. In this research field, magnetic nanoparticles (MNPs) are prominent due to fundamental peculiar properties which make them particularly appealing to materials and biomedical applications. In particular, much attention was devoted to MNPs useful as agents for Magnetic Resonance Imaging (MRI), Optical Imaging (OI) and Magnetic Fluid Hyperthermia (MFH), carriers for drugs and vectors for molecular targeting. The possibility to collect images of the regions where the MNPs are delivered through MRI and eventually OI (if functionalized with a luminescent molecule), is joint to their use under radio-frequency fields, with frequency of the order of 100 KHz, which causes a local release of heat directed to tumour cells (the MFH effect), possibly inducing their death. By such materials, theranostic agents can be obtained. On the other hand, in the field of drug delivery and molecular targeting, few examples of reproducible experiments using superparamagnetic nanoparticles are actually present in literature. Thus, the applications of MNPs to nanomedicine is currently of growing interest in the world. The main objectives of my research group in the last decade was to contribute to the knowledge of physical mechanisms at the basis of MNPs used in biomedicine (especially MRI) and to propose some novel systems in strict collaboration with different research groups of chemists and biologists. I will present a mini-review of different case studies [1-4] where I show how the chemico-physical characteristics of MNPs are strictly correlated to their properties and can be partially interpreted with the most famous heuristic model [5] used in literature for NMR relaxivity profiles. Key Words: magnetic nanoparticles, NMR relaxivity, nanomagnetism References 1. F. Brero, M. Basini, M. Avolio, F. Orsini F., P. Arosio, C. Sangregorio, C. Innocenti, A. Guerrini, J Boucard, E. Ishow, M. Lecouvey, J. Fresnais, L. Lartigue, A. Lascialfari, Nanomaterials, 10 (2020) 1660-1672. 2. M. Basini, A. Guerrini, M. Cobianchi, F. Orsini, D. Bettega, M. Avolio, C. Innocenti, C. Sangregorio, A. Lascialfari, P. Arosio, Journal of Alloys and Compounds, 770 (2019), 58-66. 3. M. Basini, T. Orlando., P. Arosio, M.F. Casula, D. Espa, S. Murgia, C. Sangregorio, C. Innocenti, A. Lascialfari, J. Chem. Phys., 146 (2017), 034703. 4. Bordonali L., Kalaivani T., Sabareesh K.P.V., Innocenti C., Fantechi E., Sangregorio C., Casula M.F., Lartigue L., Larionova J., Guari Y., Corti M., Arosio P., Lascialfari A., Journal of Physics: Condensed Matter, 25 (2013), 066008 5. A. Roch, R.N. Muller, P. Gillis, J. Chem. Phys. 110 (1999) 5403-5411