Hybrid polyphenolic Network/SPIONs aggregates with potential synergistic effects in MRI applications

the development of novel and more efficient contrast agents for diagnostic applications is necessary to lower the dosage of such substances that might accumulate in patients with toxic effects and to define new agents which effect could go beyond the simplified scheme of T1 or T2 relaxation properties. Within this context, novel directions for MRI contrast agents based on magnetic nanoparticles entrapped inside a polyphenolic network to gain water dispersibility, were explored. Investigation about the possible realization of dual-mode contrast agents chelating Gd3+ ions on the nanoparticles coating, with tunable T1 and T2 relaxivity, has been performed. Two synthetic routes were explored, based on covalently bound Tannic Acid (TA) covering magnetic nanoparticles, or PEGylated TA entangling the magnetic systems. Hybrid aggregates having optimal stability in aqueous medium, were characterized through FT-IR, DLS, ICP-MS, XPS, TGA and STEM, confirming the formation of a stable coating around the magnetic nanoparticles, able to carry Gd species. Afterwards, their longitudinal (r1) and transverse (r2) relaxivity values were measured with a 1 T preclinical MRI scanner, as preliminary test for further MRI application. This contribute represents the first step for the preparation of tunable dual-mode contrast agents, with modifiable positive-to-negative contrast according to specific diagnostic needs, aiming to a more patient-tailorable medicinal diagnosis.