Polymer-coated silver-iron nanoparticles as efficient and biodegradable MRI contrast agents.

Bimetallic nanoparticles allow new and synergistic properties compared to the monometallic equivalents, often leading to unexpected results. Here we present on silver-iron nanoparticles coated with polyethylene glycol, which exhibit a high transverse relaxivity (316 ± 13 mM-1s-1, > 3 times that of the most common clinical benchmark based on iron oxide), excellent colloidal stability and biocompatibility in vivo. Ag-Fe nanoparticles are obtained through a one-step, low-cost laser-assisted synthesis, which makes surface functionalization with the desired biomolecules very easy. Besides, Ag-Fe nanoparticles show biodegradation over a few months, as indicated by incubation in the physiological environment. This is crucial for nanomaterials removal from the living organism and, in fact, in vivo biodistribution studies evidenced that Ag-Fe nanoparticles tend to be cleared from liver over a period in which the benchmark iron oxide contrast agent persisted. Therefore, the Ag-Fe NPs offer positive prospects for solving the problems of biopersistence, contrast efficiency, difficulties of synthesis and surface functionalization usually encountered in nanoparticulate contrast agents.

Biocompatible Iron-Boron Nanoparticles Designed for Neutron Capture Therapy Guided by Magnetic Resonance Imaging.

The combination of multiple functions in a single nanoparticle (NP) represents a key advantage of nanomedicine compared to traditional medical approaches. This is well represented by radiotherapy in which the dose of ionizing radiation should be calibrated on sensitizers biodistribution. Ideally, this is possible when the drug acts both as radiation enhancer and imaging contrast agent. Here, an easy, one-step, laser-assisted synthetic procedure is used to generate iron-boron (Fe-B) NPs featuring the set of functions required to assist neutron capture therapy (NCT) with magnetic resonance imaging. The Fe-B NPs exceed by three orders of magnitude the payload of boron isotopes contained in clinical sensitizers. The Fe-B NPs have magnetic properties of interest also for magnetophoretic accumulation in tissues and magnetic hyperthermia to assist drug permeation in tissues. Besides, Fe-B NPs are biocompatible and undergo slow degradation in the lysosomal environment that facilitates in vivo clearance through the liver-spleen-kidneys pathway. Overall, the Fe-B NPs represent a new promising tool for future exploitation in magnetic resonance imaging-guided boron NCT at higher levels of efficacy and tolerability.