Multifunctional magnetic nanoparticles for enhanced intracellular drug transport

In this paper we report the synthesis and characterization of biocompatible multi-functional magnetic nanoparticles (MNPs) able to enhance the intracellular transport of N-methylated drugs. The Fe₃O₄ magnetic core was first functionalized with a mixed monolayer consisting of two different phosphonic acids having terminal acetylenic and amino groups, which provide an active platform for further functionalization with organic molecules. Then, a tetraphosphonate cavitand receptor (Tiiii) bearing an azide moiety and the N-hydroxysuccinimide (NHS) activated forms of poly(ethylene glycol) (PEG), folic acid (FA) and carboxy-X-rhodamine (Rhod) were covalently anchored on alkyne and amine moieties respectively, through 1,3-dipolar cycloaddition and EDC/NHS coupling reactions. The obtained MNPs are biocompatible and possess magnetic, luminescence and recognition properties which make them suitable for multimodal theranostic applications. In particular, combined confocal microscopy and cytotoxicity experiments showed that these multi-functional MNPs are able to recognize a specific drug "in situ" and promote its cellular internalization, thus enhancing its efficiency.