Synthesis and in vitro evaluation of novel SPION-PEG-gH625 multifunctional nanosystems for cancer theranosis

The research on supermagnetic iron oxide nanoparticles (SPIONs) has been growing exponentially over the last several years. SPIONs have been established as a promising platform because of their eclectic biomedical applications such as, cancer theranosis, i.e. therapy, by hyperthermia and/or magnetically controlled drug delivery, and diagnosis by means of magnetic resonance imaging (MRI)1 . For these kind of applications, multifunctional SPIONs simultaneously modified with biological ligands, biocompatible polymers (most often polyethylene glycol PEG), drugs and fluorescence labels are especially interesting, because they combine the possibility of targeted drug delivery and in vivo imaging of treated tumors by means of MRI and fluorescence. Once accumulated in tumors, the nanosystems are expected to recognise cancer cells and to penetrate inside them, in order to enhance the theranostic potential. However, the intracellular accumulation of the nanosystems depends on their ability to cross cellular membranes. In order to explore the possibility to improve the cellular uptake of PEGylated SPIONs, we have functionnalized the surface of their PEG5000 coating with a membranotropic peptide gH6252 . The nanosystems contained also fluorescent molecules (cyanine) covalently attached to the SPION core. The core-shell nanosystems were carefully characterized in terms of their physico-chemical properties (hydrodynamic size, zeta potential, chemical composition) prior to study the interaction with cancer cells MDA-MB-231 in vitro. Quantitative determination of the uptaken nanosystems in the cells was made using both the analysis of the cyanine fluorescence (by flow cytometry) and of the iron content (by atomic absorption spectrophotometry - SAA). Moreover, we analysed the peptide effect on the subcellular nanosystems distribution and interaction, using transmission electron microscopy (TEM) and confocal spectral imaging (CSI) of the cyanine fluorescence. The results showed the capacity of the peptide gH625 to promote cellular internalization with a possibility of modification of the uptake mechanism