Synthesis and in vitro evaluation of fluorescent and magnetic nanoparticles functionalized with a cell penetrating peptide for cancer theranosis

The enormous developments in nanotechnology have brought significant advancements to the production of multifunctional therapeutics for the prevention and/or control of diseases. For instance, superparamagnetic iron oxide nanoparticles (SPIONs) constitute an important platform of nanomaterials that are widely used for biomedical applications such as imaging [1], cell labelling [2], hyperthermia, and drug and gene delivery. We rationally designed and synthesized multifunctional nanoparticles (NPs) composed of a SPION core, cyanine fluorescent dye emitting in far red, polyethylene glycol (PEG5000) coating, and the membranotropic peptide gH625, from the cell-penetrating peptides (CPP) family. The peptide sequence was enriched with an additional cysteine so it can be involved as a reactive moiety in a certain orientation- and sequence-specific coupling of the CPP to the PEG shell of the NPs. The in vitro evaluation performed by using fluorescence confocal spectral imaging showed that after a short incubation duration SPIONs-PEG-CPP uptake was 3-fold higher than that for SPIONs-PEG. The CPP also drives the subcellular distribution of a higher NP fraction towards low polarity cytosolic locations. Therefore, the major cellular uptake mechanism for the peptide-conjugated NPs should be endocytosis. Enhancement/acceleration of this mechanism by gH625 appears promising because of potential applications of SPIONs-PEG-gH625 as a multifunctional nanoplatform for cancer theranosis involving magnetic resonance imaging, optical imaging in far red, drug delivery, and hyperthermia.