AN ADVANCED DECORATION APPROACH TO POTENTIATE ANTICANCER ACTIVITY THROUGH BIODEGRADABLE NANOPARTICLES

In the attempt to develop novel concepts in the design of nanoplatforms for cancer treatment, here we propose core-shell nanoparticles (NPs) made of amphiphilic poly(?-caprolactone)-polyethyleneglycol (PCL-PEG) block copolymers exposing on the surface an anti-FTL1 peptide (aFLT1), to complement activity of the delivered cytotoxic agent, and folate moieties (Fol), to encourage NP accumulation in cancer cells via folate receptor (FR). NPs are designed to release slowly their drug cargo in the body once reaching tumor site. Diblock PCL-PEG copolymers with longer PEG to promote exposition of aFLT1 and folate on NP surface (PCL4000-PEG1000, PCL4000-PEG1500-antiFLT1 and PCL4300-PEG1500-Fol) were synthesized by a ring-opening polymerization (ROP) of ?-CL followed by coupling with the decorating unit followed by characterization via GPC, NMR and FTIR spectroscopy. NPs were prepared by nanoprecipitation technique, filtered through 0.45 ?m filters and immediately characterized for size, polydispersity and zeta potential. Cell uptake of NPs covalently tagged with rhodamine B at PCL end was evaluated in KB cells overexpressing folate receptor and HUVEC. To evaluate receptor-mediated accumulation, competition experiments on cells pre-incubated with free ligands were performed. Nanoprecipitation gave optimized NPs spanning in the size range 110-150 nm with very low polydispersity. For Fol-decorated NPs, the highly negative surface charge of NPs, more negative as the amount of folate-conjugated copolymer increased, was suggestive of the presence of folate moieties on the surface. NPs exposing aFLT1 on the surface showed surface charge and size similar to non-decorated NPs. Once formulation parameters were selected, entrapment of Docetaxel (DTX), a model poorly water-soluble drug, was attempted. Both NPs encapsulated DTX with high efficiency and were endowed of sustained release. In order to track NP inside cells, NPs were produced from PCL-PEG linked to rhodamine at hydroxyl end group of PCL. Pre-incubation with 1 mM Fol, employed to saturate FR on the cell surface, significantly inhibited the uptake of folate-decorated NPs in KB cells, suggesting that FR is involved in the specific uptake of a large fraction of targeted NPs. However, specific uptake was observed only when the incubation was carried out in the absence of serum likely due to the screening effect exerted by serum proteins. In conclusion, conjugation of folate to long PEG chains turns as a powerful strategy to attain receptor specific endocytosis. The further step consists in the full understanding of the biological behavior of folate bearing NPs and in evaluating the impact of aFLT1 decoration on DTX cytotoxicity.