Synthesis of functionalized amphiphilic copolymers for the realization of multi-­-targeted nanoparticles

Nanoparticles (NPs) have attracted significant attention in the field of innovative anticancer therapies. The most common approach to improve selectively their accumulation in tumor tissues remains surface decoration with small targeting moieties recognizing specific receptors that are over-expressed in cancer cells. Surface-decorated NPs can be prepared by either post-modification of the surface, or by synthesizing tailored all-in-one amphiphilic copolymers. With this approach, the number and nature of molecules on the surface of the resulting NPs can be finely tuned, also avoiding the premature release of drug cargo. Furthermore, NPs made with a charged copolymer can be decorated on the surface with bioresponsive polymers through electrostatic interactions. Here we describe two different synthetic approaches: NPs made by self-assembling amphiphilic copolymers bearing the target unit covalently linked on the hydrophilic chain end, and cationic NPs, able to deeply penetrate inside tumors, decorated with hyaluronic acid (HA). In the first case, copolymers are made up of PEG as hydrophilic block and PCL as hydrophobic one; in this way, methods of synthesis aimed to asymmetrically modify PEG in order to introduce ethero end groups are largely explored in literature. Here, a simple route of synthesis to selectively obtain PCL-PEG-?Folate (Fol) copolymer, with high yield and purity is described. It is known from literature that only ?-folate conjugates retain affinity towards folate-receptor ?, that is overexpressed in the majority of cancer cells. Furthermore, we demonstrate that the extent of specific internalization of targeted nanoparticles can be improved by regulating the length of the PEG chains in PCL-PEG to attain stealth properties (1000 Da) and in PCL-PEG-?Fol to improve Fol exposition on NPs surface (1500 Da). Formulations of NPs using amphiphilic copolymers with different length of PEG blocks turned to be a good strategy to enhance exposition of Fol on their surface. In the second case, amino-terminated homopolymer PCL was synthesized to obtain PCL- or PEG-PCL-based NPs with cationic surface. Cationic NPs can be "covered" with anionic molecules, like HA, through non-covalent interaction. HA encourages NPs uptake in cell overexpressing CD44 receptors. We showed how modulation of surface charge density influences cell uptake.