Synthesis and characterization of biodegradable amphiphilic star and Y-shaped block copolymers as potential carriers for vinorelbine

Two amphiphilic block copolymers using hydrophobic poly(ε-caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) were successfully synthesized. One of them is an (A-b-B)₄ type star polymer [(PCL-b-PEG)₄] and the other one is a Y-shaped PEG-(PCL)₂. A star-shaped polymer (PCL-b-PEG)₄ was prepared by ring-opening polymerization (ROP) of ε-caprolactone continued by click reaction of (PCL-azide)₄ and PEG-alkyne. The synthesis of Y-shaped PEG-(PCL)₂ block copolymer was carried out via Diels-Alder click reaction of a furan protected maleimide end-functionalized PEG (PEG-MI) with an anthracene end-functionalized PCL following the ROP of ε-caprolactone. The characterization of micelles is carried out using both materials in aqueous media as drug delivery vehicles, which showed satisfying results and enhanced the cytotoxic effect of the anti-cancer drug vinorelbine (VLB). However, micelles consisted of Y-shaped unimers were found to be more convenient for delivery of hydrophobic drugs such as VLB because they formed in lower concentration, carrying a higher amount of drugs and owing a monomodal distribution. We concluded that the free tails of hydrophobic chains in Y-shaped block copolymer facilitate the assembly of amphiphilic material in water to form micelles.