Micelle or polymersome formation by PCL-PEG-PCL copolymers as drug delivery systems

Poly(ε-caprolactone)-b-poly(ethylene glycol)-b-poly(ε-caprolactone) (PCL-b-PEG-b-PCL, PCEC) triblock copolymers have been widely investigated in last several decades. Here, by altering the weight ratio of monomers in ring-opening polymerization, a series of PCEC triblock copolymers with varying hydrophobicity were synthesized, which were characterized by FTIR, ¹H NMR, GPC and DSC. When PCEC copolymers with different weight ratios of PCL/PEG were dispersed in different aqueous solutions, they could self-assemble and form two distinctive nanoparticular structures: micelles or polymersomes. We then chose paclitaxel (PTX) as the model drug and encapsulate PTX into PCEC polymeric micelles and polymersomes. The physicochemical characterizations of the nanoparticles such as morphology, the size and distribution, zeta potential, drug loading content, and encapsulation efficiency were also performed. Our results showed that polymeric micelles or polymersomes from PCEC both displayed narrow size distributions and could achieve high drug loading efficiencies. In vitro cellular uptake results suggested that Nile Red loaded polymeric micelles or polymersomes displayed more internalization after 24 h incubation than those after 4 h incubation. These findings suggest that polymeric micelles and polymersomes based on PCL-b-PEG-b-PCL copolymers have great potential to effectively delivery hydrophobic drugs.