Stabilization of poly(ethylene glycol)-poly(ε-caprolactone) star block copolymer micelles via aromatic groups for improved drug delivery properties.

Hypothesis: The functionalization of poly(ethylene glycol)-poly(ε-caprolactone) (PEG-PCL) block copolymers with moieties allowing for core-crosslinking is expected to result in improved micellar stability and drug delivery properties.

Experiments: PEG-(PCL) star block copolymers were functionalized with pendant benzylthioether (BTE) groups by applying an anionic post-polymerization modification technique followed by photoradical thiol-yne addition of benzyl mercaptan. The micellar properties of PEG-(PCL) and PEG-(PCL-BTE) were studied and compared in terms of critical micelle concentration (CMC), size, morphology, drug loading and release and in vitro cytotoxicity.

Findings: In comparison with unmodified PEG-(PCL) micelles, PEG-(PCL-BTE) micelles exhibited a 15-fold lower CMC, a 15-fold smaller size and a 50% higher drug loading and encapsulation efficiency thanks to the presence of pendant benzyl groups which provide the possibility for micellar core-crosslinking via supramolecular π-π stacking and additional hydrophobic interactions. Whereas the PEG-(PCL) micelles showed significant aggregation during in vitro cytotoxicity experiments, the PEG-(PCL-BTE) micelles showed no signs of aggregation and were capable of solubilizing high concentrations of curcumin, resulting in a significant decrease in MCF-7 cell viability after 48 h. Their ease of synthesis combined with promising results regarding drug delivery make the PEG-(PCL-BTE) micelles appealing for application in the field of encapsulation.