Self-assembled biodegradable micelles based on star-shaped PCL-b-PEG copolymers for chemotherapeutic drug delivery

Amphiphilic 3-armed star-shaped copolymers based on biodegradable monomethoxy poly (ethylene glycol) (MPEG) and poly (ɛ-caprolactone) (PCL) were synthesized and characterized in this study. The obtained star-shaped PCL-b-PEG copolymer (SPCE) can form micelles by self-assembly without any organic solvents with the assistance of ultrasonication. Moreover, the hydrophobic chemotherapeutic agent, honokiol, can be trapped in the hydrophobic inner core of micelles. In this paper, the drug loading capacity and encapsulation efficiency were measured with High Performance Liquid Chromatography (HPLC). The particle size distribution and zeta potential of prepared micelles were determined using Malvern laser particle sizer. The result of transmission electron microscopy (TEM) measurement showed that the micelles exhibited a spherical shape. X-ray diffraction (XRD) was explored to study the crystal structure of SPCE, free honokiol and honokiol loaded SPCE micelles to confirm whether honokiol was enclosed in the core–shell micelle structure. And honokiol could be released from SPCE micelles in an extended profile in vitro. MTT assay confirmed that the cytotoxicity of honokiol loaded SPCE micelles is very low. The results indicated that the SPCE micelles might be a candidate for honokiol delivery in cancer chemotherapy.