Polymer-drug encapsulation using various PEG- and polypeptide-based block copolymer micelles

Various novel di-or tri-block copolymers with hydrophilic PEG and/or polylysine in association with hydrophobic polycaprolactone segments namely PEG-b-PolyLys and PEG-b-PolyLys-b-PCL, have been synthesized and characterized. Poly(Lys-g-Glu)-b-PCL has been successfully synthesized where D-gluconolactone was grafted on the -NH ₂ group of PolyLys. These copolymers self-assemble in water to form micelles in the size range 165 to 365 nm and CMC from 0.1 mg/ml to 2 mg/ml. Both micelle size and CMC showed a strong dependency on the hydrophobic chain length. The encapsulation of Ketoprofen and Rifampicin in the different copolymer families was assessed and encapsulation efficiency determined using UV Spectroscopy. The % drug loaded was found to depend on the interaction between drug and copolymer system. Both drugs showed chemical conjugation with PolyLys segment and physical entrapment in the PCL hydrophobic core. Higher encapsulation efficiency was obtained with Rifampicin (17-70%).