Reverse micelles based on biocompatible β-cyclodextrin conjugated polyethylene glycol block polylactide for protein delivery

A series of linear and star-shaped amphiphilic polyethylene glycol block polylactide (PEG-b-PLA) and β-cyclodextrin (CD) conjugated PEG-b-PLA (PEG-b-PLA-CD) copolymers were synthesized. Bovine serum albumin (BSA) aqueous solution was emulsified in the copolymer organic solutions to fabricate reverse micelles (RMs), and was then further transferred into ethyl oleate (EO), a pharmaceutically acceptable vehicle, by the RMs. As identified by 1H NMR, the RMs were formed with a hydrophilic core of PEG and CD, covered with a hydrophobic corona of PLA moiety, and were spherical in shape, as observed by a scan electronic microscope. Compared with the PEG-b-PLA RMs, the PEG-b-PLA-CD RMs presented higher encapsulation efficiency. The release of BSA was influenced by the copolymer composition and architecture. BSA stability in the release aqueous phase was confirmed by circular dichroism spectroscopy. The oil-based formulation fabricated from biodegradable copolymers with high drug loading showed a great potential for protein delivery.