pH-Responsive Micelles Based on Amphiphilic Block Copolymers Bearing Ortho Ester Pendants as Potential Drug Carriers

Amphiphilic block copolymers (PEG-b-PEYM) bearing acid-labile ortho ester pendant chains were synthesized by atom transfer radical polymerization, and the effect of chain-length of the ortho-ester-bearing PEYM block on micelle properties was investigated. The length of the PEYM block affected the critical micelle concentration and pH-dependent average particle size but not the kinetics of side-chain hydrolysis. A hydrophobic dye, Nile red, was loaded in the micelles. Both the loading content and the size of the loaded micelles were influenced by the length of the PEYM block, whereas the release kinetics of Nile red was not. Provided that these acid-labile micelles are completely cell compatible, they are potentially useful bio-responsive nanocarriers for enhancing the efficacy of hydrophobic drugs.