Reduction-Responsive Core–Shell–Corona Micelles Based on Triblock Copolymers: Novel Synthetic Strategy, Characterization, and Application As a Tumor Microenvironment-Responsive Drug Delivery System

A facile and effective approach was established for fabricating core–shell–corona micelles by self-assembly of poly­(ethylene glycol)-<i>b</i>-poly­(acrylic acid-<i>co</i>-<i>tert</i>-butyl acrylate)-poly­(ε-caprolactone) (PEG₄₃-<i>b</i>-P­(AA₃₀-<i>co</i>-<i>t</i>BA₁₈)-<i>b</i>-PCL₅₃) triblock copolymer, synthesized via a combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), click chemistry, and hydrolyzation. The prenanovehicles with three different hydrolysis degrees from PEG₄₃-<i>b</i>-P<i>t</i>BA₄₈-<i>b</i>-PCL₅₃ were developed to evaluate the drug loading capacity (DLC) and drug encapsulation efficiency (DEE). After cross-linking with a disulfide bond to regulate the drug release kinetics, the spherical core–shell–corona micelles with average diameter of 52 ± 4 nm were obtained in aqueous solution. The reduction-responsive cross-linked micelles showed a slow sustained release in normal physiological conditions and a rapid release upon exposure to simulated tumor intracellular conditions. In addition, the cytotoxic analysis and HepG2 cell growth inhibition assays demonstrated their remarkable biocompatibility and similar excellent anticancer activity as the free doxorubicin (DOX), which has also been revealed by the confocal laser scanning microscope (CLSM) analysis. So the reduction-sensitive core–shell–corona micelles are expected to be promising tumor microenvironment-responsive nanovehicles for hydrophobic drugs by glutathione (GSH) triggering