Facile Construction of pH- and Redox-Responsive Micelles from a Biodegradable Poly(β-hydroxyl amine) for Drug Delivery. 
Here we demonstrate a type of pH and reduction dual-sensitive biodegradable micelles, which were self-assembled by a cationic polymer in an aqueous solution.  Due to tumor cells or tissues showing low pH and high reduction concentration, these micelles possessed specific tumor targetability and maximal drug-release controllability inside tumor cells upon changes in physical and chemical environments, but presented good stability at physiological conditions.  CCK-8 assay showed that the DOX-loaded micelles had a similar cytotoxicity for MCF-7 tumor cells as free DOX, and blank micelles had a very low cytotoxicity to the cells.  Fluorescent microscopy observation revealed that the drug-loaded micelles could be quickly internalized by endosomes to inhibit cancer cell growth.  These results indicated these biodegradable micelles, as a novel and effective pH- and redox-responsive nanocarrier, have a potential to improve drug delivery and enhance the antitumor efficacy.