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This study develops novel pH and reduction dual-sensitive micelles for the anticancer drug doxorubicin (DOX) delivery owing to the fact that the tumor tissues show low pH and high reduction environment. These sub-100 nm micelles present a core–shell structure under physiological conditions, but quickly release the loaded drugs responding to acidic and reductive stimuli. With disulfide bonds in each repeat unit of poly(β-amino ester)s, the novel copolymer was synthesized via Michael addition polymerization from 2,2′-dithiodiethanol diacrylate, 4,4′-trimethylene dipiperidine, and methoxy-PEG-NH₂. DOX released faster from micelles in a weakly acidic environment (pH 6.5) than at pH 7.4 or in the presence of a higher concentration (5 mM) of reducing agent (DTT). The release is even more effective in a scenario of both stimuli (pH 6.5 and 5 mM DTT). MTT assay showed that the DOX-loaded micelles had a …