A series of disulfide-core-cross-linked poly(ethylene glycol)-poly(amino acid)s star copolymers were synthesized through one-step ring-opening polymerization of L-phenylalanine N-carboxyanhydride (L-Phe NCA) and L-cystine N-carboxyanhydride (L-Cys NCA) with amino group terminated poly (ethylene glycol) monomethyl ether (mPEG-NH 2 ) as macroinitiator. The reduction-responsive PEGpoly(amino acid)s nanogels (NGs) were prepared by directly dispersing the resultant PEG-poly(amino acid)s in phosphate buffer solution at pH 7.4. Dynamic light scattering (DLS) measurements showed that the reducible NG swelled in response to 10 mM glutathione (GSH). Doxorubicin (DOX), an anthracycline anticancer drug, was loaded into the NGs. The in vitro release results revealed that the release behaviors could be adjusted by GSH concentration, and poly(amino acid)s content and composition. The intracellular DOX release results showed that enhanced intracellular DOX release occurred in GSH pretreated Henrietta Lacks (HeLa) cells. In vitro methyl thiazolyl tetrazolium (MTT) assays indicated that the NGs were biocompatible, and DOX-loaded NG showed higher cellular proliferation inhibition towards GSH pretreated HeLa cells than that of non-pretreated cells. Therefore, the NGs can efficiently deliver anticancer drugs into tumor cells and inhibit cell proliferation, rendering highly promising for targeted intracellular delivery of operative chemotherapeutic drugs in cancer therapy.

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