title: Ligand-directed reduction-sensitive shell-sheddable biodegradable micelles actively deliver doxorubicin into the nuclei of target cancer cells.
abstract: The therapeutic performance of biodegradable micellar drugs is far from optimal due to existing challenges like poor tumor cell uptake and intracellular drug release. Here, we report on ligand-directed reduction-sensitive shell-sheddable biodegradable micelles based on poly(ethylene glycol)-poly(ε-caprolactone) (PEG-PCL) copolymer actively delivering doxorubicin (DOX) into the nuclei of target cancer cells, inducing superb in vitro antitumor effects. The micelles were constructed from PEG-SS-PCL and galactose-PEG-PCL (Gal-PEG-PCL) block copolymers, in which Gal-PEG-PCL was designed with a longer PEG than that in PEG-SS-PCL (6.0 vs 5.0 kDa) to fully expose Gal ligands onto the surface of micelles for effective targeting to hepatocellular carcinoma cells. PEG-SS-PCL combining with 10 or 20 wt % of Gal-PEG-PCL formed uniform micelles with average sizes of 56.1 and 58.2 nm (denoted as PEG-SS-PCL/Gal10 and PEG-SS-PCL/Gal20, respectively). The in vitro release studies showed that about 81.1 and 75.0% DOX was released in 12 h from PEG-SS-PCL/Gal10 and PEG-SS-PCL/Gal20 micelles under a reducing condition containing 10 mM dithiothreitol (DTT). In contrast, minimal DOX release (<12%) was observed for PEG-SS-PCL/Gal10 and PEG-SS-PCL/Gal20 micelles under nonreducing conditions as well as for reduction-insensitive Gal-PEG-PCL and PEG-PCL/Gal20 micelles in the presence of 10 mM DTT. MTT assays in HeLa and HepG2 cells showed that DOX-loaded PEG-SS-PCL/Gal20 micelles exhibited apparent targetability and significantly enhanced antitumor efficacy toward asialoglycoprotein receptor (ASGP-R)-overexpressing HepG2 cells with a particularly low half maximal inhibitory concentration (IC50) of 1.58 μg DOX equiv/mL, which was comparable to free DOX and approximately six times lower than that for nontargeting PEG-SS-PCL counterparts under otherwise the same conditions. Interestingly, confocal microscopy observations using FITC-labeled PEG-SS-PCL/Gal20 micelles showed that DOX was efficiently delivered and released into the nuclei of HepG2 cells in 8 h. Flow cytometry revealed that cellular DOX level in HepG2 cells treated with DOX-loaded PEG-SS-PCL/Gal20 micelles was much greater than that with reduction-insensitive PEG-PCL/Gal20 and nontargeting PEG-SS-PCL controls, signifying the importance of combining shell-shedding and active targeting. Ligand-directed, reduction-sensitive, shell-sheddable, and biodegradable micelles have emerged as a versatile and potent platform for targeted cancer chemotherapy.
authors.affiliation: Biomedical Polymers Laboratory and Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou, 215123, People's Republic of China.
authors.forename: Yinan
authors.initials: Y
authors.lastname: Zhong
authors.forename: Weijing
authors.initials: W
authors.lastname: Yang
authors.forename: Huanli
authors.initials: H
authors.lastname: Sun
authors.forename: Ru
authors.initials: R
authors.lastname: Cheng
authors.forename: Fenghua
authors.initials: F
authors.lastname: Meng
authors.forename: Chao
authors.initials: C
authors.lastname: Deng
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Zhong
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D002467:Cell Nucleus / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*; D016503:Drug Delivery Systems; D004354:Drug Screening Assays, Antitumor; D005026:Ethylene Glycols / Q000008:administration & dosage / Q000737:chemistry; D056945:Hep G2 Cells; D006801:Humans; D008024:Ligands; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D008823:Micelles; D008954:Models, Biological; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010316:Particle Size; D011091:Polyesters / Q000008:administration & dosage / Q000737:chemistry; D013329:Structure-Activity Relationship; D013499:Surface Properties
chemical_list: D000970:Antineoplastic Agents; D005026:Ethylene Glycols; D008024:Ligands; D008823:Micelles; D011091:Polyesters; C476300:poly(epsilon-caprolactone)-b-poly(ethylene glycol); D004317:Doxorubicin