title: Tumor-targeting, pH-responsive, and stable unimolecular micelles as drug nanocarriers for targeted cancer therapy.
abstract: A new type of multifunctional unimolecular micelle drug nanocarrier based on amphiphilic hyperbranched block copolymer for targeted cancer therapy was developed. The core of the unimolecular micelle was a hyperbranched aliphatic polyester, Boltorn H40. The inner hydrophobic layer was composed of random copolymer of poly(ε-caprolactone) and poly(malic acid) (PMA-co-PCL) segments, while the outer hydrophilic shell was composed of poly(ethylene glycol) (PEG) segments. Active tumor-targeting ligands, i.e., folate (FA), were selectively conjugated to the distal ends of the PEG segments. An anticancer drug, i.e., doxorubicin (DOX) molecules, was conjugated onto the PMA segments with pH-sensitive drug binding linkers for pH-triggered drug release. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis showed that the unimolecular micelles were uniform with a mean hydrodynamic diameter around 25 nm. The drug loading content was determined to be 14.2%. The drug release profile, cell uptake and distribution, and cytotoxicity of the unimolecular micelles were evaluated in vitro. The folate-conjugated micelles can be internalized by the cancer cells via folate-receptor-mediated endocytosis; thus, they exhibited enhanced cell uptake and cytotoxicity. At pH 7.4, the physiological condition of bloodstream, DOX conjugated onto the unimolecular micelles exhibited excellent stability; however, once the micelles were internalized by the cancer cells, the pH-sensitive hydrazone linkages were cleavable by the intracellular acidic environment, which initially caused a rapid release of DOX. These findings indicate that these unique unimolecular micelles may offer a very promising approach for targeted cancer therapy.
authors.affiliation: Department of Mechanical Engineering, Department of Biological Sciences, and Department of Materials, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, and Department of Biomedical Engineering and Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53706.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Yang
authors.forename: Jamison J
authors.initials: JJ
authors.lastname: Grailer
authors.forename: Srikanth
authors.initials: S
authors.lastname: Pilla
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Steeber
authors.forename: Shaoqin
authors.initials: S
authors.lastname: Gong
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers / Q000138:chemical synthesis / Q000737:chemistry*; D004354:Drug Screening Assays, Antitumor; D005492:Folic Acid / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D011091:Polyesters / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D011108:Polymers / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013499:Surface Properties
chemical_list: D000970:Antineoplastic Agents; D004337:Drug Carriers; D008823:Micelles; D011091:Polyesters; D011108:Polymers; D005492:Folic Acid