title: Effect of cross-linking on the performance of micelles as drug delivery carriers: a cell uptake study.
abstract: Poly(polyethylene glycol methyl ether methacrylate-co-methacrylic acid)-block-poly(methyl methacrylate) P(PEGMEMA-co-MAA)-b-PMMA block copolymer were prepared via RAFT (reversible addition-fragmentation chain transfer) polymerization and subsequently self-assembled into micelles as a drug delivery carrier for albendazole (ABZ). For comparison, the micelles were additionally cross-linked to study the effect of shell-cross-linking on the biological activity. The hydrodynamic diameter of cross-linked and un-cross-linked micelles was approximately 40 nm in both cases. While the cross-linked micelle was stable even in good solvents for both blocks, the un-cross-linked micelle was found to lose its integrity in cell growth media. Crosslinking had a major effect on the rate of drug release reducing it dramatically from 50% (uncrosslinked) to around 20% (crosslinked) over a 30 h incubation period. Both drug delivery systems were tested on human prostate cancer cells (PC-3, DU-145) and human ovarian cancer cells (OVCAR-3, A-2780). No toxic effects were measured with the unloaded micelle while the ABZ loaded un-cross-linked micelle lead to IC(50) values between 0.2 and 0.9 μM depending on the cell line. The IC(50) dropped to values between 0.006 and 0.06 μM, depending on cell line, once the micelles were stabilized by cross-linking. Three treatment cycles with ABZ for one day, followed by two days incubation in media using ABZ-loaded drug carriers led to complete cell death even at low concentrations in the case of the cross-linked micelle only. Cellular uptake has been studied using fluorescently labeled micelles and Nile red as model drug, showing cell uptake above the CMC but no micelle uptake below the CMC. Additional biological studies, such as colony formation assay and tubulin disorganization tests, were also performed to gain more insight into the effect of cross-linking of the shell of the micelle. In conclusion, shell-cross-linking is highly recommended, even for glassy micelles, for an efficient cellular uptake at low concentrations.
authors.affiliation: Centre for Advanced Macromolecular Design (CAMD), St. George Hospital, University of New South Wales , Sydney, NSW 2052, Australia.
authors.forename: Yoseop
authors.initials: Y
authors.lastname: Kim
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Pourgholami
authors.forename: David L
authors.initials: DL
authors.lastname: Morris
authors.forename: Martina H
authors.initials: MH
authors.lastname: Stenzel
mesh_terms: D015766:Albendazole / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003114:Colony-Forming Units Assay; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004337:Drug Carriers; D016503:Drug Delivery Systems; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008689:Methacrylates / Q000737:chemistry; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000473:pathology; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization / Q000187:drug effects; D011108:Polymers / Q000737:chemistry / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology; D014404:Tubulin / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D003432:Cross-Linking Reagents; D004337:Drug Carriers; D008689:Methacrylates; D008823:Micelles; D011108:Polymers; D014404:Tubulin; D050257:Tubulin Modulators; C524499:polyethylene glycol methacrylate; D011092:Polyethylene Glycols; D015766:Albendazole