title: Biological evaluation of protein nanocapsules containing doxorubicin.
abstract: This study describes the applications of a naturally occurring small heat shock protein (Hsp) that forms a cage-like structure to act as a drug carrier. Mutant Hsp cages (HspG41C) were expressed in Escherichia coli by substituting glycine 41 located inside the cage with a cysteine residue to allow conjugation with a fluorophore or a drug. The HspG41C cages were taken up by various cancer cell lines, mainly through clathrin-mediated endocytosis. The cages were detected in acidic organelles (endosomes/lysosomes) for at least 48 hours, but none were detected in the mitochondria or nuclei. To generate HspG41C cages carrying doxorubicin (DOX), an anticancer agent, the HspG41C cages and DOX were conjugated using acid-labile hydrazone linkers. The release of DOX from HspG41C cages was accelerated at pH 5.0, but was negligible at pH 7.2. The cytotoxic effects of HspG41C-DOX against Suit-2 and HepG2 cells were slightly weaker than those of free DOX, but the effects were almost identical in Huh-7 cells. Considering the relatively low release of DOX from HspG41C-DOX, HspG41C-DOX exhibited comparable activity towards HepG2 and Suit-2 cells and slightly stronger cytotoxicity towards Huh-7 cells than free DOX. Hsp cages offer good biocompatibility, are easy to prepare, and are easy to modify; these properties facilitate their use as nanoplatforms in drug delivery systems and in other biomedical applications.
authors.affiliation: Innovation Center for Medical Redox Navigation, Department of Advanced Medical Initiatives, Kyushu University, Fukuoka, Japan.
authors.forename: Riki
authors.initials: R
authors.lastname: Toita
authors.forename: Masaharu
authors.initials: M
authors.lastname: Murata
authors.forename: Kana
authors.initials: K
authors.lastname: Abe
authors.forename: Sayoko
authors.initials: S
authors.lastname: Narahara
authors.forename: Jing Shu
authors.initials: JS
authors.lastname: Piao
authors.forename: Jeong-Hun
authors.initials: JH
authors.lastname: Kang
authors.forename: Kenoki
authors.initials: K
authors.lastname: Ohuchida
authors.forename: Makoto
authors.initials: M
authors.lastname: Hashizume
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry* / Q000493:pharmacokinetics / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004317:Doxorubicin / Q000737:chemistry* / Q000493:pharmacokinetics / Q000494:pharmacology; D004705:Endocytosis; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics; D050888:Heat-Shock Proteins, Small / Q000737:chemistry / Q000235:genetics; D056945:Hep G2 Cells; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D053769:Nanocapsules / Q000737:chemistry*; D010316:Particle Size; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D029968:Escherichia coli Proteins; D050888:Heat-Shock Proteins, Small; D053769:Nanocapsules; D011994:Recombinant Proteins; D004317:Doxorubicin
keywords: anticancer activity; biomedical application; doxorubicin; drug delivery system; protein nanocapsules; small heat shock protein