title: Self-organized nanogels responding to tumor extracellular pH: pH-dependent drug release and in vitro cytotoxicity against MCF-7 cells.
abstract: The principal objective of this study was to fabricate doxorubicin-loaded self-organized nanogels composed of hydrophobized pullulan (PUL)-Nalpha-Boc-L-histidine (bHis) conjugates. Their responses to tumor extracellular pH (pHe) were determined, and they were also evaluated with regard to their anticancer efficacy against breast cancer cell lines (MCF-7). bHis was grafted to a PUL-deoxycholic acid (DO) conjugate (PUL-DO) via an ester linkage. PUL-DO/bHis conjugates with two different degrees of bHis substitutions (PUL-DO/bHis36 and PUL-DO/bHis78) were synthesized. PUL-DO/bHis nanogels formed via dialysis at a pH of 8.5 evidenced larger particle sizes (<140 nm) and lower critical aggregation concentrations (CACs) than did the PUL-DO nanogels (90 nm). The pH-dependent CAC of PUL-DO/bHis78 changed dramatically, from 1.2 microg/mL at pH 8.5, to 10 at 7.0, and to 660 at 6.2. A similar tendency in pH-dependent size was also noted. The ionization of the imidazole ring in bHis is principally responsible for pH dependency. The bHis moieties function as a switching tool responding to external pH. Doxorubicin (DOX)-loaded nanogels were assessed for pH-dependent releasing kinetics. The release rate of DOX from the PUL-DO/bHis78 nanogels increased significantly with reductions in pH. This resulted in increased cytotoxicity (30% cell viability at a dose of 10 microg/mL DOX equivalent) against sensitive MCF-7 cells at a pH of 6.8 and low cytotoxicity at pH 7.4 (65% cell viability at an identical dose). The results show that PUL-DO/bHis nanogels may potentially be employed as anti-tumor drug carriers.
authors: Division of Biotechnology, The Catholic University of Korea, 43-1 Yeokgok 2-dong, Wonmi-gu, Bucheon-si, Gyeonggi-do 420-743, Korea.
authors: Kun
authors: K
authors: Na
authors: Eun Seong
authors: ES
authors: Lee
authors: You Han
authors: YH
authors: Bae
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor / Q000187:drug effects; D004317:Doxorubicin / Q000737:chemistry*; D004337:Drug Carriers / Q000138:chemical synthesis* / Q000494:pharmacology; D005260:Female; D006639:Histidine / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D000080385:Nanogels; D011092:Polyethylene Glycols / Q000138:chemical synthesis* / Q000494:pharmacology; D011094:Polyethyleneimine / Q000138:chemical synthesis* / Q000494:pharmacology; D013678:Technology, Pharmaceutical / Q000379:methods*
chemical_list: D000903:Antibiotics, Antineoplastic; D004337:Drug Carriers; D000080385:Nanogels; C413692:polyethylene glycol polyethyleneimine nanogel; D011092:Polyethylene Glycols; D006639:Histidine; D004317:Doxorubicin; D011094:Polyethyleneimine