Synthesis and Characterization of Amphiphilic Polyphosphates with Hydrophilic Graft Chains and Cholesteryl Groups as Nanocarriers

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• 作者：Yasuhiko Iwasaki and Kazunari Akiyoshi
• 刊名：Biomacromolecules
• 出版年：2006
• 出版时间：May 2006
• 年：2006
• 卷：7
• 期：5
• 页码：1433 - 1438
• 全文大小：225K
• 年卷期：v.7,no.5(May 2006)
• ISSN：1526-4602

文摘

Amphiphilic polyphosphate graft copolymers with varied densities of cholesteryl esters and hydrophilic graftchains were prepared, and the solution properties of the graft copolymers were evaluated. Polyphosphates weresynthesized as backbones by ring-opening polymerization of 2-isopropyl-2-oxo-1,3,2-dioxaphospholane (IPP),2-(2-oxo-1,3,2-dioxaphosphoroyloxyethyl-2-bromoisobutyrate) (OPBB), and 2-choresteryl-2-oxo-1,3,2-dioxaphospholane (ChOP) using triisobutylaluminum as an initiator. Three types of polyphosphates (PIBr_xCh_y, x = numberof OPBB units in a polymer; y = number of ChOP units in a polymer) such as PIBr₄, PIBr₆Ch₁, and PIBr₃Ch₂were obtained. The molecular weights of these polymers were 2.4 × 10⁴, 2.4 × 10⁴, and 2.6 × 10⁴ g/mol,respectively. 2-Methacryloyloxyethyl phosphorylcholine (MPC) was grafted from the OPBB sites in PIBr_xCh_yvia atom transfer radical polymerization (ATRP) in EtOH. In each polymer system, the molecular weight of thegraft polymer was linear with conversion. Furthermore, the polymer radical concentration remained constantduring polymerization; that is, the molecular weights of the graft chains were easily controllable with polymerizationtime. The solution properties of amphiphilic PIBr_xCh_y-g-PMPCs were investigated by the methods of surfacetension measurement, light scattering, and fluorescence probe. The transition point (cmc) of the surface tensionof the PIBr_xCh_y-g-PMPCs aqueous solution decreased with an increase in the number of ChOP units in a graftpolymer. Particularly, PIBr₃Ch₂-g-PMPC14.9K formed nanosized associates (R_h = 7.5 nm) with 2.2 moleculesabove 0.1 wt %. v79 cells were used to evaluate the cytotoxicity of the graft polymers, but no cytotoxicity wasobserved. The graft polymers containing cholesteryl groups effectively enhanced the solubility of paclitaxel in anaqueous solution.