Functional PEG鈥揚AMAM-Tetraphosphonate Capped NaLnF4 Nanoparticles and their Colloidal Stability in Phosphate Buffer

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• 作者：Guangyao Zhao ; Lemuel Tong ; Pengpeng Cao ; Mark Nitz ; Mitchell A. Winnik
• 刊名：Langmuir
• 出版年：2014
• 出版时间：June 17, 2014
• 年：2014
• 卷：30
• 期：23
• 页码：6980-6989
• 全文大小：451K
• 年卷期：v.30,no.23(June 17, 2014)
• ISSN：1520-5827

文摘

Developing surface coatings for NaLnF₄ nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH₂-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF₄ and NaTbF₄ nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH₂-PAMAM-4P ligand on oleate-capped NaLnF₄ NPs. The NPs were first treated with methoxy-poly(ethylene glycol)-monophosphoric acid (M_n = 750) in tetrahydrofuran. The mPEG750-OPO₃-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH₂-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (M_n = 2000) and biotin-terminated PEG (M_n = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF₄ and NaTbF₄ NPs capped with mPEG2000鈥揚AMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF₄ NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously ( Langmuir 2012, 28, 12861鈭?2870) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline.