An Effective Polymer Cross-Linking Strategy To Obtain Stable Dispersions of Upconverting NaYF4 Nanoparticles in Buffers and Biological Growth Media for Biolabeling Applications
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- 作者：Guicheng Jiang ; Jothirmayanantham Pichaandi ; Noah J. J. Johnson ; Robert D. Burke ; Frank C. J. M. van Veggel
- 刊名：Langmuir
- 出版年：2012
- 出版时间：February 14, 2012
- 年：2012
- 卷：28
- 期：6
- 页码：3239-3247
- 全文大小：553K
- 年卷期：v.28,no.6(February 14, 2012)
- ISSN：1520-5827
文摘
Ligands on the nanoparticle surface provide steric stabilization, resulting in good dispersion stability. However, because of their highly dynamic nature, they can be replaced irreversibly in buffers and biological medium, leading to poor colloidal stability. To overcome this, we report a simple and effective cross-linking methodology to transfer oleate-stabilized upconverting NaYF4 core/shell nanoparticles (UCNPs) from hydrophobic to aqueous phase, with long-term dispersion stability in buffers and biological medium. Amphiphilic poly(maleic anhydride-alt-1-octadecene) (PMAO) modified with and without poly(ethylene glycol) (PEG) was used to intercalate with the surface oleates, enabling the transfer of the UCNPs to water. The PMAO units on the phase transferred UCNPs were then successfully cross-linked using bis(hexamethylene)triamine (BHMT). The primary advantage of cross-linking of PMAO by BHMT is that it improves the stability of the UCNPs in water, physiological saline buffers, and biological growth media and in a wide range of pH values when compared to un-cross-linked PMAO. The cross-linked PMAO鈥揃HMT coated UCNPs were found to be stable in water for more than 2 months and in physiological saline buffers for weeks, substantiating the effectiveness of cross-linking in providing high dispersion stability. The PMAO鈥揃HMT cross-linked UCNPs were extensively characterized using various techniques providing supporting evidence for the cross-linking process. These UCNPs were found to be stable in serum supplemented growth medium (37 掳C) for more than 2 days. Utilizing this, we demonstrate the uptake of cross-linked UCNPs by LNCaP cells (human prostate cancer cell line), showing their utility as biolabels.