Hybrid Microgels with Confined Needle-like Lanthanide Phosphate Nanocrystals

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• 作者：Sepehr Mastour Tehrani ; Wanjuan Lin ; Sabine Rosenfeldt ; Gerald Guerin ; Yijie Lu ; Yi Liang ; Markus Drechsler ; Stephan F?rster ; Mitchell A. Winnik
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：January 26, 2016
• 年：2016
• 卷：28
• 期：2
• 页码：501-510
• 全文大小：568K
• ISSN：1520-5002

文摘

We describe the room-temperature synthesis and characterization of needle-like lanthanide phosphate (LnPOb>4b>) nanocrystals in water, based on in situ precipitation of LnPOb>4b> using functional aqueous microgels as a soft nanoreactor. The poly(NIPAm/VCL/MAA) microgels were prepared by the copolymerization of N-isopropylacrylamide, N-vinylcaprolactam, and methacrylic acid. Our goal was to prepare Ln-encoded microgels suitable for bead-based biological assays employing mass cytometry. The low solubility of nanocrystalline LnPOb>4b> avoids the problem of Ln ion leakage from the microgels. The main challenge was to find appropriate conditions to confine the LnPOb>4b> precipitate to the interior of the microgels. Various sources of phosphate ions led to precipitation of LnPOb>4b> on the exterior of the microgels. One approach worked. It involved three steps: neutralization of the MAA groups in the microgels with NaOH, ion exchange with a lanthanide salt, followed by treatment with a large excess of PBS buffer at pH 7.4. In this way, we obtained microgels containing ca. 10⁷ Ln atoms per microgel (Ln = La, Nd, Eu, Tb, Ho, Tm). The microgels were shown to be uniform in size by dynamic light scattering and transmission electron microscopy. The LnPOb>4b>-containing microgels showed much higher stability against leakage of metals to acidic buffers compared to the LnFb>3b>-containing microgels reported previously [b-group xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:ACS="http://namespace.acs.org/2008/acs" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" person-group-type="allauthors">bAuthor ">Lin, W.b-group>; Langmuir 2011, 27, 7265]. Small-angle X-ray scattering measurements and selected area electron diffraction data showed striking differences in the internal structure of hybrid microgels containing TbPOb>4b> from those containing TbFb>3b>. The TbFb>3b>-containing microgels had a core–shell structure with an amorphous TbFb>3b> core, whereas the TbPOb>4b> microgels contained needle-like nanocrystals (width ca. 2 nm, lengths on the order of 80 nm) distributed throughout the structure. These microgels are very promising materials for biological assays based on mass cytometry.