Hybrid Microgels with Confined Needle-like Lanthanide Phosphate Nanocrystals

作者：Tehrani Sepehr Mastour; Lin Wanjuan; Rosenfeld Sabine; Guerin Gerald; Lu Yijie; Liang Yi; Drechsler Markus; Foerster Stephan; Winnik Mitchell A^*

来源：Chemistry of Materials, 2016, 28(2): 501-510.

DOI：10.1021/acs.chemmater.5b03295

We describe the room-temperature synthesis and characterization of needle-like lanthanide phosphate (LnPO(4)) nanocrystals in water, based on in situ precipitation of LnPO(4) 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 LnPO(4) avoids the problem of Ln ion leakage from the microgels. The main challenge was to find appropriate conditions to confine the LnPO(4) precipitate to the interior of the microgels. Various sources of phosphate ions led to precipitation of LnPO(4) 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. 10(7) 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 LnPO(4)-containing microgels showed much higher stability against leakage of metals to acidic buffers compared to the LnF(3)-containing microgels reported previously [Lin, W.; et al. 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 TbPO4 from those containing TbF3. The TbF3-containing microgels had a core shell structure with an amorphous TbF3 core, whereas the TbPO4 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.

• 出版日期2016-1-26