Polymer-Coated\nUltrastable and Biofunctionalizable Lanthanide Nanoparticles

Abstract

Lanthanide-containing\nnanoparticles (LnNPs), for example, NaYF₄, are considered\nto be one of the most promising platforms for biological and material\napplications due to their unique and unusual magnetic and upconversion\nfluorescent properties. However, limited water dispersity, low long-term\ncolloidal stability, and difficulty in further functionalization greatly\nnarrow the scope of their application in the real world. Herein, we\nreport a facile strategy to counter\nthe aforementioned barriers to the expanding use of LnNPs that involves\nsurface-coating the LnNPs with poly­(ethylene glycol)-<i>b</i>-poly­(pentafluorophenyl methacrylate)/phosphonic acid and subsequently\nshell cross-linking with NH₂-PEG-NH₂. The cross-linked\nPEG layer provided good water dispersity, nonfouling characteristics,\nand excellent long-term colloidal stability in phosphate-buffered\nsaline in the range of 25–60 °C, whereas the high reactivity\nof the pentafluorophenyl ester with the amino group brought about\nease of incorporation of functional moieties into LnNPs. Particularly,\nit was found for the first time that LnNPs with surface coating could\nendure the freeze-drying process without any sign of aggregation,\nwhich would not only greatly decrease the weight and storage and shipping\nroom but also increase the storage shelf life with the preservation\nof their inherent properties, especially for LnNPs with some fragile\nbioconjugates while in solution.