Amphiphilic coatings for the protection of upconverting nanoparticles against dissolution in aqueous media. Issue 21 (17th May 2017)

• Record Type: Journal Article
• Authors: Plohl, Olivija; Kralj, Slavko; Majaron, Boris; Fröhlich, Eleonore; Ponikvar-Svet, Maja; Makovec, Darko; Lisjak, Darja
• Is Part Of: Dalton transactions. Volume 46:Issue 21(2017)
• Page Start: 6975
• Page End: 6984
• Publication Date: 2017-05-17
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt00529f
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Dissolution of upconverting nanoparticles (β-NaYF4 :Yb 3+, Tm 3+ ) in PBS was efficiently suppressed by a polymer coating, PMAO cross-linked with BHMT. Abstract : Upconverting nanoparticles (UCNPs) of β-NaYF4, co-doped with Yb 3+ and Tm 3+ and 21–36 nm large, were synthesized using a modified thermal decomposition method. The as-synthesized UCNPs were coated with oleic acid and dispersed in nonpolar media. Their morphology, size and crystal structure were analysed with transmission electron microscopy and X-ray diffraction. The UCNPs showed a fluorescence emission spectrum characteristic of Tm 3+ . Their dissolution in water (pH ∼ 4–5) and phosphate buffered saline (PBS, pH = 7.4) was determined from the fraction of dissolved fluoride ions using a fluoride-ion-selective electrode. The dissolution of bare UCNPs was much more prominent in PBS than in water. Two amphiphilic coatings, poly(maleic anhydride- alt -1-octadecene)−bis(hexamethylene)triamine (PMAO–BHMT) andd -α-tocopheryl polyethylene glycol succinate (TPGS) were tested for their effects on the dissolution of the UCNPs. The coatings were formed directly on the as-synthesized UCNPs as was confirmed with electrokinetic measurements, infrared spectroscopy and thermogravimetric analyses. Both coatings enabled the dispersion of UCNPs in water, and improved the fluorescence emission intensity with respect to the bare UCNPs. However, only the PMAO–BHMT coating provided an effective protection against the dissolution of the UCNPs and long-term colloidal stability in PBS, and did not show cytotoxicity in EAhy926 endothelial cells.