Amphiphilic coatings for the protection of upconverting nanoparticles against dissolution in aqueous media

Abstract

Upconverting nanoparticles (UCNPs) of β-NaYF, co-doped with Yb and Tm 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. 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) and d-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.

Effective Shielding of NaYF4:Yb3+,Er3+ Upconverting Nanoparticles in Aqueous Environments Using Layer-by-Layer Assembly

“…Recently, an amphiphilic coating was demonstrated to be successful in hindering the disintegration and thus shielding the particles’ luminescence from quenching. 26 Preventing the disintegration of the materials is vital, not only because of the optical changes harming the reproducibility of the measurements 20 , 21 but also to prevent the leaking of lanthanide and fluoride ions into the tissue or living cells in biomedical imaging. 27 , 28 This means that development of new surface modifications and methods to effectively stop the disintegration are increasingly important topics in the research of upconverting nanoparticles.…”

Fluoride in Human Health and Nutrition

“…In our laboratory classical analytics used for determining the composition of bulk material of synthesised compounds containing fluorine 118,[276][277][278][279][280][281][282][283] was extended to thermochemical investigations, 118,140,141,[280][281][282][284][285][286][287] measurement uncertainty evaluation, 171 determination of fluorine in food 149,183 and environmental samples 7,288,289 and nanomaterials. [290][291][292][293][294] Principles of thermochemistry were used for the estimation of the entropies of formation of fluorine containing aqueous anions 285 and to discuss ions containing solely fluorine atoms 286 and oxidation potential of fluorine. 287 Possible reactions proceeding during total decomposition of fluorine containing materials by pyrohydrolysis, oxygen bomb combustion and alkaline carbonate fusion were suggested and accompanying thermochemistry discussed.…”

“…We also participated in characterization of upconverting, lanthanide-doped, fluoride nanoparticles, which show a great potential in bioimaging. [290][291][292][293][294] Fluorine research remains relatively sporadic also because of a lack of sound analytical techniques enabling fast and multielemental analysis of F. Thus the predominate method for F analysis remains fluoride ion selective electrode.…”

Core@shell Fe3O4@Mn2+-doped NaYF4:Yb/Tm nanoparticles for triple-modality T1/T2-weighted MRI and NIR-to-NIR upconversion luminescence imaging agents

“…8 However, the luminescence intensity of these Fe 3 O 4 @Mn 2+ -doped NaYF 4 :Yb/Er NPs in water was signicantly reduced compared to the original hydrophobic NPs when using a ligand exchange method, the quenching effect is mainly caused by the nonradiative decay of the electronically excited states of the dopant lanthanide ions caused by surface ligands and water molecules. 8,40,41 It was found that compared with the ligand exchange method, the amphiphilic polymer coating method can maintain better UCL intensity ascribed to the presence of hydrophobic OA ligands in the later case, which could hinder at least partly the direct access of water molecules to the particle surface. 40 …”

“…8,40,41 It was found that compared with the ligand exchange method, the amphiphilic polymer coating method can maintain better UCL intensity ascribed to the presence of hydrophobic OA ligands in the later case, which could hinder at least partly the direct access of water molecules to the particle surface. 40 …”