Stability, dissolution, and cytotoxicity of NaYF4-upconversion nanoparticles with different coatings

Abstract

Upconversion nanoparticles (UCNPs) have attracted considerable attention owing to their unique photophysical properties. Their utilization in biomedical applications depends on the understanding of their transformations under physiological conditions and their potential toxicity. In this study, NaYF4:Yb,Er UCNPs, widely used for luminescence and photophysical studies, were modified with a set of four different coordinatively bound surface ligands, i.e., citrate, alendronate (AA), ethylendiamine tetra(methylene phosphonate) (EDTMP), and poly(maleic anhydride-alt-1-octadecene) (PMAO), as well as silica coatings with two different thicknesses. Subsequently, the aging-induced release of fluoride ions in water and cell culture media and their cytotoxic profile to human keratinocytes were assessed in parallel to the cytotoxic evaluation of the ligands, sodium fluoride and the lanthanide ions. The cytotoxicity studies of UCNPs with different surface modifications demonstrated the good biocompatibility of EDTMP-UCNPs and PMAO-UCNPs, which is in line with the low amount of fluoride ions released from these samples. An efficient prevention of UCNP dissolution and release of cytotoxic ions, as well as low cytotoxicity was also observed for UCNPs with a sufficiently thick silica shell. Overall, our results provide new insights into the understanding of the contribution of surface chemistry to the stability, dissolution behavior, and cytotoxicity of UCNPs. Altogether, the results obtained are highly important for future applications of UCNPs in the life sciences and bioimaging studies.

From Nanothermometry to Bioimaging: Lanthanide-Activated KY3F10 Nanostructures as Biocompatible Multifunctional Tools for Nanomedicine

“…For these reasons, we found it interesting to investigate the chemical stability of the as-prepared citrate-capped KY 3 F 10 colloids in both water and cell culture media, by monitoring the UC emission intensity as a function of their concentration and time. In fact, upconversion emission intensity strongly depends on the stability of the colloidal dispersion, since a decrease in time of the luminescence, keeping constant all the other experimental conditions, could be related to the dissolution of the nanocrystals …”

“…The citrate-capped UCNPs were kept at room temperature and the dispersions were diluted with deionized water up to a minimum concentration of around 50 μg/mL, which is the concentration at which NaYF 4 dissolve in water. 44 All the core@shell NPs present linear correlation between UC emission and concentration, also at very low nanoparticles concentrations. As shown in Figure 5a, two ranges of concentrations can be identified and correlated with the well-assessed in vitro and in vivo range of nontoxic concentrations.…”

“…It is worth remarking the importance of this behavior, clearly pointing to a successful application in aqueous environments, as well as in biological fluids, of paramount importance for applications in nanomedicine or in biological studies. 44 Cell Viability and Confocal Imaging. Assessing the toxicity toward human cell lines for the translation of NPs into clinical research and medical applications is of great importance, due to the very high potential of such nanomaterials in bioimaging and nanomedicine.…”

“…In fact, upconversion emission intensity strongly depends on the stability of the colloidal dispersion, since a decrease in time of the luminescence, keeping constant all the other experimental conditions, could be related to the dissolution of the nanocrystals. 44 Thus, the stability of the colloidal dispersions of the present KYF core@shell nanoparticles was first evaluated following the variation of UC luminescence intensity, by measuring the emission spectra of serial dilution of NPs aqueous dispersion and keeping constant the experimental setup and acquisition parameters for each measurement (Figure 5a).…”

Roll to Roll fabrication of synthesized Light Conversion Film

“…[1][2][3][4] One of the most widely researched and established UCNPs are NaYF 4 lanthanide-doped nanoparticles. [5][6][7][8] By tuning the molar ratio of the lanthanide ions taking part in the reaction, the emission of the UCNPs can be manipulated to emit different visible wavelengths of light upon excitation by near IR photons. [9,10] Taking advantage of the UCNPs ability to absorb longer wavelength photons and convert it to visible light, incoming heat can be converted to reduce temperature buildup in an enclosed envelope structure.…”