Toxicity Mechanism of Low Doses of NaGdF4:Yb3+,Er3+ Upconverting Nanoparticles in Activated Macrophage Cell Lines

Abstract

Gadolinium-doped nanoparticles (NPs) are regarded as promising luminescent probes. In this report, we studied details of toxicity mechanism of low doses of NaGdF4-based fluorescent nanoparticles in activated RAW264.7, J774A.1 macrophages. These cell lines were specifically sensitive to the treatment with nanoparticles. Using nanoparticles of three different sizes, but with a uniform zeta potential (about −11 mV), we observed rapid uptake of NPs by the cells, resulting in the increased lysosomal compartment and subsequent superoxide induction along with a decrease in mitochondrial potential, indicating the impairment of mitochondrial homeostasis. At the molecular level, this led to upregulation of proapoptotic Bax and downregulation of anti-apoptotic Bcl-2, which triggered the apoptosis with phosphatidylserine externalization, caspase-3 activation and DNA fragmentation. We provide a time frame of the toxicity process by presenting data from different time points. These effects were present regardless of the size of nanoparticles. Moreover, despite the stability of NaGdF4 nanoparticles at low pH, we identified cell acidification as an essential prerequisite of cytotoxic reaction using acidification inhibitors (NH4Cl or Bafilomycin A1). Therefore, approaching the evaluation of the biocompatibility of such materials, one should keep in mind that toxicity could be revealed only in specific cells. On the other hand, designing gadolinium-doped NPs with increased resistance to harsh conditions of activated macrophage phagolysosomes should prevent NP decomposition, concurrent gadolinium release, and thus the elimination of its toxicity.

Assessing the protective effects of different surface coatings on NaYF4:Yb3+, Er3+ upconverting nanoparticles in buffer and DMEM

“…However, adding potentially hazardous fluoride ions is not an option for applying UCNP in biological systems. Nanoparticle concentrations commonly used in in-vitro studies range from 1 to 100 ppm (µg/mL) 19,20,56 . Verma et al showed that fluoride concentrations of 120 ppm decreased cell viability up to 60% 57 .…”

Effect of different silica coatings on the toxicity of upconversion nanoparticles on RAW 264.7 macrophage cells

“…In this work, the cell viability of silica-coated particles is higher than that of non-coated NaGdF 4 nanoparticles. Wysokińska et al investigated such particles, with average sizes between 4 and 249 nm and IC 50 values below 2 µg/mL, via 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2 H -tetrazolium (MTS) assays [ 42 ].…”

“…In the present work, the cytotoxicity of UCNP cores coated with silica shells was investigated in the macrophage cell line RAW 264.7. RAW 264.7 cells are particularly sensitive to the treatment with nanoparticles [42][43][44]. They are an established model of activated macrophages and they actively take up nanomaterials from biological media.…”

“…This way, RAW264.7 cells mimic the behavior of macrophages and other immune cells, which eliminate foreign substances from the organism. Moreover, they have already been applied in studies involving uncoated NaGdF 4 [42] and silica particles [43][44][45][46].…”

Photoactive Liposomal Formulation of PVP-Conjugated Chlorin e6 for Photodynamic Reduction of Atherosclerotic Plaque

“…It could be related with the high phagocytic activity of macrophages accumulating a great variety of nanomaterial. This results in a greater sensitivity to treatments with particulate matter [44]. On the other hand, the cause of selectivity could be related to expression of scavenger receptors on macrophages [45,46].…”