Abstract:Upconversion nanoparticles (UCNPs), which are generated by doping with rare earth (RE) metals, are increasingly used for bio-imaging because of the advantages they hold over conventional fluorophores. However, because pristine RE nanoparticles (NPs) are unstable in acidic physiological fluids (e.g., lysosomes), leading to intracellular phosphate complexation with the possibility of the lysosomal injury, it is important to ensure that UCNPs are safe designed. In this study, we used commercially available NaYF4:… Show more
“…The tetrahedral phosphonic groups in this complex limit the free space around the central metal atoms, which are shielded from interacting with ligands in biological environment such as protons, biomolecules, etc . Since EDTMP was reported to have strong binding affinity with heavy metal ions [30–32], this coating may be used for a broad spectrum of toxic MOx to provide stable inert surfaces.Fig. 3Safe design of MOx by surface passivation.…”
BackgroundThe wide application of engineered nanoparticles has induced increasing exposure to humans and environment, which led to substantial concerns on their biosafety. Some metal oxides (MOx) have shown severe toxicity in cells and animals, thus safe designs of MOx with reduced hazard potential are desired. Currently, there is a lack of a simple yet effective safe design approach for the toxic MOx. In this study, we determined the key physicochemical properties of MOx that lead to cytotoxicity and explored a safe design approach for toxic MOx by modifying their hazard properties.ResultsTHP-1 and BEAS-2B cells were exposed to 0–200 μg/mL MOx for 24 h, we found some toxic MOx including CoO, CuO, Ni2O3 and Co3O4, could induce reactive oxygen species (ROS) generation and cell death due to the toxic ion shedding and/or oxidative stress generation from the active surface of MOx internalized into lysosomes. We thus hypothesized that surface passivation could reduce or eliminate the toxicity of MOx. We experimented with a series of surface coating molecules and discovered that ethylenediamine tetra (methylene phosphonic acid) (EDTMP) could form stable hexadentate coordination with MOx. The coating layer can effectively reduce the surface activity of MOx with 85-99% decrease of oxidative potential, and 65-98% decrease of ion shedding. The EDTMP coated MOx show negligible ROS generation and cell death in THP-1 and BEAS-2B cells. The protective effect of EDTMP coating was further validated in mouse lungs exposed to 2 mg/kg MOx by oropharyngeal aspiration. After 40 h exposure, EDTMP coated MOx show significant decreases of neutrophil counts, lactate dehydrogenase (LDH) release, MCP-1, LIX and IL-6 in bronchoalveolar lavage fluid (BALF), compared to uncoated particles. The haematoxylin and eosin (H&E) staining results of lung tissue also show EDTMP coating could significantly reduce the pulmonary inflammation of MOx.ConclusionsThe surface reactivity of MOx including ion shedding and oxidative potential is the dominated physicochemical property that is responsible for the cytotoxicity induced by MOx. EDTMP coating could passivate the surface of MOx, reduce their cytotoxicity and pulmonary hazard effects. This coating would be an effective safe design approach for a broad spectrum of toxic MOx, which will facilitate the safe use of MOx in commercial nanoproducts.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-017-0193-5) contains supplementary material, which is available to authorized users.
“…The tetrahedral phosphonic groups in this complex limit the free space around the central metal atoms, which are shielded from interacting with ligands in biological environment such as protons, biomolecules, etc . Since EDTMP was reported to have strong binding affinity with heavy metal ions [30–32], this coating may be used for a broad spectrum of toxic MOx to provide stable inert surfaces.Fig. 3Safe design of MOx by surface passivation.…”
BackgroundThe wide application of engineered nanoparticles has induced increasing exposure to humans and environment, which led to substantial concerns on their biosafety. Some metal oxides (MOx) have shown severe toxicity in cells and animals, thus safe designs of MOx with reduced hazard potential are desired. Currently, there is a lack of a simple yet effective safe design approach for the toxic MOx. In this study, we determined the key physicochemical properties of MOx that lead to cytotoxicity and explored a safe design approach for toxic MOx by modifying their hazard properties.ResultsTHP-1 and BEAS-2B cells were exposed to 0–200 μg/mL MOx for 24 h, we found some toxic MOx including CoO, CuO, Ni2O3 and Co3O4, could induce reactive oxygen species (ROS) generation and cell death due to the toxic ion shedding and/or oxidative stress generation from the active surface of MOx internalized into lysosomes. We thus hypothesized that surface passivation could reduce or eliminate the toxicity of MOx. We experimented with a series of surface coating molecules and discovered that ethylenediamine tetra (methylene phosphonic acid) (EDTMP) could form stable hexadentate coordination with MOx. The coating layer can effectively reduce the surface activity of MOx with 85-99% decrease of oxidative potential, and 65-98% decrease of ion shedding. The EDTMP coated MOx show negligible ROS generation and cell death in THP-1 and BEAS-2B cells. The protective effect of EDTMP coating was further validated in mouse lungs exposed to 2 mg/kg MOx by oropharyngeal aspiration. After 40 h exposure, EDTMP coated MOx show significant decreases of neutrophil counts, lactate dehydrogenase (LDH) release, MCP-1, LIX and IL-6 in bronchoalveolar lavage fluid (BALF), compared to uncoated particles. The haematoxylin and eosin (H&E) staining results of lung tissue also show EDTMP coating could significantly reduce the pulmonary inflammation of MOx.ConclusionsThe surface reactivity of MOx including ion shedding and oxidative potential is the dominated physicochemical property that is responsible for the cytotoxicity induced by MOx. EDTMP coating could passivate the surface of MOx, reduce their cytotoxicity and pulmonary hazard effects. This coating would be an effective safe design approach for a broad spectrum of toxic MOx, which will facilitate the safe use of MOx in commercial nanoproducts.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-017-0193-5) contains supplementary material, which is available to authorized users.
“…Indeed, we have measured the third order susceptibility for unstructured germanium and silicon through z-scan measurements at pump = 1650 nm (see Supporting Information section 3 for details), and found (3.84 10 −20 2 / 2 ) . We observe that the value obtained for (3) is greater than any value of (3) over the whole spectral range considered [27]. Based on the measured (3) and detected TH signals for the film and nanodisk, and considering that the emission intensity scales as ( we calculate the effective third order susceptibility of the nanostructure at the AM to be as high as , we find it to be five orders of magnitude bigger.…”
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confidence: 74%
“…Based on the measured (3) and detected TH signals for the film and nanodisk, and considering that the emission intensity scales as ( we calculate the effective third order susceptibility of the nanostructure at the AM to be as high as , we find it to be five orders of magnitude bigger. We note, however, that due to the large intrinsic absorption of germanium at the TH wavelength [31], the radiation of the green emission is not expected to be as effective as for silicon, and therefore the performance comparison cannot be made by only considering (3) values, so next we experimentally quantify the efficiency of our nanodevice. Finally, we calibrated the TH power of the germanium disk with respect to the excitation power, as exhibited in Figure 6 (pump = 1650 nm).…”
ABSTRACT. We present an all-dielectric germanium nanosystem exhibiting a strong third order nonlinear response and efficient third harmonic generation in the optical regime. A thin germanium nanodisk shows a pronounced valley in its scattering cross section close to the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third harmonic signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk generates a high effective third order susceptibility of (3) = 4.3 10 −9, corresponding to an associated third harmonic conversion efficiency of 0.0001% at a wavelength of 1650 nm, which is four orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about one order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials.
“…The water-repellent surface effectively protects the PTFE-Eu 3+ film from contacting with water molecules. The outstanding resistance is of significant importance since water or aqueous salt solution are the common service environments for rare earth materials such as in vivo and in vitro bioimaging applications474849.…”
The motivation of this work is to create luminescent rare earth/polymer films with outstanding water-resistance and superhydrophobicity. Specifically, the emulsion polymerization of styrene leads to core particles. Then core-shell-structured polymer nanoparticles are synthesized by copolymerization of styrene and acrylic acid on the core surface. The coordination reaction between carboxylic groups and rare earth ions (Eu3+ and Tb3+) generates uniform spherical rare earth/polymer nanoparticles, which are subsequently complexed with PTFE microparticles to obtain micro-/nano-scaled PTFE/rare earth films with hierarchical rough morphology. The films exhibit large water contact angle up to 161° and sliding angle of about 6°, and can emit strong red and green fluorescence under UV excitation. More surprisingly, it is found that the films maintain high fluorescence intensity after submersed in water and even in aqueous salt solution for two days because of the excellent water repellent ability of surfaces.
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