Cytotoxicity and cell imaging potentials of submicron color-tunable yttria particles

Solvent-particles interactions during composite particles formation by pulsed laser melting of α-Fe2O3

This work thoroughly investigates chemical solvent-particles interactions during the formation of composite particles by pulsed laser melting of α-Fe₂O₃. Two solvents, with different dielectric constants, such as ethyl acetate (ε_r = 6) and ethanol (ε_r = 24.6), were examined in terms of their effect on the morphology, size, and phase composition of iron oxide composites. We calculated the laser fluence curves using the heating-melting-evaporation approach to identify the critical particle size that undergoes the phase changes first. We assessed the temperature of the particles irradiated with 390 mJ/pulse^.cm² in both solvents, including the heat dissipation between the particles and the liquid. The phase diagram of the Fe-O-C-H system was calculated to determine the temperature-pressure relationship of the system in equilibrium. We also employed an in situ GC-MS analysis to identify the volatile products during irradiation. Based on our experimental results, we concluded that the final diameter of the composites increases from 400 to 600 nm, along with the decreasing dielectric constant of the solvent, which is related to the different polarization of the organic liquid and the degree of particle agglomeration. The reduction of hematite in ethanol proceeded much faster, ending up with Fe/FeC_x, while in ethyl acetate, it ended up with Fe₃O₄. Among all the particles, those with a diameter of 200 nm have the highest temperature and undergo the phase transition first. The temperature of a 200 nm composite particle in ethanol is slightly lower than in ethyl acetate, i.e. 1870 K as compared to 1902 K. Phase equilibrium diagrams proved the existence of Fe, FeO, and Fe₃O₄ as the preferred phases at about 1900 K. Our research provides a new insight into the process of submicron particle formation during pulsed laser irradiation and allows proposing a mechanism for the growth of particles of different size and phase composition depending on the solvent.

Toxicity and T₂-Weighted Magnetic Resonance Imaging Potentials of Holmium Oxide Nanoparticles

In recent years, paramagnetic nanoparticles (NPs) have been widely used for magnetic resonance imaging (MRI). This paper reports the fabrication and toxicity evaluation of polyethylene glycol (PEG)-functionalized holmium oxide (Ho₂O₃) NPs for potential T₂-weighted MRI applications. Various characterization techniques were used to examine the morphology, structure and chemical properties of the prepared PEG-Ho₂O₃ NPs. MRI relaxivity measurements revealed that PEG-Ho₂O₃ NPs could generate a strong negative contrast in T₂-weighted MRI. The pilot cytotoxicity experiments showed that the prepared PEG-Ho₂O₃ NPs are biocompatible at concentrations less than 16 μg/mL. Overall, the prepared PEG-Ho₂O₃ NPs have potential applications for T₂-weighted MRI imaging.

Eu, Gd-Codoped Yttria Nanoprobes for Optical and T₁-Weighted Magnetic Resonance Imaging

Nanoprobes with multimodal functionality have attracted significant interest recently because of their potential applications in nanomedicine. This paper reports the successful development of lanthanide-doped Y₂O₃ nanoprobes for potential applications in optical and magnetic resonance (MR) imaging. The morphology, structural, and optical properties of these nanoprobes were characterized by transmission electron microscope (TEM), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and photoluminescence (PL). The cytotoxicity test showed that the prepared lanthanide-doped Y₂O₃ nanoprobes have good biocompatibility. The obvious contrast enhancement in the T₁-weighted MR images suggested that these nanoprobes can be used as a positive contrast agent in MRI. In addition, the clear fluorescence images of the L-929 cells incubated with the nanoprobes highlight their potential for optical imaging. Overall, these results suggest that prepared lanthanide-doped Y₂O₃ nanoprobes can be used for simultaneous optical and MR imaging.

Difference between Toxicities of Iron Oxide Magnetic Nanoparticles with Various Surface-Functional Groups against Human Normal Fibroblasts and Fibrosarcoma Cells

Recently, many nanomedical studies have been focused on magnetic nanoparticles (MNPs) because MNPs possess attractive properties for potential uses in imaging, drug delivery, and theranostics. MNPs must have optimized size as well as functionalized surface for such applications. However, careful cytotoxicity and genotoxicity assessments to ensure the biocompatibility and biosafety of MNPs are essential. In this study, Fe₃O₄ MNPs of different sizes (approximately 10 and 100–150 nm) were prepared with different functional groups, hydroxyl (–OH) and amine (–NH₂) groups, by coating their surfaces with tetraethyl orthosilicate (TEOS), 3-aminopropyltrimethoxysilane (APTMS) or TEOS/APTMS. Differential cellular responses to those surface-functionalized MNPs were investigated in normal fibroblasts vs. fibrosarcoma cells. Following the characterization of MNP properties according to size, surface charge and functional groups, cellular responses to MNPs in normal fibroblasts and fibrosarcoma cells were determined by quantifying metabolic activity, membrane integrity, and DNA stability. While all MNPs induced just about 5% or less cytotoxicity and genotoxicity in fibrosarcoma cells at lower than 500 μg/mL, APTMS-coated MNPs resulted in greater than 10% toxicity against normal cells. Particularly, the genotoxicity of MNPs was dependent on their dose, size and surface charge, showing that positively charged (APTMS- or TEOS/APTMS-coated) MNPs induced appreciable DNA aberrations irrespective of cell type. Resultantly, smaller and positively charged (APTMS-coated) MNPs led to more severe toxicity in normal cells than their cancer counterparts. Although it was difficult to fully differentiate cellular responses to various MNPs between normal fibroblasts and their cancer counterparts, normal cells were shown to be more vulnerable to internalized MNPs than cancer cells. Our results suggest that functional groups and sizes of MNPs are critical determinants of degrees of cytotoxicity and genotoxicity, and potential mechanisms of toxicity.

Ligand-functionalization of BPEI-coated YVO4:Bi3+,Eu3+ nanophosphors for tumor-cell-targeted imaging applications

In this study, surface-functionalized, branched polyethylenimine (BPEI)-modified YVO4:Bi(3+),Eu(3+) nanocrystals (NCs) were successfully synthesized by a simple, rapid, solvent-free hydrothermal method. The BPEI-coated YVO4:Bi(3+),Eu(3+) NCs with high crystallinity show broad-band excitation in the λ=250 to 400 nm near-ultraviolet (NUV) region and exhibit a sharp-line emission band centered at λ=619 nm under excitation at λ=350 nm. The surface amino groups contributed by the capping agent, BPEI, not only improve the dispersibility and water/buffer stability of the BPEI-coated YVO4:Bi(3+),Eu(3+) NCs, but also provide a capability for specifically targeted biomolecule conjugation. Folic acid (FA) and epidermal growth factor (EGF) were further attached to the BPEI-coated YVO4:Bi(3+),Eu(3+) NCs and exhibited effective positioning of fluorescent NCs toward the targeted folate receptor overexpressed in HeLa cells or EGFR overexpressed in A431 cells with low cytotoxicity. These results demonstrate that the ligand-functionalized, BPEI-coated YVO4:Bi(3+),Eu(3+) NCs show great potential as a new-generation biological luminescent bioprobe for bioimaging applications. Moreover, the unique luminescence properties of BPEI-coated YVO4:Bi(3+),Eu(3+) NCs show potential to combine with a UVA photosensitizing drug to produce both detective and therapeutic effects for human skin cancer therapy.