ABSTRACT
Upconversion (UC) process in lanthanide-doped nanomaterials has attracted great research interest for its extensive biological applications in vitro and in vivo, benefiting from the high tissue penetration depth of near-infrared excitation light and low autofluorescence background. However, the 980 nm laser, typically used to trigger the Yb(3+)-sensitized UC process, is strongly absorbed by water in biological structures and could cause severe overheating effect. In this article, we report the extension of the UC excitation spectrum to shorter wavelengths, where water has lower absorption. This is realized by further introducing Nd(3+) as the sensitizer and by building a core/shell structure to ensure successive Nd(3+) â Yb(3+) â activator energy transfer. The efficacy of this Nd(3+)-sensitized UC process is demonstrated in in vivo imaging, and the results confirmed that the laser-induced local overheating effect is greatly minimized.
Subject(s)
Diagnostic Imaging/methods , Nanostructures/chemistry , Neodymium/chemistry , Phosphorus/chemistry , Absorption , Animals , Contrast Media/chemistry , Heating , Hot Temperature , Infrared Rays , Lasers , Luminescence , Mice , Mice, Inbred BALB C , Mice, Nude , Particle Size , Photochemistry , Spectroscopy, Near-Infrared , Water/chemistryABSTRACT
Monodispersed nanocrystals (NCs) can form ordered and functional binary superlattices. A variety of functional binary nanocrystal superlattices (BNSLs) and bilayer assemblies based on lanthanide-doped NaREF4 (RE = Y, Gd) were constructed with different assembly methods. These assemblies are attractive for applications in photonics as they display multicolor upconversion (UC) emissions.
ABSTRACT
Upconversion luminescent nanoparticles (UCNPs) have been widely used in many biochemical fields, due to their characteristic large anti-Stokes shifts, narrow emission bands, deep tissue penetration and minimal background interference. UCNPs-derived multifunctional materials that integrate the merits of UCNPs and other functional entities have also attracted extensive attention. Here in this paper we present a core-shell structured nanomaterial, namely, NaGdF(4):Yb,Er@CaF(2)@SiO(2)-PS, which is multifunctional in the fields of photodynamic therapy (PDT), magnetic resonance imaging (MRI) and fluorescence/luminescence imaging. The NaGdF(4):Yb,Er@CaF(2) nanophosphors (10 nm in diameter) were prepared via sequential thermolysis, and mesoporous silica was coated as shell layer, in which photosensitizer (PS, hematoporphyrin and silicon phthalocyanine dihydroxide) was covalently grafted. The silica shell improved the dispersibility of hydrophobic PS molecules in aqueous environments, and the covalent linkage stably anchored the PS molecules in the silica shell. Under excitation at 980 nm, the as-fabricated nanomaterial gave luminescence bands at 550 nm and 660 nm. One luminescent peak could be used for fluorescence imaging and the other was suitable for the absorption of PS to generate singlet oxygen for killing cancer cells. The PDT performance was investigated using a singlet oxygen indicator, and was investigated in vitro in HeLa cells using a fluorescent probe. Meanwhile, the nanomaterial displayed low dark cytotoxicity and near-infrared (NIR) image in HeLa cells. Further, benefiting from the paramagnetic Gd(3+) ions in the core, the nanomaterial could be used as a contrast agent for magnetic resonance imaging (MRI). Compared with the clinical commercial contrast agent Gd-DTPA, the as-fabricated nanomaterial showed a comparable longitudinal relaxivities value (r(1)) and similar imaging effect.
Subject(s)
Fluorescent Dyes/chemistry , Nanoparticles/chemistry , Photosensitizing Agents/chemistry , Apoptosis/drug effects , Contrast Media/chemistry , Contrast Media/toxicity , Gadolinium DTPA/chemistry , Gadolinium DTPA/toxicity , HeLa Cells , Humans , Indoles/chemistry , Magnetic Resonance Imaging , Organosilicon Compounds/chemistry , Oxidation-Reduction , Photochemotherapy , Photosensitizing Agents/toxicity , Singlet Oxygen/metabolism , Spectroscopy, Near-InfraredABSTRACT
Upconversion emissions from rare-earth nanoparticles have attracted much interest as potential biolabels, for which small particle size and high emission intensity are both desired. Herein we report a facile way to achieve NaYF(4):Yb,Er@CaF(2) nanoparticles (NPs) with a small size (10-13 nm) and highly enhanced (ca. 300 times) upconversion emission compared with the pristine NPs. The CaF(2) shell protects the rare-earth ions from leaking, when the nanoparticles are exposed to buffer solution, and ensures biological safety for the potential bioprobe applications. With the upconversion emission from NaYF(4):Yb,Er@CaF(2) NPs, HeLa cells were imaged with low background interference.
Subject(s)
Ions/chemistry , Luminescent Agents/analysis , Metals, Rare Earth/analysis , Microscopy, Confocal , Nanoparticles/analysis , HeLa Cells , Humans , Luminescent Agents/chemistry , Luminescent Measurements , Metals, Rare Earth/chemistry , Nanoparticles/chemistry , Nanoparticles/ultrastructure , Particle SizeABSTRACT
In vitro or in vivo bioimaging utilizing the upconversion (UC) luminescence of rare earth fluoride nanocrystals (NCs) has attracted much attention, especially for Yb(3+)/Tm(3+) doped NCs with a near-infrared (NIR) UC emission at 800 nm. Herein, water-soluble NaYF(4):Yb,Tm NCs with strong NIR UC emission were synthesized with a solvothermal method. In vitro and in vivo bioimaging and toxicity assessments were carried out with HeLa cell and Caenorhabditis elegans (C. elegans) cases, respectively. NaYF(4):Yb,Tm NCs afforded an efficient NIR image of the HeLa cells with an incubation concentration of 10 µg mL(-1), and CCK-8 assay revealed a low cytotoxicity. Fed with Escherichia coli (E. coli) and NCs together, the C. elegans showed a NIR image in the gut from the pharynx to the anus. Further, these NCs could be excreted out when those worms were then fed with only E. coli. Toxicity studies were further addressed with protein expression, life span, egg production, egg viability, and growth rate of the worms in comparison with those of the intact ones. The feeding of rare earth fluoride NCs with a dose of 100 µg does not arise obvious toxicity effect from the growth to procreation. The in vitro and in vivo studies confirm that NaYF(4):Yb,Tm NCs could be served as an excellent NIR emission bioprobe with low toxicity.
Subject(s)
Fluorides/analysis , Nanoparticles/analysis , Nanoparticles/toxicity , Spectroscopy, Near-Infrared/methods , Thulium/analysis , Ytterbium/analysis , Yttrium/analysis , Animals , Caenorhabditis elegans/ultrastructure , Cell Survival , Fluorides/chemistry , Fluorides/toxicity , HeLa Cells , Humans , Luminescent Agents/analysis , Luminescent Agents/chemistry , Luminescent Agents/toxicity , Nanoparticles/chemistry , Nanoparticles/ultrastructure , Thulium/chemistry , Thulium/toxicity , Ytterbium/chemistry , Ytterbium/toxicity , Yttrium/chemistry , Yttrium/toxicityABSTRACT
A fluorescent-magnetic YP(x)V(1-x)O(4):Eu@GdPO(4) core/shell nanostructure was prepared by a two-step method. The YP(x)V(1-x)O(4):Eu core was synthesized using a hydrothermal method, and it exhibits strong photoluminescence with the effective doping of phosphorus (P) and europium (Eu) into a YVO(4) matrix. The hydrothermal process provides a hydrophilic and fresh surface for coating GdPO(4) shell. As YP(x)V(1-x)O(4):Eu and GdPO(4) have the similar unit cell parameters, YP(x)V(1-x)O(4):Eu nanoparticles (NPs) were favorably coated by an epitaxial growth of GdPO(4) shell in aqueous phase. The core/shell nanostructure was identified by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The GdPO(4) shell not only possesses the paramagnetic character, but also enhances the photoluminescence efficiency by blocking the non-radiative de-excitation from the VO(4)(3-) groups to the surface quenching sites. These optical and magnetic properties promise outstanding fluorescent-magnetic bifunctional nanomaterials.
