Core–Shell Lanthanide Upconversion Nanophosphors as Four-Modal Probes for Tumor Angiogenesis Imaging

Multimodality imaging overcomes the shortage and incorporates the advantages of different imaging tools. Lanthanide-based nanoprobes are unique and have rich optical, magnetic, radioactive, and X-ray attenuation properties; however, simple doping of different lanthanide cations into one host can result in a material with multifunction but not the optimized properties. In this study, using NaLuF₄:Yb,Tm as the core and 4 nm of ¹⁵³Sm³⁺-doped NaGdF₄ (half-life of ¹⁵³Sm = 46.3 h) as the shell, we developed a lanthanide-based core–shell nanocomposite as an optimized multimodal imaging probe with enhanced imaging ability. The lifetime of upconversion luminescence (UCL) at 800 nm and relaxation rate (1/<i>T</i>₁) were at 1044 μs and 18.15 s^–1·mM^–1, respectively; however, no significant decrease in the attenuation coefficient was observed, which preserved the excellent X-ray imaging ability. The nanomaterial NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) was confirmed to be effective and applicable for UCL imaging, X-ray computed tomography (CT), magnetic resonance imaging, and single-photon emission computed tomography (SPECT) <i>in vivo</i>. Furthermore, the NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) nanoparticles were applied in tumor angiogenesis analysis by combining multimodality imaging of CT, SPECT, and confocal UCL imaging, which shows its value of multifunctional nanoparticles NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) in tumor angiogenesis imaging

Yolk–Shell Upconversion Nanocomposites for LRET Sensing of Cysteine/Homocysteine

The fabrication of lanthanide upconversion nanocomposites as probes has become a new research hotspot due to its special advantages via utilizing upconversion luminescence (UCL) as a detection signal. Herein, a hybrid organic dye modified upconversion nanophosphor is successfully developed as a nanoprobe for cysteine/homocysteine. Yolk–shell structured upconversion nanoparticles (YSUCNP) with lanthanide upconversion nanophosphor as moveable core and silica as mesoporous shell are synthesized, and a colorimetric chemodosimeter for cysteine/homocysteine is accommodated in the hollow cavities. Thus, cysteine/homocysteine can be quantitatively detected on the basis of luminescent resonance energy transfer (LRET) in a UCL turn-off pattern. The dye-loaded YSUCNP possess good dispersibility in aqueous solution; thus detection of the targeted molecule can be achieved in pure water. Cellular experiments carried out with laser-scanning upconversion luminescence microscopy further demonstrate that the dye-loaded YSUCNP can serve as an intracellular nanoprobe to detect cysteine/homocysteine. Moreover, this dye-loading protocol can be developed as a common approach to construct other chemodosimeter-modified UCNP hybrid nanoprobes, as proved by a UCL turn-on style sensor for cyanide

An Artificial Tongue Fluorescent Sensor Array for Identification and Quantitation of Various Heavy Metal Ions

Herein, a small-molecule fluorescent sensor array for rapid identification of seven heavy metal ions was designed and synthesized, with its sensing mechanism mimicking that of a tongue. The photoinduced electron transfer and intramolecular charge transfer mechanism result in combinatorial interactions between sensor array and heavy metal ions, which lead to diversified fluorescence wavelength shifts and emission intensity changes. Upon principle component analysis (PCA), this result renders clear identification of each heavy metal ion on a 3D spatial dispersion graph. Further exploration provides a concentration-dependent pattern, allowing both qualitative and quantitative measurements of heavy metal ions. On the basis of this information, a “safe-zone” concept was proposed, which provides rapid exclusion of versatile hazardous species from clean water samples based on toxicity characteristic leaching procedure standards. This type of small-molecule fluorescent sensor array could open a new avenue for multiple heavy metal ion detection and simplified water quality analysis

High-Efficiency in Vitro and in Vivo Detection of Zn²⁺ by Dye-Assembled Upconversion Nanoparticles

Development of highly sensitive and selective sensing systems of divalent zinc ion (Zn²⁺) in organisms has been a growing interest in the past decades owing to its pivotal role in cellular metabolism, apoptosis, and neurotransmission. Herein, we report the rational design and synthesis of a Zn²⁺ fluorescent-based probe by assembling lanthanide-doped upconversion nanoparticles (UCNPs) with chromophores. Specifically, upconversion luminescence (UCL) can be effectively quenched by the chromophores on the surface of nanoparticles via a fluorescence resonant energy transfer (FRET) process and subsequently recovered upon the addition of Zn²⁺, thus allowing for quantitative monitoring of Zn²⁺. Importantly, the sensing system enables detection of Zn²⁺ in real biological samples. We demonstrate that this chromophore–UCNP nanosystem is capable of implementing an efficient in vitro and in vivo detection of Zn²⁺ in mouse brain slice with Alzheimer’s disease and zebrafish, respectively

High-Efficiency in Vitro and in Vivo Detection of Zn²⁺ by Dye-Assembled Upconversion Nanoparticles

Development of highly sensitive and selective sensing systems of divalent zinc ion (Zn²⁺) in organisms has been a growing interest in the past decades owing to its pivotal role in cellular metabolism, apoptosis, and neurotransmission. Herein, we report the rational design and synthesis of a Zn²⁺ fluorescent-based probe by assembling lanthanide-doped upconversion nanoparticles (UCNPs) with chromophores. Specifically, upconversion luminescence (UCL) can be effectively quenched by the chromophores on the surface of nanoparticles via a fluorescence resonant energy transfer (FRET) process and subsequently recovered upon the addition of Zn²⁺, thus allowing for quantitative monitoring of Zn²⁺. Importantly, the sensing system enables detection of Zn²⁺ in real biological samples. We demonstrate that this chromophore–UCNP nanosystem is capable of implementing an efficient in vitro and in vivo detection of Zn²⁺ in mouse brain slice with Alzheimer’s disease and zebrafish, respectively