Mingzhen Yao

X-ray-induced nanoparticle-based photodynamic therapy of cancer

AIM In this study, Ce(3+)-doped lanthanum(III) fluoride (LaF3:Ce(3+)) nanoparticles were synthesized by a wet-chemistry method in dimethyl sulfoxide (DMSO) and their application as an intracellular light source for photodynamic activation was demonstrated. MATERIALS & METHODS The LaF3:Ce(3+)/DMSO nanoparticles have a strong green emission with a peak at approximately 520 nm, which is effectively overlapped with the absorption of protoporphyrin IX (PPIX). The nanoparticles were encapsulated into poly(D,L-lactide-co-glycolide (PLGA) microspheres along with PPIX. Upon irradiation with x-rays (90 kV), energy transfer from the LaF3:Ce(3+)/DMSO nanoparticles to PPIX occurs and singlet oxygen is generated for cancer cell damage. RESULTS The LaF3:Ce(3+)/DMSO/PLGA or LaF3:Ce(3+)/DMSO/PPIX/PLGA microspheres alone caused only sublethal cytotoxicity to the cancer cells. Upon x-ray irradiation, the LaF3:Ce(3+)/DMSO/PPIX/PLGA microspheres induced oxidative stress, mitochondrial damage and DNA fragmentation on prostate cancer cells (PC3). DISCUSSION The results indicate that x-rays can activate LaF3:Ce(3+) and PPIX nanocomposites, which can be a novel method for cancer destruction.

Hypersensitive luminescence of Eu3+ in dimethyl sulfoxide as a new probing for water measurement.

Dimethyl sulfoxide (DMSO) is a well-known organic solvent that can be used for biological applications. DMSO is miscible with water, and it is very common that the two solvents are mixed for some applications. It is important to detect water in DMSO, and this has been done using the luminescence decay lifetimes from Eu(3+) ions. We observed that the emissions of Eu(3+) in DMSO are very strong and very sensitive to water. The emission band from the (5)D(0) → (7)F(2) transition has two peaks at 613 and 617 nm, respectively, and these two peaks change in the opposite ways when water is added into DMSO. The intensity ratio of the two peaks follows nearly perfect linear dependence on the water concentration added in DMSO. This linear relationship provides a new and convenient method for water measurement in DMSO.

Luminescence enhancement of CdTe nanostructures in LaF3:Ce/CdTe nanocomposites

Radiation detection demands new scintillators with high quantum efficiency, high energy resolution, and short luminescence lifetimes. Nanocomposites consisting of quantum dots and Ce3+ doped nanophosphors may be able to meet these requirements. Here, we report the luminescence enhancement of LaF3:Ce/CdTe nanocomposites which were synthesized by a wet chemistry method. CdTe quantum dots in LaF3:Ce/CdTe nanocomposites are converted into nanowires, while in LaF3/CdTe nanocomposites no such conversion is observed. As a result, the CdTe luminescence in LaF3:Ce/CdTe nanocomposites is enhanced about five times, while in LaF3/CdTe nanocomposites no enhancement was observed. Energy transfer, light reabsorption, and defect passivation are the likely reasons for the luminescence enhancement.

X-ray luminescence of CdTe quantum dots in LaF3:Ce/CdTe nanocomposites

CdTe quantum dots have intense photoluminescence but exhibit almost no x-ray luminescence. However, intense x-ray luminescence from CdTe quantum dots is observed in LaF3:Ce/CdTe nanocomposites. This enhancement in the x-ray luminescence of CdTe quantum dots is attributed to the energy transfer from LaF3:Ce to CdTe quantum dots in the nanocomposites. The combination of LaF3:Ce nanoparticles and CdTe quantum dots makes LaF3:Ce/CdTe nanocomposites promising scintillators for radiation detection.

Synthesis and luminescence of CePO4:Tb/LaPO4 core/sheath nanowires.

CePO(4):Tb/LaPO(4) nanowires with a core/sheath architecture have been successful synthesized by a facile aqueous chemical method mediated by original CePO(4):Tb aggregation seeds. The seed crystals serve as both a luminescence center and a nucleation site for epitaxial growth. The seed nanocrystals have an irregular sphere-like shape with an average size of around 6.8 nm and a narrow size distribution. When the seed crystals are coated with LaPO(4), the resulting core/sheath CePO(4):Tb/LaPO(4) nanowires have mean diameters of about 7.6 nm and lengths up to 331 nm. Both photo- and x-ray luminescence demonstrate that the LaPO(4) coating increases the luminescence efficiency. These core/sheath structured nanowires may find potential applications in solid state lighting, medical imaging and radiation detection.

Luminescent LaF3:Ce-doped organically modified nanoporous silica xerogels

Organically modified silica compounds (ORMOSILs) were synthesized by a sol-gel method from amine-functionalized 3-aminopropyl triethoxylsilane and tetramethylorthosilicate and were doped in situ with LaF3:Ce nanoparticles, which in turn were prepared either in water or in ethanol. Doped ORMOSILs display strong photoluminescence either by UV or X-ray excitation and maintain good transparency up to a loading level of 15.66% w/w. The TEM observations demonstrate that ORMOSILs remain nanoporous with pore diameters in the 5–10 nm range. LaF3:Ce nanoparticles doped into the ORMOSILs are rod-like, 5 nm in diameter and 10–15 nm in length. Compression testing indicates that the nanocomposites have very good strength, without significant lateral dilatation and buckling under quasi-static compression. LaF3:Ce nanoparticle-doped ORMOSILs have potential for applications in radiation detection and solid state lighting.

Luminescence of Lanthanide-Dimethyl Sulfoxide Compound Solutions

Dimethyl sulfoxide (DMSO) has the ability to penetrate living tissues without causing significant damage. Of foremost importance to our understanding of the possible functions of DMSO in biological systems is its ability to replace some of the water molecules associated with the cellular constituents or to affect the structure of the omnipresent water. Luminescence probes have been widely used for biological studies such as labeling, imaging, and detection. Luminescence probes formed in DMSO may find new applications. Here luminescence compounds formed by refluxing lanthanide nitrates of Ce, La, Tb, Yb, Nd, Gd, and Eu in DMSO are reported and their luminescence properties investigated. On the basis of their luminescence spectral properties, the compounds can be classified into four classes. For compounds I with Yb, Ce, and La, the excitation and emission spectra are very broad and their excitation or emission peaks are shifted to longer wavelengths when the monitored emission or excitation wavelength is longer. For compounds II with Gd and Nd, both the excitation and emission spectra are very broad but their emission wavelengths change little at different excitation wavelengths. For Tb-DMSO as compound III, both the typical emissions from the f-f transitions of Tb(3+) and a broad emission at 445 nm are observed. At low reaction temperatures, the f-f emissions are dominant, while at high reaction temperatures such as 180 °C, the broad emission at 445 nm is dominant. For compound IV, Eu-DMSO, the dominant emissions are from the f-f transitions of Eu(3+) and only a weak broad emission is observed, which is likely from the d-f transition of Eu(2+) rather than from metal-to-ligand charge transfer states.