Ce³âº sensitized GdPO4:Tb³âº with iron oxide nanoparticles: a potential biphasic system for cancer theranostics.

We report a biphasic system (BPS) consisting of PEGylated Tb(3+)-doped GdPO4 nanorice sensitized with Ce(3+) (PEG-NRs) and glutamic acid coated iron oxide nanoparticles (IONPs) with multifunctional capabilities. The mesoporous PEG-NRs exhibit green light luminescence properties and a high degree of aqueous stability. Their drug loading and release capacities were investigated for anti-cancer chemo doxorubicin (DOX). Their mesoporous nature and availability of plenty of negatively charged functional groups (-COO(-)) on the surface of PEG-NRs facilitate approximately 94 wt% DOX loading. In vitro studies carried out for PEG-NRs and their biphasic integrated system with iron oxide using HeLa and MCF-7 cell lines demonstrated their cell killing efficacy. The green luminescence observed under confocal laser scanning microscopy (CLSM) confirms the cellular uptake of PEG-NRs by HeLa cell lines and their accumulation in the cytoplasm. Approximately 50-55% of HeLa and MCF-7 cell death was observed after 24 h of incubation with DOX loaded BPS (2 mg IONPs and 0.25 mg PEG-NRs + DOX), which further increased to about 90% when exposed to an AC magnetic field (ACMF) for 25 min. Our findings demonstrate that the therapeutic efficacy of BPS loaded with DOX could be a powerful multimodal system for imaging and synergistic chemo-thermal cancer therapy.

Luminescence switching behavior through redox reaction in Ce3+ co-doped LaPO4:Tb3+ nanorods: re-dispersible and polymer film.

Re-dispersible Tb(3+) doped LaPO(4) nanorods have been prepared using ethylene glycol (EG) as a capping agent as well as reaction medium at a relatively low temperature of 150 °C. The X-ray diffraction study reveals that all the doped samples are well crystalline with a monoclinic structure of the LaPO(4) phase. The luminescence intensity of (5)D(4)→(7)F(5) transition at 543 nm (green) is more prominent than that of (5)D(4)→(7)F(6) transition at 487 nm (blue) for all the samples. This is related to the polarizing effect from [PO(4)](3-) to the Tb(3+) site. Concentration dependent luminescence study shows that the luminescence intensity of Tb(3+) increases up to 10 at.% and decreases above this. This is due to the concentration quenching effect arising from cross relaxation among Tb(3+)-Tb(3+) ions. The results show that nanoparticles prepared in EG medium gives an enhanced luminescence compared to that prepared in water. This is attributed to the multiphonon relaxation effect from O-H groups surrounding over nanoparticles as well as the extent of increase of agglomeration among particles for samples prepared in water. Significant enhancement in the emission of Tb(3+) is also observed when Ce(3+) is used as the sensitizer in LaPO(4):Tb(3+)nanorods. The optimum concentration of Ce(3+) for maximum luminescence is found to be 7 at.% in Ce(3+) sensitized LaPO(4):Tb(3+) (5 at.%). Based on the energy transfer process from Ce(3+) to Tb(3+), the luminescence of Tb(3+) can be switched OFF and ON by performing oxidation and reduction of Ce(3+)↔Ce(4+) using KMnO(4) and ascorbic acid, respectively. The samples are re-dispersible in water, methanol and can be incorporated into polyvinyl alcohol (PVA) films. They show a dark green emission under ultraviolet radiation.