Synthesis and characterization of Na(Gd0.5Lu0.5)F4: Nd3+,a core-shell free multifunctional contrast agent.

Compared to conventional core-shell structures, core-shell free nanoparticles with multiple functionalities offer several advantages such as minimal synthetic complexity and low production cost. In this paper, we present the synthesis and characterization of Nd3+ doped Na(Gd0.5Lu0.5)F4 as a core-shell free nanoparticle system with three functionalities. Nanocrystals with 20 nm diameter, high crystallinity and a narrow particle size distributions were synthesized by the solvothermal method and characterized by various analytical techniques to understand their phase and morphology. Fluorescence characteristics under near infrared (NIR) excitation at 808 nm as well as X-ray excitation were studied to explore their potential in NIR optical and X-ray imaging. At 1.0 mol% Nd concentration, we observed a quantum yield of 25% at 1064 nm emission with 13 W/cm2 excitation power density which is sufficiently enough for imaging applications. Under 130 kVp (5 mA) power of X-ray excitation, Nd3+ doped Na(Gd0.5Lu0.5)F4 shows the characteristic emission bands of Gd3+ and Nd3+ with the strongest emission peak at 1064 nm due to Nd3+. Furthermore, magnetization measurements show that the nanocrystals are paramagnetic in nature with a calculated magnetic moment per particle of ~570 µB at 2T. These preliminary results support the suitability of the present nanophosphor as a multimodal contrast agent with three imaging features viz. optical, magnetic and X-ray.

Drug Resistance of Endocardial Endothelial Cells is Related to Higher Endogenous ABCG2.

Endocardial endothelial cells (EECs), when compared with endothelial cells of arteries and veins, possess higher resistance to apoptosis-inducing anticancer agents. The mechanism of this resistance property is unknown. We have investigated the molecular mechanism, which contributes to increased cell survival capacity in EECs. We explored whether the resistance to apoptosis is associated with the cellular expression of ATP-binding cassette transporters such as P-glycoprotein, MRP-1, and ABCG2. We used primary and immortalized porcine endocardial endothelial cells (PEECs and hTERT PEECs) and compared the results with that in porcine aortic endothelial cells (PAECs), left atrioventricular valve endothelial cells (PVECs), and human umbilical vein endothelial cell line (EA.hy926). FACS and immunoblot analysis revealed a significantly higher expression of ABCG2 in PEECs and hTERT PEECs compared to PAECs, PVECs, and EA.hy926. Using apoptosis-inducing anticancer agents such as doxorubicin and camptothecin, through chromatin condensation assay and immunoblot analysis, we demonstrated a higher resistance to apoptosis in EECs compared to PAECs, PVECs, and EA.hy926. Interestingly, resistance in EECs reversed in presence of ABCG2 specific inhibitor, fumitremorgin C. Our observations suggest that an inherently high expression of ABCG2 in EECs protects them against apoptosis in presence of anticancer agents.

Multimodal bioimaging using rare earth doped Gd2O2S: Yb/Er phosphor with upconversion luminescence and magnetic resonance properties.

While infrared upconversion imaging using halide nanoparticles are so common the search for a very efficient halide free upconverting phosphors is still lacking. In this article we report Gd2O2S:Yb/Er,YbHo,YbTm systems as a very efficient alternative phosphors that show upconversion efficiency comparable or even higher than existing halide phosphors. While the majority of rare earth dopants provide the necessary features for optical imaging, the paramagnetic Gd ion also contributes to the magnetic imaging,thereby resulting in a system with bimodal imaging features. Results from imaging of the nanoparticles together with aggregates of cultured cells have suggested that imaging of the particles in living animals may be possible. In vitro tests revealed no signficant toxicity because no cell death was observed when the nanoparticles were in the presence of growing cells in culture. Measurement of the magnetization of the phosphor shows that the particles are strongly magnetic, thus making them suitable as an MRI agent.