Gautom Kumar Das

Gadolinium oxide ultranarrow nanorods as multimodal contrast agents for optical and magnetic resonance imaging.

We demonstrate a simple synthetic strategy for the fabrication of single-phase rare earth (RE) doped gadolinium oxide (Gd(2)O(3):RE where RE = terbium (Tb), ytterbium (Yb), and erbium (Er)) nanorods (NRs) as multimodal imaging probes. The NRs are ultranarrow and exhibit both emission and magnetic characteristics. The Tb-doped and Yb/Er-codoped Gd(2)O(3) NRs exhibit down- and up-conversion fluorescence respectively, and also exhibit paramagnetism. Importantly, these codoped NRs possess excellent magnetic characteristics, as shown in their longitudinal relaxation time (T1) -weighted image contrast, which is closer to that of commercial Gadovist for magnetic resonance imaging (MRI) applications. This property opens up new avenues in the development of contrast agents.

Bimodal magnetic-fluorescent probes for bioimaging.

Fluorescent optical probes have been intensively used in the area of bio‐imaging. In this review article, we describe the recent advancements in the synthesis and application of bimodal magnetic–fluorescent probes for bioimaging. The bimodal probes consist of fluorescent [semiconducting quantum dots (e.g., CdSe/ZnS) or rare‐earth doped (e.g., NaYF4:Yb,Er)] nanoparticles (NPs) and magnetic (iron oxide or gadolinium based) NPs for optical and magnetic resonance (MR) imaging. Microsc. Res. Tech., 2011.

Cytotoxic and genotoxic characterization of titanium dioxide, gadolinium oxide, and poly(lactic-co-glycolic acid) nanoparticles in human fibroblasts†

Engineered nanomaterials have become prevalent in our everyday life. While the popularity of using nanomaterials in consumer products continues to rise, increasing awareness of nanotoxicology has also fuelled efforts to accelerate our understanding of the ill effects that different nanomaterials can bring to biological systems. In this study, we investigated the potential cytotoxicity and genotoxicity of three nanoparticles: titanium dioxide (TiO(2)), terbium-doped gadolinium oxide (Tb-Gd(2)O(3)), and poly(lactic-co-glycolic acid) (PLGA). To evaluate nanoparticle-induced genotoxicity more realistically, a human skin fibroblast cell line (BJ) with less mutated genotype compared with cancer cell line was used. The nanoparticles were first characterized by size, morphology, and surface charge. Cytotoxicity effects of the nanoparticles were then evaluated by monitoring the proliferation of treated BJ cells. Genotoxic influence was ascertained by profiling DNA damage via detection of γH2AX expression. Our results suggested that both TiO(2) and Tb-Gd(2)O(3) nanoparticles induced cytotoxicity in a dose dependent way on BJ cells. These two nanomaterials also promoted genotoxicity via DNA damage. On the contrary, PLGA nanoparticles did not induce significant cytotoxic or genotoxic effects on BJ cells.

In vitro cytotoxicity evaluation of biomedical nanoparticles and their extracts

The present study presents a new approach for evaluating in vitro cytotoxicity of nanoparticles. The approach is based on American National Standard ISO 10993-5. Hepatoma HepG2 and fibroblast NIH3T3 cell lines were incubated with nanoparticles, and their associated extracts were derived at 70 and 121 degrees C. Nanoparticles proposed as potential biomedical imaging probes were evaluated on the basis of the detection of metabolic activities and cell-morphology changes. In general, nanoparticles incubated directly with cells showed higher cytotoxicity than their associated extracts. CdSe and core-shell CdSe@ZnS quantum dots resulted in low cell viability for both cell lines. The cytotoxicity of the quantum dots was attributed to the Cd ion and the presence of the nanoparticle itself. A statistically significant (p < 0.05) decrease in cell viability was found in higher dosage concentrations. Rare earth nanoparticles and their extracts appear to affect NIH3T3 cells only, with cell viability as low as 71.4% +/- 4.8%. Magnetic nanoparticles have no observable effects on the cell viabilities for both cell lines. In summary, we found the following: (1) both direct incubation and extracts of nanoparticles are required for complete assessment of nanoparticle cytotoxicity, (2) the rare earth oxide nanoparticles are less cytotoxic than the Cd-based quantum dots, and (3) the extent of cytotoxicity is dependent upon the cell line.

Tb-doped iron oxide: bifunctional fluorescent and magnetic nanocrystals

A new class of fluorescent and superparamagnetic bifunctional nanocrystal has been successfully prepared by a facile, non-hydrolytic method. The synthesized Tb-doped γ-Fe2O3nanocrystals are highly monodispersed with a diameter of 13 nm, show superparamagnetic behaviour with saturation magnetism strength of 30 emu g−1, and exhibit photoluminescence at room temperature. The nanocrystals are amine-functionalized to render them water-dispersible and ease of further functionalization by other biomolecules. In vitro cytotoxicity tests indicate that these nanocrystals are non-toxic. Nanocrystals of such bifunctionality are envisioned to have potential as probes in integrated imaging technique, of which at least two imaging modalities (for example magnetic resonance imaging (MRI) and fluorescence microscopy) are combined to provide enhanced visualization at tissues and cellular levels.