Cellular uptake and cytotoxicity of a near-IR fluorescent corrole–TiO_2 nanoconjugate

Abstract

We are investigating the biological and biomedical imaging roles and impacts of fluorescent metallocorrole–TiO_2 nanoconjugates as potential near-infrared optical contrast agents in vitro in cancer and normal cell lines. The TiO_2 nanoconjugate labeled with the small molecule 2,17-bis(chlorosulfonyl)-5,10,15-tris(pentafluorophenyl)corrolato aluminum(III) (1-Al–TiO_2) was prepared. The nanoparticle 1-Al–TiO_2 was characterized by transmission electron microscopy (TEM) and integrating-sphere electronic absorption spectroscopy. TEM images of three different samples of TiO_2 nanoparticles (bare, H_2O_2 etched, and 1-Al functionalized) showed similarity in shapes and sizes with an average diameter of 29 nm for 1-Al–TiO_2. Loading of 1-Al on the TiO_2 surfaces was determined to be ca. 20–40 mg 1-Al/g TiO_2. Confocal fluorescence microscopy (CFM) studies of luciferase-transfected primary human glioblastoma U87-Luc cells treated with the nanoconjugate 1-Al–TiO_2 as the contrast agent in various concentrations were performed. The CFM images revealed that 1-Al–TiO_2 was found inside the cancer cells even at low doses (0.02–2 μg/mL) and localized in the cytosol. Bioluminescence studies of the U87-Luc cells exposed to various amounts of 1-Al–TiO_2 showed minimal cytotoxic effects even at higher doses (2–2000 μg/mL) after 24 h. A similar observation was made using primary mouse hepatocytes (PMH) treated with 1-Al–TiO_2 at low doses (0.0003–3 μg/mL). Longer incubation times (after 48 and 72 h for U87-Luc) and higher doses (> 20 μg/mL 1-Al–TiO_2 for U87-Luc and > 3 μg/mL 1-Al–TiO_2 for PMH) showed decreased cell viability.

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