Synthesis, Characterization, and in Vitro Evaluation of a New TSPO-Selective Bifunctional Chelate Ligand

The 18-kDa translocator protein (TSPO) is overexpressed in many types of cancers and is also abundant in activated microglial cells occurring in inflammatory neurodegenerative diseases. Thus, TSPO has become an extremely attractive subcellular target not only for imaging disease states overexpressing this protein, but also for a selective mitochondrial drug delivery. In this work we report the synthesis, the characterization, and the in vitro evaluation of a new TSPO-selective ligand, 2-(8-(2-(bis­(pyridin-2-yl)­methyl)­amino)­acetamido)-2-(4-chlorophenyl)<i>H</i>-imidazo­[1,2-<i>a</i>]­pyridin-3-yl)-<i>N</i>,<i>N</i>-dipropylacetamide (<b>CB256</b>), which fulfils the requirements for a bifunctional chelate approach. The goal was to provide a new TSPO ligand that could be used further to prepare coordination complexes of a metallo drug to be used in diagnosis and therapy. However, the ligand itself proved to be a potent tumor cell growth inhibitor and DNA double-strand breaker

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 6

Micrographs of HT-29 (A-C) and Hela (D-F) cells without treatment (A, D), or incubated for 5 mins in PEG6000 from C.E. (B, E) and S.A. (C, F) and imaged 48 h after seeding. The scale bars indicate 200 μm.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 3

MALDI measurements to determine the mass of PEG 6000 produced by S.A. (green), Merck (blue), C.E. (red).</p

Triple SEC measurement with PEG6000 from S.A., C.E., and Merck.

Triple SEC measurement with PEG6000 from S.A., C.E., and Merck.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 2

Micrographs of (A) HeLa, (B) PANC-1; and (C) Caco-2 cells imaged 72 h after seeding on PEG60000 (C.E.) pre-treated surfaces.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 5

AFM micrograph of Petri dish surfaces incubated for 1 h with 3% PEG6000 from (A) C.E.; (B) Merck; and (C) S.A. The images were recorded after replacing the PEG solution with Milli-Q water. The scale bars indicate 5 μm.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 1

Microscopic images of HT29 cells on surfaces (1 h; 37°C) treated with PEG6000 from A) C.E.; B) Acros; C) Merck; and D) S.A.. The images were recorded 48 h after cell plating.</p

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture - Fig 4

HT29 imaged by transmission light microscopy 96 h after plating in a 96 well plate treated for 1 h at 37°C with (A) PEG6000 from C.E., (B) PEG4000 (4000), (C) PEG6000 from S.A. (D) a mixture of 4000/S.A. 1/5 PRE diluted, (E) a mixture of 4000/S.A. 1/5, (F) mixture of 4000/S.A. 1/10, (G) PEG6000 from MERCK, (H) 4000/MERCK 1/5 pre-diluted, (J) 4000/MERCK 1/5, (K) 4000/MERCK 1/10, and (L) as control HT29 cells on an untreated surface. The scale bar in a) is valid for all images.</p