Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

6.3.1. Preparation and in vitro and in vivo assessment of 90 Y oxine
Yttrium-90 oxine was prepared as per the procedure reported by
Flieger et al. [6.9]. In brief, 5 mg of 8-hydroxyquinoline (oxine) was dissolved in
ethanol and reacted with ~74–111 MBq of 90 Y chloride at 50°C for 30 min. The
radiolabelling yield was determined by extraction in chloroform, and was found
to be >90%. For in vitro assessment, the Hep G2 human liver carcinoma cell
line was employed. This was procured from the accredited cell line repository
National Centre for Cell Science (India). The cells were cultured in minimal
essential medium with 10% foetal bovine serum as a growth supplement. They
were maintained at 37°C in a 5% CO 2 atmosphere. The viability of cells was
estimated using a haemocytometer count with trypan blue differential stain. Cell
viability >95% was the criterion applied when using cells for in vitro assays.
6.3.1.1. In vitro assessment
(a)
MTT cell viability assay
The viability of Hep G2 cells on exposure to 90 Y oxine was studied using
thiazolyl blue tetrazolium bromide (MTT) assay. Here, the ability of viable cells
to metabolize MTT to give formazan is used to quantitatively assess cellular
viability. Briefly, cells were plated in 96 well plates at a density of 10 4 cells/well.
Cells were exposed to differing concentrations of 90 Y oxine (dissolved in ethanol).
The total incubation volume was maintained at 200 μL and the final ethanol
concentration was 50% loss in cell viability was observed at exposure
to a minimum activity of 4.6 MBq of 90 Y oxine/10 4 cells for 24 h. Further in vitro
work was performed at this concentration.
(b)
Lactate dehydrogenase release assay
The integrity of the cell membrane was assayed using an assay of
cytoplasmic lactate dehydrogenase (LDH) released into the medium from the
cells. Here, LDH reduces nicotinamide adenine dinucleotide to its protonated
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