Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

antibody were taken, to which 90 Y acetate was added to obtain a specific activity
of >37 MBq/mg and incubated at 37°C for 60 min. The radioimmunoconjugate
was purified using a G-25 Sephadex column previously equilibrated and
stabilized with 0.9% NaCl. Fractions of 1 mL were collected and counted.
14.3.3. Labelling of DOTATATE with 90 Y
DOTATATE in the lyophilized form was dissolved in water to a
concentration of 1 mg/mL. Yttrium-90 obtained from the 90 Sr/ 90 Y generator
based on SLM as 90 Y acetate was used. A gentisic acid solution (0.33 g of
sodium acetate, 0.4 g of 2,5-dihydroxybenzoic acid, 250 µL of saturated NaOH
and 10 mL of sterile water, pH5) was prepared. Optimization experiments to
determine the optimal pH were performed using 10 µg of peptide and 37 MBq of
90 Y at 90°C for 30 min at different pH values.
In the protocol used for radiolabelling, 10 µg (10 µL) of DOTATATE
was added to 50 µL gentisic acid and 37 MBq of 90 Y acetate at pH4.5–5. The
reaction mixtures were incubated for 30 min at 90°C followed by quality
control procedures. After incubation and cooling at room temperature, 20 µL
of the labelled peptide was mixed with 200 µL of 0.25mM DTPA and passed
through a SepPak C18 cartridge and compared with paper chromatography using
10% sodium acetate and MeOH (30:70). The stability of 90 Y DOTATATE was
tested for 5 d.
14.3.4. Labelling of albumin macroaggregates with 90 Y
A direct method was used to label albumin with 90 Y. Both in house prepared
albumin and commercial (MAASOL, GE Healthcare) albumin were used. The
preparation of wet albumin particles with sizes in the range 10–30 µm was
carried out at the Nuclear Research Institute (Viet Nam). A solution of 0.16%
HSA, pH4.6, was suspended in 5% NaCl, pH6, at 80°C with stirring. The
microaggregated albumin particle sizes ranged from 10 to 30 µm. The suspended
albumin particles were centrifuged at 3000 rev./min for 5 min. The pelleted
particles were resuspended with 0.8M sodium dihydrophosphate. Two milligrams
of albumin particles were mixed with 0.5 mg of stannous chloride dihydrate in
2M HCl and the pH adjusted to 5.0 with 2M NaOH. The sizes of the particle
were examined using an optical microscope and a haemocytometer. The mixture
was washed three times with PBS, pH7.2, by centrifugation and resuspension in
a 0.5M sodium acetate buffer, pH6. Yttrium-90 in 1M acetic acid was collected
from the 90 Sr/ 90 Y generator at a concentration of 296 MBq/mL. The radiolabelling
of the particles with 90 Y was performed at pH5.5 in an acetate buffer with
agitation for 60 min at room temperature. The labelled albumin suspensions were
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