Development of 90Sr/90Y generators for radiotherapeutic applications

Abstract

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Objectives: To develop generators to obtain n.c.a grade 90Y from 90Sr for targeted therapy.

Methods: Two systems were developed. Supported Liquid membrane(SLM) generator made of 3 chambers, is based on pH dependent preferential transport of 90Y+3 from 90Sr+90Y mixture through the separating PTFE membranes incorporated with 2-ethylhexyl 2-ethylhexylphosphonicacid in the first membrane and octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide in the second membrane. 90Sr+90Y in HNO3,pH 1-2 is placed in the 1st chamber, 4M HNO3 in the 2nd and 1M acetic acid in the 3rd one. 90Y is transported to the 3rd chamber leaving 90Sr in the 1st chamber. In Electrochemical generator, electrolysis is carried out in a quartz cell with Pt electrodes on 90Sr(NO3)2 at pH 2-3, applying –2.5V and 100-200mA current, for 90 min. ~95% of 90Y gets deposited in the cathode. A second electrolysis in a new cell containing 3mM HNO3 using the above cathode as anode and a new Pt cathode, enables pure 90Y deposition on the cathode. This is dissolved in acetate buffer to obtain 90Y acetate suitable for radiolabeling studies. Both the generators were studied upto 3.7GBq level. The radionuclidic purity of 90Y obtained from both generators was estimated by extraction paper chromatography.

Results: In SLM generator, >80% of 90Y was transported to the product compartment in ~10 h. The 2 step transport resulted in highly pure 90Y. >90% 90Y yield was achieved in the electrochemical generator. The recovered 90Y had <3.7KBq of 90Sr in 3.7GBq of 90Y, in both systems.

Conclusions: Both the generator systems yielded >99.998% pure 90Y acetate, suitable for direct labeling of bio-molecules.