In-house Optimization Radiolabeling of Recombinant scFv with 99mTc-Tricarbonyl and Stability Studies: Radiolabeling scFv with technetium tricarbonyl

His-tagged scFv fragments of monoclonal antibodies have better pharmacokinetic properties than whole antibodies. Radiolabeled scFvs are considered for targeted imaging and treatment. Technetium tricarbonyl provides radiolabeling of scFvs without losing its biological activity in a fast and easy procedure. Technetium tricabonyl was prepared as follows: A freshly eluted solution of Na99mTcO4 was added to a mixture containing sodium carbonate, sodium potassium tartarate, boranocarbonate, sodium borohydride. The mixture was heated for 30 min at 100°C. Radiochemical purity was determined using radio thin lyer chromatography. Then, technetium tricarbonyl was added to a solution of scFv in PBS buffer and incubated for 2 h at 50°C, purified by PD-10 column and radiochemical purity was determined. Results showed that radiochemical purity of technetium tricarbony was over 98%. The best conditions for radiolabeling of scFv was: scFv concentration >2 mg/mL, PBS buffer, 2 h incubation at 50°C, pH 8-9, and high activity concentration of tricarbonyl. The best radiochemical purity of scFv was 70% before purificarion. Radiolabeled scFv was stable in PBS for 24 h incubation and there was no release of technetium in competition with histidine. In this study, we optimized radiolabeling of a scFv with technetium tricarbonyl using house made boranocarbonates. The results are promising and will be used for future studies. HIGHLIGHTS Radiolabeling of scFv was done directly by 99mTc-tricarbonyl. 99mTc-tricarbonyl was prepared in house from boranocarbonate. 99mTc-Radiolabeled scFv can be used for radioimmunoscintigraphy