Radiolabeling of benzylpenicillin with lutetium-177: Quality control and biodistribution study to develop theranostic infection imaging agent.

Benzylpenicillin acts through binding with beta-lactamase enzyme and inhibiting the bacterial cell wall biosynthesis. Therefore, the radiolabeling of benzylpenicillin with lutetium-177 is expected to serve as a theranostic agent for deep-seated bacterial infections. The radiolabeling of benzylpenicillin resulted ~93% radiochemical yield at optimized reaction conditions. Radiochemical purity analysis was tested with the help of Whatman No. 2 paper and instant thin layer chromatography. Biodistribution study with healthy New Zeeland white rabbit revealed moderate accumulation in different organs. Kidneys are the major organs, showed not more than 4.57±0.89% injected dose per gram organ (ID/gm organ) at 1 h time point and 3.48±1.11% ID/gm organ at 6 h time point. The accumulation of tracer agent in liver was found in the range of 7.42±2.42% to 9.09±2.76 ID/gm organ. The glomerular filtration rate studies revealed rapid clearance - omitting the chance of nephrotoxicity. The radiolabeling yield, biodistribution and glomerular filtration rate results revealed ¹⁷⁷Lu-benzylpencillin could be a potential candidate to diagnose the deep-seated bacterial infection.