Technetium-99m-based simple and convenient radiolabeling of Escherichia coli for in vivo tracking of microorganisms

We herein report a convenient radiolabeling method capable of real-time in vivo imaging and biodistribution of bacteria in a living subject. Escherichia coli (E. coli), a model microorganism in this study, was incubated with technetium-99m (^99mTc) tricarbonyl under physiological conditions provided radiolabeled bacterial cells. ^99mTc-labeled bacterial cells were obtained in high yield (42%, n = 5) and purity (> 99%) within 30 min. In vitro radiolabeling study using cellular components revealed that ^99mTc could be incorporated with cytosolic proteins and it was maintained stably in E. coli under several media including mouse serum, high salt solutions with varying pH. SPECT/CT images and organ biodistribution of ^99mTc-labeled bacterial cells showed quantitative in vivo behavior and accumulation of E. coli in mice. The radiolabeling method demonstrated here will be a promising platform tool for in vivo tracking and biodistribution of infectious microorganism.