Micro-SPECT Imaging of Acute Ischemic Stroke with Radioiodinated Riboflavin in Rat MCAO Models via Riboflavin Transporter Targeting.

Riboflavin transporter-3 (RFVT3) is a recently discovered and novel biomarker for the theranostics of nervous system diseases. RFVT3 is significantly overexpressed in cerebral injury after ischemic stroke. Herein, we first reported an RFVT3-targeted tracer 131 I-riboflavin ( 131 I-RFLA) for SPECT imaging of ischemic stroke in vivo . 131 I-RFLA was radiosynthesized by the iodogen-coating method. 131 I-RFLA possessed a radiochemical yield of 69.2 ± 3.7% and greater than 95% radiochemical purity. The representative SPECT/CT images using 131 I-RFLA demonstrated the conspicuously increased tracer uptake in the cerebral injury by comparison with the contralateral normal brain at 1 h and 3 and 7 d after stroke. Ex vivo autoradiography demonstrated that the ratio of infarcted to normal brain uptake was 3.63 and it was decreased to 1.98 after blocking, which reconfirmed the results of SPECT images. Importantly, a significant correlation was identified between RFVT3 expression and brain injury by H&E and immunohistochemistry staining. Therefore, RFVT3 is a new and potential biomarker for the early diagnosis of ischemic stroke. In addition, 131 I-RFLA is a promising SPECT tracer for imaging RFVT3-related ischemic cerebral injury in vivo .