Iodine-Rich Polymersomes Enable Versatile SPECT/CT Imaging and Potent Radioisotope Therapy for Tumor in Vivo

Emerging tumor treatment demands high sensitivity and high-spatial resolution diagnosis in combination with targeted therapy. Here, we report that iodine-rich polymersomes (I-PS) enable versatile single-photon emission computed tomography (SPECT)/computed tomography (CT) dual-modal imaging and potent radioisotope therapy for breast cancer in vivo. Interestingly, I-PS could be easily and stably labeled with radioiodine, I-125 and I-131. Dynamic light scattering and transmission electron microscopy showed that I-125-PS had a size of 106 nm and vesicular morphology, similar to those of the parent I-PS. Methyl thiazolyl tetrazolium assays displayed that I-PS and I-125-PS were noncytotoxic, whereas I-131-PS caused significant death of 4T1 cells at 5 mg PS/mL with a radioactivity of 12 mu Ci Pharmacokinetic and biodistribution studies showed that I-125-PS has a prolonged circulation and distributes mainly in tumor and the reticuloendothelial system. The intravenous injection of I-125-PS to 4T1 murine breast tumor-bearing mice allowed simultaneous high sensitivity and high-spatial resolution imaging of tumor by SPECT and CT, respectively. The therapeutic studies revealed that I-131-PS could effectively retard the growth of 4T1 breast tumor and significantly prolong mice survival time. The hematoxylin and eosin staining assay proved that I-131-PS induced tumor cell death. I-PS emerges as a robust and versatile platform for dual-modal imaging and targeted radioisotope therapy.