1 Scientific RepoRts | 6:18905 | DOI: 10.1038/srep18905 www.nature.com/scientificreports speCt/NIRF Dual Modality Imaging for Detection of Intraperitoneal Colon tumor with an Avidin/Biotin pretargeting system Chengyan Dong 1,2,* , sujuan Yang 1,* , Jiyun shi 2 , Huiyun Zhao 1,3 , Lijun Zhong 3 , Zhaofei Liu 1 , Bing Jia 1 & Fan Wang 1,2,4 We describe herein dual-modality imaging of intraperitoneal colon tumor using an avidin/biotin pretargeting system. A novel dual-modality probe, 99m Tc-HYNIC-lys(Cy5.5)-PEG 4 -biotin, was designed, synthesized and characterized. single-photon emission computed tomography/ computed tomography (SPECT/CT) imaging and near infrared luorescence (NIRF) imaging were developed using intraperitoneal LS180 human colon adenocarcinoma xenografts. Following avidin preinjection for 4 hours, 99m Tc-HYNIC-lys(Cy5.5)-PEG 4 -biotin could successfully detect colon tumors of diferent sizes inside the abdominal region using both modalities, and the imaging results showed no diferences. Biodistribution studies demonstrated that the tumors had a very high uptake of the probe 99m tc- HYNIC-lys(Cy5.5)-PEG 4 -biotin (12.74 ± 1.89% ID/g at 2 h p.i.), and the clearance from blood and other normal tissues occured very fast. The low tumor uptake in the non-pretargeted mice (1.63 ± 0.50% ID/g at 2 h p.i.) and tumor cell staining results showed excellent tumor binding speciicity of the pretargeting system. The ability of the novel probe to show excellent imaging quality with high tumor-to-background contrast, a high degree of binding speciicity with tumors and excellent in vivo biodistribution pharmacokinetics should prove that the avidin/biotin based dual-modality pretargeting probe is a promising imaging tool during the entire period of tumor diagnosis and treatment. Surgery combined with chemotherapy is regarded as the most efective treatment for cancer patients 1 . To adequately discriminate between tumor and normal tissues and determine the tumor-free margin are the key demands of oncologic surgery for a surgeon 2 . With intraoperative, tumor-speciic detection supplied by imaging modalities, surgeons in surgery could localize the tumor lesion speciically, leading to more radical excision of tumor tissue that could efectively protect the function of adjacent normal tissues and ofer an improved prognosis. Image-guided surgery using appropriate probes could assist surgeons by providing real-time feedback with visual observation and palpation 3 . Among the imaging modalities investigated to date, optical imaging, particularly near-infrared luorescence (NIRF; 700- to 900-nm wavelength) imaging, is clearly perfectly suited for image-guided surgery due to its superior resolution and sensitivity, relatively low tissue absorption and scattering, as well as minimal autoluorescence of NIR light in this spectrum 4 . Many preclinical and clinical studies have demonstrated the potential use of NIRF imaging in image-guided surgery. Recently, Gooitzen M reported the irst-in-human use of intraoperative tumor-speciic luorescence imaging for real-time surgical visualization of tumor tissue in patients with ovarian cancer 1 . However, the limited tissue penetration of NIRF imaging leads to low detection in intraperitoneal tumors before surgery. Single-photon emission computed tomography (SPECT) with its high penetration ability and sensitivity has been used routinely for clinical applications in the early detection of lesions, staging malignant tumors, and the evaluation of therapeutic eicacy 5 . In the present study, we developed a simultaneous optical and nuclear contrast 1 Medical isotopes Research center and Department of Radiation Medicine, School of Basic Medical Sciences, Peking University, Beijing 100191, China. 2 interdisciplinary Laboratory, institute of Biophysics, chinese Academy of Sciences, Beijing 100101, China. 3 Medical and Healthy Analytical Center, Peking University, Beijing 100191, China. 4 State Key Laboratory of natural and Biomimetic Drugs, center for Molecular and translational Medicine, Peking University, Beijing 100191, China. * These authors contributed equally to this work. Correspondence and requests for materials should be addressed to B.J. (email: jiabing@bjmu.edu.cn) Received: 30 April 2015 Accepted: 30 November 2015 Published: 06 January 2016 opeN