Inflammation / Infection Imaging Agent - The Radioactive Methyl Mark Ubi29 The-41 Research

The imaging for inflammation with radiopharmaceuticals has been an efficient tool of inflammation diagnosis, which can provide a lot of useful information. Over last decades, the imaging agents for inflammation have been developed rapidly: from non-bioactive chemicals to bioactive cell, and from macromolecule and antibody segments to peptides, etc.Based on the literature, antimicrobial peptide ubiquicidin29-41 (UBI29-41) has been labeled with radioactive iodine. The main purpose of this study is to develop a new imaging agent which can be used for diagnosis of bacterial infections, furthermore discriminate bacterial infections and sterile inflammations.The main research works are listed as follows:The synthesized UB129-41 was characterized by the MOLDI-TOF (matrix assisted laser desorption ionization-time of flight) and UV-VIS (ultraviolet-visible spectrophotometry) .The preparation of 131I-UBI29-41 was established and optimized successfully through orphogonal experiment methods. The labeling efficiency could reach 85%-93% under the optimized conditions . The purification of 131I-UBI29-41 was carried out using Sep-Pak carriage. After purification, the radiochemical purity could remain 95% after 24h at room temperature.The purity of iodine replaced 131I-UBI29-41 was analysed by reverse-phase high performance liquid chromatography (HPLC) on C18 reverse phase column. Gradient elution: A phase 10% acetonitrile, B phase 100% acetonitrile, 0-30min A 100%-0%; 30-32min A 0%-0%; 32-35min A 0%-100%; 35-40min A 100%-100%o wave length 220nm. The retention time of iodine replaced UBI29-41 was about 9min. The radiochemical purity of 131I-UBI29-41 was analysed by paper chromatography (PC) . Whatman No. 1 was used in PC and 75% methanol as developing system. 131I-UBI29-41 was at origin Rf=0 and 131I- was in the front Rf=0.7The biodistribution of 131I-UBI29-41 in normal mice was studied. 131I-UB129-41 showed a fast blood clearance and excreted mainly through kidney. In infectious rabbit models ,131I-UBI29-41 was accumulated at the site of bacterial infection. But there was no radioactive accumulation at the site of sterile inflammation. The imaging of infectious rabbit showed that the optimal imaging time was after 30min of being administered.In conclusion, 131I-UB129-41 showed potential of being a new imaging agent which can distinguish bacterial infection from sterile inflammation. This paper provided lots of useful and fundamental information for the development of 123I-UBI29-41 in the future.