IRANIAN JOURNAL OF NUCLEAR MEDICINE
Year:2010 | Volume:18 | Issue:2 (SERIAL NUMBER 34)|Papers Count:8

Introduction: In this research, [166Ho] Holmium chitosan complex production is described in details, followed by determination of complex radiochemical purity, stability and biodistribution (after intra-articular injection) in wild-type male rats. Finally a Ho-166 based chitosan kit for ultimate radiosynovectomy as well as radiotherapy applications was developed.Methods: 166Ho-chitosan complex was prepared using chitosan concentrations and 166HoCl3 followed by intra-articular injection and biodistribution studies in wild-type rats including and excluding injected knee.Results: The [166Ho] Holmium chitosan complex was prepared with high radiochemical yield (>95 %) in the optimized condition (35mg/3ml of chitosan  in %1 AcOH, pH. 3, >98%, ITLC) was injected to wild-type rats followed by the biodistribution studies of the compound among the tissues excluding the injected knee data. Intra-articular injection of [166Ho] holmium chitosan complex to male wild-type rats and investigation of leakage of activity in the body showed that most of injected dose has remained in injection site 144 h after injection. Conclusion: Successful development and formulation of 166Ho-chitosan kit is described. This kit has the potential for use in clinical setting namely for radiosynovectomy and cancer radiochemotherapy.

Introduction: It has been shown that some primary human tumors and their metastases, including prostate and breast tumors, over-express gastrin-releasing peptide (GRP) receptors. Bombesin is a neuropeptide with a high affinity for these GRP receptors. The purpose of this study was to prepare and evaluate the characteristics of a new Freeze-dried kit, [6-hydrazinopyridine-3-carboxylic acid (HYNIC)]-GABA-Bombesin [7-14] NH2  designed for the labeling with 99mTc using tricine and EDDA as coligand.Methods: Synthesis was performed on a solid phase using a standard Fmoc strategy and HYNIC precursor coupled at the N-terminus. Purified peptide conjugate was labeled with 99mTc at 100°C for 10 min. Radiochemical analysis involved ITLC and high-performance liquid chromatography methods. Peptide conjugate stability and affinity to human serum was challenged for 24 hours. The internalization rate was studied in GRP receptor expressing PC-3 cells. Biodistribution of radiopeptide was studied in rats.Results: Radiolabeling was performed at high specific activities, and radiochemical purity was >98%. The stability of radiolabeled peptide in human serum was excellent. In vitro studies showed >14% of activity was specific internalized into PC-3 cells up to 4 h. After injection into rat biodistribution data showed a rapid blood clearance, with renal excretion and specific binding towards GRP receptor-positive tissues such as pancreas (1.15±0.19% ID/g after 4 h).Conclusion: [99mTc-HYNIC]-GABA-Bombesin [7-14] NH2 showed favorable radiochemical and biological characteristics which make our new designed labeled peptide conjugate as a very suitable agent for diagnostic purposes in malignant tumors.

Introduction: Ubiquicidin (UBI) 29-41 is a synthetic antimicrobial peptide that binds with the microbial cell membrane at the location of infection. This study was conducted to evaluate its probable efficacy as an infection-imaging agent with potential to differentiate bacterial infection from sterile inflammation in humans.Methods: Fifteen diabetic foot patients (10 males and 5 females) with suspected bacterial infection, prior to starting antibiotic treatment, were selected for this study. First a routine three phase bone scan and later a 99mTc-UBI scan was performed for all the patients. 555-740 MBq of 99mTc-UBI was injected intravenously. A 10 minute dynamic study was followed by spot views of the suspected region of infection and corresponding normal areas (liver and kidneys) at 60 and 120 min. Whole-body anterior and posterior images were also acquired. To interpret the studies as positive or negative, visual score (0 -3) was used, with scores of 0 (minimal or no uptake; equivalent to soft tissue) and 1 (mild; less uptake than in liver) being considered negative and scores of 2 (moderate; uptake equal to or greater than that in liver) and 3 (intense uptake equal to or greater than that in kidneys) being considered positive.Results: Of 15 studies performed with 99mTc-UBI, all had positive bacterial cultures. The result of bone scan was positive for osteomyelitis in 12 patients (80%). 99mTc-UBI Scintigraphy was positive in 6 patients, but negative in nine. The sensitivity of 99mTc-UBI for detection of infection was therefore 40%. From 12 patients who had positive bone scans, only 6 had a positive 99mTc-UBI (50%) indicating the sensitivity of 50% for 99mTc-UBI in osteomyelitis cases. 99mTc-UBI was not positive in any patient who had evidence of soft tissue infection in the bone scan.Conclusion: Although 99mTc-UBI 29-41 was well tolerated by all the patients without any side effects, considering low sensitivity of this agent, this radiopharmaceutical is not of great value for diabetic foot infection diagnosis.