Development of radiotherapeutic rhenium-188 liposomes in alginate microspheres (Rhe-LAMs) for treatment of liver tumors and technetium-99m liposomes in alginate microspheres (Tech-LAMs) for image-guided treatment planning.

e15599 Background: Radio-embolic agents such as beta-emitting yttrium-90 spheres have been widely adopted as a modality for liver cancer therapy; however, their production can be timely and costly, shunting to the lungs may occur, and post-procedural visualization is limited. Alginate, a polysaccharide which can easily be formed into microspheres, has already been investigated for drug delivery applications; however, we propose utilizing alginate to manufacture radioembolic microspheres for intra-arterial delivery to liver tumors: Rhenium-188/186-labeled liposomes in alginate microspheres (Rhe-LAMS) as a radioembolic agent for the treatment of liver tumors and technetium-99m labeled liposomes in alginate microspheres (Tech-LAMs) as an agent for nuclear image-guided pre-treatment planning for liver cancer patients. Methods: Liposomes were manufactured and labeled with either Re-188/186 or Tc-99m. The liposomes were then mixed with alginate solution and then cross-linked with CaCl2 to form microspheres. Microsphere diameter was evaluated via light microscopy, and retention of radioactivity was measured over time via dosimeter. Microspheres containing free Re-186/Tc-99m (i.e. no liposomes) were also constructed for control comparison. To test in vivo stability, Tech-LAMs were intra-arterially injected into the liver of rabbits for nuclear imaging. Results: 2 ml batches of Rhe-LAMS/Tech-LAMS of 20-80 microns could be manufactured in 3 hours. Radiolabeling efficiency of the liposomes reached 85% and retention of radioactivity in microspheres reached 75%. After overnight incubation, 90% activity was retained. Control microspheres showed a retention of < 5%. In vivo imaging revealed absent activity in the lungs and high embolic activity in the liver. Conclusions: Our novel method demonstrated success regarding radioactivity retention and embolization capabilities. We envision this method to be a quickly-producible, cost-efficient, and effective means for radioembolization of liver tumors that could be adopted by any radiopharmacy.

Preliminary Development of a TRISO Fuel Performance Analysis Code: FFAT

Tristructural isotropic (TRISO) fuel particles are chosen as the major fuel type of High temperature gas cooled reactor (HTGR). The TRISO coated particle also acts as the first barrier for radioactivity retention. The performance of the TRISO coated particle has a significant influence on the safety of HTGR. A set of fuel performance analysis codes have been developed during the past decades. The main functions of these codes are conducting stress calculation and failure probability prediction. PANAMA is a widely used German version fuel performance analysis code, which simulates the mechanical performance of TRISO coated particle under normal and accident conditions. In this code, only a simple pressure vessel model is considered, which is insufficient in stress analysis and fuel failure rate prediction. Nowadays, efforts have been done to update the fuel performance model utilized in PANAMA code, and a new TRISO fuel performance analysis code, FFAT, is under developed. This paper describes the newly updated TRISO fuel performance model and presents some first results based on the updated model.

Preincubation with Sn-complexes causes intensive intracellular retention of 99mTc in thyroid cells in vitro

SummaryTechnetium radiopharmaceuticals are well established in nuclear medicine. Besides its well-known gamma radiation, 99mTc emits an average of five Auger and internal conversion electrons per decay. The biological toxicity of these low-energy, high-LET (linear energy transfer) emissions is a controversial subject. One aim of this study was to estimate in a cell model how much 99mTc can be present in exposed cells and which radiobiological effects could be estimated in 99mTc-overloaded cells. Methods: Sodium iodine symporter (NIS)- positive thyroid cells were used. 99mTc-uptake studies were performed after preincubation with a non-radioactive (cold) stannous pyro - phosphate kit solution or as a standard 99mTc pyrophosphate kit preparation or with pure pertechnetate solution. Survival curves were analyzed from colony-forming assays. Results: Preincubation with stannous complexes causes irreversible intracellular radioactivity retention of 99mTc and is followed by further pertechnetate influx to an unexpectedly high 99mTc level. The uptake of 99mTc pertechnetate in NIS-positive cells can be modified using stannous pyrophosphate from 3–5% to >80%. The maximum possible cellular uptake of 99mTc was 90 Bq/cell. Compared with nearly pure extracellular irradiation from routine 99mTc complexes, cell survival was reduced by 3–4 orders of magnitude after preincubation with stannous pyrophosphate. Conclusions: Intra cellular 99mTc retention is related to reduced survival, which is most likely mediated by the emission of low-energy electrons. Our findings show that the described experiments constitute a simple and useful in vitro model for radiobiological investigations in a cell model.

High-Throughput Microplate Phosphorylation Assays Based on DevR-DevS/Rv2027c 2-Component Signal Transduction Pathway to Screen for Novel Antitubercular Compounds

DevR-DevS (Rv3133c-Rv3132c) and DevR-Rv2027c have been established through their autophosphorylation and phospho-transfer properties to constitute bonafide regulatory 2-component systems of Mycobacterium tuberculosis. DevR has also been shown by others to play a key regulatory role in the expression of M. tuberculosis genes comprising the dormancy regulon. The authors describe high-throughput phosphorylation assays in a microplate format using DevS and Rv2027c histidine kinases and DevR response regulator proteins from M. tuberculosis. The assays were designed to measure [γ-32P]ATP-dependent autophosphorylation of DevS/Rv2027c and also the phosphotransfer reaction to DevR. First, the optimal reaction conditions were established using the conventional method of radiolabeling the 2-component proteins by [γ-32P]ATP and followed by gel electrophoresis-based analysis. Next, the assays were converted to a high-throughput format in which the radiolabeled protein retained on a filter using mixed cellulose ester-based 96-well filter plates was analyzed for radioactivity retention by scintillation counting. The utility of these assays to screen for inhibitors is illustrated using 2-mercaptobenzimidazole, ethidium bromide, and EDTA. The high quality and flexibility of these assays will enable their use in high-throughput screening for new antitubercular compounds directed against 2-component systems that comprise a novel target in dormant mycobacteria.