Comparison of different methods for removing metals from resins for applications to radiochemical seperations

Abstract only availableMetallic contamination has been a problem for many years in the environmental field. Soil, water and air have been polluted by many different trace metals that finally affect humans by consumption of natural products, liquids and simple respiration, and have the potential of producing some toxicity in the body, leading to different illnesses such as cancer. On the other hand medical and scientific studies have found many metals such as the radiolanthanides and M(3+) metals, to be useful for therapeutic purposes, including cancer treatment, and targeting specific organs in the human body by the use of radioactive isotopes. The overall goal of this project was to compare the different techniques for cleaning various resins being used in the production of radiolanthanides at MURR. This was done to determine what metals and in what quantities these metals were removed by each method. Resins are known to contain extraneous metals such as copper, zinc, calcium and iron, which can leach out of the resin and contaminate the sample of interest resulting in low radiolabeling yields. The methods examined were different acid washes of various molarities and the use of different ligand systems (chelators) to determine which method would remove the most metals without affecting the resolving power of the resins. A variety of resins that are being investigated for performing separations, extractions and clean up of radiolanthanides of interest for radiotherapy were examined. Radiolanthanides are being developed and bound to biomolecular targeting agents to treat and provide palliative care for a variety of cancers. The purity of these radiolanthanides are essential as impurities in the original target material can result in unwanted impurities that can lead to environmental waste issues and dose concerns to workers and patients. In addition, since the chelates that attach these radiolanthanides to the targeting molecule are nonselective and will bind all +3 and many +2 metals, this would lead to low radiolabeling yields and therefore result in a lower dose being delivered to the target organ. The radiopharmaceutical developed by means of this procedure is one that selectively targets only a certain receptor and effectively irradiates only the tumor without affecting the surrounding organs. Thus is a non-invasive treatment that is better tolerated by the patients, as compared to other treatment methods such as chemotherapy, radiation treatments and surgery. The resins were washed and the eluents analyzed by ICP-MS (Inductively Coupled Plasma Mass Spectrometry). This technique determines the amount of metals present in the eluents collected from each wash. The elements expected to be found in these samples are the common metals found in the environment, like iron, calcium, aluminum, zinc, chromium, copper, nickel, etc. Furthermore, by performing simple radiolabeling studies with Lutetium-177 and 1,4,7,10-tetraazaciclododecane-1,4,7,10-tetraacetic acid (DOTA), a ligand commonly used to bind radiolanthanides, the washes were compared. The percentage labeled complex was compared to evaluate which method resulted in the best extraction of unwanted metals.NSF-REU Radiochemistr

Determination of conditions for optimum labeling of DOTA-Y3-Octreotate with terbium-161 [abstract]

Abstract only availableDOTA-Y3-Octreotate (DOTA-TATE) and other somatostatin analogs can be labeled with radionuclides for cancer-fighting applications. Specifically, the radiolanthanides are of great interest to the radiopharmaceutical industry because of their similar chemistries and assortment of radioactive properties. Terbium-161 (161Tb) is considered ideal for both radiotherapy and imaging because of its half-life (6.91 days), beta (0.59 MeV) and gamma (46-48 and 74 keV) emissions. In addition, carrier-free 161Tb will have a high specific activity, meaning less drug mass is necessary to deliver the required dose to the neuroendocrine tumor. Radioactive terbium was obtained at the University of Missouri Research Reactor (MURR) via neutron capture on gadolinium-160 (160Gd) to form gadolinium-161 (161Gd), which beta decays to 161Tb. To obtain carrier-free 161Tb, 160Gd contaminant was isolated from 161Tb using ion-exchange liquid chromatography. Various parameters were tested to optimize conditions for labeling DOTA-TATE with 161Tb: pH, buffer concentration, sample volume, incubation time using a water bath, and amount of activity. 161Tb-DOTA-TATE solution was reacted in 0.4 M, pH 7 ammonium acetate (NH4OAc ) under 80˚C for 1 h. However, an experiment using lutetium-177 showed that only 5 minutes in the water bath was necessary for labeling. We determined the concentration of the NH4OAc buffer solution was insignificant as long as pH was maintained above 5. We observed a maximum labeling level of 65 μCi of 161Tb per microgram of DOTA-TATE. Future work will include a stability study of the labeled DOTA-TATE and modifications to the preparation of the terbium sample in order to achieve more activity per microgram of the chelate as required by animal studies

Labeling and purification studies on cancer targeting DOTA-TATE labeled with radiolanthanides

Abstract only availableMolecular imaging and targeted radiotherapy are emerging fields for cancer treatment. DOTA-Tyr (3)-Thr(9)-octreotate (DOTA-TATE) is used for peptide receptor-mediated radionuclide therapy (PRMRT) in neuroendocrine tumours. These biomolecules can be radiolabeled with an appropriated radioisotope to produce radiopharmaceuticals for diagnostic and therapeutic applications. The DOTA-TATE molecule is comprised of a bifunctional chelate (DOTA) that is capable of stably binding a radiolanthanide as well as being covalently attached to a targeting biomolecule (e.g.,octreotate). Among the radiolanthanides, Ho-166, Tb-161 and Lu-177, that were used to label the peptide, Lu-177 was used to obtain optimum conditions. Direct neutron capture on Lu-176 produces Lu-177. The indirect production of Lu-177 proceeds by neutron capture on Yb-176 producing Yb-177, which beta decays to Lu-177. Chromatographic separation yields high specific activity Lu-177 that minimizes the presence of cold Lu-176. Lanthanides have similar chemical properties that allow further studies to apply similar conditions as those developed for Lu-177. In addition, longevity of half-life of Lu-177 enables longer periods of dose delivery to targeted tumors. This research focused on identifying appropriate buffer solutions and volumes that could neutralize the acidic radioisotope to appropriate pH levels to label the peptide in high yield. The sample was purified from the unlabeled peptide by using HPLC separations methods and adding stabilizing agents (ascorbic and gentisic acid) to prevent radiolysis of the radiolabeled peptide. The results for the labeled peptide with various radioisotopes shows that 0.4 M NH4OAc, 0.4 M NaOAc, and 0.01 M HEPES buffer solution in 500 µL yields 99% labeling at pH ranging from 6.0 to 7.5. The labeled ligand at equimolar ratio with the metal yields 3 mCi/µg of the ligand, whereas as high specific activity sample can label up to 6.68 mCi/µg of the ligand. Carrier free Lu-177-DOTA-TATE was labeled using 0.01 M HEPES buffer at pH 6.0 and remains stable after using ascorbic acid; gentisic acid shows interference on HPLC which may cause some purification problems. (Ho- holmium, Tb- terbium Lu- lutetium)U.S. Dept. of Energy Innovations in Nuclear Infrastructure and Education Summer MURR Undergraduate Research Scholarshi

Production and optimization of 198/199 gold nanoparticles for potential use in cancer therapy [abstract]

Abstract only availableRadiopharmaceuticals are used to diagnose and treat a number of diseases such as bone cancer and non-Hodgkin's lymphoma. A radiopharmaceutical typically consists of a targeting molecule that selectively targets certain tumors. The targeting molecule is labeled with a radioactive atom(s) that delivers a dose of radiation to the tumor. The radioactive properties of Au-198 ([beta]- = 0.96 MeV; [gamma] = 411 KeV) and Au-199 ([beta]- = 0.45 MeV; [gamma] = 158 KeV) with their beta (therapeutic) and gamma (imaging) emission make them valuable candidates for both therapeutic and imaging applications. Gold nanoparticles have several properties that make them particularly interesting for use in radiopharmaceuticals. They are stable in vivo, have multiple atoms per particle and are small enough in size to deliver a radioactive dose directly to cancer cells. The purpose of this study was to gain a better understanding of the binding properties of the nanoparticles with reducing and stabilizing agents. This knowledge will aid in future attempts to label the particles with various antibodies and peptides for tumor targeted delivery of the drug. Next, investigate the relationship between particle size and the amount of reducing agent used was studied with varying amounts and types of carbohydrate stabilizers. Our goal is to establish a library of nanoparticles with varying sizes that can be conjugated with different biomolecules that are selective for receptors over expressed by the diseased tissue. In future studies we also plan to pursue an indirect method of preparing radioactive Au-199 nanoparticles at carrier free levels from beta decay of Pt-199.Life Sciences Undergraduate Research Opportunity Progra

Radioactive ^(198)Au-Doped Nanostructures with Different Shapes for In Vivo Analyses of Their Biodistribution, Tumor Uptake, and Intratumoral Distribution

With Au nanocages as an example, we recently demonstrated that radioactive ^(198)Au could be incorporated into the crystal lattice of Au nanostructures for simple and reliable quantification of their in vivo biodistribution by measuring the γ radiation from ^(198)Au decay and for optical imaging by detecting the Cerenkov radiation. Here we extend the capability of this strategy to synthesize radioactive ^(198)Au nanostructures with a similar size but different shapes and then compare their biodistribution, tumor uptake, and intratumoral distribution using a murine EMT6 breast cancer model. Specifically, we investigated Au nanospheres, nanodisks, nanorods, and cubic nanocages. After PEGylation, an aqueous suspension of the radioactive Au nanostructures was injected into a tumor-bearing mouse intravenously, and their biodistribution was measured from the γ radiation while their tumor uptake was directly imaged using the Cerenkov radiation. Significantly higher tumor uptake was observed for the Au nanospheres and nanodisks relative to the Au nanorods and nanocages at 24 h postinjection. Furthermore, autoradiographic imaging was performed on thin slices of the tumor after excision to resolve the intratumoral distributions of the nanostructures. While both the Au nanospheres and nanodisks were only observed on the surfaces of the tumors, the Au nanorods and nanocages were distributed throughout the tumors

Advancing the translation of optical imaging agents for clinical imaging

Despite the development of a large number of promising candidates, few contrast agents for established medical imaging modalities have successfully been translated over the past decade. The emergence of new imaging contrast agents that employ biomedical optics is further complicated by the relative infancy of the field and the lack of approved imaging devices compared to more established clinical modalities such as nuclear medicine. Herein, we propose a navigational approach (as opposed to a fixed “roadmap”) for translation of optical imaging agents that is (i) proposed through consensus by four academic research programs that are part of the cooperative U54 NCI Network for Translational Research, (ii) developed through early experiences for translating optical imaging agents in order to meet distinctly varied needs in cancer diagnostics, and (iii) adaptable to the rapidly changing environment of academic medicine. We describe the pathways by which optical imaging agents are synthesized, qualified, and validated for preclinical testing, and ultimately translated for “first-in-humans” studies using investigational optical imaging devices. By identifying and adopting consensus approaches for seemingly disparate optical imaging modalities and clinical indications, we seek to establish a systematic method for navigating the ever-changing “roadmap” to most efficiently arrive at the destination of clinical adoption and improved outcome and survivorship for cancer patients

Investigating High-Energy Proton-Induced Reactions on Spherical Nuclei: Implications for the Pre-Equilibrium Exciton Model

A number of accelerator-based isotope production facilities utilize 100- to 200-MeV proton beams due to the high production rates enabled by high-intensity beam capabilities and the greater diversity of isotope production brought on by the long range of high-energy protons. However, nuclear reaction modeling at these energies can be challenging because of the interplay between different reaction modes and a lack of existing guiding cross section data. A Tri-lab collaboration has been formed among the Lawrence Berkeley, Los Alamos, and Brookhaven National Laboratories to address these complexities by characterizing charged-particle nuclear reactions relevant to the production of established and novel radioisotopes. In the inaugural collaboration experiments, stacked-targets of niobium foils were irradiated at the Brookhaven Linac Isotope Producer (E$_p$=200 MeV) and the Los Alamos Isotope Production Facility (E$_p$=100 MeV) to measure $^{93}$Nb(p,x) cross sections between 50 and 200 MeV. The measured cross-section results were compared with literature data as well as the default calculations of the nuclear model codes TALYS, CoH, EMPIRE, and ALICE. We developed a standardized procedure that determines the reaction model parameters that best reproduce the most prominent reaction channels in a physically justifiable manner. The primary focus of the procedure was to determine the best parametrization for the pre-equilibrium two-component exciton model. This modeling study revealed a trend toward a relative decrease for internal transition rates at intermediate proton energies (E$_p$=20-60 MeV) in the current exciton model as compared to the default values. The results of this work are instrumental for the planning, execution, and analysis essential to isotope production.Comment: 37 pages, 62 figures. Revised version, published in Physical Review

Radioactive ^(198)Au-Doped Nanostructures with Different Shapes for In Vivo Analyses of Their Biodistribution, Tumor Uptake, and Intratumoral Distribution

With Au nanocages as an example, we recently demonstrated that radioactive ^(198)Au could be incorporated into the crystal lattice of Au nanostructures for simple and reliable quantification of their in vivo biodistribution by measuring the γ radiation from ^(198)Au decay and for optical imaging by detecting the Cerenkov radiation. Here we extend the capability of this strategy to synthesize radioactive ^(198)Au nanostructures with a similar size but different shapes and then compare their biodistribution, tumor uptake, and intratumoral distribution using a murine EMT6 breast cancer model. Specifically, we investigated Au nanospheres, nanodisks, nanorods, and cubic nanocages. After PEGylation, an aqueous suspension of the radioactive Au nanostructures was injected into a tumor-bearing mouse intravenously, and their biodistribution was measured from the γ radiation while their tumor uptake was directly imaged using the Cerenkov radiation. Significantly higher tumor uptake was observed for the Au nanospheres and nanodisks relative to the Au nanorods and nanocages at 24 h postinjection. Furthermore, autoradiographic imaging was performed on thin slices of the tumor after excision to resolve the intratumoral distributions of the nanostructures. While both the Au nanospheres and nanodisks were only observed on the surfaces of the tumors, the Au nanorods and nanocages were distributed throughout the tumors

Comparative oncology and clinical translation of glyco protein conjugated gold nano therapeutic agent (GA-198AuNP) [abstract]

Nanoscience Poster SessionAs part of our efforts toward clinical translation of GA-198AuNP, our studies are focused on therapeutic efficacy of nanoparticulate GA198AuNP agent in dogs with prostatic carcinoma. The overall goal is to gain clinical insights on therapeutic efficacy of GA198AuNP in a large animal model. We have performed a phase I clinical trial using GA-AuNP administered intravenously or intratumorally by injection or infusion. CT scans were performed prior to injection and 24 hours post injection in 3 of the 4 dogs. Following injections, dogs were allowed further treatment as recommended by the primary attending clinician. Four dogs have been treated to date. Complications related to GA-AuNP treatment were not observed, and all 4 dogs received adjunctive treatment with radiation therapy and/ or chemotherapy. These preliminary studies have clearly provided compelling evidence on the therapeutic potential of biocompatible GA-AuNP for their utility as novel therapeutic agents in treating various types of inoperable solid tumors. Intra-tumoral and intravenous administration of GA-AuNP is safe in dogs with spontaneously occurring tumors. As further therapeutic efficacy studies continue, the outcome of this clinical trial in a large animal model will generate therapeutic efficacy data which will be used for filing IND application for Phase I clinical trial studies. This clinical translation effort provides significant advances in terms of delivering optimum therapeutic payloads into prostate cancers with subsequent reduction in tumor volume, thus may effectively reduce/eliminate the need for surgical resection. This presentation will include details of clinical translation of GA198AuNP in prostate tumor bearing dogs

Multi-ancestry GWAS of the electrocardiographic PR interval identifies 202 loci underlying cardiac conduction

The electrocardiographic PR interval reflects atrioventricular conduction, and is associated with conduction abnormalities, pacemaker implantation, atrial fibrillation (AF), and cardiovascular mortality. Here we report a multi-ancestry (N=293,051) genome-wide association meta-analysis for the PR interval, discovering 202 loci of which 141 have not previously been reported. Variants at identified loci increase the percentage of heritability explained, from 33.5% to 62.6%. We observe enrichment for cardiac muscle developmental/contractile and cytoskeletal genes, highlighting key regulation processes for atrioventricular conduction. Additionally, 8 loci not previously reported harbor genes underlying inherited arrhythmic syndromes and/or cardiomyopathies suggesting a role for these genes in cardiovascular pathology in the general population. We show that polygenic predisposition to PR interval duration is an endophenotype for cardiovascular disease, including distal conduction disease, AF, and atrioventricular pre-excitation. These findings advance our understanding of the polygenic basis of cardiac conduction, and the genetic relationship between PR interval duration and cardiovascular disease. On the electrocardiogram, the PR interval reflects conduction from the atria to ventricles and also serves as risk indicator of cardiovascular morbidity and mortality. Here, the authors perform genome-wide meta-analyses for PR interval in multiple ancestries and identify 141 previously unreported genetic loci.Peer reviewe