Fishing for Isotopes: Capturing Beryllium-7 from Brookhaven LINAC Isotope Producer's 300 gallons of Cooling Water

The ability of capturing metals and/or radionuclides from large amounts of water is important for radioisotope waste treatment and environmental cleanup. We have developed an approach that rapidly optimizes the capturing of radioisotopes in large-volume aqueous environments. The approach was scaled up to capture beryllium-7 from 300 gallons of cooling water associated with a linear accelerator. Solid supports with the functional groups sulfonic acid, iminodiacetate, pyridine amine, pyridine amine acid, or quaternary amine were incubated in the cooling water for 1 week. One sulfonic acid solid support was able to capture 2.1 mCi of Be-7. Subsequent studies with the sulfonic acid solid support focused on the uptake over time of Be-7, scale-up of capturing Be-7, and subsequent purification of Be-7. The uptake over time of Be-7 was found to be linear in the first 24 h, with an equation of Y = 4.11X (% uptake/time (h)) (R ² = 0.998). The uptake of Be-7 reached the maximum at 24 h and was identical to the uptake at 168 h. To purify Be-7, the optimal purification approach was to release the Be-7 from the solid support with 10 M HCl, which could be immediately passed through an AG1 resin to remove radioimpurities. The radiopurity of the purified Be-7 was greater than 99%, and this method was used to purify 65 mCi of the isotope.

Donor and recipient plasma follistatin levels are associated with acute GvHD in Blood and Marrow Transplant Clinical Trials Network 0402

Follistatin is an angiogenic factor elevated in the circulation after allogeneic hematopoietic cell transplantation (HCT). Elevations in follistatin plasma concentrations are associated with the onset of and poor survival after acute graft versus host disease (aGVHD). Using data from the Blood and Marrow Transplant Clinical Trials Network 0402 study (n=247), we sought to further quantify the longitudinal associations between plasma follistatin levels in transplant recipients, as well as baseline HCT donor follistatin levels, and allogeneic HCT outcomes. Higher recipient baseline follistatin levels were predictive of development of aGVHD (P=0.04). High donor follistatin levels were also associated with the incidence of aGVHD (P<0.01). Elevated follistatin levels on day 28 were associated with the onset of grade II–IV aGVHD prior to day 28, higher one-year non-relapse mortality, (NRM), and lower overall survival (OS). In multivariate analyses, individuals with follistatin levels >1088 pg/mL at day 28 had a four-fold increased risk for NRM (RR=4.3, 95% CI 1.9–9.9, P<0.01) and a nearly three-fold increased overall risk for mortality (RR=2.8, 95% CI 1.5–5.2, P<0.01). Given the multiple roles of follistatin in tissue inflammation and repair, and the confirmation that this biomarker is predictive of important HCT outcomes, the pathobiology of these relationships need further study.

Consensus nomenclature rules for radiopharmaceutical chemistry - Setting the record straight

Over recent years, within the community of radiopharmaceutical sciences, there has been an increased incidence of incorrect usage of established scientific terms and conventions, and even the emergence of 'self-invented' terms. In order to address these concerns, an international Working Group on 'Nomenclature in Radiopharmaceutical Chemistry and related areas' was established in 2015 to achieve clarification of terms and to generate consensus on the utilisation of a standardised nomenclature pertinent to the field. Upon open consultation, the following consensus guidelines were agreed, which aim to.

Scale-up of high specific activity 186gRe production using graphite-encased thick 186W targets and demonstration of an efficient target recycling process

Production of high specific activity 186gRe is of interest for development of theranostic radiopharmaceuticals. Previous studies have shown that high specific activity 186gRe can be obtained by cyclotron irradiation of enriched 186W via the 186W(d,2n)186gRe reaction, but most irradiations were conducted at low beam currents and for short durations. In this investigation, enriched 186W metal targets were irradiated at high incident deuteron beam currents to demonstrate production rates and contaminants produced when using thick targets. Full-stopping thick targets, as determined using SRIM, were prepared by uniaxial pressing of powdered natural abundance W metal or 96.86% enriched 186W metal encased between two layers of graphite flakes for target material stabilization. An assessment of structural integrity was made on each target preparation. To assess the performance of graphite-encased thick 186W metal targets, along with the impact of encasing on the separation chemistry, targets were first irradiated using a 22 MeV deuteron beam for 10 min at 10, 20, and 27 μA, with an estimated nominal deuteron energy of 18.7 MeV on the 186W target material (after energy degradation correction from top graphite layer). Gamma-ray spectrometry was performed post EOB on all targets to assess production yields and radionuclidic byproducts. The investigation also evaluated a method to recover and recycle enriched target material from a column isolation procedure. Material composition analyses of target materials, pass-through/wash solutions and recycling process isolates were conducted with SEM, FTIR, XRD, EDS and ICP-MS spectrometry. To demonstrate scaled-up production, a graphite-encased 186W target made from recycled 186W was irradiated for ~2 h with 18.7 MeV deuterons at a beam current of 27 μA to provide 0.90 GBq (24.3 mCi) of 186gRe, decay-corrected to the end of bombardment. ICP-MS analysis of the isolated 186gRe solution provided data that indicated the specific activity of 186gRe in this scaled-up production run was 2.6±0.5 GBq/μg (70±10 Ci/mg).

Radiometric evaluation of diglycolamide resins for the chromatographic separation of actinium from fission product lanthanides

Actinium-225 is a potential Targeted Alpha Therapy (TAT) isotope. It can be generated with high energy (≥ 100MeV) proton irradiation of thorium targets. The main challenge in the chemical recovery of ²²⁵Ac lies in the separation from thorium and many fission by-products most importantly radiolanthanides. We recently developed a separation strategy based on a combination of cation exchange and extraction chromatography to isolate and purify ²²⁵Ac. In this study, actinium and lanthanide equilibrium distribution coefficients and column elution behavior for both TODGA (N,N,N',N'-tetra-n-octyldiglycolamide) and TEHDGA (N,N,N',N'-tetrakis-2-ethylhexyldiglycolamide) were determined. Density functional theory (DFT) calculations were performed and were in agreement with experimental observations providing the foundation for understanding of the selectivity for Ac and lanthanides on different DGA (diglycolamide) based resins. The results of Gibbs energy (ΔG_aq) calculations confirm significantly higher selectivity of DGA based resins for Ln^III over Ac^III in the presence of nitrate. DFT calculations and experimental results reveal that Ac chemistry cannot be predicted from lanthanide behavior under comparable circumstances.

Gold Nanoparticles Doped with (199) Au Atoms and Their Use for Targeted Cancer Imaging by SPECT

Gold nanoparticles have been labeled with various radionuclides and extensively explored for single photon emission computed tomography (SPECT) in the context of cancer diagnosis. The stability of most radiolabels, however, still needs to be improved for accurate detection of cancer biomarkers and thereby monitoring of tumor progression and metastasis. Here, the first synthesis of Au nanoparticles doped with (199)Au atoms for targeted SPECT tumor imaging in a mouse triple negative breast cancer (TNBC) model is reported. By directly incorporating (199)Au atoms into the crystal lattice of each Au nanoparticle, the stability of the radiolabel can be ensured. The synthetic procedure also allows for a precise control over both the radiochemistry and particle size. When conjugated with D-Ala1-peptide T-amide, the Au nanoparticles doped with (199)Au atoms can serve as a C-C chemokine receptor 5 (CCR5)-targeted nanoprobe for the sensitive and specific detection of both TNBC and its metastasis in a mouse tumor model.

Chromatographic separation of germanium and arsenic for the production of high purity (77)As

A simple column chromatographic method was developed to isolate (77)As (94±6% (EtOH/HCl); 74±11 (MeOH)) from germanium for potential use in radioimmunotherapy. The separation of arsenic from germanium was based on their relative affinities for different chromatographic materials in aqueous and organic environments. Using an organic or mixed mobile phase, germanium was selectively retained on a silica gel column as germanate, while arsenic was eluted from the column as arsenate. Subsequently, enriched (76)Ge (98±2) was recovered for reuse by elution with aqueous solution (neutral to basic). Greater than 98% radiolabeling yield of a (77)As-trithiol was observed from methanol separated [(77)As]arsenate [17].

Trithiols and their arsenic compounds for potential use in diagnostic and therapeutic radiopharmaceuticals

INTRODUCTION

Arsenic-72 ((72)As; 2.49MeV β(+), 26h) and (77)As (0.683MeV β(-), 38.8h) have nuclear properties useful for positron emission tomography (PET) and radiotherapy applications, respectively. Their half-lives are sufficiently long for targeting tumors with antibodies, as well as peptides. Potential radiopharmaceuticals based on radioarsenic require development of suitable bifunctional chelates for stable conjugation of arsenic to vectors under in vivo conditions at high dilution.

METHODS

The thiophilic nature of arsenic led to the synthesis and characterization of a simple trithiol ligand and its arsenic complex, and radiolabeling studies at the no carrier added (NCA) (77)As level.

RESULTS

(1)H- and (13)C-NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single crystal X-ray diffraction were used to characterize the trithiol ligand and its arsenic(III) complex. Radiotracer studies with no carrier added (NCA) (77)As resulted in high radiolabeling yields (>96%) with high in vitro stability.

CONCLUSIONS

The high yield and stability of a single NCA (77)As trithiol complex indicates that this framework is suitable for developing matched pair agents for non-invasive in vivo PET imaging and radiotherapy of tumors with (72,77)As. This is the first reported chelate developed for NCA radioarsenic and studies are underway for developing a trithiol bifunctional chelate conjugated to a targeting vector, such as a peptide or monoclonal antibody.

Oral chronic GVHD outcomes and resource utilization: a subanalysis from the chronic GVHD consortium

OBJECTIVES

This study evaluated the extent to which oral chronic graft-versus-host disease (cGVHD) consensus assessments are predictive of management across institutions with and without oral medicine (OM) centers, and whether ancillary care guidelines are followed within clinical practice.

METHODS

Longitudinal oral cGVHD data were abstracted from the cGVHD Consortium, and additional mouth-specific management data were analyzed across five transplant centers.

RESULTS

Seventy-nine patients with 656 visits were observed for a median of 7.1 months with one visit per follow-up month. Ancillary therapies for oral cGVHD were prescribed for 67% of patients for a median of 0.46 months (per follow-up month) at OM centers and 0.78 months at non-OM centers. Patients treated with ancillary therapy were more likely to have an National Institutes of Health (NIH) mouth score of ≥1 (P < 0.001, odds ratio: 5.1) and mouth pain (P = 0.01, odds ratio: 2.6). The odds ratios of receiving ancillary therapy from OM experts were higher than transplant physicians (53%; P = 0.03).

CONCLUSIONS

Oral cGVHD consensus assessments corresponding with ancillary therapy use were mouth pain and NIH mouth score, with higher odds ratios of receiving therapy from OM experts. Ancillary care guidelines for oral cGVHD are reflected in academic clinical practice with respect to utilization of recommended prescriptions.

Investigating the pharmacokinetics and biological distribution of silver-loaded polyphosphoester-based nanoparticles using (111) Ag as a radiotracer

Purified (111) Ag was used as a radiotracer to investigate silver loading and release, pharmacokinetics, and biodistribution of polyphosphoester-based degradable shell crosslinked knedel-like (SCK) nanoparticles as a comparison to the previously reported small molecule, N-heterocyclic silver carbene complex analog (SCC1) for the delivery of therapeutic silver ions in mouse models. Biodistribution studies were conducted by aerosol administration of (111) Ag acetate, [(111) Ag]SCC1, and [(111) Ag]SCK doses directly into the lungs of C57BL/6 mice. Nebulization of the (111) Ag antimicrobials resulted in an average uptake of 1.07 ± 0.12% of the total aerosolized dose given per mouse. The average dose taken into the lungs of mice was estimated to be 2.6 ± 0.3% of the dose inhaled per mouse for [(111) Ag]SCC1 and twice as much dose was observed for the [(111) Ag]SCKs (5.0 ± 0.3% and 5.9 ± 0.8% for [(111) Ag]aSCK and [(111) Ag]zSCK, respectively) at 1 h post administration (p.a.). [(111) Ag]SCKs also exhibited higher dose retention in the lungs; 62-68% for [(111) Ag]SCKs and 43% for [(111) Ag]SCC1 of the initial 1 h dose were observed in the lungs at 24 h p.a.. This study demonstrates the utility of (111) Ag as a useful tool for monitoring the pharmacokinetics of silver-loaded antimicrobials in vivo.

Gum arabic-coated radioactive gold nanoparticles cause no short-term local or systemic toxicity in the clinically relevant canine model of prostate cancer

Introduction

Gum arabic-coated radioactive gold nanoparticles (GA-¹⁹⁸AuNPs) offer several advantages over traditional brachytherapy in the treatment of prostate cancer, including homogenous dose distribution and higher dose-rate irradiation. Our objective was to determine the short-term safety profile of GA-¹⁹⁸AuNPs injected intralesionally. We proposed that a single treatment of GA-¹⁹⁸AuNPs would be safe with minimal-to-no evidence of systemic or local toxicity.

Methods

Nine dogs with spontaneously occurring prostatic cancer were treated. Injections were performed with ultrasound or computerized tomography guidance. Complete blood counts, chemistry panels, and urinalyses were performed at weekly intervals for 1 month and imaging was repeated 4 weeks postinjection. Planar scintigraphic images were obtained within 30 minutes of injection.

Results

No statistically significant difference was found in any hematologic or biochemical parameter studied, nor was any evidence of tumor swelling or abscessation found in eight dogs with repeat imaging; one dog died secondary to urethral obstruction 12 days following injection. At 30 minutes postinjection, an average of 53% of injected dose in seven dogs was retained in the prostate, with loss of remaining activity in the bladder and urethra; no systemic uptake was detected.

Conclusion

GA-¹⁹⁸AuNP therapy had no short-term toxicity in the treatment of prostatic cancer. While therapeutic agent was found in the prostate immediately following injection, some loss of agent was detected in the bladder and urethra. Localization of radioactivity within the prostate was lower than anticipated and likely due to normal vestigial prostatic ducts. Therefore, further study of retention, dosimetry, long-term toxicity, and efficacy of this treatment is warranted prior to Phase I trials in men.

Radioactive 198Au-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.

Diversification in the Supply Chain of (99)Mo Ensures a Future for (99m)Tc

The uncertain availability of (99m)Tc has become a concern for nuclear medicine departments across the globe. An issue for the United States is that currently it is dependent on a supply of (99m)Tc (from (99)Mo) that is derived solely by production outside the United States. Since the United States uses half the world's (99)Mo production, the U.S. (99)Mo supply chain would be greatly enhanced if a producer were located within the United States. The fragility of the old (99)Mo supply chain is being addressed as new facilities are constructed and new processes are developed to produce (99)Mo without highly enriched uranium. The conversion to low-enriched uranium is necessary to minimize the potential misuse of highly enriched uranium in the world for nonpeaceful means. New production facilities, new methods for the production of (99)Mo, and a new generator elution system for the supply of (99m)Tc are currently being pursued. The progress made in all these areas will be discussed, as they all highlight the need to embrace diversity to ensure that we have a robust and reliable supply of (99m)Tc in the future.

Chromatographic separation of selenium and arsenic: A potential (72)Se/(72)As generator

An anion exchange method was developed to separate selenium and arsenic for potential utility in a (72)Se/(72)As generator. The separation of the daughter (72)As from the (72)Se parent is based on the relative acid-base behavior of the two oxo-anions in their highest oxidation states. At pH 1.5, selenate is retained on strongly basic anion exchange resin as HSeO4(-) and SeO4(2-), while neutral arsenic acid, H3AsO4, is eluted.