Radionuclide tracing based in situ corrosion and mass transport monitoring of 316L stainless steel in a molten salt closed loop

In the study, we report an in situ corrosion and mass transport monitoring method developed using a radionuclide tracing technique for the corrosion study of 316L stainless steel (316L SS) in a NaCl-MgCl2 eutectic molten salt natural circulation loop. This method involves cyclotron irradiation of a small tube section with 16 MeV protons, later welds at the hot leg of the molten salt flow loop, generating radionuclides 51Cr, 52Mn, and 56Co at the salt-alloy interface. By measuring the activity variations of these radionuclides at different sections along the loop, both the in situ monitoring of the corrosion attack depth of 316L SS and corrosion product transport and its precipitation in flowing NaCl-MgCl2 molten salt are achieved. While 316L SS is the focus of this study, the technique reported herein can be extended to other structural materials being used in a wide range of industrial applications.

Production and radiochemistry of antimony-120m: Efforts toward Auger electron therapy with 119Sb

Targeted Meitner-Auger Therapy (TMAT) has potential for personalized treatment thanks to its subcellular dosimetric selectivity, which is distinct from the dosimetry of β- and α particle emission based Targeted Radionuclide Therapy (TRT). To date, most clinical and preclinical TMAT studies have used commercially available radionuclides. These studies showed promising results despite using radionuclides with theoretically suboptimal photon to electron ratios, decay kinetics, and electron emission spectra. Studies using radionuclides whose decay characteristics are considered more optimal are therefore important for evaluation of the full potential of Meitner-Auger therapy; 119Sb is among the best such candidates. In the present work, we develop radiochemical purification of 120Sb from irradiated natural tin targets for TMAT studies with 119Sb.

Cyclotron production of 43Sc and 44gSc from enriched 42CaO, 43CaO, and 44CaO targets

Introduction: 43Sc and 44gSc are both positron-emitting radioisotopes of scandium with suitable half-lives and favorable positron energies for clinical positron emission tomography (PET) imaging. Irradiation of isotopically enriched calcium targets has higher cross sections compared to titanium targets and higher radionuclidic purity and cross sections than natural calcium targets for reaction routes possible on small cyclotrons capable of accelerating protons and deuterons. Methods: In this work, we investigate the following production routes via proton and deuteron bombardment on CaCO3 and CaO target materials: 42Ca(d,n)43Sc, 43Ca(p,n)43Sc, 43Ca(d,n)44gSc, 44Ca(p,n)44gSc, and 44Ca(p,2n)43Sc. Radiochemical isolation of the produced radioscandium was performed with extraction chromatography using branched DGA resin and apparent molar activity was measured with the chelator DOTA. The imaging performance of 43Sc and 44gSc was compared with 18F, 68Ga, and 64Cu on two clinical PET/CT scanners. Discussion: The results of this work demonstrate that proton and deuteron bombardment of isotopically enriched CaO targets produce high yield and high radionuclidic purity 43Sc and 44gSc. Laboratory capabilities, circumstances, and budgets are likely to dictate which reaction route and radioisotope of scandium is chosen.

Evaluation of linear versus star-like polymer anti-cancer nanomedicines in mouse models

Nanomedicines are considered next generation therapeutics with advanced therapeutic properties and reduced side effects. Herein, we introduce tailored linear and star-like water-soluble nanosystems as stimuli-sensitive nanomedicines for the treatment of solid tumors or hematological malignancies. The polymer carrier and drug pharmacokinetics were independently evaluated to elucidate the relationship between the nanosystem structure and its distribution in the body. Positron emission tomography and optical imaging demonstrated enhanced tumor accumulation of the polymer carriers in 4T1-bearing mice with increased tumor-to-blood and tumor-to-muscle ratios. Additionally, there was a significant accumulation of doxorubicin bound to various polymer carriers in EL4 tumors, as well as excellent in vivo therapeutic activity in EL4 lymphoma and moderate efficacy in 4T1 breast carcinoma. The linear nanomedicine showed at least comparable pharmacologic properties to the star-like nanomedicines regarding doxorubicin transport. Therefore, if multiple parameters are considered such as its optimized structure and simple and reproducible synthesis, this polymer carrier system is the most promising for further preclinical and clinical investigations.

Multimodal imaging demonstrates enhanced tumor exposure of PEGylated FUD peptide in breast cancer

In breast cancer, the extracellular matrix (ECM) undergoes remodeling and changes the tumor microenvironment to support tumor progression and metastasis. Fibronectin (FN) assembly is an important step in the regulation of the tumor microenvironment since the FN matrix precedes the deposition of various other ECM proteins, controls immune cell infiltration, and serves as a reservoir for cytokines and growth factors. Therefore, FN is an attractive target for breast cancer therapy and imaging. Functional Upstream Domain (FUD) is a 6-kDa peptide targeting the N-terminal 70-kDa domain of FN, which is critical for fibrillogenesis. FUD has previously been shown to function as an anti-fibrotic peptide both in vitro and in vivo. In this work, we conjugated the FUD peptide with 20-kDa of PEG (PEG-FUD) and demonstrated its improved tumor exposure compared to non-PEGylated FUD in a murine breast cancer model via multiple imaging modalities. Importantly, PEG-FUD peptide retained a nanomolar binding affinity for FN and maintained in vitro plasma stability for up to 48 h. Cy5-labeled PEG-FUD bound to exogenous or endogenous FN assembled by fibroblasts. The in vivo fluorescence imaging with Cy5-labeled FUD and FUD conjugates demonstrated that PEGylation of the FUD peptide enhanced blood exposure after subcutaneous (SC) injection and significantly increased accumulation of FUD peptide in 4T1 mammary tumors. Intravital microscopy confirmed that Cy5-labeled PEG-FUD deposited mostly in the extravascular region of the tumor microenvironment after SC administration. Lastly, positron emission tomography/computed tomography imaging showed that ⁶⁴Cu-labeled PEG-FUD preferentially accumulated in the 4T1 tumors with improved tumor uptake compared to ⁶⁴Cu-labeled FUD (48 h: 1.35 ± 0.05 vs. 0.59 ± 0.03 %IA/g, P < 0.001) when injected intravenously (IV). The results indicate that PEG-FUD targets 4T1 breast cancer with enhanced tumor retention compared to non-PEGylated FUD, and biodistribution profiles of PEG-FUD after SC and IV injection may guide the optimization of PEG-FUD as a therapeutic and/or imaging agent for use in vivo.

Spleen-Targeted Glabridin-Loaded Nanoparticles Regulate Polarization of Monocyte/Macrophage (Mo /Mφ ) for the Treatment of Cerebral Ischemia-Reperfusion Injury

During cerebral ischemia-reperfusion (I-R) injury, the infiltration of monocyte/macrophages (Mo /Mφ ) into the ischemic penumbra causes inflammatory damage but also regulates tissue repair in the penumbra. The regulation and balance of Mo /Mφ polarization is considered as a potential therapeutic target for treating cerebral I-R injury. Herein, these findings demonstrate that glabridin (Gla)-loaded nanoparticles (i.e., NPGla -5k) can effectively inhibit M1-polarization and enhance M2-polarization of Mo /Mφ . Positron emission tomography (PET) imaging shows that NPGla -5k can selectively accumulate in the spleen following intravenous injection. Spleen-targeted Cy5-NPGla -5k can co-localize with peripheral macrophages in the penumbra at 24 h after tail-vein injection. Interestingly, NPGla -5k treatment can reduce inflammatory damage, protect dying neurons, and improve nervous system function. The protective effect of spleen-targeted NPGla -5k against cerebral I-R injury in mice encourages an exploration of their use for clinical treatment of patients with cerebral I-R injury.

A Third Generation Potentially Bifunctional Trithiol Chelate, Its nat,1XXSb(III) Complex, and Selective Chelation of Radioantimony (119Sb) from Its Sn Target

The therapeutic potential of the Meitner-Auger- and conversion-electron emitting radionuclide ¹¹⁹Sb remains unexplored because of the difficulty of incorporating it into biologically targeted compounds. To address this challenge, we report the development of ¹¹⁹Sb production from electroplated tin cyclotron targets and its complexation by a novel trithiol chelate. The chelation reaction occurs in harsh solvent conditions even in the presence of large quantities of tin, which are necessary for production on small, low energy (16 MeV) cyclotrons. The ¹¹⁹Sb-trithiol complex has high stability and can be purified by HPLC. The third generation trithiol chelate and the analogous stable ^natSb-trithiol compound were synthesized and characterized, including by single-crystal X-ray diffraction analyses.

Characterization of actinide resin for separation of 51,52gMn from bulk target material

We report an extraction chromatography-based method via Actinide Resin for the isolation of radio-manganese from both natural chromium and isotopically enriched iron targets for cyclotron production of ^52gMn and ⁵¹Mn. For the separation of ^52gMn from n^atCr, a decay-corrected radiochemical yield of 83.7 ± 8.4% was achieved. For ⁵¹Mn from ⁵⁴Fe, a decay-corrected radiochemical yield of 78 ± 11% was achieved. This automatable method efficiently isolates both radionuclides from accelerator target material.

Meitner-Auger Electron Emitters for Targeted Radionuclide Therapy: Mercury-197m/g and Antimony-119

Targeted Radionuclide Therapies (TRTs) based on Auger emitting radionuclides have the potential to deliver extremely selective therapeutic payloads on the cellular level. However, to fully exploit this potential, suitable radionuclides need to be applied in combination with appropriate delivery systems. In this review, we summarize the state-of-the-art production, purification, chelation and applications of two promising candidates for Targeted Auger Therapy, namely antimony- 119 (119Sb) and mercury-197 (197Hg). Both radionuclides have great potential to become efficient tools for TRT. We also highlight our current progress on the production of both radionuclides at TRIUMF and the University of Wisconsin.

Chelation with a twist: a bifunctional chelator to enable room temperature radiolabeling and targeted PET imaging with scandium-44

Scandium-44 has emerged as an attractive, novel PET radioisotope with ideal emission properties and half-life (t 1/2 = 3.97 h, E mean β+ = 632 keV) well matched to the pharmacokinetics of small molecules, peptides and small biologics. Conjugates of the current gold-standard chelator for 44Sc, 1,4,7,10-tetraaza-cyclododecane-1,4,7,10-tetraacetic acid (DOTA), require heating to achieve radiochemical complexation, limiting application of this isotope in conjunction with temperature-sensitive biologics. To establish Sc(iii) isotopes as broadly applicable tools for nuclear medicine, development of alternative bifunctional chelators is required. To address this need, we characterized the Sc(iii)-chelation properties of the small-cavity triaza-macrocycle-based, picolinate-functionalized chelator H3mpatcn. Spectroscopic and radiochemical studies establish the [Sc(mpatcn)] complex as kinetically inert and appropriate for biological applications. A proof-of-concept bifunctional conjugate targeting the prostate-specific membrane antigen (PSMA), picaga-DUPA, chelates 44Sc to form 44Sc(picaga)-DUPA at room temperature with an apparent molar activity of 60 MBq μmol-1 and formation of inert RRR-Λ and SSS-Δ-twist isomers. Sc(picaga)-DUPA exhibits a K i of 1.6 nM for PSMA, comparable to the 18F-based imaging probe DCFPyL (K i = 1.1 nM) currently in phase 3 clinical trials for imaging prostate cancer. Finally, we successfully employed 44Sc(picaga)-DUPA to image PSMA-expressing tumors in a preclinical mouse model, establishing the picaga bifunctional chelator as an optimal choice for the 44Sc PET nuclide.

Establishing Radiolanthanum Chemistry for Targeted Nuclear Medicine Applications

We report the first targeted nuclear medicine application of the lanthanum radionuclides ^132/135 La. These isotopes represent a matched pair for diagnosis via the positron emissions of ¹³² La and therapy mediated by the Auger electron emissions of ¹³⁵ La. We identify two effective chelators, known as DO3Apic and macropa, for these radionuclides. The 18-membered macrocycle, macropa, bound ^132/135 La with better molar activity than DO3Apic under similar conditions. These chelators were conjugated to the prostate-specific membrane antigen (PSMA)-targeting agent DUPA to assess the use of radiolanthanum for in vivo imaging. The ^132/135 La-labeled targeted constructs showed high uptake in tumor xenografts expressing PSMA. This study validates the use of these radioactive lanthanum isotopes for imaging applications and motivates future work to assess the therapeutic effects of the Auger electron emissions of ¹³⁵ La.

Improved production of 76Br, 77Br and 80mBr via CoSe cyclotron targets and vertical dry distillation

INTRODUCTION

The radioisotopes of bromine are uniquely suitable radiolabels for small molecule theranostic radiopharmaceuticals but are of limited availability due to production challenges. Significantly improved methods were developed for the production and radiochemical isolation of clinical quality ⁷⁶Br, ⁷⁷Br, and ^80mBr. The radiochemical quality of the radiobromine produced using these methods was tested through the synthesis of a novel ⁷⁷Br-labeled inhibitor of poly (ADP-ribose) polymerase-1 (PARP-1), a DNA damage response protein.

METHODS

⁷⁶Br, ⁷⁷Br, and ^80mBr were produced in high radionuclidic purity via the proton irradiation of novel isotopically-enriched Co⁷⁶Se, Co⁷⁷Se, and Co⁸⁰Se intermetallic targets, respectively. Radiobromine was isolated through thermal chromatographic distillation in a vertical furnace assembly. The ⁷⁷Br-labeled PARP inhibitor was synthesized via copper-mediated aryl boronic ester radiobromination.

RESULTS

Cyclotron production yields were 103 ± 10 MBq∙μA^-1∙h^-1 for ⁷⁶Br, 88 ± 10 MBq∙μA^-1∙h^-1 for ^80mBr at 16 MeV and 17 ± 1 MBq∙μA^-1∙h^-1 for ⁷⁷Br at 13 MeV. Radiobromide isolation yields were 76 ± 11% in a small volume of aqueous solution. The synthesized ⁷⁷Br-labeled PARP-1 inhibitor had a measured apparent molar activity up to 700 GBq/μmol at end of synthesis.

CONCLUSIONS

A novel selenium alloy target enabled clinical-scale production of ⁷⁶Br, ⁷⁷Br, and ^80mBr with high apparent molar activities, which was used to for the production of a new ⁷⁷Br-labeled inhibitor of PARP-1.

ADVANCES IN KNOWLEDGE

New methods for the cyclotron production and isolation of radiobromine improved the production capacity of ⁷⁷Br by a factor of three and ⁷⁶Br by a factor of six compared with previous methods.

IMPLICATIONS FOR PATIENT CARE

Preclinical translational research of ⁷⁷Br-based Auger electron radiotherapeutics, such as those targeting PARP-1, will require the production of GBq-scale ⁷⁷Br, which necessitates next-generation, high-yielding, isotopically-enriched cyclotron targets, such as the novel intermetallic Co⁷⁷Se.

Chemically imaging bacteria with super-resolution SERS on ultra-thin silver substrates

Plasmonic hotspots generate a blinking Surface Enhanced Raman Spectroscopy (SERS) effect that can be processed using Stochastic Optical Reconstruction Microscopy (STORM) algorithms for super-resolved imaging. Furthermore, by imaging through a diffraction grating, STORM algorithms can be modified to extract a full SERS spectrum, thereby capturing spectral as well as spatial content simultaneously. Here we demonstrate SERS and STORM combined in this way for super-resolved chemical imaging using an ultra-thin silver substrate. Images of gram-positive and gram-negative bacteria taken with this technique show excellent agreement with scanning electron microscope images, high spatial resolution at <50 nm, and spectral SERS content that can be correlated to different regions. This may be used to identify unique chemical signatures of various cells. Finally, because we image through as-deposited, ultra-thin silver films, this technique requires no nanofabrication beyond a single deposition and looks at the cell samples from below. This allows direct imaging of the cell/substrate interface of thick specimens or imaging samples in turbid or opaque liquids since the optical path doesn’t pass through the sample. These results show promise that super-resolution chemical imaging may be used to differentiate chemical signatures from cells and could be applied to other biological structures of interest.

Clinical comparison of high-speed rare-earth screen and par-speed screen for diagnostic efficacy and radiation dosage

One hundred patients underwent excretory urography and a comparison was made of ten-minute, well-collimated images that were obtained with both par-speed and rare-earth screens, the latter being 6.5 times faster than the par-speed calcium tungstate screens. Radiation dose was greatly reduced with the rare-earth screens. There were fewer inferior examinations, even though fine detail was imaged poorly, and there was a slightly increased quantum mottle, which was only a minor problem at this low 65 kVp. Since quantum mottle increases with kVp, however, our results are not applicable to higher kVp examinations. Despite reduced detail and increased mottle, the overall image quality obtained with the rare-earth screen was superior to the image quality obtained with the par-speed screen.

Chemical effects of alkali on polymethylmethacrylate intraocular lenses

Polymethylmethacrylate intraocular lenses were left in 10% NaOH or 10% KOH for various periods of time. Contact angles were unaltered and electron spectroscopy for chemical analysis was unchanged. This concentration of alkali does not appear to chemically change the lens surface during the study period.

Radiation exposure to the pediatric patient during cardiac catheterization and angiocardiography. Emphasis on the thyroid gland

Thermoluminescent dosimetry was used to measure the radiation exposure to the skin, thyroid and gonads in 50 consecutive pediatric patients undergoing cardiac catheterization and angiocardiography using cine photofluorography. Average exposures were 17.1 R to the skin, 2.3 R to the thyroid and 0.1 R to the gonads. Fluoroscopy accounted for approximately 80% of the skin and thyroid exposure and cine photofluorography for 20-25%. Occasional primary-beam irradiation was the major contributor to gonad exposure. Internal scatter of the incident x-ray beam was primarily responsible for thyroid exposure, so that infants received relatively high exposures; one receiving 7.3 R. The thyroid was not frequently in the primary beam. The significance of high radiation exposure to the thyroid, and in particular its relationship to thyroid carcinoma, are discussed. The results are compared with other series in the literature and relative exposures of cine photofluorography and serial filming are contrasted.

Split-Twig Figurines from Northern Arizona: New Radiocarbon Dates

Recently released radiocarbon dates for split-twig figurines from Marble Canyon, Arizona, are 4095 +/- 100 years ago; they substantiate previously determined dates of 3530 +/- 300 and 3100 +/- 110 years ago. A recently excavated site in Walnut Canyon, Arizona, extends the geographical range of the figurines. The dates of samples from this site are 3500 +/- 100 and 3880 +/- 90 years ago. It is hypothesized that the figurines were magicoreligious artifacts related to the Pinto complex of the Desert Culture.