Development of Drugs and Technology for Radiation Theragnosis

Imaging Constructs: The Rise of Iron Oxide Nanoparticles

Over the last decade, an important challenge in nanomedicine imaging has been the work to design multifunctional agents that can be detected by single and/or multimodal techniques. Among the broad spectrum of nanoscale materials being investigated for imaging use, iron oxide nanoparticles have gained significant attention due to their intrinsic magnetic properties, low toxicity, large magnetic moments, superparamagnetic behaviour and large surface area-the latter being a particular advantage in its conjunction with specific moieties, dye molecules, and imaging probes. Tracers-based nanoparticles are promising candidates, since they combine synergistic advantages for non-invasive, highly sensitive, high-resolution, and quantitative imaging on different modalities. This study represents an overview of current advancements in magnetic materials with clinical potential that will hopefully provide an effective system for diagnosis in the near future. Further exploration is still needed to reveal their potential as promising candidates from simple functionalization of metal oxide nanomaterials up to medical imaging.

Photonuclear production, chemistry, and in vitro evaluation of the theranostic radionuclide 47Sc

Background

In molecular imaging and nuclear medicine, theranostic agents that integrate radionuclide pairs are successfully being used for individualized care, which has led to rapidly growing interest in their continued development. These compounds, which are radiolabeled with one radionuclide for imaging and a chemically identical or similar radionuclide for therapy, may improve patient-specific treatment and outcomes by matching the properties of different radionuclides with a targeting vector for a particular tumor type. One proposed theranostic radionuclide is scandium-47 (⁴⁷Sc, T_1/2 = 3.35 days), which can be used for targeted radiotherapy and may be paired with the positron emitting radionuclides, ⁴³Sc (T_1/2 = 3.89 h) and ⁴⁴Sc (T_1/2 = 3.97 h) for imaging. The aim of this study was to investigate the photonuclear production of ⁴⁷Sc via the ⁴⁸Ti(γ,p)⁴⁷Sc reaction using an electron linear accelerator (eLINAC), separation and purification of ⁴⁷Sc, the radiolabeling of somatostatin receptor-targeting peptide DOTATOC with ⁴⁷Sc, and in vitro receptor-mediated binding of [⁴⁷Sc]Sc-DOTATOC in AR42J somatostatin receptor subtype two (SSTR2) expressing rat pancreatic tumor cells.

Results

The rate of ⁴⁷Sc production in a stack of natural titanium foils (n = 39) was 8 × 10⁷ Bq/mA·h (n = 3). Irradiated target foils were dissolved in 2.0 M H₂SO₄ under reflux. After dissolution, trivalent ⁴⁷Sc ions were separated from natural Ti using AG MP-50 cation exchange resin. The recovered ⁴⁷Sc was then purified using CHELEX 100 ion exchange resin. The average decay-corrected two-step ⁴⁷Sc recovery (n = 9) was (77 ± 7)%. A radiolabeling yield of > 99.9% of [⁴⁷Sc]Sc-DOTATOC (0.384 mg in 0.3 mL) was achieved using 1.7 MBq of ⁴⁷Sc. Blocking studies using Octreotide illustrated receptor-mediated uptake of [⁴⁷Sc]Sc-DOTATOC in AR42J cells.

Conclusions

⁴⁷Sc can be produced via the ⁴⁸Ti(γ,p)⁴⁷Sc reaction and separated from natural Ti targets with a yield and radiochemical purity suitable for radiolabeling of peptides for in vitro studies. The data in this work supports the potential use of eLINACs for studies of photonuclear production of medical radionuclides and the future development of high-intensity eLINAC facilities capable of producing relevant quantities of carrier-free radionuclides currently inaccessible via routine production pathways or limited due to costly enriched targets.

Electronic supplementary material

The online version of this article (10.1186/s13550-019-0515-8) contains supplementary material, which is available to authorized users.

Molecular Imaging: A Useful Tool for the Development of Natural Killer Cell-Based Immunotherapies

Molecular imaging is a relatively new discipline that allows visualization, characterization, and measurement of the biological processes in living subjects, including humans, at a cellular and molecular level. The interaction between cancer cells and natural killer (NK) cells is complex and incompletely understood. Despite our limited knowledge, progress in the search for immune cell therapies against cancer could be significantly improved by dynamic and non-invasive visualization and tracking of immune cells and by visualization of the response of cancer cells to therapies in preclinical and clinical studies. Molecular imaging is an essential tool for these studies, and a multimodal molecular imaging approach can be applied to monitor immune cells in vivo, for instance, to visualize therapeutic effects. In this review, we discuss the usefulness of NK cells in cancer therapies and the preclinical and clinical usefulness of molecular imaging in NK cell-based therapies. Furthermore, we discuss different molecular imaging modalities for use with NK cell-based therapies, and their preclinical and clinical applications in animal and human subjects. Molecular imaging has contributed to the development of NK cell-based therapies against cancers in animal models and to the refinement of current cell-based cancer immunotherapies. Developing sensitive and reproducible non-invasive molecular imaging technologies for in vivo NK cell monitoring and for real-time assessment of therapeutic effects will accelerate the development of NK cell therapies.

Advances in Molecular Imaging Strategies for In Vivo Tracking of Immune Cells

Tracking of immune cells in vivo is a crucial tool for development and optimization of cell-based therapy. Techniques for tracking immune cells have been applied widely for understanding the intrinsic behavior of immune cells and include non-radiation-based techniques such as optical imaging and magnetic resonance imaging (MRI), radiation-based techniques such as computerized tomography (CT), and nuclear imaging including single photon emission computerized tomography (SPECT) and positron emission tomography (PET). Each modality has its own strengths and limitations. To overcome the limitations of each modality, multimodal imaging techniques involving two or more imaging modalities are actively applied. Multimodal techniques allow integration of the strengths of individual modalities. In this review, we discuss the strengths and limitations of currently available preclinical in vivo immune cell tracking techniques and summarize the value of immune cell tracking in the development and optimization of immune cell therapy for various diseases.