Nanoparticles labeled with gamma-emitting radioisotopes: an attractive approach for in vivo tracking using SPECT imaging

Providing accurate molecular imaging of the body and biological process is critical for diagnosing disease and personalizing treatment with the minimum side effects. Recently, diagnostic radiopharmaceuticals have gained more attention in precise molecular imaging due to their high sensitivity and appropriate tissue penetration depth. The fate of these radiopharmaceuticals throughout the body can be traced using nuclear imaging systems, including single-photon emission computed tomography (SPECT) and positron emission tomography (PET) modalities. In this regard, nanoparticles are attractive platforms for delivering radionuclides into targets because they can directly interfere with the cell membranes and subcellular organelles. Moreover, applying radiolabeled nanomaterials can decrease their toxicity concerns because radiopharmaceuticals are usually administrated at low doses. Therefore, incorporating gamma-emitting radionuclides into nanomaterials can provide imaging probes with valuable additional properties compared to the other carriers. Herein, we aim to review (1) the gamma-emitting radionuclides used for labeling different nanomaterials, (2) the approaches and conditions adopted for their radiolabeling, and (3) their application. This study can help researchers to compare different radiolabeling methods in terms of stability and efficiency and choose the best way for each nanosystem.

Radiolabeled nanomaterial for cancer diagnostics and therapeutics: principles and concepts

In the last three decades, radiopharmaceuticals have proven their effectiveness for cancer diagnosis and therapy. In parallel, the advances in nanotechnology have fueled a plethora of applications in biology and medicine. A convergence of these disciplines has emerged more recently with the advent of nanotechnology-aided radiopharmaceuticals. Capitalizing on the unique physical and functional properties of nanoparticles, radiolabeled nanomaterials or nano-radiopharmaceuticals have the potential to enhance imaging and therapy of human diseases. This article provides an overview of various radionuclides used in diagnostic, therapeutic, and theranostic applications, radionuclide production through different techniques, conventional radionuclide delivery systems, and advancements in the delivery systems for nanomaterials. The review also provides insights into fundamental concepts necessary to improve currently available radionuclide agents and formulate new nano-radiopharmaceuticals.

Image-guided drug delivery in nanosystem-based cancer therapies

The past decades have shown significant advancements in the development of solid tumor treatment. For instance, implementation of nanosystems for drug delivery has led to a reduction in side effects and improved delivery to the tumor region. However, clinical translation has faced challenges, as tumor drug levels are still considered to be inadequate. Interdisciplinary research has resulted in the development of more advanced drug delivery systems. These are coined "smart" due to the ability to be followed and actively manipulated in order to have better control over local drug release. Therefore, image-guided drug delivery can be a powerful strategy to improve drug activity at the target site. Being able to visualize the inflow of the administered smart nanosystem within the tumor gives the potential to determine the right moment to apply the facilitator to initiate drug release. Here we provide an overview of available nanosystems, imaging moieties, and imaging techniques. We discuss preclinical application of these smart drug delivery systems, the strength of image-guided drug delivery, and the future of personalized treatment.

Methods for Radiolabelling Nanoparticles: SPECT Use (Part 1)

The use of nanoparticles (NPs) is rapidly increasing in nuclear medicine (NM) for diagnostic and therapeutic purposes. Their wide use is due to their chemical–physical characteristics and possibility to deliver several molecules. NPs can be synthetised by organic and/or inorganic materials and they can have different size, shape, chemical composition, and charge. These factors influence their biodistribution, clearance, and targeting ability in vivo. NPs can be designed to encapsulate inside the core or bind to the surface several molecules, including radionuclides, for different clinical applications. Either diagnostic or therapeutic radioactive NPs can be synthetised, making a so-called theragnostic tool. To date, there are several methods for radiolabelling NPs that vary depending on both the physical and chemical properties of the NPs and on the isotope used. In this review, we analysed and compared different methods for radiolabelling NPs for single-photon emission computed tomography (SPECT) use.

Radiolabelling of nanomaterials for medical imaging and therapy

Nanomaterials offer unique physical, chemical and biological properties of interest for medical imaging and therapy. Over the last two decades, there has been an increasing effort to translate nanomaterial-based medicinal products (so-called nanomedicines) into clinical practice and, although multiple nanoparticle-based formulations are clinically available, there is still a disparity between the number of pre-clinical products and those that reach clinical approval. To facilitate the efficient clinical translation of nanomedicinal-drugs, it is important to study their whole-body biodistribution and pharmacokinetics from the early stages of their development. Integrating this knowledge with that of their therapeutic profile and/or toxicity should provide a powerful combination to efficiently inform nanomedicine trials and allow early selection of the most promising candidates. In this context, radiolabelling nanomaterials allows whole-body and non-invasive in vivo tracking by the sensitive clinical imaging techniques positron emission tomography (PET), and single photon emission computed tomography (SPECT). Furthermore, certain radionuclides with specific nuclear emissions can elicit therapeutic effects by themselves, leading to radionuclide-based therapy. To ensure robust information during the development of nanomaterials for PET/SPECT imaging and/or radionuclide therapy, selection of the most appropriate radiolabelling method and knowledge of its limitations are critical. Different radiolabelling strategies are available depending on the type of material, the radionuclide and/or the final application. In this review we describe the different radiolabelling strategies currently available, with a critical vision over their advantages and disadvantages. The final aim is to review the most relevant and up-to-date knowledge available in this field, and support the efficient clinical translation of future nanomedicinal products for in vivo imaging and/or therapy.

Radiolabeling nanomaterials for multimodality imaging: New insights into nuclear medicine and cancer diagnosis

Nuclear medicine imaging has been developed as a powerful diagnostic approach for cancers by detecting gamma rays directly or indirectly from radionuclides to construct images with beneficial characteristics of high sensitivity, infinite penetration depth and quantitative capability. Current nuclear medicine imaging modalities mainly include single-photon emission computed tomography (SPECT) and positron emission tomography (PET) that require administration of radioactive tracers. In recent years, a vast number of radioactive tracers have been designed and constructed to improve nuclear medicine imaging performance toward early and accurate diagnosis of cancers. This review will discuss recent progress of nuclear medicine imaging tracers and associated biomedical imaging applications. Radiolabeling nanomaterials for rational development of tracers will be comprehensively reviewed with highlights on radiolabeling approaches (surface coupling, inner incorporation and interface engineering), providing profound understanding on radiolabeling chemistry and the associated imaging functionalities. The applications of radiolabeled nanomaterials in nuclear medicine imaging-related multimodality imaging will also be summarized with typical paradigms described. Finally, key challenges and new directions for future research will be discussed to guide further advancement and practical use of radiolabeled nanomaterials for imaging of cancers.

Biodistribution and PET imaging of 89-zirconium labeled cerium oxide nanoparticles synthesized with several surface coatings

Cerium oxide nanoparticles (CONPs) have unique surface chemistry allowing catalyst-like antioxidant properties, and are being investigated for several disease indications in medicine. Studies have utilized surface modified CONPs toward this application, but have been lacking in comprehensive biodistribution and pharmacokinetic data and a direct comparison to uncoated CONPs. We developed an enhanced single-pot synthesis of several coated CONPs and an efficient intrinsic core labeling of CONPs with the clinical PET isotope, zirconium-89, allowing detailed PET imaging and ex vivo biodistribution. All coated [89Zr]-CONPs showed benefit in terms of biodistribution compared to uncoated [89Zr]-CONPs, while retaining the intrinsic antioxidant properties. Among these, poly(acrylic acid) coated CONPs demonstrated excellent candidacy for clinical implementation due to their enhanced renal clearance and low reticuloendothelial system uptake. This work also demonstrates the value of intrinsic core labeling and PET imaging for evaluation of nanoparticle constructs to better inform future studies towards clinical use.

Compound Copper Chalcogenide Nanocrystals

This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), energy storage (lithium-ion batteries, hydrogen generation), emissive materials (plasmonics, LEDs, biolabelling), sensors (electrochemical, biochemical), biomedical devices (magnetic resonance imaging, X-ray computer tomography), and medical therapies (photochemothermal therapies, immunotherapy, radiotherapy, and drug delivery). The confluence of advances in the synthesis, assembly, and application of these NCs in the past decade has the potential to significantly impact society, both economically and environmentally.

Biomineralization: From Material Tactics to Biological Strategy

Biomineralization is an important tactic by which biological organisms produce hierarchically structured minerals with marvellous functions. Biomineralization studies typically focus on the mediation function of organic matrices on inorganic minerals, which helps scientists to design and synthesize bioinspired functional materials. However, the presence of inorganic minerals may also alter the native behaviours of organic matrices and even biological organisms. This progress report discusses the latest achievements relating to biomineralization mechanisms, the manufacturing of biomimetic materials and relevant applications in biological and biomedical fields. In particular, biomineralized vaccines and algae with improved thermostability and photosynthesis, respectively, demonstrate that biomineralization is a strategy for organism evolution via the rational design of organism-material complexes. The successful modification of biological systems using materials is based on the regulatory effect of inorganic materials on organic organisms, which is another aspect of biomineralization control. Unlike previous studies, this study integrates materials and biological science to achieve a more comprehensive view of the mechanisms and applications of biomineralization.

Insight into the interactions between nanoparticles and cells

This review summarizes the latest advances in nanoparticle (NP)–cell interactions. The influence of NP size, shape, shell structure, surface chemistry and protein corona formation on cellular uptake and cytotoxicity is highlighted in detail. Their impact on other cellular responses such as cell proliferation, differentiation and cellular mechanics is also discussed.

Nanoparticles and radiotracers: advances toward radionanomedicine

In this study, we cover the convergence of radiochemistry for imaging and therapy with advances in nanoparticle (NP) design for biomedical applications. We first explore NP properties relevant for therapy and theranostics and emphasize the need for biocompatibility. We then explore radionuclide-imaging modalities such as positron emission tomography (PET), single-photon emission computed tomography (SPECT), and Cerenkov luminescence (CL) with examples utilizing radiolabeled NP for imaging. PET and SPECT have served as diagnostic workhorses in the clinic, while preclinical NP design examples of multimodal imaging with radiotracers show promise in imaging and therapy. CL expands the types of radionuclides beyond PET and SPECT tracers to include high-energy electrons (β- ) for imaging purposes. These advances in radionanomedicine will be discussed, showing the potential for radiolabeled NPs as theranostic agents. WIREs Nanomed Nanobiotechnol 2016, 8:872-890. doi: 10.1002/wnan.1402 For further resources related to this article, please visit the WIREs website.

Synthesis of radioactively labelled CdSe/CdS/ZnS quantum dots for in vivo experiments

During the last decades of nanoparticles research, many nanomaterials have been developed for applications in the field of bio-labelling. For the visualization of transport processes in the body, organs and cells, luminescent quantum dots (QDs) make for highly useful diagnostic tools. However, intercellular routes, bio-distribution, metabolism during degradation or quantification of the excretion of nanoparticles, and the study of the biological response to the QDs themselves are areas which to date have not been fully investigated. In order to aid in addressing those issues, CdSe/CdS/ZnS QDs were radioactively labelled, which allows quantification of the QD concentration in the whole body or in ex vivo samples by γ-counting. However, the synthesis of radioactively labelled QDs is not trivial since the coating process must be completely adapted, and material availability, security and avoidance of radioactive waste must be considered. In this contribution, the coating of CdSe/CdS QDs with a radioactive (65)ZnS shell using a modified, operator-safe, SILAR procedure is presented. Under UV illumination, no difference in the photoluminescence of the radioactive and non-radioactive CdSe/CdS/ZnS colloidal solutions was observed. Furthermore, a down-scaled synthesis for the production of very small batches of 5 nmol QDs without loss in the fluorescence quality was developed. Subsequently, the radio-labelled QDs were phase transferred by encapsulation into an amphiphilic polymer. γ-counting of the radioactivity provided confirmation of the successful labelling and phase transfer of the QDs.