Rapid Hepatobiliary Excretion of Micelle-Encapsulated/Radiolabeled Upconverting Nanoparticles as an Integrated Form

Design and Characterization of Peptide-Conjugated Solid Lipid Nanoparticles for Targeted MRI and SPECT Imaging of Breast Tumors

Triple-negative breast cancer (TNBC) presents significant challenges due to its aggressive behavior and lack of targeted treatments. High-resolution imaging techniques and targeted nanoparticles offer potential solutions for early detection and monitoring of TNBC. In this study, we developed and characterized solid lipid nanoparticles (SLNs) conjugated with a C-peptide derived from endostatin to target integrin αvβ3, overexpressed in TNBC. These SLNs were loaded with superparamagnetic iron oxide nanoparticles (SPIONs) for enhanced magnetic resonance imaging (MRI) and radiolabeled with technetium-99m (99mTc) for single-photon emission computed tomography (SPECT), enabling dual-modality imaging. Extensive characterization of the nanoparticles was performed utilizing a variety of advanced techniques, including dynamic light scattering (DLS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), field-emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). This comprehensive analysis validated the successful synthesis and functionalization of the nanoparticles, along with their remarkable magnetic properties, while also revealing their distinct spherical morphology, optimal size, uniform distribution, and colloidal stability. The conjugation of C-peptide significantly enhanced the targeting efficiency in vitro, as evidenced by the MTT and receptor-binding assays in 4T1 cells using flow cytometry and MRI. In vivo studies using a 4T1 murine model demonstrated that peptide-conjugated SLNs accumulated in tumor tissues, providing superior contrast in MRI and enhanced tumor-specific localization in SPECT imaging. Biodistribution analysis confirmed reduced off-target accumulation, particularly in the liver, compared to nontargeted formulations. Collectively, C-peptide-conjugated SLNs provide a promising dual-modality imaging platform for TNBC, offering improved diagnostic accuracy and tumor targeting.

Design and development of nanoprobes radiolabelled with 99mTc for the diagnosis and monitoring of therapeutic interventions in oncology preclinical research

BACKGROUND

Previous studies employing polymeric micelles and molecular imaging for in vivo nanosystem characterization have led to the development of radionanoprobes (RNPs) designed for diagnosing and monitoring therapeutic interventions in preclinical oncology research, specifically within breast and colon cancer models. These models exhibit high GLUT1 expression on tumor cells and VEGFR expression on the tumor vasculature. We aimed to enhance the tumor-targeting specificity of these RNPs by functionalizing micelles with glucose and bevacizumab. The choice of 99mTc to label the nanoprobes is based on its availability and that direct labeling method is a widespread strategy to prepare radiopharmaceuticals using cold reagents and a 99Mo/99mTc generator. Soluplus® is an attractive polymer for synthesizing micelles that also allows their functionalization. With all the above, the objective of this work was to design, develop and characterize nanoprobes based on polymeric micelles and radiolabeled with 99mTc for the characterization of biological processes associated to the diagnosis, prognosis and monitoring of animal models of breast and colon cancer in preclinical research using molecular images.

RESULTS

Four RNPs ([99mTc]Tc-Soluplus®, [99mTc]Tc-Soluplus®+TPGS, [99mTc]Tc-Soluplus®+glucose and [99mTc]Tc-Soluplus®+bevacizumab) were produced with high radiochemical purity (> 95% in all cases) and stability in murine serum for up to 3 h. The RNPs maintained the 100 nm size of the Soluplus® polymeric micelles even when they were functionalized and labeled with 99mTc. The image acquisition protocol enabled the visualization of tumor uptake in two cancer experimental models using the assigned RNPs. In vivo biological characterization showed signal-to-background ratios of 1.7 ± 0.03 for [99mTc]Tc-Soluplus®+TPGS, 1.8 ± 0.02 for [99mTc]Tc-Soluplus®, and 2.3 ± 0.02 for [99mTc]Tc-Soluplus®+glucose in the breast cancer model, and 1.8 ± 0.04 for [99mTc]Tc-Soluplus® and 3.7 ± 0.07 for [99mTc]Tc-Soluplus®+bevacizumab in the colon cancer model. Ex vivo biodistribution, showed that the uptake of the tumors, regardless of the model, is < 2% IA/g while the blood activity concentration is higher, suggesting that the enhanced permeability and retention effect (EPR) would be one of the mechanisms involved in imaging tumors in addition to the active targeting of RNPs.

CONCLUSIONS

Soluplus®-based polymeric micelles provide a promising nanotechnological platform for the development of RNPs. The functionalization with glucose and bevacizumab enhances tumor specificity enabling effective imaging and monitoring of cancer in animal models.

Development of Alginate-Based Biodegradable Radioactive Microspheres Labeled with Positron Emitter through Click Chemistry Reaction: Stability and PET Imaging Study

Biodegradable radioactive microspheres labeled with positron emitters hold significant promise for diagnostic and therapeutic applications in cancers and other diseases, including arthritis. The alginate-based polymeric microspheres offer advantages such as biocompatibility, biodegradability, and improved stability, making them suitable for clinical applications. In this study, we developed novel positron emission tomography (PET) microspheres using alginate biopolymer radiolabeled with gallium-68 (68Ga) through a straightforward conjugation reaction. Polyethylenimine (PEI)-decorated calcium alginate microspheres (PEI-CAMSs) were fabricated and further modified using azadibenzocyclooctyne-N-hydroxysuccinimide ester (ADIBO-NHS). Subsequently, azide-functionalized NOTA chelator (N3-NOTA) was labeled with [68Ga]Ga to obtain [68Ga]Ga-NOTA-N3, which was then reacted with the surface-modified PEI-CAMSs using strain-promoted alkyne-azide cycloaddition (SPAAC) reaction to develop [68Ga]Ga-NOTA-PEI-CAMSs, a novel PET microsphere. The radiolabeling efficiency and radiochemical stability of [68Ga]Ga-NOTA-PEI-CAMSs were determined using the radio-instant thin-layer chromatography-silica gel (radio-ITLC-SG) method. The in vivo PET images were also acquired to study the in vivo stability of the radiolabeled microspheres in normal mice. The radiolabeling efficiency of [68Ga]Ga-NOTA-PEI-CAMSs was over 99%, and the microspheres exhibited high stability (92%) in human blood serum. PET images demonstrated the stability and biodistribution of the microspheres in mice for up to 2 h post injection. This study highlights the potential of biodegradable PET microspheres for preoperative imaging and targeted radionuclide therapy. Overall, the straightforward synthesis method and efficient radiolabeling technique provide a promising platform for the development of theranostic microspheres using other radionuclides such as 90Y, 177Lu, 188Re, and 64Cu.

Solubilization of Paclitaxel with Natural Compound Rubusoside toward Improving Oral Bioavailability in a Rodent Model

Paclitaxel, which features low water solubility and permeability, is an efflux pump substrate. The current paclitaxel drugs are given intravenously after resolving the solubility issue. Yet, oral delivery to achieve therapeutic bioavailability is not effective due to low absorption. This study evaluated a natural compound, rubusoside, to improve oral bioavailability in an animal model. Free paclitaxel molecules were processed into nano-micelles formed in water with rubusoside. The particle size of the nano-micelles in water was determined using dynamic light scattering. The oral bioavailability of paclitaxel in nano-micelles was determined against Cremophor/alcohol-solubilized Taxol after oral and intravenous administration to pre-cannulated Sprague Dawley rats. When loaded into the rubusoside-formed nano-micelles, paclitaxel reached a supersaturated concentration of 6 mg/mL, 60,000-fold over its intrinsic saturation of 0.1 µg/mL. The mean particle size was 4.7 ± 0.7 nm in diameter. Compared with Taxol®, maximum blood concentration was increased by 1.5-fold; the time to reach maximum concentration shortened to 0.8 h from 1.7 h; and, relative oral bioavailability increased by 88%. Absolute oral bioavailability was 1.7% and 1.3% for the paclitaxel nano-micelles and Taxol®, respectively. Solubilizing paclitaxel with rubusoside was successful, but oral bioavailability remained low. Further inhibition of the efflux pump and/or first metabolism may allow more oral paclitaxel to enter systemic circulation.

Optimization of micelle-encapsulated extremely small sized iron oxide nanoparticles as a T1 contrast imaging agent: biodistribution and safety profile

BACKGROUND

Iron oxide nanoparticles (IONPs) have been cleared by the Food and Drug Administration (FDA) for various clinical applications, such as tumor-targeted imaging, hyperthermia therapy, drug delivery, and live-cell tracking. However, the application of IONPs as T1 contrast agents has been restricted due to their high r2 values and r2/r1 ratios, which limit their effectiveness in T1 contrast enhancement. Notably, IONPs with diameters smaller than 5 nm, referred to as extremely small-sized IONPs (ESIONs), have demonstrated potential in overcoming these limitations. To advance the clinical application of ESIONs as T1 contrast agents, we have refined a scale-up process for micelle encapsulation aimed at improving the hydrophilization of ESIONs, and have carried out comprehensive in vivo biodistribution and preclinical toxicity assessments.

RESULTS

The optimization of the scale-up micelle-encapsulation process, specifically employing Tween60 at a concentration of 10% v/v, resulted in ESIONs that were uniformly hydrophilized, with an average size of 9.35 nm and a high purification yield. Stability tests showed that these ESIONs maintained consistent size over extended storage periods and dispersed effectively in blood and serum-mimicking environments. Relaxivity measurements indicated an r1 value of 3.43 mM- 1s- 1 and a favorable r2/r1 ratio of 5.36, suggesting their potential as T1 contrast agents. Biodistribution studies revealed that the ESIONs had extended circulation times in the bloodstream and were primarily cleared via the hepatobiliary route, with negligible renal excretion. We monitored blood clearance and organ distribution using positron emission tomography and magnetic resonance imaging (MRI). Additionally, MRI signal variations in a dose-dependent manner highlighted different behaviors at varying ESIONs concentrations, implying that optimal dosages might be specific to the intended imaging application. Preclinical safety evaluations indicated that ESIONs were tolerable in rats at doses up to 25 mg/kg.

CONCLUSIONS

This study effectively optimized a scale-up process for the micelle encapsulation of ESIONs, leading to the production of hydrophilic ESIONs at gram-scale levels. These optimized ESIONs showcased properties conducive to T1 contrast imaging, such as elevated r1 relaxivity and a reduced r2/r1 ratio. Biodistribution study underscored their prolonged bloodstream presence and efficient clearance through the liver and bile, without significant renal involvement. The preclinical toxicity tests affirmed the safety of the ESIONs, supporting their potential use as T1 contrast agent with versatile clinical application.

Development of finely tuned liposome nanoplatform for macrophage depletion

BACKGROUND

Immunotherapy with clodronate-encapsulated liposomes, which induce macrophage depletion, has been studied extensively. However, previously reported liposomal formulation-based drugs (Clodrosome® and m-Clodrosome®) are limited by their inconsistent size and therapeutic efficacy. Thus, we aimed to achieve consistent therapeutic effects by effectively depleting macrophages with uniform-sized liposomes.

RESULTS

We developed four types of click chemistry-based liposome nanoplatforms that were uniformly sized and encapsulated with clodronate, for effective macrophage depletion, followed by conjugation with Man-N3 and radiolabeling. Functionalization with Man-N3 improves the specific targeting of M2 macrophages, and radioisotope labeling enables in vivo imaging of the liposome nanoplatforms. The functionalized liposome nanoplatforms are stable under physiological conditions. The difference in the biodistribution of the four liposome nanoplatforms in vivo were recorded using positron emission tomography imaging. Among the four platforms, the clodronate-encapsulated mannosylated liposome effectively depleted M2 macrophages in the normal liver and tumor microenvironment ex vivo compared to that by Clodrosome® and m-Clodrosome®.

CONCLUSION

The newly-developed liposome nanoplatform, with finely tuned size control, high in vivo stability, and excellent ex vivo M2 macrophage targeting and depletion effects, is a promising macrophage-depleting agent.

A bone-targeting near-infrared luminescence nanocarrier facilitates alpha-ketoglutarate efficacy enhancement for osteoporosis therapy

Osteoporosis (OP), which largely increases the risk of fractures, is the most common chronic degenerative orthopedic disease in the elderly due to the imbalance of bone homeostasis. Alpha-ketoglutaric acid (AKG), an endogenous metabolic intermediate involved in osteogenesis, plays critical roles in osteogenic differentiation and mineralization and the inhibition of osteoclastogenic differentiation. However, the low bioavailability and poor bone-targeting efficiency of AKG seriously limit its efficacy in OP treatment. In this work, a bone-targeting, near-infrared emissive lanthanide luminescence nanocarrier loaded with AKG (β-NaYF4:7%Yb, 60%Nd@NaLuF4@mSiO2-EDTA-AKG, abbreviated as LMEK) is developed for the enhancement of AKG efficacy in OP therapy. By utilizing the NIR-II luminescence (>1000 nm) of LMEK, whole-body bone imaging with high spatial resolution is achieved to confirm the bone enrichment of AKG noninvasively in vivo. The results reveal that LMEK exhibits a remarkable OP therapeutic effect in improving the osseointegration of the surrounding bone in the ovariectomized OP mice models, which is validated by the enhanced inhibition of osteoclast through hypoxia-inducible factor-1α suppression and promotion of osteogenic differentiation in osteoblast. Notably, the dose of AKG in LMEK can be reduced to only 0.2 % of the dose when pure AKG is used in therapy, which dramatically improves the bioavailability of AKG and mitigates the metabolism burden. This work provides a strategy to conquer the low utilization of AKG in OP therapy, which not only overcomes the challenges in AKG efficacy for OP treatment but also offers insights into the development and application of other potential drugs for skeletal diseases. STATEMENT OF SIGNIFICANCE: Alpha-ketoglutarate (AKG) is an intermediate within the Krebs cycle, participating in diverse metabolic and cellular processes, showing potential for osteoporosis (OP) therapy. However, AKG's limited bioavailability and inefficient bone-targeting hinder its effectiveness in treating OP. Herein, a near-infrared emissive nanocarrier is developed that precisely targets bones and delivers AKG, bolstering its effectiveness in OP therapy. Thanks to this efficient bone-targeting delivery, the AKG dosage is reduced to 0.2 % of the conventional treatment level. This marks the first utilization of a bone-targeting nanocarrier to amplify AKG's bioavailability and OP therapy efficacy. Furthermore, the mechanism of AKG-loaded nanocarrier regulating the biological behavior of osteoclasts and osteoblasts mediated is tentatively explored.

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.

Fluorophore Localization Determines the Results of Biodistribution of Core-Shell Nanocarriers

Introduction

Methods

Results

Conclusion

Opportunities and Challenges for Nanotherapeutics for the Aging Population

Nanotherapeutics utilize the properties of nanomaterials to alter the pharmacology of the drugs and therapies being transported, leading to changes in their biological disposition (absorption, distribution, cellular uptake, metabolism and elimination) and ultimately, their pharmacological effect. This provides an opportunity to optimize the pharmacology of drugs, particularly for those that are dependent on hepatic action. Old age is associated with changes in many pharmacokinetic processes which tend to impair drug efficacy and increase risk of toxicity. While these age-related changes are drug-specific they could be directly addressed using nanotechnology and precision targeting. The benefits of nanotherapeutics needs to be balanced against toxicity, with future use in humans dependent upon the gathering of information about the clearance and long-term safety of nanomaterials.

Biodistribution of 68/67Ga-Radiolabeled Sphingolipid Nanoemulsions by PET and SPECT Imaging

Background and Purpose

Non-invasive imaging methodologies, especially nuclear imaging techniques, have undergone an extraordinary development over the last years. Interest in the development of innovative tracers has prompted the emergence of new nanomaterials with a focus on nuclear imaging and therapeutical applications. Among others, organic nanoparticles are of the highest interest due to their translational potential related to their biocompatibility and biodegradability. Our group has developed a promising new type of biocompatible nanomaterials, sphingomyelin nanoemulsions (SNs). The aim of this study is to explore the potential of SNs for nuclear imaging applications.

Methods

Ready-to-label SNs were prepared by a one-step method using lipid derivative chelators and characterized in terms of their physicochemical properties. Stability was assessed under storage and after incubation with human serum. Chelator-functionalized SNs were radiolabeled with ⁶⁷Ga and ⁶⁸Ga, and the radiochemical yield (RCY), radiochemical purity (RCP) and radiochemical stability (RCS) were determined. Finally, the biodistribution of ^67/68Ga-SNs was evaluated in vivo and ex vivo.

Results

Here, we describe a simple and mild one-step method for fast and efficient radiolabeling of SNs with ⁶⁸Ga and ⁶⁷Ga radioisotopes. In vivo experiments showed that ^67/68Ga-SNs can efficiently and indistinctly be followed up by PET and SPECT. Additionally, we proved that the biodistribution of the ^67/68Ga-SNs can be conveniently modulated by modifying the surface properties of different hydrophilic polymers, and therefore the formulation can be further adapted to the specific requirements of different biomedical applications.

Conclusion

This work supports ^67/68Ga-SNs as a novel probe for nuclear imaging with tunable biodistribution and with great potential for the future development of nanotheranostics.

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.

Effectual Labeling of Natural Killer Cells with Upconverting Nanoparticles by Electroporation for In Vivo Tracking and Biodistribution Assessment

Natural killer (NK) cells, which are cytotoxic lymphocytes of the innate immune system and recognize cancer cells via various immune receptors, are promising agents in cell immunotherapy. To utilize NK cells as a therapeutic agent, their biodistribution and pharmacokinetics need to be evaluated following systemic administration. Therefore, in vivo imaging and tracking with efficient labeling and quantitative analysis of NK cells are required. However, the lack of the phagocytic capacity of NK cells makes it difficult to establish breakthroughs in cell labeling and subsequent in vivo studies. Herein, an effective labeling of upconverting nanoparticles (UCNPs) in NK cells is proposed using electroporation with high sensitivity and stability. The labeling performance of UCNPs functionalized with carboxy-polyethylene glycol (PEG) is better than with methoxy-PEG or with amine-PEG. The labeling efficiency becomes higher, but cell damage is greater as electric field increases; thus, there is an optimum electroporation condition for internalization of UCNPs into NK cells. The tracking and biodistribution imaging analyses of intravenously injected NK cells show that the labeled NK cells are initially distributed primarily in lungs and then spread to the liver and spleen. These advances will accelerate the application of NK cells as key components of immunotherapy against cancer.

64Cu-labeled melanin nanoparticles for PET/CT and radionuclide therapy of tumor

Melanin is a group of natural pigments found in living organism. It can be used for positron emission tomography (PET) imaging due to its inherent chelating ability to radioactive cupric ion. This study was to prepare ⁶⁴Cu-labeled PEGylated melanin nanoparticles (⁶⁴Cu-PEG-MNPs), and to further take advantage of the enhanced permeability and retention (EPR) effect of radiolabeled nanoparticles to realize the integration of tumor diagnosis and treatment. We successfully synthesized PEG-MNPs. Saline and serum stability experiments demonstrated good stability. PET/CT showed high tumor aggregation. Moreover, ⁶⁴Cu-PEG-MNPs resulted in a therapeutic effect on the A431 tumor-bearing mice in the treatment group. The pathological results further confirmed that the therapeutic doses of ⁶⁴Cu-PEG-MNPs cause pathological changes of tumor tissues while showing minimal toxicity to normal tissues. Our data successfully demonstrate the good imaging performance of ⁶⁴Cu-PEG-MNPs on A431 tumors and further proved its therapeutic effect, highlighting a great potential in targeted radionuclide therapy.

Physiologic constraints of using exosomes in vivo as systemic delivery vehicles

Systemic delivery of exosomes meets hurdles which had not been elucidated using live molecular imaging for their biodistribution. Production and uptake of endogenous exosomes are expected to be nonspecific and specific, respectively, where external stimuli of production of exosomes and their quantitative degree of productions are not understood. Despite this lack of understanding of basic physiology of in vivo behavior of exosomes including their possible paracrine or endocrine actions, many engineering efforts are taken to develop therapeutic vehicles. Especially, the fraction of exosomes’ taking the routes of waste disposal and exerting target actions are not characterized after systemic administration. Here, we reviewed the literature about in vivo distribution and disposal/excretion of exogenous or endogenous exosomes and, from these limited resources of knowledge currently available, summarized the knowledge and the uncertainties of exosomes on physiologic standpoints. An eloquent example of the investigations to understand the roles and confounders of exosomes’ action in the brain was highlighted with emphasis on the recent discovery of brain lymphatics and hypothesis of glymphatic/lymphatic clearance pathways in diseases as well as in physiologic processes. The possibility of delivering therapeutic exosomes through the systemic circulation, across blood-brain barriers and finally to target cells such as microglia, astrocytes and/or neurons is a good testbed in which the investigators can formulate problems to solve for both understanding (science) and application (engineering).

Brain Theranostics and Radiotheranostics: Exosomes and Graphenes In Vivo as Novel Brain Theranostics

Brain disease is one of the greatest threats to public health. Brain theranostics is recently taking shape, indicating the treatments of stroke, inflammatory brain disorders, psychiatric diseases, neurodevelopmental disease, and neurodegenerative disease. However, several factors, such as lack of endophenotype classification, blood-brain barrier (BBB), target determination, ignorance of biodistribution after administration, and complex intercellular communication between brain cells, make brain theranostics application difficult, especially when it comes to clinical application. So, a more thorough understanding of each aspect is needed. In this review, we focus on recent studies regarding the role of exosomes in intercellular communication of brain cells, therapeutic effect of graphene quantum dots, transcriptomics/epitranscriptomics approach for target selection, and in vitro/in vivo considerations.

Fully Automated Production and Characterization of 64 Cu and Proof-of-Principle Small-Animal PET Imaging Using 64 Cu-Labelled CA XII Targeting 6A10 Fab

⁶⁴ Cu is a cyclotron-produced radionuclide which offers, thanks to its characteristic decay scheme, the possibility of combining positron emission tomography (PET) investigations with radiotherapy. We evaluated the Alceo system from Comecer SpA to automatically produce ⁶⁴ Cu for radiolabelling purposes. We established a ⁶⁴ Cu production routine with high yields and radionuclide purity in combination with excellent operator radiation protection. The carbonic anhydrase XII targeting 6A10 antibody Fab fragment was successfully radiolabelled with the produced ⁶⁴ Cu, and proof-of-principle small-animal PET experiments on mice bearing glioma xenografts were performed. We obtained a high tumor-to-contralateral muscle ratio, which encourages further in vivo investigations of the radioconjugate regarding a possible application in diagnostic tumor imaging.

Upconversion processes: versatile biological applications and biosafety

Lanthanide-doped photon upconverting nanomaterials are evolving as a new class of imaging contrast agents, offering highly promising prospects in the area of biomedical applications. Owing to their ability to convert long-wavelength near-infrared excitation radiation into shorter-wavelength emissions, these nanomaterials are well suited to yield properties of low imaging background, large anti-Stokes shift, along with high optical penetration depth of NIR light for deep tissue optical imaging or light-activated drug release and therapy. Such materials have potential for significant advantages in analytical applications compared to molecular fluorophores and quantum dots. The use of IR radiation as an excitation source diminishes autofluorescence and scattering of excitation radiation, which leads to a reduction of background in optical experiments. The upconverting nanocrystals show exceptional photostability and are constituted of materials that are not significantly toxic to biological organisms. Excitation at long wavelengths also minimizes damage to biological materials. In this detailed review, various mechanisms operating for the upconversion process, and methods that are utilized to synthesize and decorate upconverting nanoparticles are investigated to elucidate by what means absorption and emission can be tuned. Up-to-date reports concerning cellular internalization, biodistribution, excretion, cytotoxicity and in vivo toxic effects of UCNPs are discussed. Specifically, studies which assessed the relationship between the chemical and physical properties of UCNPs and their biodistribution, excretion, and toxic effects are reviewed in detail. Finally, we also deliberate the challenges of guaranteeing the biosafety of UCNPs in vivo.

Positron emission tomography and nanotechnology: A dynamic duo for cancer theranostics

Development of novel imaging probes for cancer diagnosis is critical for early disease detection and management. The past two decades have witnessed a surge in the development and evolution of radiolabeled nanoparticles as a new frontier in personalized cancer nanomedicine. The dynamic synergism of positron emission tomography (PET) and nanotechnology combines the sensitivity and quantitative nature of PET with the multifunctionality and tunability of nanomaterials, which can help overcome certain key challenges in the field. In this review, we discuss the recent advances in radionanomedicine, exemplifying the ability to tailor the physicochemical properties of nanomaterials to achieve optimal in vivo pharmacokinetics and targeted molecular imaging in living subjects. Innovations in development of facile and robust radiolabeling strategies and biomedical applications of such radionanoprobes in cancer theranostics are highlighted. Imminent issues in clinical translation of radiolabeled nanomaterials are also discussed, with emphasis on multidisciplinary efforts needed to quickly move these promising agents from bench to bedside.

Radiolabeled inorganic nanoparticles for positron emission tomography imaging of cancer: an overview

Over the last few years, a plethora of radiolabeled inorganic nanoparticles have been developed and evaluated for their potential use as probes in positron emission tomography (PET) imaging of a wide variety of cancers. Inorganic nanoparticles represent an emerging paradigm in molecular imaging probe design, allowing the incorporation of various imaging modalities, targeting ligands, and therapeutic payloads into a single vector. A major challenge in this endeavor is to develop disease-specific nanoparticles with facile and robust radiolabeling strategies. Also, the radiolabeled nanoparticles should demonstrate adequate in vitro and in vivo stability, enhanced sensitivity for detection of disease at an early stage, optimized in vivo pharmacokinetics for reduced non-specific organ uptake, and improved targeting for achieving high efficacy. Owing to these challenges and other technological and regulatory issues, only a single radiolabeled nanoparticle formulation, namely "C-dots" (Cornell dots), has found its way into clinical trials thus far. This review describes the available options for radiolabeling of nanoparticles and summarizes the recent developments in PET imaging of cancer in preclinical and clinical settings using radiolabeled nanoparticles as probes. The key considerations toward clinical translation of these novel PET imaging probes are discussed, which will be beneficial for advancement of the field.

Microfluidic Synthesis and Biological Evaluation of Photothermal Biodegradable Copper Sulfide Nanoparticles

The continuous synthesis of biodegradable photothermal copper sulfide nanoparticles has been carried out with the aid of a microfluidic platform. A comparative physicochemical characterization of the resulting products from the microreactor and from a conventional batch reactor has been performed. The microreactor is able to operate in a continuous manner and with a 4-fold reduction in the synthesis times compared to that of the conventional batch reactor producing nanoparticles with the same physicochemical requirements. Biodegradation subproducts obtained under simulated physiological conditions have been identified, and a complete cytotoxicological analysis on different cell lines was performed. The photothermal effect of those nanomaterials has been demonstrated in vitro as well as their ability to generate reactive oxygen species.

Clear-cut observation of clearance of sustainable upconverting nanoparticles from lymphatic system of small living mice

The significance of lymphatic system has gathered great attention for immunotechnology related to cancer metastasis and immunotherapy. To develop innovative immunodiagnostics and immunotherapy in in vivo environments, it is very important to understand excretion pathways and clearance of injected cargoes. Herein, we employed Tm(3+)-doped upconverting nanoparticles (UCNPs) with versatile advantages suitable for long-term non-invasive in vivo optical imaging and tracking. Transport and retention of the UCNPs in the lymphatic system were evaluated with high-quality NIR-to-NIR upconversion luminescence (UCL) imaging. We obtained their kinetic luminescence profiles for the injection site and sentinel lymph node (SLN) and observed luminescence signals for one month; we also examined UCL images in SLN tissues, organs, and faeces at each time point. We speculate that the injected UCNPs in a footpad of a small mouse are transported rapidly from the lymphatic system to the blood system and then eventually result in an efficient excretion by the hepatobiliary route. These results will support development of novel techniques for SLN biopsy as well as immunotechnology.

A potentially versatile nano-platform

Radionanomedicine is the medical field which uses radioisotope labeled nanomaterials for diagnostic, therapeutic or theranostic purposes. An amphiphile- encapsulation method has been developed to hydrophilize nanoparticles and the introduction of multifunctional ligands. A copper-free click chemistry has been applied for introduction of various ligands to the nanoparticles. The combination of the amphiphile-encapsulation method and click chemistry might provide a versatile nano-platform to radionanomedicine, which might contribute to the earlier clinical application of radionanomedicine for theragnosis of various diseases.

Translational radionanomedicine: a clinical perspective

Many nanomaterials were developed for the anticipated in vivo theranostic use exploiting their unique characteristics as a multifunctional platform. Nevertheless, only a few nanomaterials are under investigation for human use, most of which have not entered clinical trials yet. Radionanomedicine, a convergent discipline of radiotracer technology and use of nanomaterials in vivo, can facilitate clinical nanomedicine because of its advantages of radionuclide imaging and internal radiation therapy. In this review, we focuse on how radionanomedicine would impact profoundly on clinical translation of nanomaterial theranostics. Up-to-date advances and future challenges are critically reviewed regarding the issues of how to radiolabel and engineer radionanomaterials, in vivo behavior tracing of radionanomaterials and then the desired clinical radiation dosimetry. Radiolabeled extracellular vesicles were further discussed as endogenous nanomaterials radiolabeled for possible clinical use.

Development of a complementary PET/MR dual-modal imaging probe for targeting prostate-specific membrane antigen (PSMA)

We tried to develop a dual-modal PET/MR imaging probe using a straightforward one-pot method by encapsulation with specific amphiphiles. In this study, iron oxide (IO) nanoparticles were encapsulated with three amphiphiles containing PEG, DOTA and the prostate-specific membrane antigen (PSMA)-targeting ligand in aqueous medium. The diameter of the prepared nanoparticle DOTA-IO-GUL was 11.01±1.54nm. DOTA-IO-GUL was labeled with (68)Ga in high efficiency. The DOTA-IO-GUL showed a dose-dependent binding to LNCaP (PSMA positive) cells via a competitive binding study against (125)I-labeled MIP-1072 (PSMA-targeting agent). Additionally, PET and MR imaging results showed PSMA selective uptake by only 22Rv1 (PSMA positive) but not PC-3 (PSMA negative) in dual-tumor xenograft mouse model study. MR imaging showed high resolution, and PET imaging enabled quantification and confirmation of the specificity. In conclusion, we have successfully developed the specific PSMA-targeting IO nanoparticle, DOTA-IO-GUL, as a dual-modality probe for complementary PET/MR imaging.

FROM THE CLINICAL EDITOR

The combination of using Positron Emission Tomography (PET) and computed tomography (CT) in clinical practice is now the norm. With advances in technology, the next step would be to develop combined PET and Magnetic Resonance (MR) dual-imaging. In this article, the authors described their positive study on the development of a dual-modal PET/MR imaging probe using a prostate cancer model.