Biological Carrier Molecules of Radiopharmaceuticals for Molecular Cancer Imaging and Targeted Cancer Therapy

Carrier systems of radiopharmaceuticals and the application in cancer therapy

Radiopharmaceuticals play a vital role in cancer therapy. The carrier of radiopharmaceuticals can precisely locate and guide radionuclides to the target, where radionuclides kill surrounding tumor cells. Effective application of radiopharmaceuticals depends on the selection of an appropriate carrier. Herein, different types of carriers of radiopharmaceuticals and the characteristics are briefly described. Subsequently, we review radiolabeled monoclonal antibodies (mAbs) and their derivatives, and novel strategies of radiolabeled mAbs and their derivatives in the treatment of lymphoma and colorectal cancer. Furthermore, this review outlines radiolabeled peptides, and novel strategies of radiolabeled peptides in the treatment of neuroendocrine neoplasms, prostate cancer, and gliomas. The emphasis is given to heterodimers, bicyclic peptides, and peptide-modified nanoparticles. Last, the latest developments and applications of radiolabeled nucleic acids and small molecules in cancer therapy are discussed. Thus, this review will contribute to a better understanding of the carrier of radiopharmaceuticals and the application in cancer therapy.

Radiopharmaceuticals: navigating the frontier of precision medicine and therapeutic innovation

This review article explores the dynamic field of radiopharmaceuticals, where innovative developments arise from combining radioisotopes and pharmaceuticals, opening up exciting therapeutic possibilities. The in-depth exploration covers targeted drug delivery, delving into passive targeting through enhanced permeability and retention, as well as active targeting using ligand-receptor strategies. The article also discusses stimulus-responsive release systems, which orchestrate controlled release, enhancing precision and therapeutic effectiveness. A significant focus is placed on the crucial role of radiopharmaceuticals in medical imaging and theranostics, highlighting their contribution to diagnostic accuracy and image-guided curative interventions. The review emphasizes safety considerations and strategies for mitigating side effects, providing valuable insights into addressing challenges and achieving precise drug delivery. Looking ahead, the article discusses nanoparticle formulations as cutting-edge innovations in next-generation radiopharmaceuticals, showcasing their potential applications. Real-world examples are presented through case studies, including the use of radiolabelled antibodies for solid tumors, peptide receptor radionuclide therapy for neuroendocrine tumors, and the intricate management of bone metastases. The concluding perspective envisions the future trajectory of radiopharmaceuticals, anticipating a harmonious integration of precision medicine and artificial intelligence. This vision foresees an era where therapeutic precision aligns seamlessly with scientific advancements, ushering in a new epoch marked by the fusion of therapeutic resonance and visionary progress.

Radiolabeling of Nucleic Acid Aptamers for Highly Sensitive Disease-Specific Molecular Imaging

Aptamers are short single-stranded DNA or RNA oligonucleotide ligand molecules with a unique three-dimensional shape, capable of binding to a defined molecular target with high affinity and specificity. Since their discovery, aptamers have been developed for various applications, including molecular imaging, particularly nuclear imaging that holds the highest potential for the clinical translation of aptamer-based molecular imaging probes. Their easy laboratory production without any batch-to-batch variations, their high stability, their small size with no immunogenicity and toxicity, and their flexibility to incorporate various functionalities without compromising the target binding affinity and specificity make aptamers an attractive class of targeted-imaging agents. Aptamer technology has been utilized in nuclear medicine imaging techniques, such as single photon emission computed tomography (SPECT) and positron emission tomography (PET), as highly sensitive and accurate biomedical imaging modalities towards clinical diagnostic applications. However, for aptamer-targeted PET and SPECT imaging, conjugation of appropriate radionuclides to aptamers is crucial. This review summarizes various strategies to link the radionuclides to chemically modified aptamers to accomplish aptamer-targeted PET and SPECT imaging.

Enhancing Osteosarcoma Killing and CT Imaging Using Ultrahigh Drug Loading and NIR-Responsive Bismuth Sulfide@Mesoporous Silica Nanoparticles

Despite its 5-year event-free survival rate increasing to 60-65% due to surgery and chemotherapy, osteosarcoma (OS) remains one of the most threatening malignant human tumors, especially in young patients. Therefore, a new approach that combines early diagnosis with efficient tumor eradication and bioimaging is urgently needed. Here, a new type of mesoporous silica-coated bismuth sulfide nanoparticles (Bi2 S3 @MSN NPs) is developed. The well distributed mesoporous pores and large surface areas hold great promise for drug protection and encapsulation (doxorubicin (DOX), 99.85%). Moreover, the high photothermal efficiency of Bi2 S3 @MSNs (36.62%) offers great possibility for cancer synergistic treatment and highly near-infrared-triggered drug release (even at an ultralow power density of 0.3 W cm-2 ). After covalently conjugated to arginine-glycine-aspartic acid (RGD) peptide [c(RGDyC)], the NPs exhibit a high specificity for osteosarcoma and finally accumulate in the tumor cells (tenfold more than peritumoral tissues) for computed tomography (CT) imaging and tumor ablation. Importantly, the synergistic photothermal therapy-chemotherapy of the RGD-Bi2 S3 @MSN/DOX significantly ablates the highly malignant OS. It is further proved that the superior combined killing effect is achieved by activating the mitochondrial apoptosis pathway. Hence, the smart RGD-Bi2 S3 @MSN/DOX theranostic platform is a promising candidate for future applications in CT monitoring and synergistic treatment of malignant tumors.

Scintigraphic imaging of Staphylococcus aureus infection using 99mTc radiolabeled aptamers

Staphylococcus aureus is a specie of great medical importance associated with many infections as bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device related infections. Early identification of infectious foci is crucial for successful treatment. Scintigraphy could contribute to this purpose since specific radiotracers were available. Aptamers due to their high specificity have great potential for radiopharmaceuticals development. In the present study scintigraphic images of S. aureus infectious foci were obtained using specific S. aureus aptamers radiolabeled with ^99mTc.

A nanobody targeting carcinoembryonic antigen as a promising molecular probe for non-small cell lung cancer

Carcinoembryonic antigen (CEA) is a biomarker and therapy target for non-small cell lung cancer (NSCLC), which is the most common type of lung cancer. Nanobodies with high target specificity are promising candidates to function as anti-CEA probes. In the present study, the targeting effects of an anti-CEA nanobody obtained from phage display were investigated using technetium-99 m (^99mTc) and fluorescence labeling. In vitro binding and immunofluorescent staining assays, as well as in vivo blood clearance and biodistribution assays were performed. High specificity and affinity of the nanobody for CEA-positive H460 cells was observed in vitro. The pharmacokinetics assay of the ^99mTc-nanobody in Wistar rats demonstrated that the nanobody had appropriate T_1/2α and T_1/2β, which were 20.2 and 143.5 min, respectively. The biodistribution assay using H460 xenograft-bearing nude mice demonstrated a high ratio of signal in tumor compared with background, which confirmed that the nanobody may be useful as a molecular probe for CEA-positive cancer, particularly in NSCLC.

Aptamers as radiopharmaceuticals for nuclear imaging and therapy

Today, radiopharmaceuticals belong to the standard instrumentation of nuclear medicine, both in the context of diagnosis and therapy. The majority of radiopharmaceuticals consist of targeting biomolecules which are designed to interact with a disease-related molecular target. A plethora of targeting biomolecules of radiopharmaceuticals exists, including antibodies, antibody fragments, proteins, peptides and nucleic acids. Nucleic acids have some significant advantages relative to proteinaceous biomolecules in terms of size, production, modifications, possible targets and immunogenicity. In particular, aptamers (non-coding, synthetic, single-stranded DNA or RNA oligonucleotides) are of interest because they can bind a molecular target with high affinity and specificity. At present, few aptamers have been investigated preclinically for imaging and therapeutic applications. In this review, we describe the use of aptamers as targeting biomolecules of radiopharmaceuticals. We also discuss the chemical modifications which are needed to turn aptamers into valuable (radio-)pharmaceuticals, as well as the different radiolabeling strategies that can be used to radiolabel oligonucleotides and, in particular, aptamers.

Joint research towards a better radiation protection-highlights of the Fifth MELODI Workshop

MELODI is the European platform dedicated to low-dose radiation risk research. From 7 October through 10 October 2013 the Fifth MELODI Workshop took place in Brussels, Belgium. The workshop offered the opportunity to 221 unique participants originating from 22 countries worldwide to update their knowledge and discuss radiation research issues through 118 oral and 44 poster presentations. In addition, the MELODI 2013 workshop was reaching out to the broader radiation protection community, rather than only the low-dose community, with contributions from the fields of radioecology, emergency and recovery preparedness, and dosimetry. In this review, we summarise the major scientific conclusions of the workshop, which are important to keep the MELODI strategic research agenda up-to-date and which will serve to establish a joint radiation protection research roadmap for the future.