Critical analysis of radioiodination techniques for micro and macro organic molecules

Synthesis Principle and Practice with Radioactive Iodines and Astatine: Advances Made So Far

Radioactive iodines and astatine, possessing distinct exploitable nuclear properties, play indispensable roles in the realms of nuclear imaging and therapy. Their analogous chemical characteristics shape the design, preparation, and substrate range for tracers labeled with these radiohalogens through interconnected radiosynthetic chemistry. This perspective systematically explores the labeling methods by types of halogenating reagents─nucleophilic and electrophilic─underpinning the rational design of such compounds. It delves into the rapidly evolving synthetic strategies and reactions in radioiodination and radioastatination over the past decade, comparing their intrinsic relationships and highlighting variations. This comparative analysis illuminates potential radiosynthetic methods for exploration. Moreover, stability concerns related to compounds labeled with radioactive iodines and astatine are addressed, offering valuable insights for radiochemists and physicians alike.

Atorvastatin-loaded cubosome: a repurposed targeted delivery systems for enhanced targeting against breast cancer

Cancer ranks as one of the most challenging illnesses to deal with because progressive phenotypic and genotypic alterations in cancer cells result in resistance and recurrence. Thus, the creation of novel medications or alternative therapy approaches is mandatory. Repurposing of old drugs is an attractive approach over the traditional drug discovery process in terms of shorter drug development duration, low-cost, highly efficient and minimum risk of failure. In this study Atorvastatin, a statin drug used to treat abnormal cholesterol levels and prevent cardiovascular disease in people at high risk, was introduced and encapsulated in cubic liquid crystals as anticancer candidate aiming at sustaining its release and achieving better cellular uptake in cancer cells. The cubic liquid crystals were successfully prepared and optimized with an entrapment effieciency of 73.57% ±1.35 and particle size around 200 nm. The selected formulae were effectively doped with radioactive iodine 131I to enable the noninvasive visualization and trafficking of the new formulae. The in vivo evaluation in solid tumor bearing mice was conducted for comparing131I-Atorvastatin solution,131I-Atorvastatin loaded cubosome and 131I-Atorvastatin chitosan coated cubosome. The in vivo biodistribution study revealed that tumor radioactivity uptake of 131I-Atorvastatin cubosome and chitosan coated cubosome exhibited high accumulation in tumor tissues (target organ) scoring ID%/g of 5.67 ± 0.2 and 5.03 ± 0.1, respectively 1h post injection compared to drug solution which recorded 3.09 ± 0.05% 1h post injection. Concerning the targeting efficiency, the target/non target ratio for 131I-Atorvastatin chitosan coated cubosome was higher than that of 131I-Atorvastatin solution and 131I ATV-loaded cubosome at all time intervals and recorded T/NT ratio of 2.908 2h post injection.

Future Prospective of Radiopharmaceuticals from Natural Compounds Using Iodine Radioisotopes as Theranostic Agents

Natural compounds provide precursors with various pharmacological activities and play an important role in discovering new chemical entities, including radiopharmaceuticals. In the development of new radiopharmaceuticals, iodine radioisotopes are widely used and interact with complex compounds including natural products. However, the development of radiopharmaceuticals from natural compounds with iodine radioisotopes has not been widely explored. This review summarizes the development of radiopharmaceuticals from natural compounds using iodine radioisotopes in the last 10 years, as well as discusses the challenges and strategies to improve future discovery of radiopharmaceuticals from natural resources. Literature research was conducted via PubMed, from which 32 research articles related to the development of natural compounds labeled with iodine radioisotopes were reported. From the literature, the challenges in developing radiopharmaceuticals from natural compounds were the purity and biodistribution. Despite the challenges, the development of radiopharmaceuticals from natural compounds is a golden opportunity for nuclear medicine advancement.

Synthesis of Radioiodinated Compounds. Classical Approaches and Achievements of Recent Years

This review demonstrates the progress in the synthesis of radioiodinated compounds over the past decade. The possibilities and limitations of radiopharmaceuticals with different iodine isotopes, as well as the synthesis of low and high molecular weight compounds containing radioiodine, are discussed. An analysis of synthesis strategies, substrate frameworks, isolation methods, and metabolic stability, and the possibility of industrial production of radioiodinated organic derivatives which can find applications in the synthesis of drugs and diagnostics are presented.

Radioiodination of Modified Porous Silica Nanoparticles as a Potential Candidate of Iodine-131 Drugs Vehicle

There are challenges related to cancer treatment, namely, targeting and biocompatibility associated with a drug vehicle. This research aims to prepare a theranostic cancer vehicle based on porous silica nanoparticles (PSN) with controllable nanoparticle size, supporting targeting properties, and biocompatible. The synthesis method combined the Stöber process and liquid crystal templating using a dispersant and pore expander. Triethanolamine (TEA) and Pluronic F-127 were combined as a steric stabilizer and dispersing agent, while n-hexane was used as a pore expander. The amine functionalization was carried out using the 3-aminopropyl-triethoxysilane solution. Furthermore, radiolabeling of PSN using Iodine-131 and iodogen as oxidizing agents was carried out. The results showed that the best achievable PSN size was 100-150 nm with a polydispersity index of 0.24 using TEA-Pluronic F-127. The functionalization results did not significantly affect the radioiodination result. Radiochemical purity (RCP) values up to 95% were obtained in the radioiodination, while the labeled compounds were relatively stable with 12 mCi radioactivity, indicating the absence of radiolysis. The synthesized PSN was not toxic to normal cell samples up to a concentration of 150 μg/mL for PSN and 170 μg/mL for PSN-NH2. The cellular uptake testing results of the PSN-131I in cancer cell samples showed promising uptake ability.

Experimental and computational study of rafoxanide radioiodination via isotopic exchange reaction

The current study is an attempt to confirm the possibility of using rafoxanide (Raf) for diagnostic or radiotherapeutic purpose based on the radioiodine used in the labeling process. The isotopic exchange reaction was performed to radiolabel Raf. The maximum radiochemical yield of [125I]Raf (90%) was obtained when 20 μL of Na[125I]I (7.4 MBq (200 μCi)) in the reaction flask was added to 100 μg of Raf (0.799 mM) within 20 min at 140 °C. High pressure liquid chromatography was used to purify the labeled product of [125I]Raf. The activation energy was calculated experimentally in both ethyl acetate and methanol as reaction medium and found to be 22.82 kJ/mol and 24.43 kJ/mol, respectively. Furthermore, Gaussian 09 used the density function theory (DFT) to calculate the activation energy of the reaction in the two solvents.

Radioanalytical Techniques to Quantitatively Assess the Biological Uptake and In Vivo Behavior of Hazardous Substances

Concern about environmental exposure to hazardous substances has grown over the past several decades, because these substances have adverse effects on human health. Methods used to monitor the biological uptake of hazardous substances and their spatiotemporal behavior in vivo must be accurate and reliable. Recent advances in radiolabeling chemistry and radioanalytical methodologies have facilitated the quantitative analysis of toxic substances, and whole-body imaging can be achieved using nuclear imaging instruments. Herein, we review recent literature on the radioanalytical methods used to study the biological distribution, changes in the uptake and accumulation of hazardous substances, including industrial chemicals, nanomaterials, and microorganisms. We begin with an overview of the radioisotopes used to prepare radiotracers for in vivo experiments. We then summarize the results of molecular imaging studies involving radiolabeled toxins and their quantitative assessment. We conclude the review with perspectives on the use of radioanalytical methods for future environmental research.

Recent Advances in Synthetic Methods for Radioiodination

Organic compounds bearing radioisotopes of iodine are widely used for biological research, diagnostic imaging, and radiotherapy. Early reported synthetic methods for the incorporation of radioiodine have generally involved high temperature reactions or strongly oxidizing conditions. To overcome these limitations and to cope with the demand for novel radioiodinated probes, there has been a surge in the development of new synthetic methodology for radioiodination. This synopsis describes the key transformations developed recently.

Review of Therapeutic Applications of Radiolabeled Functional Nanomaterials

In the last two decades, various nanomaterials have attracted increasing attention in medical science owing to their unique physical and chemical characteristics. Incorporating radionuclides into conventionally used nanomaterials can confer useful additional properties compared to the original material. Therefore, various radionuclides have been used to synthesize functional nanomaterials for biomedical applications. In particular, several α- or β-emitter-labeled organic and inorganic nanoparticles have been extensively investigated for efficient and targeted cancer treatment. This article reviews recent progress in cancer therapy using radiolabeled nanomaterials including inorganic, polymeric, and carbon-based materials and liposomes. We first provide an overview of radiolabeling methods for preparing anticancer agents that have been investigated recently in preclinical studies. Next, we discuss the therapeutic applications and effectiveness of α- or β-emitter-incorporated nanomaterials in animal models and the emerging possibilities of these nanomaterials in cancer therapy.

Nuclear Imaging of Glucose Metabolism: Beyond 18F-FDG

Glucose homeostasis plays a key role in numerous fundamental aspects of life, and its dysregulation is associated with many important diseases such as cancer. The atypical glucose metabolic phenomenon, known as the Warburg effect, has been recognized as a hallmark of cancer and serves as a promising target for tumor specific imaging. At present, 2-deoxy-2-[¹⁸F]fluoro-glucose (¹⁸F-FDG)-based positron emission tomography/computed tomography (PET/CT) represented the state-of-the-art radionuclide imaging technique for this purpose. The powerful impact of ¹⁸F-FDG has prompted intensive research efforts into other glucose-based radiopharmaceuticals for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging. Currently, glucose and its analogues have been labeled with various radionuclides such as ^99mTc, ¹¹¹In, ¹⁸F, ⁶⁸Ga, and ⁶⁴Cu and have been successfully investigated for tumor metabolic imaging in many preclinical studies. Moreover, ^99mTc-ECDG has advanced into its early clinical trials and brings a new era of tumor imaging beyond ¹⁸F-FDG. In this review, preclinical and early clinical development of glucose-based radiopharmaceuticals for tumor metabolic imaging will be summarized.

Efficient and Site-Specific 125I-Radioiodination of Bioactive Molecules Using Oxidative Condensation Reaction

In this report, the novel and site-specific radioiodination of biomolecules by using aryl diamine and alkyl aldehyde condensation reaction in the presence of a Cu²⁺ catalyst under ambient conditions was reported. ¹²⁵I-labeled alkyl aldehyde was synthesized using a tin precursor with a high radiochemical yield (72 ± 6%, n = 5) and radiochemical purity (>99%). The utility of the radioiodinated precursor was demonstrated through aryl diamine-installed c[RGDfK(C)] peptide and human serum albumin (HSA). Radioiodinated c[RGDfK(C)] peptide and HSA protein were synthesized with high radiochemical yields and purity. ¹²⁵I-HSA protein showed excellent in vivo stability and negligible thyroid uptake as compared with directly radioiodinated HSA by using the tyrosine group. Excellent reaction kinetics and the in vitro and in vivo stabilities of ¹²⁵I-labeled alkyl aldehyde have suggested the usefulness of the strategy for the radioiodination of bioactive molecules.

A Practical Method for the Preparation of 18F-Labeled Aromatic Amino Acids from Nucleophilic [18F]Fluoride and Stannyl Precursors for Electrophilic Radiohalogenation

In a recent contribution of Scott et al., the substrate scope of Cu-mediated nucleophilic radiofluorination with [¹⁸F]KF for the preparation of ¹⁸F-labeled arenes was extended to aryl- and vinylstannanes. Based on these findings, the potential of this reaction for the production of clinically relevant positron emission tomography (PET) tracers was investigated. To this end, Cu-mediated radiofluorodestannylation using trimethyl(phenyl)tin as a model substrate was re-evaluated with respect to different reaction parameters. The resulting labeling protocol was applied for ¹⁸F-fluorination of different electron-rich, -neutral and -poor arylstannyl substrates in RCCs of 16-88%. Furthermore, this method was utilized for the synthesis of ¹⁸F-labeled aromatic amino acids from additionally N-Boc protected commercially available stannyl precursors routinely applied for electrophilic radiohalogenation. Finally, an automated synthesis of 6-[¹⁸F]fluoro-l-m-tyrosine (6-[¹⁸F]FMT), 2-[¹⁸F]fluoro-l-tyrosine (2-[¹⁸F]F-Tyr), 6-[¹⁸F]fluoro-l-3,4-dihydroxyphenylalanine (6-[¹⁸F]FDOPA) and 3-O-methyl-6-[¹⁸F]FDOPA ([¹⁸F]OMFD) was established furnishing these PET probes in isolated radiochemical yields (RCYs) of 32-54% on a preparative scale. Remarkably, the automated radiosynthesis of 6-[¹⁸F]FDOPA afforded an exceptionally high RCY of 54 ± 5% (n = 5).