Chloramine-T in radiolabeling techniques. IV. Penta-O-acetyl-N-chloro-N-methylglucamine as an oxidizing agent in radiolabelling techniques

Methods for Radiolabeling Nanoparticles (Part 3): Therapeutic Use

Following previously published systematic reviews on the diagnostic use of nanoparticles (NPs), in this manuscript, we report published methods for radiolabeling nanoparticles with therapeutic alpha-emitting, beta-emitting, or Auger's electron-emitting isotopes. After analyzing 234 papers, we found that different methods were used with the same isotope and the same type of nanoparticle. The most common type of nanoparticles used are the PLGA and PAMAM nanoparticles, and the most commonly used therapeutic isotope is 177Lu. Regarding labeling methods, the direct encapsulation of the isotope resulted in the most reliable and reproducible technique. Radiolabeled nanoparticles show promising results in metastatic breast and lung cancer, although this field of research needs more clinical studies, mainly on the comparison of nanoparticles with chemotherapy.

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.

Radioiodine Labeling Reagents and Methods for New Chemical Entities and Biomolecules

Several radioisotopes of iodine (¹²³I, ¹²⁴I, ¹²⁵I, and ¹³¹I) are available for medical use. One of them can be used, depending on the application, for radioiodine labeling of New Chemical Entities (NCEs) and biomolecules (peptides, proteins, protein fragments, monoclonal antibodies, etc.) for the development of novel imaging and therapeutic pharmaceuticals. Direct, using inorganic and organic oxidizing agents and enzyme catalysts, and indirect, using prosthetic groups, radioiodine-labeling methods have been used routinely in the past. In this report, a comprehensive review of the physical properties of various iodine radionuclides, their medical applications, and a summary of various radioiodine labeling reagents and methods for NCEs and biomolecules are provided.

A Novel Reagent for Radioiodine Labeling of New Chemical Entities (NCEs) and Biomolecules

Radioiodine labeling of peptides and proteins is routinely performed by using various oxidizing agents such as Chloramine T, Iodobeads, and Iodogen reagent and radioactive iodide (I-), although some other oxidizing agents were also investigated. The main objective of the present study was to develop and test a novel reagent, inorganic monochloramine (NH2Cl), for radioiodine labeling of new chemical entities and biomolecules which is cost-effective, easy to make and handle, and is selective to label amino acids, peptides, and proteins. The data presented in this report demonstrate that the yields of the non-radioactive iodine labeling reactions using monochloramine are >70% for an amino acid (tyrosine) and a cyclic peptide (cyclo Arg-Gly-Asp-d-Tyr-Lys, cRGDyK). No evidence of the formation of N-chloro derivatives in cRGDyK was observed, suggesting that the reagent is selective in iodinating the tyrosine residue in the biomolecules. The method was successfully translated into radioiodine labeling of amino acid, a peptide, and a protein, Bovine Serum Albumin (BSA).

Radiochemistry, Production Processes, Labeling Methods, and ImmunoPET Imaging Pharmaceuticals of Iodine-124

Target-specific biomolecules, monoclonal antibodies (mAb), proteins, and protein fragments are known to have high specificity and affinity for receptors associated with tumors and other pathological conditions. However, the large biomolecules have relatively intermediate to long circulation half-lives (>day) and tumor localization times. Combining superior target specificity of mAbs and high sensitivity and resolution of the PET (Positron Emission Tomography) imaging technique has created a paradigm-shifting imaging modality, ImmunoPET. In addition to metallic PET radionuclides, 124I is an attractive radionuclide for radiolabeling of mAbs as potential immunoPET imaging pharmaceuticals due to its physical properties (decay characteristics and half-life), easy and routine production by cyclotrons, and well-established methodologies for radioiodination. The objective of this report is to provide a comprehensive review of the physical properties of iodine and iodine radionuclides, production processes of 124I, various 124I-labeling methodologies for large biomolecules, mAbs, and the development of 124I-labeled immunoPET imaging pharmaceuticals for various cancer targets in preclinical and clinical environments. A summary of several production processes, including 123Te(d,n)124I, 124Te(d,2n)124I, 121Sb(α,n)124I, 123Sb(α,3n)124I, 123Sb(3He,2n)124I, natSb(α, xn)124I, natSb(3He,n)124I reactions, a detailed overview of the 124Te(p,n)124I reaction (including target selection, preparation, processing, and recovery of 124I), and a fully automated process that can be scaled up for GMP (Good Manufacturing Practices) production of large quantities of 124I is provided. Direct, using inorganic and organic oxidizing agents and enzyme catalysis, and indirect, using prosthetic groups, 124I-labeling techniques have been discussed. Significant research has been conducted, in more than the last two decades, in the development of 124I-labeled immunoPET imaging pharmaceuticals for target-specific cancer detection. Details of preclinical and clinical evaluations of the potential 124I-labeled immunoPET imaging pharmaceuticals are described here.

Comparative Study of Two Oxidizing Agents, Chloramine T and Iodo-Gen®, for the Radiolabeling of β-CIT with Iodine-131: Relevance for Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta, leading to alteration of the integrity of dopaminergic transporters (DATs). In recent years, some radiopharmaceuticals have been used in the clinic to evaluate the integrity of DATs. These include tropane derivatives such as radiolabeled β-CIT and FP-CIT with iodine-123 (¹²³I), and TRODAT-1 with metastable technetium-99 (^99mTc). Radiolabeling of β-CIT with radioactive iodine is based on electrophilic radioiodination using oxidizing agents, such as Chloramine T or Iodo-Gen^®. For the first time, the present work performed a comparative study of the radiolabeling of β-CIT with iodine-131 (¹³¹I), using either Chloramine T or Iodo-Gen^® as oxidizing agents, in order to improve the radiolabeling process of β-CIT and to choose the most advantageous oxidizing agent to be used in nuclear medicine. Both radiolabeling methods were similar and resulted in high radiochemical yield (> 95%), with suitable ¹³¹I-β-CIT stability up to 72 h. Although Chloramine T is a strong oxidizing agent, it was as effective as Iodo-Gen^® for β-CIT radiolabeling with ¹³¹I, with the advantage of briefer reaction time and solubility in aqueous medium.

Novel control of S phase of the cell cycle by ubiquitin-conjugating enzyme H7

Timely degradation of regulatory proteins by the ubiquitin proteolytic pathway (UPP) is an established paradigm of cell cycle regulation during the G2/M and G1/S transitions. Less is known about roles for the UPP during S phase. Here we present evidence that dynamic cell cycle-dependent changes in levels of UbcH7 regulate entrance into and progression through S phase. In diverse cell lines, UbcH7 protein levels are dramatically reduced in S phase but are fully restored by G2. Knockdown of UbcH7 increases the proportion of cells in S phase and doubles the time to traverse S phase, whereas UbcH7 overexpression reduces the proportion of cells in S phase. These data suggest a role for UbcH7 targets in the completion of S phase and entry into G2. Notably, UbcH7 knockdown was coincident with elevated levels of the checkpoint kinase Chk1 but not Chk2. These results argue that UbcH7 promotes S phase progression to G2 by modulating the intra-S phase checkpoint mediated by Chk1. Furthermore, UbcH7 levels appear to be regulated by a UPP. Together the data identify novel roles for the UPP, specifically UbcH7 in the regulation of S phase transit time as well as in cell proliferation.

Comparison of two methods for radioiodination on the oxidizability properties of low density lipoprotein

Radiolabeling of low density lipoprotein (LDL) apoB100 with 125I, an oxidative process, is commonly used in lipoprotein investigation. Since 1) LDL is unstable and oxidation-prone, 2) the modification of apoB100 by oxidation increases the negative charge of particles and leads to the uptake of modified LDL through the scavenger receptor pathway, and 3) oxidized LDL is cytotoxic, it is relevant to investigate whether the oxidative stability of LDL is influenced by its labeling with 125I. The aim of this study was to investigate and compare lipid and protein oxidation markers in human LDL after labeling with 125I by two widely adopted methods that use ICl or the chloramide 1,3,4,6-tetrachloro-3alpha,6alpha-diphenylglycoluril as the oxidizing agent. Native LDL served as a common control and sham-iodinated LDL as a handling control for each procedure. The resistance against copper-induced oxidation of 125I-LDL labeled with ICl was similar to that of controls with regard to the lag time and maximal amount of conjugated diene formed, as there were levels of initial conjugated diene, alpha-tocopherol, and tryptophan. However, radioiodination with the chloramide accelerated the onset of the rapid phase of LDL oxidation due to a drastic depletion of alpha-tocopherol and increased conjugated diene content. Measurements of copper-induced LDL oxidizability showed enhanced indices of lipid oxidation. The lag time and the time to maximal diene production were 65% and 30% shorter than controls. This was accompanied by a 50% reduced tryptophan fluorescence. The anionic surface charge of the LDL particle increased moderately with both labeling procedures. The results indicate that labeling of LDL with 125I may oxidize lipids and apoB100 to a variable extent, depending on the nature of the iodinating agent. This is why assessment of the oxidizability properties of 125I-labeled LDL is recommended for reliable biological studies.