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Radiolabeled Nanoparticles for Cancer Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
The most commonly employed radioisotopes for SPECT imaging include technetium (99Tc, t1/2: 6.0 h), indium (111In, t1/2: 2.8 days), and radioiodine (131I, t1/2: 8.0 days) and other radioisotopes as given in Table 3.1. Technetium-99m (99mTc, is an isotope of technetium, short-lived metastable radionuclide) is the most commonly employed radionuclide for nuclear imaging. Owing to the remarkable physical properties of 99mTc including the short half-life (6 h) and gamma photon emission (140 keV), this material is highly beneficial for efficient imaging as well as good for patient’s safety. Additionally, 99mTc holds latent chemical properties, which allow this material to be used in kits of numerous types for labeling for multipurpose diagnostic applications. SPECT is often used for imaging ligands, including antibodies, peptides, hormones, and selectins, which are labeled with 99mTc or with other radioisotopes. These molecules slowly diffuse into tissue and exhibit slow clearance from blood that extends for several hours to even days. Some SPECT isotopes with long half-life, such as thallium-201 (201Tl), tin-117m (117mSn), and iodine-125 (125I), are used for imaging of slow biological processes, including cell division, inflammatory process, and effect of therapeutic radiopharmaceuticals.
Alternative Tumor-Targeting Strategies
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
Radioactivity has been used to kill cancer cells for many decades, and a detailed discussion of the various approaches and radioisotopes used is beyond the scope of this section. However, researchers have used radioactive nanoparticles to treat cancer, and a few of these treatment strategies are described below.
Radionuclide imaging
Published in Damian Tolan, Rachel Hyland, Christopher Taylor, Arnold Cowen, Get Through, 2020
Damian Tolan, Rachel Hyland, Christopher Taylor, Arnold Cowen
True – the biological half-life determines how quickly the radioisotope is eliminated from the body and, together with the radioactive half-life, determines the effective half-life of the material.False – the dose will be directly proportional to the activity.True – injected material will not be taken up by tissues in the same way as orally administered or inhaled material. The effective dose, which depends on the doses to different tissues, is likely to be different.False – the dose relates to the type and quantity of radioisotope administered, not to image acquisition time.True – typically an effective dose of 18 mSv is quoted.
Combination therapies in clinical trials for renal cell carcinoma: how could they impact future treatments?
Published in Expert Opinion on Investigational Drugs, 2021
RCC has traditionally been thought of as radioresistant. Conventional fractionation (2 Gy per fraction) has been examined in multiple studies with no benefit thought to be due to inherent radioresistance. Radiobiology centers around the 5 Rs: Radiosensitivity, Reoxygenation, Radioresistance, Repopulation, Redistribution, and Repair, with the initial two being relevant for the effects of conventional radiotherapy in RCC. Modern radiotherapy techniques allow us to give ablative doses (8–10 Gy per fraction) overcoming radioresistance and providing excellent local control rates in metastatic disease [65]. The combination of radiotherapy and immunotherapy has shown promise in increasing response rates to immunotherapy in metastatic disease, probably by neoantigen generation and the so-called abscopal effect [66,67]. Further potential work would be interesting around the HIF inhibitors; reoxygenation is a key component of response to conventionally fractionated radiotherapy and the addition of HIF inhibition may enhance this process. Trials combining immunotherapy, radiotherapy, and HIF inhibition could investigate a theoretical additive and synergistic effect. Radioisotopes are licensed in a number of malignancies. Radium-223 dichloride (radium-223), an alpha emitter, selectively targets bone metastases with alpha particles and can modulate the symptomatic effect of bone metastases; bone metastases are common in kidney cancer [68]. A phase 2 trial where investigators are adding radium-223 dichloride to cabozantinib will improve our understanding as to the role of radioisotopes [NCT04071223].
Employing in vitro metabolism to guide design of F-labelled PET probes of novel α-synuclein binding bifunctional compounds
Published in Xenobiotica, 2021
Chukwunonso K. Nwabufo, Omozojie P. Aigbogun, Kevin J.H Allen, Madeline N. Owens, Jeremy S. Lee, Christopher P. Phenix, Ed S. Krol
Our first objective was to determine the in vitro hepatic metabolites of C8-6-C8, C8-6-I and C8-6-N in HLM, MLM, and RLM in order to direct our design of 18F labelled analogues. Since the biotransformation of PET imaging probes can alter the information obtained from biodistribution studies, it was important to perform metabolism studies of these compounds to determine the least metabolically labile position for the attachment of a radioisotope. These first metabolism studies addressed three major questions: are C8-6-N, C8-6-I, and C8-6-C8 metabolized in HLM, MLM, and RLM; are the metabolic pathways of C8-6-N, C8-6-I, and C8-6-C8 the same in HLM, MLM and RLM; and what are the least metabolically labile positions for the inclusion of fluorine in C8-6-N, C8-6-I, and C8-6-C8.
The Impacts of Episcleral Plaque Brachytherapy on Ocular Motility
Published in Journal of Binocular Vision and Ocular Motility, 2021
Kaveh Abri Aghdam, Mostafa Soltan Sanjari, Masood Naseripour, Navid Manafi, Ahad Sedaghat, Shohreh Bakhti
Intraocular tumors impose a great risk on the sight and life of patients and they can arise from different eye structures. The most common primary intraocular neoplasms include choroidal melanoma and choroidal hemangioma in adults, and retinoblastoma in children.1–4 The aim of therapy for malignant ocular tumors is to offer the best prognosis for patient survival, globe retention, and sight preservation.5–9 Brachytherapy is used for the treatment of uveal melanoma, choroidal osteoma and hemangioma, retinoblastoma, capillary hemangioma, vasoproliferative tumor, conjunctival lymphoma, and even choroidal metastasis.9–15 Furthermore, for small to the middle-sized ciliary body and choroidal melanomas, episcleral plaque brachytherapy is the most widely used treatment modality.10 While ionizing radiation has a strong effect on intraocular tumors, it also has multiple destructive effects on adjacent normal tissues. Therefore, it is necessary to give a sufficient dose to the affected tissue while protecting the adjacent areas from the destructive radiation. Brachytherapy is a suitable option for this means.9,10 Radium-226, Cobalt-60, Ruthenium-106, Iodine-125, palladium-103, and strontium-90 are common radioisotopes used for this purpose. The usual dose in brachytherapy is between 0.4 to 1 Gy/h.9,10 A similar dose of different isotopes does not have a similar biologic effect on tissues.10