Radioisotope (RI)

Radioisotopes, also known as radionuclides, are unstable forms of chemical elements that release ionizing radiation as they decay toward a stable state [1][2]. In the context of pharmacology, they are not biological targets (such as receptors or enzymes) but are instead the active therapeutic or diagnostic moieties within radiopharmaceutical agents [3]. When utilized for therapy, radioisotopes like Lutetium-177 or Actinium-225 are typically conjugated to a ligand that directs the radiation to a specific biological target, such as the prostate-specific membrane antigen (PSMA) or somatostatin receptors [4][5]. Their primary mechanism of action involves the emission of alpha or beta particles, which induce double-strand DNA breaks and generate reactive oxygen species to cause cell death in targeted tissues [6]. Diagnostic radioisotopes, such as Fluorine-18 or Technetium-99m, emit positrons or gamma rays to allow for non-invasive visualization of physiological processes through PET or SPECT imaging [7]. Although highly effective in treating advanced malignancies and thyroid disorders, radioisotopes carry significant safety considerations, including potential damage to healthy bystander tissues and the risk of radiation-induced secondary cancers [8][9].

Other names

RadionuclideRadioactive isotopeRadioactive nuclideRadio-labelRadioactive tracer

Radioisotopes function by emitting ionizing radiation (alpha particles, beta particles, or gamma rays) that causes direct and indirect DNA damage, leading to cytotoxic effects in target cells or providing a signal for external imaging.