Copper(2+)

copper(2+) (Cu²⁺), commonly called the cupric ion, is the divalent cation of the transition metal copper and the predominant oxidation state of copper in extracellular biological fluids. As an essential trace element, copper serves as a catalytic cofactor for metalloenzymes involved in mitochondrial respiration, antioxidant defense, iron mobilization, and connective tissue cross-linking. Because free ionic copper is toxic, its distribution is tightly controlled by membrane transporters, ATPase copper-transporting proteins, and intracellular copper chaperones, which keep the unbound cytosolic pool vanishingly small. glutathione and other thiols buffer the labile fraction. Disturbed copper handling has been linked to neurodegenerative conditions such as Alzheimer's disease, where Cu²⁺ binds amyloid beta (Aβ), as well as to cancer, insulin resistance, and cardiovascular disease.

The defining chemical property of Cu²⁺ is its redox activity: cycling between the cupric (Cu²⁺) and cuprous (Cu⁺) states allows it to react with hydrogen peroxide in Fenton-like chemistry, generating reactive oxygen species that damage lipids, proteins, and nucleic acids and impose oxidative stress. This same reactivity is exploited therapeutically. copper overload triggers cuproptosis, a copper-dependent form of cell death distinct from apoptosis and ferroptosis that proceeds through mitochondrial lipoylated-protein aggregation and depends on ferredoxin 1 (FDX1); related strategies deplete glutathione or engage the Nrf2/GPx4 axis and the cGAS-STING pathway to sensitize tumors and support cancer immunotherapy. In materials chemistry, Cu²⁺ acts as a coordinating node: it templates metal-organic frameworks and histidine-containing peptide metallogels used as drug carriers, and copper-based nanozymes display peroxidase-like catalytic activity that is harnessed for signal amplification in electrochemical biosensors. Cu²⁺ is likewise a common analytical target as an environmental heavy-metal contaminant, detected by CRISPR-Cas12a and nanomaterial platforms or removed by cellulose-based adsorbent hydrogels, and its antimicrobial oxidative activity is active against organisms including Staphylococcus aureus and Pseudomonas aeruginosa.