Free iron (null)

Free iron refers to iron ions that are not bound to protective proteins such as transferrin or ferritin, and instead exist in a chemically labile, reactive state either in plasma or inside cells[4][5][6][7][8]. Free iron is present at extremely low levels in healthy individuals because of its pronounced toxicity: it catalyzes the formation of highly reactive hydroxyl radicals (via the Fenton reaction), causes oxidative damage to lipids, proteins, and DNA, and can lead to cell death and tissue injury[4][8]. The major forms of free iron are unbound Fe2+ (ferrous) and Fe3+ (ferric) ions, collectively contributing to non-transferrin-bound iron (NTBI) in the bloodstream and to the "labile iron pool" (LIP) within cells[5][6][7]. Under physiological conditions, virtually all iron is tightly regulated and sequestered by protein carriers to avoid free iron toxicity[3][4]. While drugs exist to chelate excess free iron in pathological states (such as iron overload disorders), free iron itself is not considered a conventional molecular target (e.g., receptor, enzyme, transporter) in therapeutic development—instead, it is a biochemical hazard tightly controlled by the body[4][8].

Other names

Labile iron poolNon-transferrin-bound iron (NTBI)Unbound ironLabile plasma ironFree Fe2+Free Fe3+

Chelation and removal of free iron to reduce toxicity and lower oxidative stress