Calcium

Calcium (Ca; atomic number 20) is the most abundant mineral in the human body and a divalent cation (Ca²⁺) essential to a wide range of physiological processes. Beyond its structural role as the primary mineral constituent of bones and teeth—where it exists predominantly as hydroxyapatite—calcium functions as a ubiquitous intracellular second messenger regulating cell signaling, muscle contraction, neurotransmitter release, enzyme activation, and apoptotic pathways. Intracellular Ca²⁺ concentrations are tightly maintained at nanomolar levels in the cytoplasm, while organelles such as the endoplasmic reticulum (ER), mitochondria, and lysosomes serve as dynamic Ca²⁺ reservoirs whose coordinated release and uptake govern excitability, metabolic coupling, and cell death decisions. Dysregulation of calcium homeostasis is implicated in a broad spectrum of pathologies, including neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, acute pancreatitis, eryptosis, and neoplastic transformation, making Ca²⁺ signaling axes a prominent target in pharmacological and biomaterial research.

In pharmaceutical and materials science contexts, the Ca²⁺ ion is exploited for its ability to ionically crosslink anionic polymers—most notably sodium alginate—forming stable hydrogel and capsule networks used in drug delivery, wound management, and food science. The versatility of calcium across biological signaling, clinical diagnostics, nutritional supplementation, and advanced biomaterial engineering has positioned it as one of the most actively investigated chemical entities in contemporary biomedical research.