Extracellular calcium ion (Ca2+)

Extracellular calcium ions (Ca2+) are essential divalent cations that function as structural cross-linkers within the matrices of human mucus and bacterial biofilm extracellular polymeric substances (EPS) (PMID: 18485910). By forming ionic bridges between negatively charged polymers such as mucins, extracellular DNA, and alginate, calcium significantly increases the viscosity and mechanical rigidity of these biological barriers (PMID: 10831446). In pathological states like cystic fibrosis and chronic wound infections, this calcium-mediated stabilization prevents effective mucociliary clearance and shields bacteria from both the host immune system and antibiotic penetration (PMID: 25100615). Pharmacological intervention typically involves the use of chelating agents, such as EDTA or sodium citrate, or competitive displacement agents like the alginate oligosaccharide OligoG (PMID: 27153944). These agents sequester or replace the calcium ions, leading to the rapid liquefaction of mucus and the destabilization of the biofilm architecture. This disruption facilitates the physical removal of secretions and enhances the bactericidal activity of antimicrobial therapies (PMID: 30249644).

Other names

Extracellular Ca2+Matrix-associated calciumBiofilm calciumMucus calciumDivalent calcium cation

Chelation or competitive displacement of divalent calcium ions to disrupt electrostatic cross-linking between anionic polymers (such as mucins, eDNA, and alginate), thereby reducing matrix viscosity and increasing permeability.