Hydroxyl-carbonate apatite (HCA)

Hydroxyl-carbonate apatite (HCA) is the primary inorganic constituent of vertebrate bone and dental tissues, representing a non-stoichiometric, carbonated form of hydroxyapatite [1, 18]. Unlike pure hydroxyapatite, HCA contains carbonate ions substituted into its crystal lattice, which increases its solubility and metabolic reactivity, facilitating the dynamic process of natural bone remodeling [15, 21]. In clinical medicine, HCA is a critical component of bioactive glasses and ceramics used in bone grafts and dental implants, where its formation on the material surface promotes a strong chemical bond with host tissues [9, 17]. While not a traditional protein target, HCA serves as the pharmacological site of action for bone-seeking agents such as bisphosphonates, which adsorb to the mineral surface to inhibit osteoclast-mediated bone resorption [6, 14]. Additionally, HCA nanoparticles are being investigated as pH-sensitive drug delivery vehicles for cancer therapy, exploiting their tendency to dissolve in the acidic tumor microenvironment to release therapeutic payloads [3, 4, 11].

Other names

Carbonated hydroxyapatiteCarbonate-hydroxyapatiteBiological apatiteBone mineralDahllite

Adsorption to the mineral surface, inhibition of crystal dissolution, and pH-dependent dissolution for targeted drug release.