Abstract
Octacalcium phosphate (OCP) has been considered as the layer component of calcium phosphate, but whether it achieves the ionic-exchange ability of conventional layer components is unclear. As OCP is highly biocompatible, understanding its ionic-exchange properties would potentially expand its pharmaceutical and medical applications. Herein, we demonstrate that the substituted cations in ammonium (NH4)-substituted octacalcium phosphate (OCP-NH4) and sodium (Na)-containing ammonium phosphate solutions undergo ion exchanges with OCP interlayers. Replacing NH4+ with Na+ did not alter the crystal structure of OCP, confirming that a substituted cation exchange process similar to that in other layered compounds occurs in OCP.
Highlights
Octacalcium phosphate [OCP: Ca8H2(PO4)6$5H2O] is an attractive material in biomedical applications because its components—calcium (Ca), phosphate (PO4), and water (H2O)—are partially found in biological tissues and especially in bone.[1,2,3] OCP has a layered crystal structure with relatively high stability and low environmental loading
We demonstrate that the substituted cations in ammonium (NH4)-substituted octacalcium phosphate (OCP-NH4 was an inversely proportional to (NH4)) and sodium (Na)-containing ammonium phosphate solutions undergo ion exchanges with OCP interlayers
In a case study of ammonium-substituted OCP (OCP-NH4) and Nacontaining solutions, the present study examines the ionicexchange process of guest ions substituted in the interlayers of OCP
Summary
Octacalcium phosphate [OCP: Ca8H2(PO4)6$5H2O] is an attractive material in biomedical applications because its components—calcium (Ca), phosphate (PO4), and water (H2O)—are partially found in biological tissues and especially in bone.[1,2,3] OCP has a layered crystal structure with relatively high stability and low environmental loading. When OCP was synthesized in the presence of NH4 and Na, the Na ions (rather than NH4) were preferentially substituted because their ionic radius is similar to that of Ca (Na+: 0.102 nm, NH4+: 0.175 nm, Ca2+: 0.100 nm).[14,15,16]
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