Citrate Stabilizes Hydroxylapatite Precursors: Implications for Bone Mineralization
Metadatos
Mostrar el registro completo del ítemAutor
Ruiz Agudo, Encarnación; Di Lorenzo, Fulvio; Ibáñez Velasco, Aurelia María; Rodríguez Navarro, Carlos ManuelEditorial
American Chemical Society
Materia
Citrate Calcium phosphate Liquid-like precursor Prenucleation species Amorphous calcium phosphate
Fecha
2021-05-11Referencia bibliográfica
ACS Biomater. Sci. Eng. 2021, 7, 2346−2357. [https://doi.org/10.1021/acsbiomaterials.1c00196]
Patrocinador
Spanish Government European Commission RTI2018.099565.B.I00 CGL2015-64683-P; European Commission European Commission Joint Research Centre; University of Granada ("Unidad Cientifica de Excelencia") UCE-PP2016-05; Junta de Andalucia P11-RNM-7550 RNM-179; DFG-Deutsche Forschungsgemeinschaf SFB1214; Zukunftstkolleg (University of Konstanz)Resumen
Mineralization of hydroxylapatite (HAp), the main inorganic phase
in bone, follows nonclassical crystallization routes involving metastable precursors
and is strongly influenced by organic macromolecules. However, the effect of small
organic molecules such as citrate on the formation of HAp is not well constrained.
Using potentiometric titration experiments and titration calorimetry, in
combination with a multianalytical approach, we show that citrate stabilizes
prenucleation species as well as a liquid-like calcium phosphate precursor formed
before any solid phase nucleates in the system. The stabilization of a liquid-like
precursor phase could facilitate infiltration into the cavities of the collagen fibrils
during bone mineralization, explaining the enhancement of collagen-mediated
mineralization by citrate reported in previous studies. Hence, citrate can influence
bone mineralization way before any solid phase (amorphous or crystalline) is
formed. We also show that HAp formation after amorphous calcium phosphate
(ACP) in the absence and presence of citrate results in nanoplates of about 5−12 nm thick, elongated along the c axis. Such
nanoplates are made up of HAp nanocrystallites with a preferred c axis orientation and with interspersed ACP. The nanoplatelet
morphology, size, and preferred crystallographic orientation, remarkably similar to those of bone HAp nanocrystals, appear to be an
intrinsic feature of HAp formed from an amorphous precursor. Our results challenge current models for HAp mineralization in bone
and the role of citrate, offering new clues to help answer the long-standing question as to why natural evolution favored HAp as the
mineral phase in bone.