Origin of the biphase nature and surface roughness of biogenic calcite secreted by the giant barnacle Austromegabalanus psittacus
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Checa González, Antonio G.; Macías Sánchez, Elena; Rodríguez Navarro, Alejandro B.; Sánchez Navas, Antonio; Lagos, Nelson A.Editorial
Springer Nature
Materia
Biomaterials Mineralogy Nanoscale biophysics Structural materials
Date
2020-10-08Referencia bibliográfica
Checa, A.G., Macías-Sánchez, E., Rodríguez-Navarro, A.B. et al. Origin of the biphase nature and surface roughness of biogenic calcite secreted by the giant barnacle Austromegabalanus psittacus. Sci Rep 10, 16784 (2020). [https://doi.org/10.1038/s41598-020-73804-8]
Sponsorship
Instituto de Salud Carlos III Spanish Government CGL2017-85118-P CGL2015-64683-P; Unidad Cientifica de Excelencia of the University of Granada UCE-PP2016-05; Junta de Andalucía RNM363; ANID-Chile FONDECYT 1140938 PCI ANID REDES 170106 PIA ANID ANILLOS ACT172037Abstract
The calcite grains forming the wall plates of the giant barnacle Austramegabalanus psittacus have
a distinctive surface roughness made of variously sized crystalline nanoprotrusions covered by
extremely thin amorphous pellicles. This biphase (crystalline-amorphous) structure also penetrates
through the crystal’s interiors, forming a web-like structure. Nanoprotrusions very frequently
elongate following directions related to the crystallographic structure of calcite, in particular,
the <− 441> directions, which are the strongest periodic bond chains (PBCs) in calcite. We propose
that the formation of elongated nanoprotrusions happens during the crystallization of calcite from
a precursor amorphous calcium carbonate (ACC). This is because biomolecules integrated within the
ACC are expelled from such PBCs due to the force of crystallization, with the consequent formation of
uninterrupted crystalline nanorods. Expelled biomolecules accumulate in adjacent regions, thereby
stabilizing small pellicle-like volumes of ACC. With growth, such pellicles become occluded within
the crystal. In summary, the surface roughness of the biomineral surface reflects the complex shape
of the crystallization front, and the biphase structure provides evidence for crystallization from an
amorphous precursor. The surface roughness is generally explained as resulting from the attachment
of ACC particles to the crystal surface, which later crystallised in concordance with the crystal lattice.
If this was the case, the nanoprotrusions do not reflect the size and shape of any precursor particle.
Accordingly, the particle attachment model for biomineral formation should seek new evidence.