pH-Dependent Schemes of Calcium Carbonate Formation in the Presence of Alginates

Abstract

Artículo de publicación ISIFrom recent studies on bone and shell formation, the importance of polysaccharides in biomineralization processes is gradually being recognized. Through ion-complexation and self-assembly properties, such macromolecules have remarkable effects on mineralization. However, their influences on the different regimes of crystallization including the interactions with precursor species are unclear. The present study therefore addresses calcium carbonate mineralization in the presence of alginates, a class of linear copolymeric saccharides composed of beta-1,4 linked D-mannuronic and L-guluronic acid. During mineralization, this biopolymer is found to exert pH-dependent control over mineralization pathways in terms of the stability of prenucleation dusters, inhibitory effect toward nucleation and initially formed postnucleation products. Remarkably in the presence of this macromolecular additive; either amorphous or crystalline vaterite particles can be selectively nucleated in a pH-dependent manner. This is validated by electron microscopy wherein vaterite particles are intimately associated with alginate assemblies after nucleation at pH 9.75. At lower pH, aggregates, of amorphous particles are formed. Thus, in addition to the general focus on biochemical properties of additives, solution pH, a physiologically fundamental parameter significantly alters the scheme of mineralization.Chilean Council for Science and Technology (CONICYT); CONICYT/DAAD; Program U-Redes, Vice-presidency of Research and Development, University of Chil

Effect of Alginate from Chilean Lessonia nigrescens and MWCNTs on CaCO3 Crystallization by Classical and Non-Classical Methods

“…In this regard, it is demonstrated that the nature of glycosidic linkages, polarity, ion binding sites and stereochemistry has strong influence on CaCO 3 crystallization [13]. With this in mind and following our previous results, here we used an alginate (ALG) sample obtained from Chilean brown algae Lessonia nigrescens (ALG Les) in order to add more experimental evidence to the relationship between PS and IPS [12,[14][15][16].…”

On Mineral Retrosynthesis of a Complex Biogenic Scaffold

“…An important aspect of the structural integration involving organic and inorganic elements during shell development is the hydrogel-like nature of membrane-associated macromolecules. An organic matrix constituted by diverse macromolecules is likely to exhibit gelation properties in relation to mineralization [12]. Previous studies have shown that the degree of porosity presented by gels regulates mineral structure and form.…”

“…In relation, microscopic observations of the swelling of ethanol-dehydrated mammillae sites indicate changes in light transmittance and, hence, reveal the hydrogel-like properties of membrane-associated macromolecular assemblies (Figure 3A,B; An important aspect of the structural integration involving organic and inorganic elements during shell development is the hydrogel-like nature of membrane-associated macromolecules. An organic matrix constituted by diverse macromolecules is likely to exhibit gelation properties in relation to mineralization [12]. Previous studies have shown that the degree of porosity presented by gels regulates mineral structure and form.…”

Modulating Nucleation by Kosmotropes and Chaotropes: Testing the Waters

“…Additives that induce equilibrium shifts towards ion-association, also stimulate the formation of nucleated phase with lower solubility values. This relation has been previously identified with respect to conditions of pH and also in the presence of certain additives [28,67,68]. The applied color scheme represents a chao/kosmotropicity scale based on a previous systematic study wherein (i) chaotropes are defined as solutes that induce conformational disorder in macromolecules by either weakening water-macromolecule interactions or associating non-covalently with macromolecules and (ii) kosmotropes are solutes that preferentially hydrogen bond with water molecules and promote intermolecular interactions [69].…”

“…Therefore, the effects of sugars on mineralization cannot be absolutely associated with either the D or L enantiomeric forms but are also determined by pH-dependent parameters such as the CO 3 2− :HCO 3 − ratio and the additive conformation. Conditions of pH can alter the chemical nature of ion-clusters and the subsequent interactions between additives and mineral precursors [68,71]. Therefore, the selective trends of mineral nucleation are likely due to direct interactions with mineral species and associated hydration rather than perturbations to the bulk water phase.…”