Selective Crystal Growth Regulation by Chiral α-Hydroxycarboxylic Acids Improves the Strength and Toughness of Calcium Sulfate Cements

Abstract

Natural biominerals, such as bones and teeth, use acidic matrix biomolecules to control growth, morphology, and organization of the brittle hydroxyapatite crystals. This interplay provides biominerals with outstanding mechanical properties. Recently, we reported that the l-enantiomer of chiral tartaric acid has a potent regulatory effect on the crystal structure and mechanical performance of brushite cement, a mineral with a monoclinic crystal system. We hypothesized that this strategy could be applied using various chiral α-hydroxycarboxylic acids to enhance the mechanical performance of calcium sulfate dihydrate cements, another mineral belonging to the monoclinic crystal system. Calcium sulfate cements are widely used in dentistry, medicine, and construction, but these cements have low mechanical properties. In this work, we first determined the impact of different chiral α-hydroxycarboxylic acids on the properties of calcium sulfate cements. After that, we focused on identifying the regulation effect of chiral tartaric acid on gypsum crystals precipitated in a supersaturated solution. Here, we show that the selective effect of α-hydroxycarboxylic acid l-enantiomers on calcium sulfate crystals improved the mechanical performance of gypsum cements, while d-enantiomer had a weak impact. Compare to the calcium sulfate cements prepared without additives, the presence of l-enantiomer enhanced the compressive strength and the fracture toughness of gypsum cements by 40 and 70%, respectively. Thus, these results prove the generalizability of this approach and help us to fabricate high-strength cements.

Chirality Supramolecular Systems: Helical Assemblies, Structure Designs, and Functions

“…They found the compressive strength and fracture toughness of the brushite bioceramics can prominently improve by incorporating L-tartaric acid, but is the opposite when introducing the D-enantiomer. Moussa et al [197] explored the calcium sulfate cement properties under the induction of the chiral 𝛼hydroxycarboxylic acids. Figure 11a shows the morphology and mechanical performance of the cement under the regulations of different chiral additives.…”

Understanding Hierarchical Structure Construction Strategies and Biomimetic Design Principles: A Review

“…Figure 11e shows the chiral additives on the regulation of mineral properties. [ 267 ] Compared with the D‐enantiomer, the minerals combined with the L‐enantiomer exhibit better mechanical performances, suggesting the importance of chiral selectivity in the mineralization process. Tremel et al discovered that macromolecular additives can create defects in the crystal lattice and strengthen the crystal against fracture.…”

“…Reproduced with permission. [267] Copyright 2020, American Chemical Society. chiral photonic crystals by Langmuir-Schaefer assembly of colloidal inorganic nanowires, where the composite materials show different colors when changing the stacking angles.…”

“…e) The incorporation of chiral molecules on the mechanical performance regulation of minerals. Reproduced with permission [267]. Copyright 2020, American Chemical Society.…”

Tuning Sugar‐Based Chiral and Flower‐Like Microparticles

“…Among all the reported chiral and porous microparticles, precise control and manipulation of the morphology are still a big challenge. To date, only a few methods are reported to tune the morphology of the superstructures, including the addition of amino acids [8,20] or α-hydroxycarboxylic acids, [21] controlling temperature [7c] or pH, [22] adjusting the solvents quality [22,23] and using external forces like surface tension torque. [2b] Nevertheless, the formation of chiral and porous flower-like microparticles using the same materials, especially monosaccharides without applying external stimuli, is still understudied.…”