A comparative study of the dissolubility of pure and silicon substituted hydroxyapatite from density functional theory calculations

The Mutual Incorporation of Mg2+ and CO32- into Hydroxyapatite: A DFT Study

Hydroxyapatite (HA) with a stoichiometry composition of Ca₁₀(PO₄)₆(OH)₂ is widely applied for various biomedical issues, first of all for bone defect substitution, as a catalyst, and as an adsorbent for soil and water purification. The incorporation of foreign ions changes the acid-base relation, microstructure, porosity, and other properties of the HA materials. Here, we report the results of calculations of the density functional theory and analyze the possibility of two foreign ions, CO₃^2- and Mg²⁺, to be co-localized in the HA structure. The Na⁺ was taken into account for charge balance preservation. The analysis revealed the favorable incorporation of CO₃^2- and Mg²⁺ as a complex when they interact with each other. The energy gain over the sole ion incorporation was pronounced when CO₃^2- occupied the A position and Mg²⁺ was in the Ca(2) position and amounted to -0.31 eV. In the most energy-favorable complex, the distance between Mg²⁺ and the O atom of carbonate ion decreased compared to Mg…O distances to the surrounding phosphate or hydroxide ions, and amounted to 1.98 Å. The theoretical calculations agree well with the experimental data reported earlier. Understating the structure-properties relationship in HA materials varying in terms of composition, stoichiometry, and morphology paves the way to rational designs of efficient bio-based catalytic systems.

Understanding Zinc-Doped Hydroxyapatite Structures Using the First-Principles Calculations and Convolutional Neural Network Algorithm

Element doping is widely used to improve the performance of materials by changing their intrinsic properties. However, the lack of direct crystallographic structures for dopants has restricted the effective high-throughput...

The Morphology of Hydroxyapatite Nanoparticles Regulates Cargo Recognition in Clathrin-Mediated Endocytosis

The clathrin-associated protein adaptin-2 (AP2) is a distinctive member of the hetero-tetrameric clathrin adaptor complex family. It plays a crucial role in many intracellular vesicle transport pathways. The hydroxyapatite (HAp) nanoparticles can enter cells through clathrin-dependent endocytosis, induce apoptosis, and ultimately inhibit tumor metastasis. Exploring the micro process of the binding of AP2 and HAp is of great significance for understanding the molecular mechanism of HAp's anti-cancer ability. In this work, we used molecular modeling to study the binding of spherical, rod-shaped, and needle-shaped HAps toward AP2 protein at the atomic level and found that different nanoparticles' morphology can determine their binding specificity through electrostatic interactions. Our results show that globular HAp significantly changes AP2 protein conformation, while needle-shaped HAP has more substantial binding energy with AP2. Therefore, this work offers a microscopic picture for cargo recognition in clathrin-mediated endocytosis, clarifies the design principles and possible mechanisms of high-efficiency nano-biomaterials, and provides a basis for their potential anti-tumor therapeutic effects.