Tubular Nanoclay-Enhanced Calcium Phosphate Mineralization and Assembly to Impart High Stiffness and Antimicrobial Properties.

Achieving superior mechanical properties of composite materials in artificially engineered materials is a great challenge due to technical bottlenecks in the size and morphological modulation of inorganic nanominerals. Hence, a "bioprocess-inspired fabrication" is proposed to create multilayered organic-inorganic columnar structures. The sequential assembly of halloysite nanotubes (HNTs), polyelectrolytes (PAAs), and calcium phosphates (CaPs) results in organic-inorganic structures. PAA plays a crucial role in controlling the formation of CaP, guiding it into amorphous particles with smaller nanosizes. The introduction of HNT induces the assembly and maturation of CaP-PAA, leading to the formation of a highly crystalline hydroxyapatite. Poly(vinyl alcohol) was then woven into HNT-encapsulated hydroxyapatite nanorods, resulting in composite materials with basic hierarchical structures across multiple scales. The fabricated composite exhibits exceptional hardness (4.27 ± 0.33 GPa) and flexural strength (101.25 ± 1.72 MPa), surpassing those of most previously developed biological hard tissue materials. Additionally, the composite demonstrates effective antibacterial properties and corrosion resistance, attributed to the dense crystalline phase of CaP. This innovative approach showcases the potential of clay minerals, particularly HNT, in the advancement of biomaterial design. The outstanding mechanical and antimicrobial properties of clay-based composites make them a promising candidate for applications in hard tissue repair, offering versatility in biomedicine and engineering.

Differential Adsorption of Dissolved Organic Matter and Phosphorus on Clay Mineral in Water-Sediment System.

Lake sediments connection to the biogeochemical cycling of phosphorus (P) and carbon (C) influences streamwater quality. However, it is unclear whether and how the type of sediment controls P and C cycling in water. Here, the adsorption behavior of montmorillonite (Mt) with different interlayer cations (Na+, Ca2+, or Fe3+) on dissolved organic matter (DOM) and P was investigated to understand the role of Mt in regulating the organic carbon-to-phosphate (OC/P) ratio within freshwater systems. The adsorption capacity of Fe-Mt for P was 3.2-fold higher than that of Ca-Mt, while it was 1/3 lower for DOM. This dissimilarity in adsorption led to an increased OC/P in Fe-Mt-dominated water and a decreased OC/P in Ca-Mt-dominated water. Moreover, an in situ atomic force microscope and high-resolution mass spectrometry revealed molecular fractionation mechanisms and adsorptive processes. It was observed that DOM inhibited the nucleation and crystallization processes of P on the Mt surface, and P affected the binding energy of DOM on Mt through competitive adsorption, thereby governing the interfacial P/DOM dynamics on Mt substrates at a molecular level. These findings have important implications for water quality management, by highlighting the role of clay minerals as nutrient sinks and providing new strategies for controlling P and C dynamics in freshwater systems.