Growth of Hydroxyapatite Crystal in the Presence of Organic Film

The growth of hydroxyapatite (HAp) crystal in the presence of hexadecylamine was investigated. Due to its high polarity and high charge density, the organic film could increase the ion supersaturation on its surface. Therefore the growth of pure HAp crystals was accelerated. Moreover, the positive headgroups of the organic film could act as recognized nucleation sites and orient the growth of HAp crystals along the <0001> direction.     

Accelerated bioactive behavior of Nagelschmidtite bioceramics: Mimicking the nano and microstructural aspects of biological mineralization

The ability of the Nagelschmidtite (Nagel) phase to promote osteogenesis, cementogenesis, and angiogenesis increased the interest in using this calcium silicophosphate bioceramic for tissue regeneration and vascularization applications. Nagel phase is a solid solution with the general formula Ca_7-xNa_x(PO₄)_2+x(SiO₄)_2-x, which allows several substitutions being Ca₇(PO₄)₂(SiO₄)₂ the most reported stoichiometry. Inspired by the well-known 45S5 bioactive glass chemical composition, we developed a synthesis route to obtain a Na-rich Nagel single phase. The effect of this bioceramic chemical and structural properties on apatite formation and crystallization mechanism is reported. The structural aspects at the nano and microscale of the mechanism of apatite growth and crystallization from the Nagel phase were compared to the formation process of Extra-Cellular Matrix (ECM) deposits in biological systems, revealing a biomimetic behavior during the apatite biomineralization process from the bioceramic.     

Use of pre-wetted lightweight fine expanded shale aggregates as internal nutrient reservoirs for microorganisms in bio-mineralized mortar

Interest in developing bio-based self-healing cement-based materials has gained broader attention in the concrete community. One of challenges in developing bio-based self-healing cement-based materials is that cell death or insufficient metabolic activity might occur when the cells are inoculated to the cement paste. This paper investigates the use of internal nutrient reservoirs via pre-wetted lightweight fine expanded shale aggregates to improve cell viability in mortar. Incorporation of internal nutrient reservoirs resulted in an increase in the vegetative cells remaining without any substantial loss in strength. These results pave the way to develop a self-healing and self-curing concrete with an extended service life.     

Mixed protein-templated luminescent metal clusters (Au and Pt) for H2O2 sensing

A simple and cost-effective method to synthesize the luminescent noble metal clusters (Au and Pt) in chicken egg white aqueous solution at room temperature is reported. The red-emitting Au cluster is used as fluorescent probe for sensitive detection of H₂O₂.     

Nanometer‐Scale Mapping of Elastic Modules in Biogenic Composites: The Nacre of Mollusk Shells

In this study, a newly developed nanoscale modulus mapping is applied in order to visualize the 2D‐distribution of mechanical characteristics in the aragonitic nacre layer of Perna canaliculus (green mussel) shells. Modulus maps provide lateral resolution of about 10 nm. They allow the aragonitic mineral (CaCO₃) tablets and the interfaces between them to be clearly resolved, which are filled by an organic substance (mainly beta‐chitin). The experimental data are compared with finite element simulations that also take into account the tip radius of curvature and the thickness of organic layers, as measured by means of scanning electron microscopy with back‐scattered electrons. Based on this comparison, the Young modulus of beta‐chitin is extracted. The obtained number, E_β = 40 GPa, is higher than previously evaluated. The collected maps reveal that the elastic modules in the nacre layer change gradually across the ceramic/organic interfaces within a spatial range four times wider than the thickness of the organic layers. This is possibly due to inhomogeneous distribution of organic macromolecules within ceramic tablets. According to the data, the concentration of macromolecules gradually increases when approaching the organic/ceramic interfaces. A behavior of this type is unique to biogenic materials and distinguishes them from synthetic composite materials. Finally, three possible mechanisms that attempt to explain why gradual changes of elastic modules significantly enhance the overall resistance to fracture of the nacre layer are briefly discussed. The experimental findings support the idea that individual ceramic tablets, comprising the nacre, are built of the compositionally and functionally graded ceramic material. This sheds additional light on the origin of the superior mechanical properties of biogenic composites.