A bio-inspired nacre-like layered hybrid structure of calcium carbonate under the control of carboxyl graphene

Schematic illustration of the fabrication of GO-COOH/CaCO₃ multilayer hybrid structures: GO-COOH, the GO-COOH/CaCl₂ multilayer hybrid structure, and the GO-COOH/CaCO₃ hybrid multilayer structure (from left to right).

Peptide induced crystallization of calcium carbonate on wrinkle patterned substrate: implications for chitin formation in molluscs

We here present the nucleation and growth of calcium carbonate under the influence of synthetic peptides on topographically patterned poly(dimethylsiloxane) (PDMS) substrates, which have a controlled density of defects between the wrinkles. Experiments with two lysine-rich peptides derived from the extracellular conserved domain E22 of the mollusc chitin synthase Ar-CS1, AKKKKKAS (AS8) and EEKKKKKES (ES9) on these substrates showed their influence on the calcium carbonate morphology. A transition from polycrystalline composites to single crystalline phases was achieved with the peptide AS8 by changing the pH of the buffer solution. We analyzed three different pH values as previous experiments showed that E22 interacts with aragonite biominerals more strongly at pH 7.75 than at pH 9.0. At any given pH, crystals appeared in characteristic morphologies only on wrinkled substrates, and did not occur on the flat, wrinkle-free PDMS substrate. These results suggest that these wrinkled substrates could be useful for controlling the morphologies of other mineral/peptide and mineral/protein composites. In nature, these templates are formed enzymatically by glycosyltransferases containing pH-sensitive epitopes, similar to the peptides investigated here. Our in vitro test systems may be useful to gain understanding of the formation of distinct 3D morphologies in mollusc shells in response to local pH shifts during the mineralization of organic templates.

Biomimetic calcium carbonate concentric microgrooves with tunable widths for promoting MC3T3-E1 cell functions

Biomimetic, self-assembled calcium carbonate (CaCO(3) ) concentric microgrooves with groove widths of 5.0 and 10 μm were fabricated through simply controlling incubation temperature. Mouse pre-osteoblastic MC3T3-E1 cells were cultured on flat and microgrooved substrates of CaCO(3) and their adhesion, spreading, proliferation, alkaline phosphatase activity, and calcium content were remarkably enhanced by the microgrooves, in particular, the narrower ones. Furthermore, focal adhesions and actin filaments of MC3T3-E1 cells could be aligned on both 5.0-μm and 10-μm-wide CaCO(3) grooves. Compared with the original round nuclei on the flat substrates and expanded round nuclei on the narrower microgrooves, the MC3T3-E1 cell nuclei on 10-μm-wide CaCO(3) grooves demonstrated preferred entrapment in the grooves and significant alignment with a smaller area after two-day culture.

Facile synthesis of hierarchically mesoporous silica particles with controllable cavity in their surfaces

Novel and uniform mesoporous silica particles with controllable cavities in their surface have been fabricated using PAA and CTAB as dual templates in a mild reaction system. Herein, a series of hierarchically distinct silica particles can be obtained by simply adjusting the mass ratios (R) of PAA to CTAB. When the R value continues to decrease, the corresponding number and opening size of these cavities are also increased. However, if no PAA added, only unique monodisperse mesoporous silica spheres with uniform size of approximately 400 nm can be obtained. These specific silica particles were characterized by means of small-angle X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier-transform infrared (FT-IR) spectra, and nitrogen adsorption-desorption measurements. Results show that these unique mesoporous silica particles totally behave as an hexagonally ordered mesophase. The maximum BET surface area can be as high as 891 m(2)/g, and the maximum pore volumes can be as large as 0.27 cm(3)/g. Notably, the specific cavity features including opening size and cavity number almost do not change after calcination treatment. Moreover, a possible formation mechanism of the hierarchically distinct silica particles has been put forward, considering that the specific interface instability effect, the reduction in the surface free energy, and the synergic self-assembly of PAA and CTAB in solution can play a key role in mediating the formation of the hierarchical silica nanostructures. In general, the synthesis route is simple and straightforward for the preparation of the other biomineral nanostructures and may play an important role in microencapsulation.