Embryonic States of Fluorapatite–Gelatine Nanocomposites and Their Intrinsic Electric‐Field‐Driven Morphogenesis: The Missing Link on the Way from Atomistic Simulations to Pattern Formation on the Mesoscale

Abstract

The shape development of fluorapatite (FAP)–gelatine nanocomposites is revealed by means of HRTEM investigations starting from molecular dimensions up to the formation of mesoscaled (elongated) hexagonal prisms. The composite nature of the aggregates is proved by IR spectroscopy and by chemical analyses on all states of shape development. The initial states are characterized by triple‐helical fiber protein bundles, which are mineralized step‐by‐step forming and fixing nanoplatelets of FAP in a mosaic arrangement. After being fully mineralized the bundles form elongated composite nanoboards. In the next step of the growth process the boards aggregate to bundles of boards which are in a more or less parallel alignment with respect to each other. By adding up more and more composite nanoboards a critical size is reached and an electric field is developed, which takes over control and directs the further development of the aggregates. This kind of electric‐field‐directed growth of the elongated polar nanoboards additionally leads to the formation and inclusion of protein nanofibrils into the growing composite aggregate. By this method, cone‐like nanofibril structures develop along the long axis of the aggregates accompanied by more perfect parallel alignment of the composite boards within the aggregates. Further shape development is characterized by adding up composite nanoboards, in particular to increase the third dimension in volume. This thickening process preferably takes place in the middle part of the elongated aggregates and finally proceeds to their basal ends until a perfect hexagonal prismatic seed is formed, which then is ready for further shape development on the micrometer scale.

Polar Nature of Biomimetic Fluorapatite/Gelatin Composites: A Comparison of Bipolar Objects and the Polar State of Natural Tissue

“…Here, biomimetic materials provide an interesting approach to study such self-assembly principles by excluding complex cell activities.The biomimetic fluoraptite/gelatin composite shows both compositional and structural similarities to natural hard tissues. [1][2][3][4][5] We are interested to investigate particularly the polar state of the composite, because the formation of a polar material requires a mechanism of growth relying on a process of molecular recognition. It is known that the collagen framework of natural tissues as found in bone, dentin or tendon show a macroscopic polarization.…”

Reversed Crystal Growth of Calcite in Naturally Occurring Travertine Crust

“…For example, crystals of CaCO 3 [18][19][20][21][22][23][24], ZnO [25][26][27][28], and fluorapatite [29,30] have been grown in gel matrices or in the presence of polymers such as gelatin, chitosan, gum arabic and agarose. During the preparation process, these structure directing agents may play the role of a template and a surfactant.…”

Otoconia: Mimicking a calcite-based functional material of the human body. From basic research to medical aspects

“…The real challenge for deeper understanding of the nucleation and shape development of a biomineral (or a biomimetic material) is to clarify the structural relations between the inorganic and the organic components from the atomic level to the meso/macro-scale. This strategy was successfully followed in recent investigations on fluorapatitegelatine composites, and it was shown that even perfectly developed hexagonal prismatic individuals (the Bragg diffraction pattern corresponds to a single crystal) are not just "simple" single crystals, but actually represent a nano-composite superstructure with an additionally integrated (mesoscopic) hierarchy of gelatine microfibrils [22,23].…”