Intrinsic Electric Dipole Fields and the Induction of Hierarchical Form Developments in Fluorapatite–Gelatine Nanocomposites: A General Principle for Morphogenesis of Biominerals?

Abstract

Die Form folgt aus dem Dipol: Die Verteilung des elektrischen Potentials (siehe Phasenbild eines Elektronenhologramms) um die Basis‐ und Prismenflächen eines hexagonalen Fluorapatit‐Gelatine‐Nanokompositkeimes beeinflusst das Wachstum des Nanokomposits. Der Keim besteht aus Elementardipolen auf der Nanometerskala, die alle mit der gleichen Orientierung entlang der c‐Achse ausgerichtet sind. Die weitere Formentwicklung des Keimes führt zu fraktalen Mustern.

“Hidden” Hierarchy of Microfibrils within 3D‐Periodic Fluorapatite–Gelatine Nanocomposites: Development of Complexity and Form in a Biomimetic System

“…The central (orthogonal) part of Figure 7 a (marked in black) represents the young seed which-in accordance with areas 1-3 in Figure 3-is subdivided into an orange region (1), a region with bent microfibrils (2; red curves), and a waist region (3). By taking into account the experimental evidence for the presence of an electrical potential around a growing young seed, [11] the orientation of the microfibrils (red curves in Figure 7 a) follows the directions of electrical field lines generated inside the permanent dipole matrix given by the apatite-gelatine nanocomposite. During the morphogenesis of the hierarchically structured system, microfibrils are formed by the intrinsic electrical field.…”

“…The clear observation of a previously unknown ("hidden") microfibril pattern within young composite seeds was only made possible by using the FIB technique (see Experimental Section) for the careful preparation of oriented thin slices. Now it also becomes evident that the microfibril pattern within mature composite seeds, first reported a year ago, [3,11] is nothing else but a continuous pattern development passed forward by the intrinsic concept of the young seeds. The morphological details of a mature seed are shown in Figure 4 (top right) with the characteristic face developments extending at both ends of the individual.…”

“…The polar triple helices exhibit opposite charges at their ends, and by adding up all these microscopic dipoles a macroscopic electric dipole of the nanocomposite is formed. [11] Thin cuts (II [001]) of young seeds with a perfect hexagonal-prismatic habit, and without any signs of contour steps on their prism faces, were prepared by careful treatment with a focused ion beam (FIB) technique and investigated by TEM. The TEM image ( Figure 3) clearly shows that the 3D nanocomposite arrangement (as presented schematically in Figure 2) is distinctively overlaid by a pattern consisting of gelatine microfibrils with diameters scaling around 10 nm.…”

“…This, however, would imply that even the young seed bears the intrinsic conception for its future shape development. No experimental evidence for such a kind of "equipment/talent" has been obtained so far, apart from the fact that the young seed builds up an intrinsic electrical dipole field, [11] which, however, is not a sufficient condition for the shape development alone. An additional condition should be expected to explain the observation of controlled outgrowth from the inner seed volume in more detail.…”

Observation of permanent polarization distributions in bioorganic materials using a highly sensitive scanning pyroelectric microscope

“…The biomimetic growth of fluorapatite in a gelatin matrix at room temperature closely resembles the in-vivo conditions for teeth formation and is a good starting point for verifying pyroelectric responses of bio-organic materials 6 . SPEM measurements have indicated that it is a pyroelectric material with two opposed polarization domains around a central bipolar seed crystal (Fig.…”