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

Abstract

The correspondence of the state of alignment of macromolecules in biomimetic materials and natural tissues is demonstrated by investigating a mechanism of electrical polarity formation: An in vitro grown biomimetic FAp/gelatin composite is investigated for its polar properties by second harmonic (SHGM) and scanning pyroelectric microscopy (SPEM). Hexagonal prismatic seed crystals formed in gelatin gels represent a monodomain polar state, due to aligned mineralized gelatin molecules. Later growth stages, showing dumbbell morphologies, develop into a bipolar state because of surface recognition by gelatin functionality: A reversal of the polar alignment of macromolecules, thus, takes place close to that basal plane of the seed. In natural hard tissues (teeth and bone investigated by SPEM) and the biomimetic FAp/gelatin composite, we find a surprising analogy in view of growth-induced states of polarity: The development of polarity in vivo and in vitro can be explained by a Markov-type mechanism of molecular recognition during the attachment of macromolecules.

Stochastic polarity formation in molecular crystals, composite materials and natural tissues

“…The analysis allowed us to conclude that, in the second growth phase, the N-termini of the collagen helices are mostly aligned in the direction of growth. Because a final FAP object is bipolar and the seed represents a mono-domain state, we find here also a growth-related reversal of polarity (Burgener et al, 2015).…”

Biomineralization‐Inspired Green Synthesis of Zinc Phosphate‐Based Nanosheets in Gelatin Hydrogel

“…Note that, the ionic strength of gelatin can be modulated via zinc ions, therefore, the number of hydrogen bonds and the coupling of zinc ions with the gelatin carboxylate anions can be changed due to pH changes in gel. We postulate that zinc ions are probably able to produce parallel conformations of peptides and ordering of triple helices resulting to sheet‐like structures of ZP …”

“…We postulate that zinc ions are probably able to produce parallel conformations of peptides and ordering of triple helices resulting to sheet-like structures of ZP. 21,22 The XRD diffractograms recorded for gelatin-free ZP as well as the ZP/gelatin nanocomposite sheets synthesized at different pH are presented in Fig. 3.…”

Growth of strontium hydrogen phosphate/gelatin composites: a biomimetic approach

“…35 Hydrogels provide an effective medium with high cross-linking density for controlling the morphology of a crystal by adjusting the ratio of ion diffusion. 36 On the other hand, SrHP is known as a transient in vivo phase to produce apatite. Strontium ions bear a chemical resemblance to calcium ions due to their charge-to-size ratio, and strontium ions play a special role in bone remodeling via apatite lattice distortion, osteoblast proliferation, osteoclast differentiation, bone strength promotion and alkaline phosphatase activation.…”