Uniaxial Hydroxyapatite Growth on a Self-Assembled Protein Scaffold.

Alexander L Danesi,Bernhard Ganss,Dimitra Athanasiadou,Mehrnoosh Neshatian,Johan Bonde,Karina M M Carneiro,Alina Phen,James Holcroft,Ahmad Mansouri

doi:10.3390/ijms222212343

Alexander L Danesi, Bernhard Ganss + Show 7 more

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https://doi.org/10.3390/ijms222212343

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Abstract

Biomineralization is a crucial process whereby organisms produce mineralized tissues such as teeth for mastication, bones for support, and shells for protection. Mineralized tissues are composed of hierarchically organized hydroxyapatite crystals, with a limited capacity to regenerate when demineralized or damaged past a critical size. Thus, the development of protein-based materials that act as artificial scaffolds to guide hydroxyapatite growth is an attractive goal both for the design of ordered nanomaterials and for tissue regeneration. In particular, amelogenin, which is the main protein that scaffolds the hierarchical organization of hydroxyapatite crystals in enamel, amelogenin recombinamers, and amelogenin-derived peptide scaffolds have all been investigated for in vitro mineral growth. Here, we describe uniaxial hydroxyapatite growth on a nanoengineered amelogenin scaffold in combination with amelotin, a mineral promoting protein present during enamel formation. This bio-inspired approach for hydroxyapatite growth may inform the molecular mechanism of hydroxyapatite formation in vitro as well as possible mechanisms at play during mineralized tissue formation.

Highlights

The formation of mineralized tissues is an intrinsically hierarchical process, where cells first deposit an extracellular matrix (ECM) that must achieve the appropriate nanoscale order to guide and promote mineral growth
The dimensions of nanoengineered (recombinant) amelogenin (NA) nanoribbons were comparable to those obtained with recombinant amelogenin after 21 days of incubation, as characterized by optical microscopy (OM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images (Supplementary Figure S1)
We demonstrated for the first time that two recombinant proteins, amelotin and NA, can promote guided HAP mineralization along self-assembled nanostructures in vitro

Summary

Introduction

The formation of mineralized tissues is an intrinsically hierarchical process, where cells first deposit an extracellular matrix (ECM) that must achieve the appropriate nanoscale order to guide and promote mineral growth. During the process of enamel formation, ECM proteins, predominantly amelogenins, in combination with mineral promoting proteins guide the formation of highly ordered, complex crystal structures before being degraded by proteases and almost completely removed from the tissue [3]. Amelotin (AMTN), an enamel protein, has been shown to be a mineral promoter both in vitro and in vivo [11,12,13,14]. The mineral formation rate depends on factors such as the supersaturation, temperature, and organic matrix. Organic matrices and especially proteins can increase the nucleation rate and subsequent crystal growth [15].

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