The guiding principle for mineralized tissue formation is that mineral growth occurs through the interaction of Ca2+ and phosphate ions with extracellular matrix (ECM) proteins. Recently, nanoengineered DNA structures have been proposed as mimics to ECM scaffolds. However, these principles have not been applied to mineralized tissues. Here, we describe DNA nanostructures, namely, a DNA nanotube and a DNA origami rectangle that are site specifically functionalized with a mineral-promoting “SSEE” peptide derived from ECM proteins present in mineralized tissues. In the presence of Ca2+ and phosphate ions (mineralizing conditions), site-specific calcium phosphate formation occurred on the DNA nanostructures. Amorphous calcium phosphate or hydroxyapatite was formed depending on the incubation time, shape of the DNA nanostructure, and amount of Ca2+ and phosphate ions present. The ability to design and control the growth of hydroxyapatite through nanoengineered scaffolds provides insights into the mechanisms that may occur during crystal nucleation and growth of mineralized tissues and can inspire mineralized tissue regeneration strategies.

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.

Strategies to improve hydroxyapatite mineralization for enamel repair are essential for tissue regeneration. Amelogenin and amelotin (AMTN) are enamel matrix proteins playing critical roles in enamel formation. Amelogenin acts as a scaffold for hydroxyapatite, while AMTN (specifically its ‘SSEEL’ domain) is necessary for proper enamel mineralization. The functional relationship between recombinant AMTN and amelogenin, and their combined ability to guide uniaxial hydroxyapatite growth in vitro has been investigated recently. However, incorporation of the active domain of AMTN within recombinant amelogenins has not been studied yet. Here we describe the synthesis of modified amelogenin by inserting, internally and at its C‐terminus, the mineralizing AMTN‐derived motif SSEEL. C‐terminus modified amelogenin promoted hydroxyapatite formation, whereas internal incorporation of the motif initially resulted in amorphous calcium phosphate formation. Here we show that modified amelogenin with the mineralizing AMTN‐motif SSEEL can promote hydroxyapatite growth. These results give new insights for mineralized tissue regeneration using recombinamer proteins.