Functionalized DNA Nanostructures as Templates for Mineralization

Objectives: DNA nanotechnology uses synthetic DNA strands as building blocks for designed complex shapes in one-, two- and three-dimensions. These nanostructures have been used as scaffolds to precisely organize proteins, polymers, nanoparticles and antibodies. Here we investigate whether DNA nanostructures are feasible platforms for the precise organization of polyaspartic acid (PAsp), a known mineral carrier, with a goal towards biomimetic mineralization for enamel regeneration. The aims of this project were: 1) to co-assemble PAsp with DNA nanostructures and 2) to test their potential use in guided mineralization. Our hypothesis is that DNA nanostructures functionalized with PAsp confer a high level of control over mineral formation.
Methods: PAsp was either co-incubated with, or covalently attached to DNA via thiol-ene click chemistry. DNA nanostructures containing PAsp were assembled through a thermal anneal cycle (90-4^oC) and characterized using atomic force microscopy. Mineralization experiments were performed by adding phosphate ions to PAsp-DNA solutions containing calcium ions. Minerals were characterized by atomic, optical and transmission electron microscopy.
Results: At low concentrations, passively added PAsp selectively deposited along DNA nanostructures. Covalent attachment between DNA and PAsp was optimized to a 97% yield. PAsp-DNA conjugates self-assembled into nanostructures with up to 100% PAsp incorporation. PAsp groups were organized on DNA nanostructures with a distance of 28.7±5.2 nm for adjacent PAsp groups (n=28, theoretical distance of 28.6 nm). All DNA-PAsp nanostructures promoted mineral growth.
Conclusions: DNA nanostructures were functionalized with PAsp groups, and these can act as platforms to investigate guided mineralization; this knowledge may be used for the design of enamel regeneration therapeutics.