Nowadays, DNA tetrahedron nanostructure materials, formed by self-assembly based on DNA nanotechnology, have become a hot topic in the field of DNA nanomaterials because of their stable structures, superior mechanical properties, rich modification sites, and convenient fabrication methods with high yield. The synthesis of DNA tetrahedron only needs one step of thermal denaturation using four single nucleotides as raw materials. Their functionalization molecules can be modified on the vertexes, embedded between the double-stranded DNA of the tetrahedron edges, hanged on the edges, or encapsulated in the cage-like structure of the tetrahedron. The structure of tetrahedron can also be intelligently controlled through smart design such as integrating DNA hairpin loop structure onto the edges. This review introduces the design principle of the DNA tetrahedron nanostructure materials, the functionalization and intellectualization methods based on their unique nanostructure, as well as their applications on molecular diagnosis, bioimaging and targeted drug delivery, and finally discusses the considerations in the future research of this field.

Contents
1 Introduction
2 DNA tetrahedron nanostructures
2.1 The self-assembly principle
2.2 The functional modification and intellectualization
3 The applications of tetrahedron nanostructures
3.1 Molecular diagnosis
3.2 Bioimaging
3.3 Molecular transport and targeted drug delivery
4 Conclusion and outlook