Toward Visualizing Genomic DNA Using Electron Microscopy via DNA Metallization

Abstract

Electron microscopy-based DNA imaging is a powerful tool that provides a high resolution for observing genomic structures involved in biochemical processes. The first method, heavy metal shadow casting, was developed in 1948. Uranyl acetate has been widely used for DNA electron microscopic imaging since the 1960s. However, for this method, scientists must deal with government regulations for the safety and disposal. Additionally, sample preparation is often complicated and time-consuming. Recently, nanoparticles and nanowires have emerged as a new way of imaging DNA molecules under both transmission and scanning electron microscopes. However, as this technology is still in its early stages, there is room for further development. In this review, heavy metal staining, nanoparticle staining, and nanowire growth for DNA visualization are introduced. The applications of shadow casting and uranyl acetate staining in the visualization of DNA structures and protein–DNA complexes are discussed. Then, nanomaterial-based DNA staining methods are covered, including electrostatic interactions, DNA chain modification, reducing-group-modified DNA ligands and DNA–peptide/protein interactions. This review provides up-to-date information on different DNA staining approaches and their applications in DNA studies. Ultimately, it offers a new direction for genome analysis through DNA visualization.