DNA reusability and optoelectronic characteristics of streptavidin-conjugated DNA crystals on a quartz substrate

We demonstrate self-assembled double-crossover (DX) DNA crystal growth and coverage on quartz by the substrate assisted growth method. Here we introduced the novel concept of a reusability process to fabricate the DX crystals on a given substrate with a 10 nM DNA concentration, which is equal to the saturation concentration and this concentration is enough to fully cover the substrate with DX crystals. Also the DX crystals with biotinylated oligonucleotides (DXB) were constructed based on the structure of immobile crossover branched junctions. Upon streptavidin conjugation with DNA, the Raman band intensities were increased as compared to pristine DX crystals which indicate the strong bonding between the biotinylated DXB crystals and streptavidin. The DX crystals showed a relatively higher current than streptavidin conjugated DXB crystals because of the electrically insulating characteristic of streptavidin. Furthermore, the optical band gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) as well as the second band onset were determined and discussed. The HOMO-LUMO band gaps of DNA crystals, DNA crystals with biotins, and DNA crystals with biotins and streptavidin showed an inverted V-shape and the second band onsets-consistent with the electrical characteristics-revealed the increasing behavior with protein conjugation.