Application Of DNA Origami-Gold Nanoparticle Nanocomposites In The Detection Of Small Molecules

DNA origami is a DNA-based 2-dimensional(2D) or 3-dimensional(3D) nanoscale structure, which was first proposed by Rothemund in 2006. Since it has a number of advantages such as facile and rapid synthesis, high spatial resolution, easy modification at specific locations, precise spatial addressability, as well as biocompatibility, DNA origami has been widely applied in the fabrication of DNA-templated nanomaterials, bio/chemical sensors, drug nanocarriers and super-resolution molecular rulers. Very recently, DNA origami has been utilized to capture macromolecules like protein and DNA. Atomic force microscopy(AFM) can differentiate the alteration of height of the origami templates. However, so far, the application of DNA origami for the detection of small molecules has not been realized.In this project parameters affected the assembly of Au NPs with DNA origami templates were investigated. Then, aptamers were combined with the Au NPs-DNA origami nanocomposites for the detection of aflatoxin B1(AFB1). Details of this project are as follows: 1. Oligonucleotide length- and probe number-dependent assembly of gold nanoparticle on triangular DNA origamiFirst, in the fabrication process, concentrations of scaffold and staples were adjusted to achieve the high yield of the origami. The AFM sample preparation was optimized to obtain high spatial resolution images of the origami at ambient conditions. And then, we investigate the influences of the lengths of Au NPs surface-immobilized oligonucleotide and the origami-attached capture probe, as well as the number of the capture probes on the assembly efficiency of Au NPs on the origami templates. It is found that Au NPs modified with 20-mer oligonucleotides have good mono-dispersibility for the construction of DNA origami-based metamaterials. In order to enhance the assembly rate, DNA origami with 3 capture probes could be selected as the templates for the Au NPs anchoring. Although the length of DNA origami-anchored joint strand has no influence on the assembly of Au NPs on the templates, capture probes with 20-mer length is recommended to reduce the cost for the fabrication process. 2. Application of aptamer-tagged DNA origami for spatially addressable detection of aflatoxin B1A nanobiosensor involving DNA origami, Au NPs and aptamer was fabricated for the detection of AFB1. Aptamers that can specifically recognize AFB1 were tagged with triangular DNA origami templates. The binding of AFB1 molecules with the aptamer blocks the assembly of oligonucleotide-coated Au NPs on the origami, resulting in the reduction of origami-attached spots in AFM images. The DNA origami-based biosensor can be used to determine the AFB1 concentration in aqueous systems. The limit of detection(LOD) of the origami-based sensor can be as low as 0.8 ng m L-1.In this project the optimal length and probe number are proposed to efficiently anchor Au NPs for the construction of plasmonic chiral nanostructures. A novel DNA origami-based biosensor involving Au NPs and aptamer was developed for the efficient detection of AFB1. The finding of this project may not only provide useful information for the construction of DNA origami-based nanocomposites, but also extend the application of DNA origami in the small molecule sensing.