Precise Control Of Nano Biological Interface And Its Application In Biological Sensing

The precision control of nano biological interfaces(NBIs) can achieve the construction of the device and improve the biosensor detection, DNA nanotechnology based on the Watson-Crick base pairing can control the distance, structure, size and conformation. This research is based on DNA nanostructure to construct a series of nano biological interfaces and used them to detect sarcosine which lack of powerful detect method. At last, we realize DNA assembling on the surface of the cancer cells based one the precise nano biological interface and use this method to detect the breast cancer cells by bare eyes. The following is the details:Firstly, the static structures of NBIs were constructed and regulated. We used DNA origami to construct two dimentional(2D) NBI based on Watson-Crick base pairing, and then the interface was used to control the distance of two enzymes from 10 nm to 70 nm. After constructing the 2D NBI, we continue to construct three dimentional(3D) NBI with tetrahedron DNA nanostructure. This 3D NBI was control the distance of bio-molecules from micro to nano meter. After successfully controlling the distances between the molecules from 2D to 3D, we designed five different tetrahedron DNA nanostructures, it was also to say, we designed five different NBI conformations and different conformations would influence the performance of biosensor.Secondly, after realizing the static adjustment of the NBIs, we also want to control the dynamic action of the NBIs. Reference in the study of biological enzyme allosteric effect and based on 2D static control of NBIs, we used DNA tetrahedron nanostructures with stem-loop structure, which would be influenced by effector, inhibitor, p H value and hybridization values, to control the dynamic process of the NBIs. At the same time, we found the dynamic process will influence the binding ability of probe and target so that influence the biosensor detection ability. We use the different binding ability to control the capture and release process of the target.Thirdly, after successfully precise controlling of NBIs from 2D to 3D, from static to dynamic, from distance to conformational change, we use these NBIs in biosensors. Sarcosine, which is a marker of prostate cancer, is lack of high sensitive and high specific method to detect because of small weight and low concentration in body. We used sarcosine oxidase and horseradish peroxidase to detect sarcosine by enzyme reactions to improve the specific of detection, the distance between enzymes could be control by NBIs. Combining with electrochemical method, the detection of sarcosine would be more sensitive,the detection limit of sarcosine was 50 n M. At last, we use this method to detect many serum samples from prostate cancer, prostate hyperplasia and normal males.Fourthly, based on the construction of NBIs, we used DNA aptamer binding with epithelial cell adhesion molecule(Ep CAM) on the surface of breast cancer cells(MCF-7) to assemble DNA on the surface of the cells. And then the initiator could be assembled on the surface of the cancer cells by DNA hybridization. The initiator would trigger the hybridization chain reaction to form DNA hydrogels. We could detect the cancer cells by bare eyes quantitatively with DNA protected gold nanoparticles.