The Study Of DNA Monolayer Regulated By Stimulus-Responsive Polymers

Deoxyribonucleic acid(DNA)monolayer is an important component of DNA microarray and biosensor,which has a wide application in bioengineering.The structure of DNA monolayer includes the height,the orientation and the density of DNA.The regulation of the structure has great influence on the application of DNA monolayer.The electrical property of the surface which the DNA monolayer attached have a significant impact on the property of the DNA monolayer.The control of the DNA orientation can improve the hybridization rate and sensitivity of DNA monolayer.There are many methods to regulate of DNA orientation.Usually electric field is used to control the orientation of DNA probes,but additional electrostatic effects which caused by the applied electric field will limit the application of DNA monolayer.Based on this,a new methods is considered to regulate the orientation of DNA in this thesis.The specific research contents are as follows:(1)The surface electrical properties of nanoparticles regulated by the p H-responsive polymer polyethylenimide(PEl)is studied by a molecular theory.The effective net charge density of nanoparticle surface is calculated to characterize the charge inversions of nanoparticle surface.Then,the effect of the affinity of PEI to the surface and the surface charge density on the charge inversions are studied,and the reason why double charge reversal is not easy to occur is revealed.Further,the influence of salt concentration,PEI concentration,PEI length and particle radius on bare surface charge density is considered.The theoretical results agree with the experiments.(2)The temperature-responsive polymer poly(N-isopropylacrylamide)(PNIPAm)is used to regulate the orientation of DNA.Firstly,the theoretical model of DNA orientation regulated by PNIPAm is established,and molecular theory is used to analyze the model.Secondly,the influence on surface coverage of PNIPAm to DNA orientation under different temperatures is explored.The physical mechanism of the temperature-regulated orientation of DNA is revealed according to the molecular structure and potential of mean force of the system.Finally,the DNA orientation influenced by other factors in the system is explored.