DNA adsorption and desorption on mica surface studied by atomic force microscopy

The adsorption of DNA molecules on mica surface and the following desorption of DNA molecules at ethanol-mica interface were studied using atomic force microscopy. By changing DNA concentration, different morphologies on mica surface have been observed. A very uniform and orderly monolayer of DNA molecules was constructed on the mica surface with a DNA concentration of 30 ng/μL. When the samples were immersed into ethanol for about 15 min, various desorption degree of DNA from mica (0-99%) was achieved. It was found that with the increase of DNA concentration, the desorption degree of DNA from the mica at ethanol-mica interface decreased. And when the uniform and orderly DNA monolayers were formed on the mica surface, almost no DNA molecule desorbed from the mica surface in this process. The results indicated that the uniform and orderly DNA monolayer is one of the most stable DNA structures formed on the mica surface. In addition, we have studied the structure change of DNA molecules after desorbed from the mica surface with atomic force microscopy, and found that the desorption might be ascribed to the ethanol-induced DNA condensation.

DNA adsorption and desorption on the mica surface have been studied. It is interesting that the desorption degree of DNA decreases as the DNA concentration increases. When DNA concentration is very low (1 ng/μL), almost all of the DNA molecules have desorbed from the mica surface (as shown in above scheme). The further reasons of DNA adsorption and desorption on mica have been discussed in the article.Highlights► DNA adsorption and desorption on mica surface was studied by AFM. ► The influence of DNA concentration on DNA structure and desorption was investigated. ► Most stable DNA structure was found. ► Reason for DNA desorption degree was discussed.