Morphology of sodium salt of calf thymus DNA on mica, alumina, and silica surfaces: Effect of solvent and drying method

Abstract

Investigation of morphology of deoxyribonucleotide triphosphate (DNA) dried on different surfaces by atomic force microscopy (AFM) is important in DNA research that is focused on subjects of condensation for gene therapy, sizing, DNA mapping, and cancer examination. The solvent, the surface type, and the method of drying effect the morphology of DNA on solid surfaces. Ethanol and water were used as solvents, flat mica, silica, and alumina surfaces were used as the substrates in the present study. Different methods such as ambient air-drying, N2-forced flow regime drying, and freeze-drying have been applied to droplets of DNA solutions in water or ethanol on the substrates. Forced flow drying regime causes nonlinear DNA attachment on the surface and self-assembly. DNA vertical distance on mica surface was found to be 6 and 1.4 nm for DNA dried in ambient air from ethanol and water solutions, respectively. It was 1.6 nm for N2 flow drying of aqueous DNA solution on mica surface. It was 4.6, 4.6, and 1.99 nm for ambient, N2 flow, and freeze-dried aqueous DNA on alumina surfaces, respectively. Aqueous solution of DNA dried under N2 flow on silica surface had 0.8 nm vertical distance. The smallest standard deviation of 0.05 nm was observed for DNA dried under N2 flow on alumina surface.