论文部分内容阅读
Many DNA-based devices need to build stable and controllable DNA films on surfaces.However,the most commonly used method of film characterization,namely,the probe-like microscopes which may destroy the sample and substrate.Surface Forces Apparatus (SFA) technique,specializing in surface interaction studies,is introduced to investigate the effects of DNA concentration on the formation of single-stranded DNA (ss-DNA) film.The result demonstrates that 50 ng/μL is the lowest concentration that ss-DNA construct a dense layer on mica.Besides,it is also indicated that at different DNA concentrations,ss-DNA exhibit diverse morphology:lying flat on surface at 50 ng/μL while forming bilayer or cross-link at 100 ng/μL,and these ss-DNA structures are stable enough due to the repeatability even under the load of 15 mN/m.At the same time,an obvious adhesion force is measured:-6.5 mN/m at 50 ng/μL and-5.3 mN/m at 100 ng/μL,respectively,which is attributed to the ion-correlation effect.Moreover,the atomic force microscopy (AFM) images reveal the entire surface is covered with wormlike ss-DNA and the measured surface roughness (1.8±0.2 nm) also matches well with the film thickness by SFA.The desorption behaviors of ss-DNA layer from mica surface occur by adding sodium salt into gap buffer,which is mainly ascribed to the decreased ion-ion correlation force.This paper employing SFA and AFM techniques to characterize the DNA film with flexibility and stable mechanical ability achieved by ion bridging method,is helpful to fabricate the DNA-based devices in nanoscale.