Self-sieving DNA over superhydrophobic surfaces: a Raman spectroscopy study

The Raman spectra of DNA fibers were studied before and after suspension over superhydrophobic surface (SHS). At the end of the dehydration process of a droplet of nucleic acids solution over SHS, two structural areas appear: (i) a thicker droplet residual spot and (ii) a thinner free-standing, self-oriented DNA extended fibers region. For specimens deposited on reference samples (CaF2 slides), buffer contribution overrides the total Raman spectrum, while for free-standing lDNA, biological signature comes out readily with no interference. Our spectroscopy results confirm that a mechanical sieving effect occurs spontaneously during lDNA suspension process over superhydrophobic devices. Tailored designed devices and sample preparation separate small non-interacted molecules from the bundles and remove, concentrating, the non-suspended material in a defined area of the SHS. At the end of the process, helices retain only the ions that effectively have interacted with the DNA strand in solution, while all the other compounds were sieved away from the areas of interest. The self-sieving effect herein shown will provide a step forward for biomaterials studies as it allows the characterization of dilutions otherwise not detectable. The samples, autonomously purified, retain the effective interaction with environmental stresses free from any other misleading contribution allowing for characterization in optimal condition.