Sorption of nucleic acids and proteins on polyaniline and polyaramide nano-coatings as studied by spectral-correlation interferometry in a real time mode.

Polyaniline (PANI) and polyaramides deposited on the surfaces of glass slides and particulate silica were studied as adsorbents of nucleic acids and proteins by flow-through spectral correlation interferometry and solid-state extraction using spin-cartridges. Double stranded DNA from E. coli as well as pepsin, bovine serum albumin and lysozyme were the analytes studied in contact with the polymer nanolayers in phosphate buffer solution, pH 7.2. None of the coated glass slides could bind the DNA, which passed them practically without adsorption. In contact with polyaramides, the proteins of pI > 4 reversibly formed the 0.2-2.5 nm-thick adsorption layers decomposing on further rinsing with the protein-free eluent. In contact with PANI, the proteins formed stable adsorption layers at pH 7.2, which needed the pH 3.0 to be eluted. Thus, in a neutral aqueous medium optimal for separation of biopolymers, polyaramides, although did not retain DNA, had a weaker affinity to proteins as compared to PANI. Since the recovery of DNA passed through the PANI-coated silica was the maximal among the particulate adsorbents, the PANI-modified composites were preferred as the carriers for the single-step isolation of nucleic acids from complex biological mixtures.