RESUMO

We describe the preparation of a membrane composed of polypyrrole-polystyrene (PPy-PS) and its application in DNA extraction. We adopted the electrospinning technique to prepare polystyrene (PS) membranes, which we used as substrates for incorporating polypyrrole chains through an in situ chemical procedure. As a model system, we initially investigated the use of PPy-PS membranes for the extraction of salmon sperm DNA from aqueous solutions. These studies have shown that the PPy-PS membrane has a maximum adsorption capacity of 236.0 mg of DNA per gram of PPy after 30 min of exposure to a DNA solution (100 mg/L). We incorporated the PPy-PS membranes into centrifugation columns, which we used to carry out experiments for extracting and purification of DNA from curly lettuce leaves. The protocol was initially optimized by first examining the most appropriate concentration of the three components of the lysis buffer (Tris/HCl, NaCl, and EDTA-Na). We then investigated the most adequate volumes of the concentrated surfactant solution (SDS 20%) and that used in the protein and polysaccharide precipitation step (5 M potassium acetate, pH 6.3), factors that directly influence the quality and quantity of the fraction of DNA obtained. For curly lettuce leaves, both in their mature and young stages, the yield and purity of the DNA purified using the PPy-PS membrane were comparable to those obtained using a commercial kit. In both cases, the collected DNA samples presented excellent integrity and quality. These results are suggestive that these composite membranes are competitive with the commercial kits available for the extraction and purification of DNA from plants.