A composite sorbent modified with fluorinated aromatic polyamide, for single-step isolation of DNA from biological mixtures is developed. The sorbent is prepared by the polymer deposition from solution onto the surface of porous silica. It is shown that the polymer coating with a thickness of 4 nm is formed not only on the outer surface of the carrier particles but also on the inner pore surfaces. It is found that the material produced largely retained porosity of the pristine support and the material is selective in a one-step separation of nucleic acids and proteins by passing the bacterial lysate through a sorbent. The degree of purification of the isolated preparations of DNA is sufficient to be used directly in PCR analysis.