The invention relates to a structured mixed phase formed by the incorporation of a biological macromolecule into a liquid-crystal phase of amphiphiles, preferably a lamellar phase, wherein said biological macromolecule is present in said structured mixed phase in an amount of at least 5% by weight, based on the amphiphilic compounds constituting said liquid-crystal phase of amphiphiles, and wherein at least one of the two entities consisting of the biological macromolecules, on the one hand, and all the amphiphilic compounds, on the other, is of an uncharged nature.The biological macromolecules incorporated into the structured mixed phases of the invention are preferably selected from polynucleotides, particularly DNA or RNA, proteins and polysaccharides.The invention further relates to vesicles obtained by dispersion of the above structured mixed phases.