Advances in peptides and nucleic acids synthesis, areas where BioSynthesis has over twenty years of experience, have promoted the development of bioconjugates where these molecules are either cross-linked to each other or to other compounds to yield products with distinct properties. BioSynthesis, benefiting of its expertise in peptides and nucleic acids synthesis, is developing new methods for the efficient production of bioconjugates. These bioconjugates are not limited to peptide-nucleic acid derivatives, but either of these two moieties can be substituted by another compound such as a polysaccharide, lipid, synthetic polymer and small molecules. Depending on the bioconjugates? nature they can have applications in qualitative/quantitative assays, targeting of specific cells for diagnostic and/or therapeutic purposes, transfer of compounds across cell membranes, modulation of certain biological activities and other uses. BioSynthesis? synthetic approach to produce peptides and nucleic acids allows the introduction of modifications, such as residues with certain functional groups, e.g. hydroxyl, thiol, amine and others, to select the chemical reaction needed to link both moieties of bioconjugates covalently. It also allows the insertion of a spacer with an optimal length to allow the cross-linking of both moieties without steric hindrance. Although bioconjugates are products with physical chemical properties, e.g. lipophilicity and charge, different from their original free moieties, each cross-linked moiety retains largely its biological activity. This feature makes bioconjugates an attractive approach to allow particular compounds circumvent certain barriers, enter the cell and exert their biological activities. Although the first bioconjugates were largely proteins linked to peptides, enzymes, or small reporting molecules like fluorescein, the most promising uses of bioconjugates are in the nucleic acids/oligonucleotides area where these compounds are linked largely to peptides, and in some cases to lipids. While oligonucleotides are polar, hydrophilic and have a negative net charge, peptides can be polar and/or non-polar, have both hydrophilic and lipophilic regions and have a negative, positive or neutral net charge. Due to their properties, nucleic acids cannot pass across the cell membrane, which is lipophilic and negatively charged because of its sialic acid content. Conjugation of an oligonucleotide to some peptides that can move through the cell membrane would facilitate the passage of this conjugate across it for delivery into the cell's cytosol. Oligonucleotides can also be conjugated to lipids to yield derivatives with lipophilic properties that are capable to pass across the cell membrane.