Bioconjugates

Bioconjugates are molecules that combine a biological component, such as a protein, peptide, nucleic acid, or carbohydrate, with a non-biological moiety like a drug, fluorophore, polymer, or nanoparticle. The conjugation merges the specific recognition or function of the biological part with the properties of the attached entity, enabling uses in therapy, diagnostics, and research.

Conjugation strategies rely on reactive functional groups such as amines, thiols, and carboxylates, and on either stable or cleavable linkers. Common chemistries include amide bond formation, hydrazone and disulfide linkages, and bioorthogonal reactions like azide–alkyne cycloadditions. Site-specific conjugation methods aim to attach the payload at defined positions to preserve the biological activity, employing engineered residues, enzymatic tagging, or specialized motifs.

Applications span therapeutics, diagnostics, and tools for life science research. In medicine, antibody-drug conjugates and other targeted bioconjugates enable delivery of cytotoxic agents or nucleic acids to specific cells. In diagnostics and imaging, bioconjugates act as targeted reporters for PET, SPECT, or optical modalities, and as fluorescent probes or radiolabels. They also serve as research reagents, such as affinity tags, capture probes, or immobilized sensors.

Manufacturing and regulatory considerations focus on stability, safety, and product homogeneity. Design challenges include ensuring in vivo stability, minimizing off-target effects and immunogenicity, and achieving controlled release. Ongoing advances in site-specific chemistries, cleavable linkers, and precision delivery continue to expand the scope and utility of bioconjugates.