Bioconjugation refers to the process of joining molecules together, wherein at least one of the substances involved is a biomolecule, often an antibody, protein, or oligonucleotide. These bioconjugates find application in various fields such as biotechnology, medicine, and nanotechnology for tasks like biomolecule detection, assays, targeting, and monitoring. Practical uses encompass attaching fluorescent markers to antibodies for microscopy and flow cytometry, linking antibodies to beads for immunoprecipitation, joining antibodies with drugs for therapeutic progress, and interlinking proteins to identify their interactions in biological contexts.

The technique of Antibody-Drug Conjugation (ADC) utilizes monoclonal antibodies to deliver potent pharmaceutical ingredients specifically to intended cells. This conjugated form enhances the therapeutic efficacy of the pharmaceuticals while sparing non-targeted cells, contributing to targeted and safer drug delivery. Optimal bioconjugation depends on factors like the reagent’s chemical and physical attributes, length, molecular size, water compatibility, cleavability, application requirements, and targeted functional groups for coupling.

Diverse types of crosslinkers are involved in bioconjugation, categorized as homobifunctional or heterobifunctional. Most bioconjugate reagents possess two reactive groups positioned at opposite ends of an organic spacer. Homobifunctional compounds feature identical reactive groups, while heterobifunctional compounds have different ones. Heterobifunctional reagents offer advantages in forming bioconjugates, with each end reacting specifically with distinct functional groups.

The choice of crosslinker or modification reagent is influenced by the pre- and post-conjugation size of the target molecule. The spacer arm of the reagent determines the length of the final compound, serving as a molecular ruler to measure distances between functional groups in biomolecules.

Selecting cleavable or non-cleavable crosslinkers hinges on whether the interacting biomolecules require isolation and analysis, as in the case of protein-protein interactions. Hydrophobic crosslinkers benefit applications involving cell membrane penetration, while hydrophilic ones prevent aggregation and maintain solubility in water. Hydrophilic bioconjugation reagents offer enhanced biocompatibility.

Bioconjugation typically targets the most reactive functional groups in biomolecules, often associated with N, O, and S heteroatoms. These groups possess unshared electron pairs and can spontaneously react with compatible electrophilic groups on crosslinkers. When required functional groups are absent, specialized reagents can create suitable groups for bioconjugation. Commonly targeted natural functional groups in biomolecules include amines, thiols, hydroxyls, carboxylates, aldehydes, organic phosphates, and reactive hydrogens.

The development and manufacturing of Antibody-Drug Conjugates (ADCs) necessitate expertise in both small and large molecule development, formulation, testing, and manufacturing. Partnering with experienced entities possessing the required skills and containment facilities can facilitate the progression of ADCs to market. ADCs pose challenges, demanding advanced manufacturing setups and specialized equipment to ensure purity, homogeneity, and stability during characterization.