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  • ADC and Other Drug Conjugates (ODC)
  • AqT® Reagents and Kits
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    • Custom Bioconjugation

    Since 2008, CellMosaic has grown into a premier service provider of custom bioconjugation services, offering deep expertise across projects involving complex chemistry, larger production volumes, and tight product specifications. Leveraging advanced conjugation processes, we support customers seeking both fully customized solutions and "off the shelf" conjugation products.

    CellMosaic has the resources and technical expertise to manage the entire workflow—from molecular design to final manufacturing. Our capabilities span small-molecule synthesis, biopolymer modification and conjugation, purification, analytical characterization, and product testing. Customers simply specify the molecules to be conjugated, whether commercial or proprietary, and our team designs and produces the final conjugate using high-quality commercial linkers and proven processes.

    Features and Benefits:

      • Comprehensive Solution: We source all required raw materials—internally or externally—and deliver a complete, ready-to-use final product.
      • Flexible conjugation chemistry: CellMosaic tailors conjugation strategies to each molecule and application, ensuring the best fit for your research needs.
      • High Quality: Our services include full analytical data packages, providing confidence and transparency in every final product.

    For standardized custom bioconjugation services available for direct online ordering, please click routine synthesis.

    Below are some of the typical custom bioconjugation services we offer.

    Antibody-Production Tools (Hapten-Carrier)

    CellMosaic provides comprehensive hapten–carrier bioconjugation services for antibody production. Common haptens include proteins, peptides, oligonucleotides, and small molecules, while typical carrier proteins include keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA), and ovalbumin (Ova). KLH is widely used as a carrier protein for generating antibodies, and CellMosaic routinely conjugates low–molecular weight haptens—such as peptides, small proteins, and drug molecules—to KLH. At your request, CellMosaic can also employ synthetically designed organic molecules or natural polymers as alternative carriers.

      • Antibody-production tool reagents such as modified BSA, KLH, and Ova—please click here.
      • Personalized Conjugation Kits (PerKit®) for producing your own antibodies—please click here.
      • For large-scale projects or those beyond the scope of the PerKit® configuration or our routine synthesis, please contact us for a quote.

    Assay Development Tools

    CellMosaic supports your assay development needs with high-quality custom bioconjugation services. Whether you're using a commercial detection kit or developing your own assay, we provide tailored solutions such as fluorescent- or colorimetric–labeled biopolymers, biotin- or enzyme-labeled antibodies and proteins, and peptide or nucleic acid conjugates. Common enzymes used include HRP, AP, and glucose oxidase.

    Protein Labeling and Conjugation

    The most common functional groups targeted for protein bioconjugation include hydroxyl groups (found on Thr, Ser, and the phenolic group in Tyr), carboxylic acids (at the C-terminus and on Asp and Glu), sulfhydryls (on Cys), and amines (at the N-terminus and on Lys). Histidine's imidazolyl nitrogen and arginine's guanidinyl groups can also be modified, though they are less frequently used.

    Because most proteins contain multiple copies of these same amino acids, conjugation methods using native functional groups often produce heterogeneous bioconjugates. To achieve site-specific labling, an orthogonal functional group must be introduced. The most widely used strategy is cysteine incorporation through mutagenesis. At CellMosaic, we specialize in working with Cys-mutant proteins and labeling them with a variety of molecules.

    If the protein is glycosylated, another site-specific approach is glycan-based labeling. Adjacent hydroxyl groups on the carbohydrate moiety can be oxidized to form reactive formyl groups. CellMosaic offers a range of custom linkers and reagents designed to react specifically with these formyl groups under very mild conditions.

    A less controlled method for generating more homogeneous protein conjugates involves optimizing reaction conditions in combination with effective purification strategies.

    Antibody Labeling and Conjugation

    Antibodies, like other proteins, contain natural amino acid functional groups that can be used for labeling and conjugation—for example, surface amines from Lys or the N-terminus; surface carboxylic acids from Asp, Glu, or the C-terminus; and phenolic groups from Tyr. Antibodies also have unique disulfide bonds in the hinge region that can be selectively reduced and used as specific labeling sites.

    Traditional antibody labeling methods often target multiple Lys residues. However, modifying Lys groups can alter the antibody’s overall pI, leading to increased nonspecific binding. If any modified Lys residues are located within the antigen-binding region, the resulting conjugate may become partially active or completely inactive.

    At CellMosaic, we devote significant effort to developing processes that label antibodies at a single site or a small number of predictable sites while preserving antigen-binding affinity and specificity. These optimized methods form the basis of our Personalized Conjugation Kits (PerKit®) for antibody fragmentation, labeling, and conjugation.

    Enzyme Labeling and Conjugation

    Similar to other proteins, enzyme labeling is typically non-specific and carried out through surface amines, carboxyl groups, or phenolic groups. However, some enzymes possess unique properties that can be leveraged for more selective bioconjugation. By carefully optimizing reaction conditions and applying the appropriate purification methods, it is possible to obtain single-species or more homogeneous enzyme bioconjugates.

    Nucleic Acid and Oligonucleotide Labeling and Conjugation

    The modification and conjugation of nucleic acids and oligonucleotides is quite different from other biopolymers, as they are rather inert to common bioconjugation reagents and conditions. Although there are reagents that can modify the base units, base modification may affect the binding capacity or propensity of nucleic acids and oligonucleotides. Many biopolymers cannot withstand the final basic cleavage conditions of solid phase oligo synthesis, so oligo bioconjugation usually is done in solution after oligo synthesis. On the other hand, small molecules may be incorporated into the oligo during oligo synthesis. Oligos are generally modified first with extra functional groups suitable for bioconjugation at the 5’ or 3’ end during oligo synthesis. 

    CellMosaic offers versatile oligonucleotide labeling and conjugation strategies, depending on the application of the product. Usually a single pure labeled oligo can be obtained. The advantages of our oligo labeling strategy are:

      • Freedom to attach a drug or molecule of interest at any point in the oligo.
      • Other functional groups in the molecule, such as OH, NH2, and SH, will not be affected by the labeling step.

    Oligo modification through an amino functional group is the most straightforward labeling method that often used at CellMosaic. Aliphatic primary amine can be introduced to 5' or 3' end of the oligo during synthesis. Exo-cyclic amino groups in Cytosine and Guanine are usually not modified under the reaction conditions. An amino group can also be introduced to the 5'-phosphate via carbodiimide coupling. Oligo modification through a thiol functional group is another straightforward labeling method that used at CellMosaic®. 

    Peptide and Peptidomimetic Labeling and Conjugation

    At CellMosaic, we offer custom synthesis of natural peptides as well as a wide range of modified peptides, including peptidomimetics, peptides with orthogonal functional groups, fully protected peptides, chimeric peptides, fluorescent- or biotin-labeled peptides, peptide–oligo conjugates, and peptide–antibody/protein/enzyme conjugates.

    We use automated peptide synthesizers for milligram- to gram-scale production. To ensure the highest quality, all peptides are synthesized using highly efficient HATU or HCTU coupling reagents, rather than the less efficient HBTU commonly used by other peptide providers to reduce costs. Our synthesis is performed using an Fmoc peptide protocol with method adjustments as needed to produce the highest-quality, racemization-free peptides.

    Fluorescence Labeling

    Fluorescence technologies are widely used in diagnostics, detection, drug screening, and life science research. These methods rely on the excitation of a fluorescent compound by UV light and the emission of light at a lower energy. Two main types of fluorescent compounds are commonly used for bioconjugation: small organic fluorophores, such as fluorescein, and fluorescent proteins with covalently bound chromophores, such as phycobiliproteins. Both types can be conjugated to antibodies, proteins, and other biomolecules for detection applications.

    Many fluorescent compounds are highly hydrophobic and chemically unstable, making labeling challenging. At CellMosaic, we have extensive experience in synthesizing fluorescent compounds and conjugating them to biomolecules. We can support customers with any specialized fluorescent labeling needs.

    Biotinylation

    Biotin, also known as vitamin H, is a coenzyme involved in the metabolism of fatty acids, leucine, and glucose. It binds noncovalently to streptavidin and avidin with exceptionally high affinity and specificity. In fact, the avidin–biotin interaction is the strongest known noncovalent protein–ligand interaction (Ka ≈ 10¹⁵ M⁻¹). This powerful binding has been widely applied in biotechnology for protein purification, detection, and assay development.

    The process of attaching biotin or a biotin analog to a biomolecule is called biotinylation. Because biotin is highly hydrophobic, it must be dissolved in an organic solvent before being used in bioconjugation reactions carried out in aqueous buffers. Excessive biotinylation of biomolecules—particularly proteins—can lead to aggregation, so controlling the degree of labeling is critical. Various strategies are available to achieve controlled biotinylation. Typically, the carboxyl group of biotin is derivatized to create functional derivatives suitable for conjugation without affecting its binding properties.

    Immobilization

    CellMosaic provides comprehensive immobilization services for attaching biopolymers and small molecules onto solid supports such as agarose, dextran gels, glass beads/plates, and functionalized resins/beads. Available functional groups include amine, carboxyl, hydroxyl, aminooxy, hydrazine, thiol, keto, and aldehyde. Common biopolymers we work with include proteins, peptides, and oligonucleotides, as well as small molecules such as ligands, haptens, and therapeutic compounds.

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