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Secondary Antibody

Secondary antibodies are polyclonal or monoclonal antibodies that bind to a primary antibody rather than directly to the target antigen. They are generally defined by:

  • Host species: such as goat or donkey
  • Target: such as mouse IgG or rabbit IgG
  • Specificity: whole IgG, Fc, Fab, or light chain
  • Cross-adsorption: reduction of cross-reactivity with immunoglobulins from other species

Why Use Secondary Antibodies?

  • Signal amplification: Multiple secondary antibodies may bind to one primary antibody, increasing assay sensitivity.
  • Flexible detection: One labeled secondary antibody can detect many primary antibodies from the same host species and antibody class.
  • Cost efficiency: Each primary antibody does not need to be labeled individually.
  • Broad applications: Suitable for ELISA, Western blotting, immunohistochemistry, immunofluorescence, flow cytometry, and other immunoassays.

Choosing a Detection Label

A detectable label converts antibody binding into a measurable signal. Common options include:

  • Fluorescent dyes: Direct detection for immunofluorescence, flow cytometry, fluorescent Western blotting, and multiplex assays
  • Biotin: Flexible, sensitive detection using enzyme-, fluorophore-, or reporter-labeled streptavidin
  • Enzymes: HRP and alkaline phosphatase generate colorimetric, chemiluminescent, or fluorescent signals

Why Labeling Quality Matters

Labeling must be carefully controlled to achieve a suitable degree of labeling (DOL) while preserving antibody performance. Insufficient labeling may produce weak signals, while excessive labeling can reduce binding activity, increase nonspecific binding, or cause aggregation.

Conventional NHS-activated biotin and fluorescent dyes randomly modify surface lysine residues and may increase conjugate hydrophobicity. CellMosaic’s super-hydrophilic AqT® linker technology and site-specific labeling approaches can help:

  • Maintain antibody solubility
  • Reduce aggregation
  • Preserve antigen-binding activity
  • Improve consistency at higher labeling levels
  • Deliver reliable performance in sensitive immunoassays

CellMosaic offers fluorescent dye–, biotin-, and enzyme-labeled secondary antibodies. We combine our proprietary AqT® linker technology, where applicable, with advanced conjugation processes to produce high-quality, application-ready antibody conjugates.

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