Biotinylated anti-human primary antibodies are immunoreagents designed for signal amplification through avidin–biotin detection systems. Produced by immunizing hosts such as goat, rabbit, mouse, or rat with purified human immunoglobulins or specific human proteins, the antibodies are affinity-purified and chemically conjugated with biotin, a water-soluble vitamin with exceptionally high affinity for streptavidin (Kd ≈ 10−14 M) and avidin. The conjugation process typically introduces 3–6 biotin molecules per antibody molecule via NHS-ester chemistry targeting primary amines on lysine residues, forming stable amide bonds that resist cleavage under standard assay conditions. Biotin's small size (244 Da) minimizes interference with antigen-binding affinity and specificity. Available specificities include anti-human IgG (H+L), anti-human IgG (Fc), anti-human IgG (Fab), isotype-specific reagents (IgG1, IgG2, IgG3, IgG4, IgA, IgM, IgE, IgD), anti-human CD markers (CD3, CD4, CD8, CD19, CD20, CD25, CD45, etc.), cytokines (IL-2, IL-4, IL-6, IFN-γ, TNF-α), and signaling proteins. Extensive cross-adsorption against serum proteins from mouse, rat, rabbit, goat, and bovine eliminates nonspecific binding in multi-species samples.
Applications
Biotinylated anti-human antibodies are employed across numerous immunoassay formats where signal amplification is desired. In ELISA, the biotin–streptavidin–peroxidase system provides substantial signal enhancement (5- to 10-fold), enabling detection of low-abundance human cytokines, antibodies, and disease biomarkers in serum, plasma, or cell culture supernatants. In immunohistochemistry and immunocytochemistry, biotinylated antibodies followed by streptavidin-HRP or streptavidin-alkaline phosphatase conjugates produce intense staining suitable for visualizing antigens in formalin-fixed, paraffin-embedded human tissues or cultured cells. In Western blotting, these antibodies enable sensitive chemiluminescent detection when combined with streptavidin-HRP and luminol-based substrates. Immunoprecipitation and pull-down assays benefit from biotinylated reagents for efficient antigen capture using streptavidin-conjugated magnetic beads or agarose resins. In flow cytometry, biotinylated antibodies with streptavidin-PE or streptavidin-APC enable signal amplification for detecting low-density human surface markers. Additional applications include tissue microarrays, dot blots, in situ hybridization, and Luminex® multiplex assays. Working dilutions are application-dependent: 1:500–1:10,000 for ELISA, 1:100–1:1,000 for immunohistochemistry, 1:1,000–1:20,000 for Western blotting. These reagents are intended for research use only and are not for diagnostic procedures.