Enzyme-labelled antibodies and biotin-based probe systems

High-performance fluorescent secondary antibody conjugates for immunoassays, imaging and signal amplification

Enzyme and probe conjugates are essential tools for accurate, sensitive detection in immunoassays. Whether you are performing western blotting, ELISA, immunohistochemistry (IHC), or in situ hybridisation, selecting the right conjugate directly impacts signal strength, specificity, and reproducibility.

Our range of conjugates includes enzyme-labelled antibodies and biotin-based probe systems, enabling both direct detection and signal amplification strategies tailored to your application.

Key features

• High sensitivity detection: perfect for low-abundance targets
• Multiple formats available: enzyme- and biotin-based
• Flexible detection outputs: chromogenic, chemiluminescent, or amplified
• Optimised for low background and reproducibility

Enzyme and probe conjugates

Enzyme conjugates

Enzyme-conjugated secondary antibodies generate signal through substrate-driven reactions producing either visible (chromogenic) colour or light emission (chemiluminescent output).

Enzyme-conjugated secondary antibodies generate signal through substrate-driven reactions producing either visible (chromogenic) colour or light emission (chemiluminescent output).

Horseradish peroxidase (HRP) conjugates

• Highly sensitive with fast signal development
• Compatible with multiple substrates
• Block endogenous peroxidase activity in tissue samples and avoid azide in buffers

Alkaline phosphatase (AP) conjugates

• Stable enzyme activity
• Reduced signal variability over time
• Larger enzyme size may limit tissue penetration

Biotin (probe) conjugates

Biotinylated antibodies enable powerful amplification strategies with flexible detection options.

Biotin conjugates

• Strong and specific interactions
• Multi-step amplification

Biotin-SP conjugates (long spacer)

• 6-atom space increases binding efficiency and sensitivity
• Reduced steric hindrance

Schematic representation of three commonly used antibody conjugates for immunodetection assays

Left: A biotin-conjugated antibody in which biotin is chemically linked to the antibody, enabling detection through high-affinity binding to streptavidin or avidin. Center: An HRP-conjugated antibody carrying horseradish peroxidase, an enzyme that catalyzes chromogenic, chemiluminescent, or fluorescent substrate reactions for signal generation. Right: An AP-conjugated antibody carrying alkaline phosphatase, which produces detectable signals through enzymatic conversion of phosphatase substrates. Biotin conjugates generally require a secondary streptavidin/avidin detection step, whereas HRP- and AP-conjugated antibodies provide direct enzymatic signal amplification.

Streptavidin detection systems

Bioinylated antibodies are typically detected using streptavidin-conjugated to enzymes such as HRP or AP.

• Lower background compared to avidin systems
• High specificity and stability
• Compatible with multiple amplification workflows

Choosing the right conjugate

Selecting the optimal conjugate depends on your assay requirements

Available formats

• Whole IgG secondary antibodies
• F(ab')2 fragments
• Fab fragments
• Streptavidin conjugates
• Anti-biotin reagents
• Control proteins

Materials available for download

Western blotting: Introduction and sample preparation

Colorimetric western blotting

Chemilumiscent western blotting

Direct and indirect western blotting

Fluorescent western blotting

Western blot troubleshooting guide