Encoder Troubleshooting – Encoding Primaries at Concentrations Other than 1 µg/mL

Our HCR™ HiFi Encoding protocol is optimized around a working primary antibody concentration of 1µg/mL. In our experience, this condition gives a good balance between encoding efficiency and signal for most primaries.

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The ideal ratio between primary antibody and Encoder A/B volumes can vary by antibody. If your working concentration is much higher or much lower than 1 µg/mL, HCR™ Gold IF performance can be affected, and you may need to adjust either the primary concentration, the amount of Encoder, or both.

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In most cases, we recommend first adjusting your primary to 1 µg/mL and using the standard Encoding conditions described below.If you prefer to keep your existing primary concentration, you can instead scale the amount of Encoder A/B proportionally to match your primary concentration.

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If you have too much primary antibody compared to the amount of Encoder A/B, then not all of the antibodies will be encoded. The extra, unencoded antibodies can still bind to the target and take up binding sites. This blocks the encoded antibodies from binding, so fewer of them are available to start HCR™ Gold amplification. And as a result, the signal is weaker.

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Below are example workflows for standard, higher, and lower primary concentrations.  

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Standard Condition: 1µg/mL Primary

For a primary antibody at 1 µg/mL concentration and a final volume of 1 mL HCR™ HiFi Antibody Probe solution, use 1 µL of Encoder A and 1 µL of Encoder B per 100 µL of final probe solution.

Example: Encoding 1 mL of HCR™ HiFi Antibody Probe Solution

1. Aliquot 1 µg of your primary antibody into a clean tube.
2. Add 10 µL of HCR™ HiFi Encoder A. Mix gently and incubate at room temperature for ≥ 5 min.
3. Add 10 µL of HCR™ HiFi Encoder B. Mix gently and incubate at room temperature for ≥ 5 min.
4. Bring to a final volume of 1 mL with HCR™ HiFi Antibody Buffer to prepare your HCR™ HiFi Antibody Probe solution.

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High Concentration Primary: Example at 3 µg/mL

If your working primary concentration is higher than 1 µg/mL, you can compensate by increasing the amount of Encoder A/B proportionally.

For a primary antibody at 3 µg/mL concentration, we recommend using 3× the standard Encoder amount (i.e., 3µL of Encoder A and 3 µL of Encoder B per 100 µL of final probe solution).

Example: Encoding 1 mL of HCR™ HiFi Antibody Probe Solution at 3 µg/mL

1. Aliquot 3 µg of your primary antibody into a clean tube.
2. Add 30 µL (3 ×10 µL) of HCR™ HiFi Encoder A. Mix gently and incubate at room temperature for ≥ 5 min.
3. Add 30 µL (3 ×10 µL) of HCR™ HiFi Encoder B. Mix gently and incubate at room temperature for ≥ 5 min.
4. Bring to a final volume of 1 mL with HCR™ HiFi Antibody Buffer to prepare your HCR™ HiFi Antibody Probe solution.

If signal is still low, you can:

• Increase Encoder volumes further (e.g., 4×), or
• Consider reducing primary concentration toward 1 µg/mL, especially if you suspect competition from unencoded primaries or see elevated background.

Low Concentration Primary: Example at 0.1 µg/mL

If your primary is at a lower concentration than 1 µg/mL, our first recommendation is to increase your working concentration toward 1 µg/mL if possible (e.g., by concentrating the antibody or adjusting your dilution). If you can’t do that, you can scale EncoderA/B volumes down proportionally.

For a primary antibody at 0.1 µg/mL concentration, use 0.1× the standard Encoder amount (i.e., 0.1 µL of Encoder A and 0.1 µL of Encoder B per 100 µL of final probe solution).

Example: Encoding 1 mL of HCR™ HiFi Antibody Probe Solution at 0.1 µg/mL

1. Aliquot 0.1 µg of your primary antibody into a clean tube.
2. Add 1 µL (0.1× 10 µL) of HCR™ HiFi Encoder A. Mix gently and incubate at room temperature for ≥ 5 min.
3. Add 1 µL (0.1× 10 µL) of HCR™ HiFi Encoder B. Mix gently and incubate at room temperature for ≥ 5 min.
4. Bring to a final volume of 1 mL with HCR™ HiFi Antibody Buffer to prepare your HCR™ HiFi Antibody Probe solution.

Note: 0.1 µg/mL is the lowest primary concentration we recommend for Encoding. Going any lower can reduce encoding efficiency and may result in poor signal.

If signal is suboptimal at this low concentration, you may need to:

• Increase the primary concentration, or
• Carefully titrate Encoder amounts (e.g., slightly higher than 0.1×) while monitoring for changes in signal and background.

In practice, you may need to titrate Encoder volumes (up or down) and/or titrate primary concentrations (up or down) to find the sweet spot for your specific antibody. Running a small panel of conditions (e.g., ±2–3× around your starting Encoder volumes) can quickly guide you to a robust, reproducible Encoding setup for HCR™ Gold IF.