Excessive Non-Specific Background Signal in Competitive ELISA

Symptom

High background optical density readings are observed across wells, obscuring the difference between standards and samples. Signal persists even in wells without primary antibody or sample.

1. 1 Detector conjugate concentration too high causing non-specific plate binding
2. 2 Inadequate blocking of non-specific binding sites on microplate surface
3. 3 Insufficient washing allowing unbound conjugate to remain in wells
4. 4 Blocking buffer composition not optimal for the specific antibody-antigen system

1. 1 Run control wells omitting primary antibody and sample to identify non-specific detector conjugate binding
2. 2 Decrease detector conjugate concentration through serial dilution optimization
3. 3 Test alternative blocking buffers (BSA, casein, or commercial blockers) and increase blocking time or temperature
4. 4 Increase number of wash cycles from 3 to 5-6 and extend wash duration to 60 seconds per cycle

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