Poorly Defined or Fuzzy Spots

Symptom

Spots lack sharp borders and appear fuzzy or poorly defined, making automated or manual counting difficult. The reader has trouble distinguishing individual spots.

1. 1 Membrane not pretreated with ethanol before coating
2. 2 Plate movement during cell incubation causing cells to migrate and create multiple spots
3. 3 Coating antibody concentration too low (especially for fluorescence detection)
4. 4 Residual ethanol trapped between membrane and plate bottom due to inadequate washing
5. 5 Cells distributed unevenly creating irregular cell density

1. 1 Pretreat membrane with 35% ethanol; wash thoroughly with PBS 3× to remove all ethanol
2. 2 Do not move, stack, or tap plates during cell incubation; use dedicated incubator
3. 3 Increase antibody concentrations for both coating and detection steps
4. 4 Ensure complete washing after ethanol pretreatment to remove trapped ethanol
5. 5 Mix cells gently to obtain homogenous suspension before pipetting into wells

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