How signal behaviour depends on assay design — and why it matters for your results.
The Amperia™ platform supports multiple assay formats to accommodate different types of analytes and interaction mechanisms. While all assays use the same dip-style sensors and Redox Electrochemical Detection (RED), the way the detection component is introduced and how it relates to the analyte determines the signal direction and behaviour.
This post introduces the three assay formats currently supported on Amperia™, and explains what each one means for your data.
The three assay formats
- Inverse Occupancy
In this format, the target analyte binds directly to the sensor surface and blocks a detection analogue from binding.
✅ Suitable for high-affinity analytes or abundant targets
📉 Signal decreases as analyte concentration increases
- Sandwich Format
This format relies on sequential binding — the target analyte is captured by the surface, then detected by a second molecule.
✅ Common in immunoassays
📈 Signal increases with analyte concentration
- Premix Competition
Here, the target analyte and a detection analogue compete for the same binding site. Detection is reduced when analyte is present.
✅ Useful for small molecules or ligands
📉 Signal decreases with analyte concentration
Why it matters
Different signal behaviours (direct or inverse) are not better or worse, they’re chosen based on what’s most appropriate for the target and detection chemistry.
Amperia™ software is pre-configured for each kit to recognise the correct format. During analysis, the system:
- Applies the appropriate calibration model
- Fits a direct or inverse standard curve
- Reports interpolated concentrations accordingly
For users, this means you can trust the results even if your standard curve slopes downward.
In practice
- The mAb assay uses the Inverse Occupancy format
- The AAV assay uses the Sandwich format
- The His-tag assay uses the Premix Competition format
Each kit is optimised to provide reliable quantification across relevant concentration ranges — regardless of format.
Final tip
Always refer to your assay protocol to confirm which format is being used, especially when setting up standards or interpreting curve shape. And if in doubt, Amperia™ handles the rest behind the scenes so you can focus on your results.