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Development of a capacitive immunosensor: a comparison of monoclonal and polyclonal capture antibodies as the primary
H C Berney1, J Alderman, W A Lane
1National Microelectronics Research Centre, University College, Cork, Ireland.
Insights
Mechanical degradation of a silicon nitride surface improved capacitance immunosensor response to antigen binding. This enhancement allowed for effective detection of transferrin using different antibody configurations, revealing differences in antibody performance.
Area of Science:
- Biosensors
- Surface Science
- Immunotechnology
Background:
- Capacitance immunosensors detect antigen-antibody interactions on immobilized antibodies.
- Initial systems using silicon-silicon dioxide-silicon nitride (Si-SiO2-Si3N4) surfaces showed poor reproducibility.
- Mechanical surface degradation was explored to improve sensor performance.
Purpose of the Study:
- To investigate the effect of mechanical surface degradation on capacitance immunosensor response.
- To compare the effectiveness of different capture antibodies for detecting human transferrin.
- To analyze the dielectric and blocking properties of monoclonal versus polyclonal antibodies.
Main Methods:
- Fabrication of a Si-SiO2-Si3N4 surface with an active biolayer of antibodies.
- Mechanical degradation of the sensor surface.
- Monitoring capacitive responses upon addition of transferrin.
- Comparing monoclonal antibody (1D2A4), polyclonal antibody (PcAb), and pre-bound transferrin as capture layers.
Main Results:
- Mechanical degradation enabled capacitive detection of affinity reactions.
- No response was observed with 1D2A4 as the capture layer.
- Polyclonal antibodies and pre-bound antigen layers showed a decrease in measured capacitance upon transferrin addition.
- Monoclonal and polyclonal antibodies exhibited different dielectric/blocking effectiveness.
Conclusions:
- Mechanical surface modification is crucial for reproducible capacitance immunosensor operation.
- The choice of capture antibody significantly impacts sensor performance and detection capabilities.
- Differences in dielectric properties between antibody types influence signal generation in capacitance immunosensing.
Abstract:
There is widespread interest in capacitance immunosensor systems which directly detect antigen binding to immobilized antibody. Our system comprises an active biolayer of antibodies bound to a silicon--silicon dioxide--silicon nitride (Si-SiO2-Si3N4) surface. As with other groups, our system initially gave poorly reproducible responses on addition of antigen. We mechanically degraded the Si-SiO2-Si3N4 surface, and the responses on addition of transferrin were monitored. The mechanical degradation allowed the affinity reaction to be 'seen' capacitively. Once the system was established, a comparison of capture antibodies was performed to establish the most effective biolayer. Three affinity reactions were examined: (a) 1D2A4, monoclonal antibody (mAb) to human transferrin, as the capture layer; (b) polyclonal goat anti-human transferrin antibody (PcAb) as the capture layer; and (c) 1D2A4 with transferrin (Tf) prebound as the capture layer. There was no response to addition of transferrin where 1D2A4 was the capture layer. Addition of transferrin when the polyclonal antibody was used as the primary layer resulted in a drop in measured capacitance. Addition of goat anti-human transferrin antibody to a device with 1D2A4 plus transferrin as the capture layer also resulted in a measured capacitance decrease. There is a difference in dielectric/blocking effectiveness between the monoclonal and polyclonal antibodies.
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