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Updated: Aug 9, 2026
Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms
Published on: April 17, 2017
Capacitance measurements of antibody-antigen interactions in a flow system
1Chemical Center, University of Lund, Sweden.
Insights
This study developed a novel capacitive immunosensor using self-assembled monolayers on gold electrodes. The sensor accurately detects low concentrations of biomarkers like human chorionic gonadotropin, offering a sensitive diagnostic tool.
Area of Science:
- Electrochemistry
- Biosensor technology
- Nanomaterials
Background:
- Capacitive immunosensors offer label-free detection of biomolecules.
- Self-assembled monolayers (SAMs) on gold electrodes provide a stable platform for biosensor development.
- Precise control over electrode surface modification is crucial for sensor performance.
Purpose of the Study:
- To develop and characterize a novel capacitive immunosensor for sensitive biomarker detection.
- To evaluate the performance of the immunosensor using various target analytes.
- To investigate the potential of self-assembled monolayers in enhancing immunosensor capabilities.
Main Methods:
- Monoclonal antibodies were immobilized onto gold electrodes via thioctic acid self-assembled monolayers.
- 1-dodecanethiol was used to passivate uncovered surface areas, creating a dense insulating layer.
- Cyclic voltammetry confirmed the blocking of hexacyanoferrate redox reactions.
- Capacitance measurements were performed using potentiostatic steps and current transients.
- The immunosensor was integrated into a flow system for real-time analysis.
Main Results:
- A decrease in capacitance correlated linearly with antigen concentration over three orders of magnitude.
- The immunosensor demonstrated high sensitivity for human chorionic gonadotropin (detection limit 0.5 pg/mL).
- Immobilized F(ab)2 fragments and antibodies against interleukin-2 and human albumin also showed sensitive detection (1 pg/mL detection limits).
- No cross-reactivity was observed with structurally similar hormones like thyrotropic hormone.
Conclusions:
- The developed capacitive immunosensor provides a sensitive and specific platform for biomarker detection.
- Self-assembled monolayers are effective for creating robust and insulating layers on electrode surfaces.
- The sensor technology shows promise for clinical diagnostics and biochemical analysis.
Abstract:
Capacitive immunosensors were made by coupling monoclonal antibodies to thioctic acid, which had self-assembled on a gold electrode. Surface areas that were not covered were plugged with 1-dodecanethiol to make the layer dense and insulating. Cyclic voltammetry showed that the hexacyanoferrate redox reactions were blocked by this procedure. The capacitance of the electrode was evaluated from the current transients obtained when a potentiostatic step was applied. The immunosensor was placed in a flow system, and a capacitance decrease could be observed after injection of an unlabeled antigen. It was linear over almost three decades when plotted vs the logarithm of the antigen concentration. Human chorionic gonadotropin hormone could be determined in the range 1 pg/mL-1 ng/mL, with a detection limit of 0.5 pg/mL (15 10(-15) M). A similar response was obtained with immobilized F(ab)2 fragments. No cross-reactivity was observed with the thyrotropic hormone, which has one chain in common with gonadotropin. Monoclonal antibodies toward interleukin-2 immobilized on the immunosensor gave also a response over 1 pg/mL-1 ng/mL, with a detection limit of 1 pg/mL. An immunosensor with monoclonal antibodies toward human albumin gave a calibration curve with lower slope than the other proteins but still with a detection limit of 1 pg/mL.
