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Published on: June 13, 2010
Effect of the nonspecific binding in differential impedance biosensing
Mathias Buff1, Ewa Drab1, Kaori Sugihara1
1Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.
Insights
Nonspecific binding in impedance biosensors significantly impacts detection limits. This study shows serum proteins, not the target analyte, generated the signal, worsening detection by tenfold.
Area of Science:
- Biosensing
- Electrochemistry
- Biomaterials
Background:
- Detection limits of impedance biosensors are often overestimated in clean buffers.
- Nonspecific binding (NSB) presents a significant challenge in real-world biosensing applications.
- Understanding NSB effects is crucial for developing accurate and reliable biosensors.
Purpose of the Study:
- To investigate the impact of nonspecific binding on differential impedance biosensing performance.
- To analyze the source of the differential signal in the presence of background serum proteins.
- To evaluate the detection limits of a poly-l-lysine-polyethylene glycol-biotin coated impedance biosensor for streptavidin.
Main Methods:
- Fabrication of a differential impedance biosensor using functionalized gold electrodes (poly-l-lysine-polyethylene glycol-biotin).
- Detection of streptavidin in a buffer containing 0.1% fetal calf serum to simulate biological conditions.
- Analysis of impedance signals to determine the influence of serum proteins on biosensor performance.
Main Results:
- The presence of fetal calf serum increased the detection limit for streptavidin by one order of magnitude (5 μg/ml) compared to previous studies without serum.
- The differential impedance signal originated from the serum proteins, not the streptavidin analyte.
- Streptavidin binding indirectly modulated the electrical signal by altering serum protein accessibility to the electrode surface.
Conclusions:
- Nonspecific binding significantly hinders the performance and accuracy of impedance biosensors.
- The differential signal in this system is primarily attributed to background serum components, not the target analyte.
- Current methods for determining detection limits in clean buffers do not reflect real-world biosensing challenges.
Abstract:
The detection limits of impedance biosensors are dictated by the presence of background nonspecific binding, yet almost all the detection limits reported in the literature are determined using a clean buffer solution without confronting this real challenge. In this work, the authors employed the simplest "differential" impedance biosensor, composed of poly-l-lysine-polyethylene glycol-biotin-coated gold electrodes for the detection of streptavidin in the presence of 0.1% fetal calf serum, and studied the effect of the nonspecific binding on the performance of the differential impedance biosensing. The lowest streptavidin concentration detected by the system (5 μg/ml) was 1 order of magnitude higher (worse) than that from a previously demonstrated impedance biosensor where avidin was detected in the absence of background proteins. Interestingly, the origin of the differential signal was not due to the electrochemical properties of streptavidin itself but was that of the serum, where the coverage of the electrode by streptavidin indirectly modulated the electrical signal by suppressing the accessibility of the serum to the electrode.
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