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An electrochemical lipopolysaccharide sensor based on an immobilized Toll-Like Receptor-4
R M Mayall1, M Renaud-Young1, N W C Chan2
1Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4.
Abstract:
Infections affect millions of people each year and yet methods to ascertain their cause can take more than 24h to be effective. This delay between the presentation with symptoms and the ability to make an informed decision about treatment can have adverse consequences, including death in severe cases. Additionally, pathogen identification is a concern for public safety amid the growing threat of bioterrorism. Developing a detection system based on the immune system offers the advantage of broad specificity, while still remaining pertinent to human health. In this work, human Toll-Like Receptor-4 (TLR-4), a protein responsible for detecting lipopolysaccharide (LPS) of Gram-negative bacteria, was immobilized on both a large area and micro gold electrode via the tethering interaction of a modified Self-Assembled Monolayer (mSAM). In response to varying concentrations of its target, the protein-electrode combination showed a logarithmically proportional increased resistance to charge transfer from a solution-based redox probe, due to the formation of TLR-4 protein dimers. It also demonstrated excellent sensitivity to trace levels of Gram-negative bacteria, while remaining insensitive to both Gram-positive and viral challenges. Further characterization of our mSAM revealed that maintaining the appropriate receptor orientation on the electrode surface, mimicking TLR-4's role in a cellular context, was essential in producing a responsive sensor.
Insights
A novel biosensor using human Toll-Like Receptor-4 (TLR-4) protein detects Gram-negative bacteria rapidly. This immune system-based approach offers a sensitive and specific method for pathogen identification, improving diagnostic speed.
Area of Science:
- Biomedical Engineering
- Immunology
- Biosensor Technology
Background:
- Current methods for infection diagnosis exceed 24 hours, delaying critical treatment decisions.
- Rapid and accurate pathogen identification is crucial for public health and bioterrorism defense.
- Immune system components offer broad specificity for developing effective detection systems.
Purpose of the Study:
- To develop a rapid biosensor for detecting Gram-negative bacteria using immobilized human Toll-Like Receptor-4 (TLR-4).
- To investigate the sensor's sensitivity and specificity against various bacterial and viral challenges.
- To optimize receptor orientation on the electrode surface for enhanced sensor performance.
Main Methods:
- Immobilization of human TLR-4 protein onto gold electrodes using a modified Self-Assembled Monolayer (mSAM).
- Electrochemical impedance spectroscopy was used to measure changes in charge transfer resistance.
- Testing sensor response to varying concentrations of lipopolysaccharide (LPS) and different types of bacteria/viruses.
Main Results:
- The TLR-4 biosensor exhibited a logarithmic response to increasing concentrations of its target, lipopolysaccharide (LPS).
- The sensor demonstrated high sensitivity to trace levels of Gram-negative bacteria.
- The system showed no cross-reactivity with Gram-positive bacteria or viral samples.
- Proper orientation of TLR-4 on the electrode surface was critical for sensor responsiveness.
Conclusions:
- A functional biosensor for Gram-negative bacteria detection was successfully developed by immobilizing TLR-4 on gold electrodes.
- The biosensor offers a rapid, sensitive, and specific detection method, addressing limitations of current diagnostic techniques.
- Optimizing receptor orientation is key to mimicking cellular immune responses and ensuring sensor efficacy.
