Thiol-SAM Concentration Effect on the Performance of Interdigitated Electrode-Based Redox-Free Biosensors

Area of Science:

• Biosensor technology
• Nanomaterials
• Biomarker detection

Background:

• Non-faradaic impedimetric biosensors offer direct, redox-free detection but require performance optimization.
• Interfacial capacitance is key to non-faradaic impedimetric biosensor performance.
• Optimizing self-assembled monolayer concentration can enhance signal transduction.

Purpose of the Study:

• To investigate the impact of alkanethiolate (cysteamine) concentration on gold interdigitated electrode (Au-IDE) biosensor performance.
• To determine the optimal cysteamine concentration for enhanced sensitivity and limit of detection.
• To explore cysteamine layer characteristics for improved non-faradaic impedimetric sensing.

Main Methods:

• Fabrication of Au-IDE biosensors with varying cysteamine concentrations (100 nM to 10 mM).
• Immobilization of LDL antibodies on cysteamine layers using glutaraldehyde cross-linking.
• Direct detection of LDL cholesterol using non-faradaic electrochemical impedance spectroscopy (EIS).

Main Results:

• Biosensor sensitivity increased from 6.7 to 16.2 nF/ln (ng/mL) with cysteamine concentration from 100 nM to 100 μM.
• Limit of detection improved from 400 ng/mL to 59 pg/mL with cysteamine concentration from 100 nM to 100 μM.
• Higher cysteamine concentrations (1 mM, 10 mM) led to decreased sensitivity and a worse limit of detection.

Conclusions:

• Cysteamine concentration significantly impacts non-faradaic impedimetric biosensor performance.
• Optimal cysteamine concentration (around 100 μM) maximizes sensitivity and minimizes the limit of detection.
• A thin, uniformly covering cysteamine layer is essential for maximizing signal readout and improving biosensor performance.