TiO₂ nanotube array-modified electrodes for L-cysteine biosensing: experimental and density-functional theory study.

Area of Science:

• Electrochemistry
• Materials Science
• Biomedical Sensing

Background:

• L-cysteine (L-Cyst) is a crucial amino acid involved in various biological processes.
• Accurate detection of L-Cyst is vital for diagnosing and monitoring several diseases.
• Existing detection methods often rely on enzymes, which can be unstable and costly.

Purpose of the Study:

• To develop a facile, enzyme-free electrochemical method for L-Cyst detection.
• To utilize free-standing titanium dioxide (TiO2) nanotube (TNT) arrays for enhanced sensing.
• To investigate the electrochemical properties and performance of TNT-modified electrodes for L-Cyst detection.

Main Methods:

• Fabrication of self-organized, vertically oriented TNT arrays on glassy carbon electrodes (GCEs) via anodization.
• Electrochemical characterization using cyclic voltammetry and amperometry.
• Optimization of detection parameters including pH and temperature.
• Real sample analysis using human blood serum.
• Density Functional Theory (DFT) calculations to understand adsorption mechanisms.

Main Results:

• The TNT-modified GCE exhibited significantly higher current response compared to the pristine GCE.
• High sensitivity (∼1.68 µA mM⁻¹ cm⁻²) and a low detection limit (∼0.1 mM) were achieved.
• The electrode showed sensitivity to pH and temperature variations.
• Successful detection of L-Cyst in human blood serum with good recovery rates.
• DFT analysis confirmed strong affinity and chemisorption of L-Cyst on TNTs, reducing the energy gap.

Conclusions:

• The developed non-enzymatic method using TNT-modified GCEs is highly sensitive, selective, and stable for L-Cyst detection.
• TNT arrays offer excellent electrocatalytic activity and surface area for biosensing applications.
• This approach holds promise for the development of advanced enzyme-free biosensors for various biological analytes.