Development of a Label-Free LSPR-Apta Sensor for Staphylococcus aureus Detection

Area of Science:

• Biosensing
• Nanotechnology
• Food Safety

Background:

• Rising incidence of foodborne illnesses necessitates advanced detection methods.
• Current methods for detecting Staphylococcus aureus often require pre-enrichment and are time-consuming.
• Need for rapid, sensitive, and portable diagnostic tools in food safety applications.

Purpose of the Study:

• To develop a simple, portable, and label-free optical sensor for Staphylococcus aureus detection.
• To utilize aptamer recognition coupled with localized surface plasmon resonance (LSPR) for enhanced sensitivity.
• To optimize sensor design and evaluate its performance in complex matrices like milk.

Main Methods:

• Fabrication of a localized surface plasmon resonance (LSPR) sensing device functionalized with aptamers.
• Detection of Staphylococcus aureus in pure cultures and artificially contaminated milk samples.
• Optical response simulation using finite-difference time-domain (FDTD) analysis for sensor design optimization.
• Comparative analysis of aptamer vs. antibody-based recognition and varying nanostructure sizes (100 nm vs. 200 nm disks).

Main Results:

• Achieved a limit of detection of 10^3 CFU/mL for Staphylococcus aureus in milk.
• Reduced total analysis time from 30 minutes to 120 seconds without pre-enrichment.
• Demonstrated higher sensitivity with 200 nm gold nanodisks compared to 100 nm disks.
• Identified thinner aptamer layers as critical for enhanced sensing response.

Conclusions:

• The developed gold nanodisk-based LSPR sensing chips offer a sensitive and rapid platform for Staphylococcus aureus detection in food.
• The label-free, aptamer-based approach provides a significant improvement over traditional methods in terms of speed and simplicity.
• Optimized sensor design, including nanostructure size and aptamer layer thickness, is crucial for maximizing detection performance.