SERS-based immunosensor for E. coli contaminants detection in milk using silver-coated nanoporous silicon substrates

Area of Science:

• Materials Science
• Biosensing
• Veterinary Diagnostics

Background:

• Bovine mastitis (BM) is a prevalent dairy industry issue caused by various pathogens.
• Rapid and accurate detection of causative agents like Escherichia coli is crucial for effective disease management.

Purpose of the Study:

• To develop a silver-decorated porous silicon (Ag-pSi) surface-enhanced Raman spectroscopy (SERS) platform for sensitive and selective detection of Escherichia coli.
• To optimize the Ag-pSi SERS platform for enhanced signal amplification and evaluate its performance in various milk matrices.

Main Methods:

• Fabrication and physical optimization of Ag-pSi substrates for SERS.
• Development of an indirect immunoassay using a modified Ag-pSi SERS platform.
• Characterization of sensitivity, selectivity, and specificity against target and interfering bacteria.
• Validation of the platform using real milk samples (bovine, goat, sheep) and comparison with conventional culture techniques.

Main Results:

• Achieved a high SERS enhancement factor (>4.6 × 10^7) using 4-aminothiophenol (4ATP).
• Demonstrated high sensitivity for Escherichia coli detection (limit of detection of 3 CFU mL^-1) with a linear response range of 10^1-10^5 CFU mL^-1.
• Validated applicability in diverse milk samples with recovery rates of 78-115%, showing high reliability and accuracy.

Conclusions:

• The developed Ag-pSi SERS platform provides a rapid, sensitive, and reliable method for detecting Escherichia coli in milk.
• This miniaturized sensing system is suitable for routine on-site analysis, aiding in bovine mastitis management.
• The platform's performance in complex media highlights its potential for broader applications in pathogen detection.