Self-assembled monolayers as a base for immunofunctionalisation: unequal performance for protein and bacteria...

Area of Science:

• Biosensor development
• Surface functionalization
• Immunotechnology

Background:

• Optimizing surface functionalization is crucial for biosensor performance.
• Self-assembled monolayers (SAMs) on gold are a preferred immunofunctionalization strategy.
• SAM-based antibody incorporation generally outperforms antibody physisorption for small targets.

Purpose of the Study:

• To evaluate SAM-based gold immunofunctionalization strategies for bacteria detection.
• To compare chemical antibody conjugation versus antibody physisorption for bacterial targets.
• To investigate the suitability of protein detection methods for complex targets like bacteria.

Main Methods:

• Chemical conjugation of antibodies onto mercaptopropanoic acid, mercaptoundecanoic acid, and dextranized cysteamine SAMs.
• Assessment of functionalized surfaces for direct detection of enzyme-labeled proteins.
• Evaluation of SAM-based and physisorption methods for bacteria detection using a sandwich assay format.
• Testing with E. coli as a bacterial target.

Main Results:

• All tested SAM-based strategies successfully detected enzyme-labeled proteins.
• None of the SAM-based immunofunctionalization strategies detected bacterial targets in a sandwich assay.
• Antibody physisorption on gold enabled E. coli detection via a sandwich enzyme-linked assay.
• Bacteria size and cell wall complexity were identified as critical factors.

Conclusions:

• Immunofunctionalization strategies effective for protein detection are not directly transferable to bacteria detection.
• Antibody physisorption presents a suitable alternative to SAM-based functionalization for bacterial biosensing.
• Surface chemistry and target complexity significantly influence biosensor design and success.