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Optical biosensor for monitoring microbial cells
H J Watts1, C R Lowe, D V Pollard-Knight
1Institute of Biotechnology, University of Cambridge, U.K.
Analytical Chemistry
|August 1, 1994
Summary
A novel resonant mirror biosensor effectively detects Staphylococcus aureus (Cowan-1) whole cells. This optical biosensor shows high sensitivity, particularly in a sandwich assay format for analyzing milk samples.
Area of Science:
- Biomedical Engineering
- Biosensor Technology
- Microbiology
Background:
- Whole cell detection is crucial for diagnostics.
- Protein-A expressing Staphylococcus aureus strains pose a significant challenge.
- Optical biosensors offer label-free detection capabilities.
Purpose of the Study:
- To demonstrate the potential of a resonant mirror biosensor for whole cell detection.
- To optimize ligand immobilization for enhanced binding response.
- To improve sensitivity using a sandwich assay format.
Main Methods:
- Immobilization of human immunoglobulin G (IgG) on aminosilane-derivatized surfaces.
- Detection of Staphylococcus aureus (Cowan-1) cells via Protein-A/IgG binding.
- Comparison of sensor surfaces with and without carboxymethyl-dextran coating.
- Application of a sandwich assay using human IgG-colloidal gold conjugate.
Main Results:
- Resonant mirror biosensor detected S. aureus (Cowan-1) at 8 x 10^6-8 x 10^7 cells/mL.
- Non-dextran-coated surfaces yielded the greatest binding response.
- Sandwich assay increased sensitivity 1000-fold, detecting cells down to 4 x 10^3 cells/mL in milk.
- Control S. aureus strain (Wood-46) showed no significant response.
Conclusions:
- The resonant mirror biosensor is a viable tool for whole cell detection.
- Optimized immobilization and sandwich assay significantly enhance sensitivity.
- This technique shows promise for detecting S. aureus in complex matrices like milk.