Optical Biosensor for Monitoring Microbial Cells

• Published in: Analytical chemistry (Washington) 1994-08, Vol.66 (15), p.2465-2470
• Main Authors: Watts, Helen J, Lowe, Christopher R, Pollard-Knight, Denise V
• Format: Article
• Language: English
• Subjects: Biochemistry; Biological and medical sciences; Biosensing Techniques; Biosensors; Biotechnology; Dextrans - chemistry; Fundamental and applied biological sciences. Psychology; Humans; Immunoglobulin G - metabolism; Methods. Procedures. Technologies; Silanes - chemistry; Staphylococcal Protein A - biosynthesis; Staphylococcus aureus - isolation & purification; Staphylococcus aureus - metabolism; Various methods and equipments
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac00087a010

The potential of a new optical biosensor, the resonant mirror, for detecting whole cells is demonstrated. Staphylococcus aureus (Cowan-1) cells, which express protein-A at their surface, were detected by binding to human immunoglobulin G (IgG) immobilized on an aminosilane-derivatized sensor surface at concentrations in the range 8 x 10(6)-8 x 10(7) cells/mL. A control S. aureus strain (Wood-46), which does not express protein-A, gave no significant response. Immobilization of the capture ligand on aminosilane surfaces with and without a hydrogel coating of carboxymethyl-dextran was compared. The greatest binding response was observed with non-dextran-coated surfaces. The sensitivity of the technique was increased a 1000-fold by using a human IgG-colloidal gold conjugate (30 nm) in a sandwich assay format. S. aureus (Cowan-1) cells were detected in spiked milk samples at cell concentrations from 4 x 10(3)-1.6 x 10(6) cells/mL using the sandwich assay.