title: Real-Time Detection of Staphylococcus Aureus Using Whispering Gallery Mode Optical Microdisks.
abstract: Whispering Gallery Mode (WGM) microresonators have recently been studied as a means to achieve real-time label-free detection of biological targets such as virus particles, specific DNA sequences, or proteins. Due to their high quality (Q) factors, WGM resonators can be highly sensitive. A biosensor also needs to be selective, requiring proper functionalization of its surface with the appropriate ligand that will attach the biomolecule of interest. In this paper, WGM microdisks are used as biosensors for detection of Staphylococcus aureus. The microdisks are functionalized with LysK, a phage protein specific for staphylococci at the genus level. A binding event on the surface shifts the resonance peak of the microdisk resonator towards longer wavelengths. This reactive shift can be used to estimate the surface density of bacteria that bind to the surface of the resonator. The limit of detection of a microdisk with a Q-factor around 10⁴ is on the order of 5 pg/mL, corresponding to 20 cells. No binding of Escherichia coli to the resonators is seen, supporting the specificity of the functionalization scheme.
authors.affiliation: Department of Engineering Physics, Polytechnique Montreal, Montreal, QC, H3T 1J4, Canada. hala.ghali@polymtl.ca.
authors.forename: Hala
authors.initials: H
authors.lastname: Ghali
authors.affiliation: Department of Biomedical Engineering, McGill University, Montreal, QC, H3A 2B4, Canada. hicham.chibli@mcgill.ca.
authors.forename: Hicham
authors.initials: H
authors.lastname: Chibli
authors.affiliation: Department of Biomedical Engineering, McGill University, Montreal, QC, H3A 2B4, Canada. jay.nadeau@mcgill.ca.
authors.forename: Jay L
authors.initials: JL
authors.lastname: Nadeau
authors.affiliation: Physics Department, Concordia University, Montreal, QC, H4B 1R6, Canada. pablo.bianucci@concordia.ca.
authors.forename: Pablo
authors.initials: P
authors.lastname: Bianucci
authors.affiliation: Department of Engineering Physics, Polytechnique Montreal, Montreal, QC, H3T 1J4, Canada. yves-alain.peter@polymtl.ca.
authors.forename: Yves-Alain
authors.initials: YA
authors.lastname: Peter
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods; D012680:Sensitivity and Specificity; D012825:Silicon; D013211:Staphylococcus aureus
chemical_list: D012825:Silicon
keywords: bacterial sensing; optical microdisk; specific binding; surface functionalization