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.

On the challenges of detecting wholeStaphylococcus aureuscells with biosensors

“…More recently, the same group described optical resonators functionalized with the LysK protein and enabling the label‐free and real‐time detection of SA (Ghali et al . ). Although the sampling conditions (2 × 10 −6 l containing 10 7 bacteria) are still far from real SA contaminating levels, such example strengthens the possibility of decorating a large panel of sensors with phages for SA detection.…”

Label-Free Biological and Chemical Sensing Using Whispering Gallery Mode Optical Resonators: Past, Present, and Future

“…A partial list includes microrings [40,41], disks [12], knots/coils [42], bottles [43], droplets [44], goblets [45], rolled-up microcavities [46], bubbles [47], polystyrene microspheres [48,49], asymmetric cavities [50], cylinders [51], vertically coupled race track resonators [52], nearly spherical diamond resonators [53], crystalline CaF 2 cavities [54], and liquid-core optical ring resonators (LCORR) [55]. White-light WGM resonators have also been developed [56].…”

“…In contrast, mechanical cantilevers, while having high sensitivity in air and vacuum [11], are dampened in water and typically do not operate well in aqueous environments. At the level of individual particles, WGM sensors have been used to detect and size bacteria [12], viruses [13,14], DNA [15], exosomes [16], ribosomes [1], antibodies [1], and single protein molecules [1,17,18]. …”

All-polymer whispering gallery mode sensor for application in optofluidics

“…In the last few years WGM based sensors are continuously enhanced with respect to detection limit and sensitivity [6,7]. Nevertheless the realised sensors are often large in size and complex for real world applications [8]. With the goal to realize a robust and easy to fabricate sensor, a completely polymer based sensor was developed [9], based on a concept, rst presented by Schweiger et al [10][11][12][13].…”