The Detection of Helicobacter hepaticus Using Whispering-Gallery Mode Microcavity Optical Sensors

Abstract

Current bacterial detection techniques are relatively slow, require bulky instrumentation, and usually require some form of specialized training. The gold standard for bacterial detection is culture testing, which can take several days to receive a viable result. Therefore, simpler detection techniques that are both fast and sensitive could greatly improve bacterial detection and identification. Here, we present a new method for the detection of the bacteria Helicobacter hepaticus using whispering-gallery mode (WGM) optical microcavity-based sensors. Due to minimal reflection losses and low material adsorption, WGM-based sensors have ultra-high quality factors, resulting in high-sensitivity sensor devices. In this study, we have shown that bacteria can be non-specifically detected using WGM optical microcavity-based sensors. The minimum detection for the device was 1 × 104 cells/mL, and the minimum time of detection was found to be 750 s. Given that a cell density as low as 1 × 103 cells/mL for Helicobacter hepaticus can cause infection, the limit of detection shown here would be useful for most levels where Helicobacter hepaticus is biologically relevant. This study suggests a new approach for H. hepaticus detection using label-free optical sensors that is faster than, and potentially as sensitive as, standard techniques.

Other Helicobacters and gastric microbiota

“…As helicobacters have a unique irregular and large shape, optical detection systems with whispering gallery mode devices might be used as an alternative detection method for NHPH infections. Using this technique, Anderson et al . were able to detect H. hepaticus in samples in a fast and sensitive way, with a minimum detection level of 1×10 4 cells/mL and a minimum detection time of 750 seconds.…”

Label-Free Biosensors Based onto Monolithically Integrated onto Silicon Optical Transducers

“…At the same time, the detection of the bacteria, Helicobacter hepaticus, at a density of 1 × 10 4 cells/mL within 750 s has been demonstrated using an optical microcavity-based sensor [66]. Toroidal structures have also been fabricated on low-loss polymer [40] or polymer-silica hybrid materials [67]. These devices are expected to have lower Q factors (10 5 -10 7 ) as compared to silicon based ones, but still their sensitivity should be higher compared to planar ring resonators.…”

Label-Free Biosensors Based Onto Monolithically Integrated Onto Silicon Optical Transducers

“…At the same time, the detection of detection of the bacteria Helicobacter hepaticus at a density of 1 ×10 4 cells/mL within 750 s has been demonstrated using an optical microcavity-based sensor [58]. Toroidal structures have been also fabricated on low-loss polymer [40] or polymer-silica hybrid materials [59]. These devices are expected to have lower Q factors (10 5 -10 7 ) as compared to silicon based ones, but still their sensitivity should be higher compared to planar ring resonators.…”

“…The spectral position of the defect mode is influenced by the refractive-index changes in the vicinity of the defect, thus, offering a way to exploit the photonic crystal as biosensor. This is in practice achieved through careful design of the nanostructure so as to define the photonic bandgap and the defect mode wavelength and thus, define the sensitivity of the transducer to refractive index changes [59]. The structures more usually implemented are linear or 2D gratings on which discrete or line defects are introduced to create the transduction sites ( figure 5).…”