An optofluidic imaging system to measure the biophysical signature of single waterborne bacteria

Abstract

In this paper, for the first time, an on-chip optofluidic imaging system is innovated to measure the biophysical signatures of single waterborne bacteria, including both their refractive indices and morphologies (size and shape), based on immersion refractometry. The key features of the proposed optofluidic imaging platform include (1) multiple sites for single-bacterium trapping, which enable parallel measurements to achieve higher throughput, and (2) a chaotic micromixer, which enables efficient refractive index variation of the surrounding medium. In the experiments, the distinctive refractive index of Echerichia coli, Shigella flexneri and Vibrio cholera are measured with a high precision of 5 × 10(-3) RIU. The developed optofluidic imaging system has high potential not only for building up a database of biophysical signatures of waterborne bacteria, but also for developing single-bacterium detection in treated water that is in real-time, label-free and low cost.

Live E. coli bacteria label-free sensing using a microcavity in-line Mach-Zehnder interferometer

“…The addition of bacterial solutions with a concentration of up to 10 4 CFU/mL shifted the spectrum toward longer wavelengths. It is expected at this stage of the experiment that the n co is mainly affected, while the RI of bacterial solution stays equal to 1.388 RIU 32 . Considering that the size of bacteria spans form 2 µm 23 and the length of the fimbriae 1 µm 33 – the last layer is the thickest one in the system.…”

Kinetics of Antibody Binding to Membranes of Living Bacteria Measured by a Photonic Crystal-Based Biosensor

“…Changes in the adsorbed layer thickness d are derived from changes of the resonance angle $\mathrm{normal\Delta }{\theta }_{SW}$ and ones of the sample refractive index $\mathrm{normal\Delta }{n}_{sample}$, assuming that the RI of a single bacteria is equal to 1.388 [10]. Thus, the adlayer thickness d is calculated as a function of the measured angles $\mathrm{normal\Delta }{\theta }_{TIR}$ and $\mathrm{normal\Delta }{\theta }_{SW}$: $d=ffalse(\mathrm{normal\Delta }{\theta }_{TIR},\mathrm{normal\Delta }{\theta }_{SW}false)$ .…”

Compact off-axis holographic slide microscope: design guidelines

“…E.coli is a prokaryotic organism known to cause a variety of disease syndromes, making it an important indicator in environmental water quality monitoring and food security [44,45]. The E.coli cells are rod shaped, with typical lengths of 2 − 3 µm and a diameter of 0.5 − 1 µm [44,46,47], with an almost uniform refractive index n = 1.384. Their small dimensions challenge the resolution of conventional microscopes.…”