Towards a fast, high specific and reliable discrimination of bacteria on strain level by means of SERS in a microfluidic device

Abstract

The interest in a fast, high specific and reliable detection method for bacteria identification is increasing. We will show that the application of vibrational spectroscopy is feasible for the validation of bacteria in microfluidic devices. For this purpose, reproducible and specific spectral pattern as well as the establishment of large databases are essential for statistical analysis. Therefore, short recording times are beneficial concerning the time aspect of fast identification. We will demonstrate that the requirements can be fulfilled by measuring ultrasonic busted bacteria by means of microfluidic lab-on-a-chip based SERS. With the applied sample preparation, high specificity and reproducibility of the spectra are achieved. Taking advantage of the SERS enhancement, the spectral recording time is reduced to 1 s and a database of 11,200 spectra is established for a model system E. coli including nine different strains. The validation of the bacteria on strain level is achieved accomplishing SVM accuracies of 92%. Within this contribution the potential of our approach of bacterial identification for future application is discussed, focusing on the time-benefit and the combination with other microfluidic applications.

Arsenic interception by cell wall of bacteria observed with surface-enhanced Raman scattering

“…Ag NPs were used to enhance signals of Raman spectra, and the combination of Ag colloid and bacteria can influence the spectra of bacteria. Nanoparticles can either attach to the outside of the bacterial cell wall or enter the interior of the cell (Walter, et al, 2011), which may result in SERS spectral features from the cell wall alone, and from combinations of cell wall and protoplast. The inhomogenous information may constrain the application of SERS spectra to identify or assess the impact of environmental factors on bacteria.…”

“…The inhomogenous information may constrain the application of SERS spectra to identify or assess the impact of environmental factors on bacteria. To solve this problem, Angela et al obtained disrupted bacteria cells using ultrasound (Walter, et al, 2011) so that both cell wall and protoplast were able to associate with Ag NPs for SERS detection. However, this approach cannot differentiate which target component, cell wall or protoplast, would respond to the environmental stress.…”

“…The cell wall fraction was collected by the modified ultrasonic method (Knox and Brandsen, 1962;Walter et al, 2011). The collected biomass was re-suspended in deionized water and homogenized 5 s intermittently every 5 s in an ultrasonic cleaner (VWR, B5500A-DTH, 510 W maximum level).…”

Surface-enhanced Raman scattering microfluidic sensor

“…35 The microfluidic channel matches the size of bacteria very well which is conducive to the cultivation of the bacteria or cell 141,[145][146][147] that offers the possibility of system integration issues for bio/chemical molecular analysis at the trace and even single molecule level. 3,148,149 Walter et al 150 presented a fast, reliable and specific test of bacteria by means of SERS in a microfluidic device (Fig. 4(a)).…”

An Examination of the Validity of MRPS Method for the Detection of Label-free E. Coli and Enterococci in Ships Ballast Water

“…The quality of ship's ballast water will be accessed before discharging and it becomes a technical challenge. The most well-known methods of detection for indicative microorganisms sample from ships ballast water are Adenosine triphosphate (ATP) [6][7][8] [22,23], fluorescent in-situ hybridization (FISH) [24,25] and surface enhanced Raman scattering (SERS) [26,27]. Some of their techniques can detect single cell with high accuracy.…”