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. 2025 Jul 26;25(15):4629.
doi: 10.3390/s25154629.

Surface-Enhanced Raman Spectroscopy for Adenine Detection in Five Selected Bacterial Strains Under Stress Conditions

Mona Ghazalová  1 , Pavlína Modlitbová  1 , Ota Samek  1 , Katarína Rebrošová  2 , Martin Šiler  1 , Jan Ježek  1 , Zdeněk Pilát  1
Affiliations

Surface-Enhanced Raman Spectroscopy for Adenine Detection in Five Selected Bacterial Strains Under Stress Conditions

Mona Ghazalová et al. Sensors (Basel). .

Abstract

This pilot study investigated the metabolic responses of five selected bacteria to physiological stress. Surface-enhanced Raman spectroscopy was used to analyze spectral changes associated with the release of adenine, a key metabolite indicative of stress conditions. Laboratory-synthesized spherical silver and gold nanoparticles, which remained stable over an extended period, were employed as enhanced surfaces. Bacterial cultures were analyzed under standard conditions and in the presence of a selected stressor-demineralized water-inducing osmotic stress. The results showed that the adenine signal originated from metabolites released into the surrounding environment rather than directly from the bacterial cell wall. The study confirms the suitability of these cost-effective and easily synthesized stable nanoparticles for the qualitative detection of bacterial metabolites using a commercially available Raman instrument.

Keywords: Ag-NPs; Au-NPs; Escherichia coli; SERS; Staphylococcus aureus; phenylalanine.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could influence the work reported in this paper.

Figures

Figure 1
Figure 1
Schematic representation of the NP synthesis process.
Figure 2
Figure 2
SERS measurement approach. 1. Mix the spent medium or bacterial suspension with NPs in 1:1 ratio. 2. Deposit 1 μL of the mixture on Al foil. 3. Allow to dry. Followed by SERS measurement.
Figure 3
Figure 3
(a) Size distribution of Au-NPs and Ag-NPs 6 months after synthesis. The DLS measurements showing the size distribution. (b) STEM image of synthesized Ag-NPs and (c) STEM image of synthesized Au-NPs. The scale bars are shown directly in the figures.
Figure 4
Figure 4
Raman spectrum of bacterium S. aureus (blue) and E. coli (red) without NPs, averaged from 10 spectra per sample. The spectra were normalized to the phenylalanine peak at 1002 cm−1.
Figure 5
Figure 5
(i) The SERS spectra of bacteria with NPs in physiological conditions. The figure presents SERS spectra of bacterial cells with Au-NPs and Ag-NPs. (a) Bacterial suspension with Ag-NPs; (b) bacterial suspension with Au-NPs. (ii) The SERS spectra of bacteria with NPs in osmotic stress caused by DI water. (c) Bacterial suspension with Ag-NPs; (d) bacterial suspension with Au-NPs. A dominant peak of adenine was observed at 730 cm−1. Averaged from 10 spectra per sample. The spectra were normalized to the adenine peak at 730 cm−1.
See this image and copyright information in PMC

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