To the best of our knowledge we here for the first time demonstrate surface enhanced Raman spectroscopy
(SERS) to detect a quorum sensing (QS) signal molecule below 1 nM concentration in both ultrapure water and under
physiological conditions. Based on our results, SERS shows promise as a highly suitable tool for in situ measurements of
low Acyl-Homoserine Lactone (AHL) concentrations in biofilms containing QS bacteria. Signal molecules communicate
information about their environment and coordinate certain physiological activities in QS systems that exist in many
bacteria. SERS enables detection of different AHLs at low concentrations due to structural differences observed in the
corresponding SERS spectra. Ag colloidal nanoparticles, produced by the hydroxylamine reducing method, were used for
the SERS measurements. SERS spectra of C12-HSL suspended in ultrapure water and in supplemented minimal medium
were collected for 5 concentrations ranging from 2 μM to 0.2 nM, and a comparison between the spectra from these two
media is also presented. We have been able to detect biologically relevant concentrations of AHL molecules ranging from
1 nM to 1 μM using SERS.
Keywords: Acyl-Homoserine Lactone, N-Dodecanoyl-DL-homoserine lactone, Signal molecules, Autoinducer, Surfaceenhanced
Raman spectroscopy, Quorum sensing.
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