Abstract
It is well known that microbial populations and their interactions are largely influenced by their secreted metabolites. Noninvasive and spatiotemporal monitoring and imaging of such extracellular metabolic byproducts can be correlated with biological phenotypes of interest and provide new insights into the structure and development of microbial communities. Herein, we report a surface-enhanced Raman scattering (SERS) hybrid substrate consisting of plasmonic Au@Ag@mSiO2 nanorattles for optophysiological monitoring of extracellular metabolism in microbial populations. A key element of the SERS substrate is the mesoporous silica shell encapsulating single plasmonic nanoparticles, which furnishes colloidal stability and molecular sieving capabilities to the engineered nanostructures, thereby realizing robust, sensitive, and reliable measurements. The reported SERS-based approach may be used as a powerful tool for deciphering the role of extracellular metabolites and physicochemical factors in microbial community dynamics and interactions.
Highlights
Microbial biofilms, the most common form of existence of microorganisms in nature, are indispensable living entities governing the global biogeochemical cycle and the healthy activity of the microbiota.[1]
We demonstrate the application of plasmonic nanorattles encoded with a pHdependent Raman active molecule, 4-mercaptobenzoic acid (4MBA),[40] and embedded in a block of nutrient agar as a multifunctional surface-enhanced Raman scattering (SERS) platform for highly sensitive detection and spatiotemporal imaging of metabolic pH changes in colonies of Escherichia coli
The Au@Ag@ZIF-8 nanocrystals are coated with mSiO242 through a sol−gel process in the presence of cetyltrimethylammonium bromide (CTAB) (Figures 1B3 and S1B in the Supporting Information)
Summary
The most common form of existence of microorganisms in nature, are indispensable living entities governing the global biogeochemical cycle and the healthy activity of the microbiota.[1]. Biofilms composed of multiple microbial species or by a single species are enclosed at high cell densities within a selfproduced extracellular matrix In such densely populated environments, as a result of their metabolic activities, microbes excrete bioactive chemical compounds that can act as cues and signals for intercellular communication,[6,7] as well as metabolic byproducts that can greatly influence the development and composition of biofilms.[8,9] For instance, microbial fermentation can lead to the production of acids that can lower the local pH significantly. Our results highlight the great potential of the Au@Ag@mSiO2 nanoparticles as a SERS sensor for diagnostic and environmental applications
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