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Metabolomics reveals synergy between Ag and g-C3N4 in Ag/g-C3N4 composite photocatalysts: a unique feature among Ag-doped biocidal materials



The silver/graphitic carbon nitride (Ag/g-C3N4) composite system exerts biocidal activity against the pathogenic bacterium Escherichia coli 1337-H that is stronger than that of well-known silver and titanium oxide (TiO2)-based composites. However, whether the Ag/g-C3N4 composite system has biocidal properties that the parent components do or do not have as separate chemical entities and whether they differ from those in Ag/TiO2 composite photocatalysts have not been clarified.


We investigated the chemical (cooperative charge handling and electronic properties) and biological (metabolic) effects exerted by the addition of Ag to g-C3N4 and to TiO2.


In this work, we undertook metabolome-wide analysis by liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry to compare the metabolite profiles of untreated E. coli 1337-H cells or those subjected to disinfection with Ag, g-C3N4, 2Ag/g-C3N4, TiO2 and 2Ag/TiO2.


While Ag or g-C3N4 moderately affected microbial metabolism according to the mean of the altered metabolites, multiple cell systems contributing to rapid cell death were immediately affected by the light-triggered radical species produced when Ag and g-C3N4 were as xAg/g-C3N4. The effects include drastically reduced production of small metabolites essential for detoxifying reactive oxygen species and those that regulate DNA replication fidelity, cell morphology and energy status. These biological consequences were different from those caused by Ag/TiO2-based biocides, demonstrating the uniqueness of the Ag/g-C3N4 system.


Our results support the idea that the unique Ag/g-C3N4 biocidal properties are based on synergistic action and reveal new directions for designing future photocatalysts for use in disinfection and microbial control.

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Data availability

The mass spectrometry metabolomics data were deposited in the MetaboLights repository with the dataset identifier MTBLS1771 (


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Financial support by Fundación General CSIC (programa ComFuturo) and AEI (PID2019-105490RB-C31) is acknowledged. C.B. and D.R. acknowledge funding from the Ministry of Science, Innovation and Universities (RTI2018-095166-B-I00).

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Authors and Affiliations



AK, MF-G and MF designed the study. AK, MJM-B and MF-G prepared the nanocomposites and performed the photocatalytic activity and radical species determination analyses; AK and MF performed disinfection tests and metabolite extractions. DR and CB performed metabolomics analyses. MF and DR analysed the metabolomics data. MF, MF-G and AK wrote the first version of the manuscript, which was revised and approved by all coauthors.

Corresponding authors

Correspondence to Marcos Fernández-García or Manuel Ferrer.

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This article does not contain any studies with human and/or animal participants performed by any of the authors.

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Kubacka, A., Rojo, D., Muñoz-Batista, M.J. et al. Metabolomics reveals synergy between Ag and g-C3N4 in Ag/g-C3N4 composite photocatalysts: a unique feature among Ag-doped biocidal materials. Metabolomics 17, 53 (2021).

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