Gated Nanosensor for Sulphate-Reducing Bacteria Detection

Abstract

Desulfovibrio vulgaris is an anaerobic microorganism belonging to the group of sulphate-reducing bacteria (SRB). SRB form biofilms on metal surfaces in water supply networks, producing a microbiologically influenced corrosion (MIC). This process produces the deterioration of metal surfaces, leading to high economic costs and different environmental safety and health problems related to its chemical treatment. For that reason, rapid and accurate detection methods of SRB are needed. In this work, a new detection system for Desulfovibrio has been developed using gated nanoporous materials. The probe is based on hybrid nanoporous alumina films encapsulating a fluorescent molecule (rhodamine B), whose release is controlled by an oligonucleotide gate. Upon exposure to Desulfovibrio's genomic material, a movement of the oligonucleotide gatekeeper happens, resulting in the selective delivery of the entrapped rhodamine B. The developed material shows high selectivity and sensitivity for detecting Desulfovibrio DNA in aqueous buffer and biological media. The implementation of this technology for the detection of Desulfovibrio as a tool for monitoring water supply networks is innovative and allows real-time in situ monitoring, making it possible to detect the growth of Desulfovibrio inside of pipes at an early stage and perform timely interventions to reverse it.

Keywords: microbiologically influenced corrosion; molecular gates; nanomaterials; oligonucleotide probe; sulphate-reducing bacteria.

Figure 1

Scheme of the controlled release system. The sensor S3, loaded with rhodamine B and capped with the O2 sequence, delivers the encapsulated rhodamine B dye in response to the target DNA from D. vulgaris.

Figure 2

HR-FESEM images of NAA supports during the fabrication process (scale bars: 100 nm). (A) NAA plate without modification (S0). (B) Loaded and functionalized NAA plate with rhodamine B and isocyanate (S1). (C) Loaded, functionalized, and capped NAA plate with O2 (S3).

Figure 3

Elemental mapping images of the support surfaces for samples S0, S1, and S3, obtained by energy-dispersive X-ray spectroscopy (EDXS). The spatial distribution of key elements (Al, C, N, Si, and P) is shown to illustrate the progressive surface modification throughout the functionalization process.

Figure 4

Fluorescence emission kinetics of released RhB from supports S3 in control media TRIS solution with Desulfovibrio vulgaris (a) genomic DNA and (b) cell culture sample. The red line shows the release profile in the presence of D. Vulgaris gDNA or cells, and the black line represents the release in the absence of DNA or the bacteria. Data are expressed as mean values and standard deviations derived from measurements for 3 distinct supports.

Figure 5

Rhodamine B release in response to increasing concentrations of D. vulgaris cell culture.

Figure 6

Interference assay: dye release in the presence of different bacterial species, including E. coli, S. aureus, S. epidermidis, L. rhamnosus, and D. vulgaris cell cultures.

Figure 7

Fluorescence emission from support S3 in TRIS/water samples containing D. vulgaris cells. The red bars show the release in the presence of D. vulgaris cells from bacterial cultures at different concentrations, and the black bar represents the release in the absence of the bacterial cells.