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Rapid measurement of waterborne bacterial viability based on difunctional gold nanoprobe



. 2022 Jan 11;12(3):1675-1681.


doi: 10.1039/d1ra07287k.


eCollection 2022 Jan 5.

Affiliations

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Junlin Wen et al.


RSC Adv.


.

Abstract

Rapid measurement of waterborne bacterial viability is crucial for ensuring the safety of public health. Herein, we proposed a colorimetric assay for rapid measurement of waterborne bacterial viability based on a difunctional gold nanoprobe (dGNP). This versatile dGNP is composed of bacteria recognizing parts and signal indicating parts, and can generate color signals while recognizing bacterial suspensions of different viabilities. This dGNP-based colorimetric assay has a fast response and can be accomplished within 10 min. Moreover, the proposed colorimetric method is able to measure bacterial viability between 0% and 100%. The method can also measure the viability of other bacteria including Staphylococcus aureus, Shewanella oneidensis, and Escherichia coli O157H7. Furthermore, the proposed method has acceptable recovery (95.5-104.5%) in measuring bacteria-spiked real samples. This study offers a simple and effective method for the rapid measurement of bacterial viability and therefore should have application potential in medical diagnosis, food safety, and environmental monitoring.

Conflict of interest statement

There are no conflicts to declare.

Figures



Scheme 1. Schematic illustration of the proposed colorimetric method. The dGNP is composed of bacteria recognizing part and signal indicating part. Living bacterial sample reacted with dGNPs displays characteristic wine-red due to the dispersed state of dGNPs. Dead bacterial sample containing dGNPs develops significant color change because of the reduced inter-particle distance of dGNPs that induced by intracellular components such as nucleic acid.


Fig. 1


Fig. 1. Characterization of the synthesized dGNP. (A) Photograph and UV-vis spectra of dGNPs; (B) TEM image of dGNPs; (C) HAADF mage of dGNPs; (D) element mapping of dGNPs including gold (Au), sulfur (S), nitrogen (N) and carbon (C).


Fig. 2


Fig. 2. Feasibility evaluation of the proposed colorimetric method. (A) Photograph and UV-vis spectra of dGNPs incubated with live bacteria (tube a, line a), dead bacteria (tube b, line b), supernatant of dead bacteria suspension after centrifugation (tube c, line c), and deposited cells (suspended in ultrapure water) of dead bacteria suspension after centrifugation (tube d, line d). TEM images of dGNPs incubated with (B) live bacteria, (C) dead bacteria, (D) supernatant of dead bacterial suspension after centrifugation, and (E) deposited cells of dead bacterial suspension.


Fig. 3


Fig. 3. Influence of volume ratio of bacteria/dGNP on the responsive color signal. The initial concentrations of employed dGNP and E. coli K12 suspensions were 1.62 nM and 1.0 × 109 CFU mL−1, respectively. Blank control was measured with dGNPs by using ultrapure water instead of bacteria suspension.


Fig. 4


Fig. 4. Colorimetric responses of the proposed method challenged with bacterial suspensions of different viabilities. (A) UV-vis spectra of dGNP in measuring E. coli K12 suspensions of 0–100% viability. (B) Plot of the A528 value against bacterial viability. Error bars represent the standard deviation of three independent measurements.


Fig. 5


Fig. 5. Responsive color signal of the detection system challenged with different bacterial species. Live and dead bacterial suspensions containing S. aureus, S. oneidensis and E. coli O157:H7 were measured. The tested mixture sample contained S. aureus, S. oneidensis and E. coli O157:H7. Blank control was measured with dGNPs by using ultrapure water instead of bacteria suspension.

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