Fluorimetric Determination of E. coli in Water by Binding with Modified Magnetite and Fluorescent Carbon Dots

Le résumé fourni par la source

Most approaches to detecting bacteria in water are aimed at the identification of species by using specific techniques. Developing non-specific (broad-spectrum) methods for bacterial detection is crucial for rapid, cost-effective, and proactive screening of water quality. This paper proposes a non-specific method for detecting E. coli in water based on the interaction of the negatively charged cell wall with a positively charged fluorophore and magnetite; the resulting aggregate (“sandwich”) is extracted from the solution by magnetic separation and washed to remove excess fluorophore. The signal is detected using a photographic method, followed by digitization of the photographs, which makes it possible to avoid using full-spectrum equipment. A number of fluorophores of different structures (fluorescent dyes and carbon dots) and variants of magnetite modification with chitosan were studied. The carbon-dot system achieved an LOD of 3×104 CFU mL-1 for E. coli in deionized water, whereas the fluorescein system reached 4×103 CFU mL-1 but required spectrofluorimetric detection. Although the LODs are higher than those reported for biospecific assays based on antibodies or aptamers (1×102 CFU mL-1), the proposed approach does not use unstable or expensive biomolecules and can be completed within approximately 30 min. In addition, the method is faster than classical bacterial cultivation, and the synthetic protocols are simple. Therefore, the proposed approach is therefore intended as a proof-of-concept platform for inexpensive preliminary screening rather than selective pathogen identification.

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