CdTe quantum dots as a novel biosensor for Serratia marcescens and Lipopolysaccharide

• CdTe QDs conjugated with Con A as a novel selective biosensor for Lipopolysaccharide.
• CdTe QDs–Con A was used as fluorescence labels to Serratia marcescens bacteria.
• Fluorescence of CdTe QDs–Con A decreased linearly with LPS concentration from 10 to 90 fg/mL.
• Linear relationship between the fluorescence and cell population of bacteria was obtained.

The main objective of this work is to synthesize CdTe quantum dots (QDs) conjugated with Concanavalin A (Con A) as a novel biosensor to be selective and specific for the detection of Lipopolysaccharide (LPS). In addition, the conjugated CdTe QDs–Con A was used as fluorescence labels to capture Serratia marcescens bacteria through the recognition between CdTe QDs–Con A and LPS of S. marcescens. The appearance of the lattice plans in the high resolution transmission electron photograph indicated a high crystalline with an average size of 4–5 nm for the CdTe QDs. The results showed that the relative fluorescence intensity of CdTe QDs–Con A decreased linearly with LPS concentration in the range from 10 to 90 fg/mL and with correlation coefficient (R2) equal to 0.9713. LPS surrounding the S. marcescens bacteria was bound to the CdTe QDs–Con A and leads to quenching of PL intensity. It was found that a good linear relationship between the relative PL intensity and the logarithmic of cell population of S. marcescens in range from 1 × 10 to 1 × 106 CFU/mL at pH 7 with R2 of 0.952 was established.

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