Gold nanoparticles
(GNPs) have been used as detection probes for
rapid and sensitive detection of various analytes, including bacteria.
Here, we demonstrate a simple strategy for bacterial detection using
GNPs functionalized with 4-mercaptophenylboronic acid (4-MPBA). 4-MPBA
can interact with peptidoglycan or lipopolysaccharides present in
bacterial organelles. After the addition of a high concentration of
sodium hydroxide (NaOH), the functionalization of the surface of 50
nm GNPs with 4-MPBA (4-MPBA@GNPs) in the presence of polyethylene
glycol results in a color change because of the aggregation of 4-MPBA@GNPs.
This color change is dependent on the amount of bacteria present in
the tested samples. Escherichia coli (E. coli) K-12 and Staphylococcus aureus (S. aureus) are used as Gram-negative and Gram-positive bacterial models, respectively.
The color change can be detected within an hour by the naked eye.
A linear relationship is observed between bacterial concentrations
and the absorbance intensity at 533 nm; R
2 values of 0.9152 and 0.8185 are obtained for E. coli K-12 and S. aureus, respectively.
The limit of detection of E. coli K-12
is ∼2.38 × 102 CFU mL–1 and
that of S. aureus is ∼4.77 ×
103 CFU mL–1. This study provides a promising
approach for the rapid detection of target Gram-negative and Gram-positive
bacteria.
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