Abstract
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.