Sensitive visual detection of gram-positive bacteria by composite filter membrane combined with antibiotic modified nanoparticles

Bacterial detection is a daily work closely related to human health. Although many detection methods can achieve rapid and sensitive bacterial detection, they usually focus on detecting small-volume samples. Due to the uneven distribution of bacterial particles in the liquid, the total bacterial content calculated based on small-volume samples may deviate significantly from the actual state. Here, a simple visual assay for the detection of bacteria in large-volume samples was reported, and the Gram-positive bacteria detection was taken as an example to verify its practicability. By using a composite filter membrane with a hydrophobic layer and an adjustable interception area to filter the sample, the bacteria can be confined to a small detection area. After the obvious chromogenic reaction was catalyzed by antibiotic-modified nanoparticles specifically bound to bacteria, the naked eye can more easily perceive the highly concentrated color molecules, thus realizing more sensitive bacterial detection. As a result, samples containing more than 20 Staphylococcus aureus cells (2 cfu/mL) can be easily identified by naked eyes within 30 min, and show reasonable specificity and practicability. Given the advantages of easy preparation, simple operation, and low dependence on instruments, the visual assay is worthy of being widely used.