Colorimetric detection of lipopolysaccharides based on a lipopolysaccharide-binding peptide and AuNPs

Abstract

In this study, a novel label-free colorimetric assay for the detection of lipopolysaccharides (LPSs) was developed based on a LPS-binding peptide (LBP) and unmodified gold nanoparticles (AuNPs). Cationic LBP probes with a C-terminal cysteine thiol are used to anchor the surface of unmodified AuNPs with anionic surface charge and cause the aggregation of AuNPs, resulting in the red-to-purple color change and the appearance of a new absorbance peak at 586 nm in the absorption spectrum of AuNPs. In the presence of an LPS, specific binding between the LPS and the LBP leads to the formation of LPS–LBP complexes and subsequently prohibits the aggregation of unmodified AuNPs, which exhibits distinct differences in both the color and the absorption spectrum of AuNPs. On this basis, the concentration of the LPS can be visualized through the purple-to-red color change of the AuNPs and quantitatively determined by UV-vis spectroscopy. Under the optimized conditions, the proposed assay is capable of sensitively and selectively measuring LPSs in the range of 10–1000 nM with a detection limit of 2.0 nM.