Colorimetric allergenic fungal spore detection using peptide-modified gold nanoparticles

The rapid and sensitive detection of allergenic fungal spores is of great interest owing to the potentially negative impact of these spores on personal and public health and safety. We present a simple and prompt colorimetric strategy for detecting Aspergillus niger based on interactions between fungal spores and gold nanoparticles (AuNPs) modified with a specific binding peptide. The A. niger spore-binding peptide ligand was identified by phage display screening, which exhibited enhanced affinity through multivalent effects with specificity over common airborne bacteria. Immobilization of peptide ligands on AuNPs enabled rapid binding to A. niger spores, resulting in a visible change in the color intensity of the supernatant after sedimentation of the spores. This simple colorimetric approach displayed a high sensitivity of ∼50 spores and a rapid detection time of <10 min when used with a smartphone-based image analysis application. This strategy can be adapted for the simple and rapid detection of target microorganisms of relatively large size by exploiting the specificity of ligands and the optical properties of gold nanoparticles.