Colorimetric Detection of DDAC Based on Aggregation of Gold Nanoparticles Modified with Phage-Displayed Affinity Peptides

Abstract The recent outbreak of the COVID-19 pandemic caused a surge in disinfection demands across public and private spaces, significantly increasing the usage of non-antibiotic disinfectants. Among these, dialkyl dimethyl ammonium compounds (DDAC), a class of quaternary ammonium compounds, are widely utilized in household and industrial antibacterial products. However, the extensive reliance on and overuse of this type of disinfectant, even in the post-pandemic era, has led to a significant increase in DDAC levels in wastewater. This trend underscores the urgent requirement to monitor DDAC levels in wastewater, soil, and food sources. In this study, we discovered affinity peptides for DDAC through the phage display technology and employed them as the bioreceptor to develop a gold nanoparticle (AuNP)-based colorimetric detection system. When the peptide interacts with DDAC first, the peptide undergoes conformational changes that shorten the interparticle distance between AuNP, thus causing a visible color change corresponding to a red shift in the absorption peak that is also visible with the naked eye. The proposed nanobiosensor exhibited excellent performance, achieving a detection limit as low as 26.5 ppb with high sensitivity and specificity. Furthermore, the AuNP-peptide biosensing platform demonstrated strong resistance to salt-induced aggregation, maintained stability across a wide range of pH levels, and maintained its sensitivity even in the presence of interfering metal cations or anions. This robustness ensures reliable detection of DDAC contamination in tap or pond water environments with high recovery rates.