Smartphone-assisted paper-based colorimetric aptasensor for rapid detection of N-acetylneuraminic acid

N-Acetylneuraminic acid (Neu5Ac) is a bioactive compound that supports health across all age groups and plays an irreplaceable physiological role in food fortification and disease prevention and control. Herein, N-acetylneuraminic acid-functionalized gold nanoparticles (Neu5Ac-AuNPs) signal probes with peroxidase-like catalytic activity were synthesized and, based on these probes, a novel paper-based colorimetric aptasensor integrated with a smartphone was developed for the intuitive and highly sensitive detection of Neu5Ac. The sensing mechanism relies on the competitive binding between free Neu5Ac and the Neu5Ac-AuNPs signal probes for the binding sites on the aptamer immobilized on the paper substrate. Coupled with a TMB-H₂O₂ colorimetric signal amplification system, the assay employs a smartphone to capture colorimetric images and extract grayscale values for quantitative analysis of Neu5Ac. The developed sensor achieved a limit of detection (LOD) of 4.99 µM and a limit of quantification (LOQ) of 5 µM and was successfully applied to milk and beef samples, yielding spiked recoveries ranging from 92.80% to 102.30%. This work provides a promising strategy for the simple, rapid, and reliable on-site detection of Neu5Ac in food matrices.