Sensitive colorimetric detection of melamine in milk with an aptamer-modified nanogold probe

Abstract

We report a rapid and facile colorimetric sensing method for melamine detection in milk using aptamer based nanoparticles (AuNPs). Aptamers can absorb on the surface of AuNPs and electrostatically interact with poly(diallyldimethylammonium chloride) (PDDA), which protects the AuNPs from aggregation. The introduction of melamine causes a melamine–aptamer complex to form via hydrogen bonding, thus the resulting cationic polymer can aggregate the AuNPs and cause a remarkable change in color. As a result of this, the presence of melamine can be determined by the naked eye and by measuring absorbance. This sensor is selective for the detection of melamine in milk samples and has a limit of detection of 34 nM. Since aptamer-modified AuNPs are more stable and selective than unmodified AuNPs in the sensing of melamine, we hope that this type of detection method will be helpful for the detection of other small molecules.