Visual and absorption spectroscopic detections of melamine with 3-mercaptopriopionic acid-functionalized gold nanoparticles: A synergistic strategy induced nanoparticle aggregates

• Nanoparticle aggregates induced by 3-mercaptopriopionic acid and gold nanoparticles can be used for detection of melamine.
• This method allows a detection limit of melamine was 0.4 μg/ml by UV–vis absorption spectroscopy.
• Color change can be observed with naked eye at 30 μg/ml melamine without the aid of any advanced instruments.
• This method has been successfully applied to detect melamine in infant formula with good reproducibility.

Nanoparticle aggregates induced by synergistic effect of electrostatic interaction and hydrogen-bonding recognition between melamine and 3-mercaptopriopionic acid (MA), which conjugated on the surface of gold nanoparticles (AuNPs) are used for detection of melamine. MA molecules are conjugated on AuNP surfaces to form MA-modified AuNPs (MA-AuNPs), acting as nanoprobes in the detection of melamine. Since such nanoparticle aggregates-mediated signal amplification can be measured by absorption spectroscopy, the method enables sensitive and real-time detection of melamine at the detection limit as low as 0.4 μg/ml, and the linear detection ranging from 0.6 μg/ml to 42 μg/ml. The color change can be readily seen by the naked eye at 30 μg/ml melamine without the aid of any advanced instruments. This method has been successfully applied to detect melamine in infant formula with good reproducibility, and it has the potential of being used in food safety detection.