Determination of melamine and melamine-Cu(II) complexes in milk using a DNA-Ag hydrocolloid as the sensor

Simple and sensitive methods are required for the detection of melamine since melamine is harmful to human health. To detect the content of melamine and metal-melamine species in milk products, a new luminescent DNA silver hydrocolloid (AgNC₅₃) was synthesized using a modified C3A-rich aptamer as the template. The emission of AgNC₅₃ at 617 nm is sensitive to both melamine-Cu(II) and melamine, while almost no response to the free Cu(II) ion was detected. Moreover, AgNC₅₃ is used to detect precisely the content of melamine in milk with a detection limit as low as 2.7 × 10^-8 M. Thus, the AgNC₅₃-based fluorescence method is a "label-free" fluorescence technology that can be used for the determination of melamine or the melamine-Cu(II) complex in milk products.