Melamine (C3H6N6) (Mel; 1,3,5-triazine-2,4,6-triamine) is a small polar nitrogen rich compound (67% by mass) which is widely used for the production of plastics, amino resins and flame retardants. In September 2008 the illegal adulteration of infant milk powder with melamine in China led to adverse kidney and urinary tract failure and nearly 54000 children were hospitalized and at least six children died. The ingestion of melamine above the safety levels (2.5 ppm in the USA and EU; 1 ppm for infant formula in China) can induce renal failure and death in infants. The imports of milk and milk products for the nutritional use of children was banned and led to the implementation procedures to test illegal adulteration of milk products for melamine. The traditional method for the determination of melamine was not very specific, color forming agent, unstable and standardization difficult. A more specific, stable and simple biosensor for the determination of melamine is necessary.

Our research group is developing an electrochemical biosensor for melamine based on gold nanoparticles and poly(L-Arginine)/multiwall carbon nanotubes (P-L-Arg/MWCNTS) composite film as a rapid and robust method for the analysis of infant milk and milk product samples. Carbon nanotubes (CNTs) are novel types of carbon material. The modification of electrode based CNTs provide excellent electron transfer capabilities for the oxidation of biomolecules with gold nanoparticles (AuNPs) used as enhancing interfacial platform for the development of nanotube based sensor. The CNTs electrode has a high surface area and is biocompatible to provide stronger affinity for melamine. Chitosan (CHIT) is a natural polymer (one amino group and two hydroxyl groups) to form a biocompatible matrix in conjunction with CNTs or other redox mediators or nanoparticles. The appropriate combination of pLys/MWCNT–AuNPs/Chi nano-composite membranes are used for the development of the electrochemical biosensor. We hope to develop to detect a low concentration of melamine (ppm) in raw milk and milk products and fabricate electrochemical chip to conveniently indicate to consumers the level of melamine present in raw milk/milk products from the local market.