Abstract
In the past few years, melamine has been illegally added into dairy products to increase the apparent crude protein levels. If humans or animals drink the milk adulteration of melamine, it can form insoluble melamine–cyanurate crystals in their kidneys which causes kidney damage or even death. In the present work, we constructed a simple and label-free fluorescent method for melamine detection based on melamine-thymine recognition. SYBR Green I was utilized as a reporter for this method as it did not require any modification or expensive equipment. In the absence of melamine, polythymine DNA was digested by Exo I, which caused a decrease in the fluorescence signal. In the presence of melamine, the polythymine DNA was able to fold into a double chain structure, however this was done with the help of T-melamine-T mismatches to prevent degradation. Then, the SYBR Green I combined with the double-stranded DNA to result in an intense fluorescence signal. The limit of detection in this method was 1.58 μM, which satisfied the FDA standards. This method also had a good linear relationship within the range of 10–200 μM. In addition, this new method has a good selectivity to distinguish melamine from the component of milk. As a result, we developed a simple and highly selectivity method for melamine detection.
Highlights
Melamine (2,4,6-triamino-1,3,5-triazine) is a small organic compound widely used in the production of plastics, fertilizer, resins and other products [1,2]
When the SYBR Green I was added, no by Exonuclease I (Exo I) because it existed as a singleIn strand of DNA
We developed a simple and label-free fluorescent method for melamine
Summary
Melamine (2,4,6-triamino-1,3,5-triazine) is a small organic compound widely used in the production of plastics, fertilizer, resins and other products [1,2]. In the past few years, melamine has been illegally added into dairy products to increase the apparent crude protein levels. This is because the standard method for protein level in food is the Kjeldahl method, which is done by measuring nitrogen content, and the nitrogen content of melamine (66% by mass) is much higher than protein (~16%). Many countries have formulated regulations on the maximum content limits of melamine in food, especially milk products. The Federal Food and Drug Administration (FDA) has defined a limitation of melamine as 2.5 ppm (19.8 μM) for non-infant products and 1 ppm (7.9 μM) for infant milk products [8,9]. Sensitive and selective detection melamine is very important for people’s health
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