Study On The Genetic Toxicity And Rapid Detections Of Melamine In Raw Milk

Melamine (1,3,5-triazine-2,4,6-triamine) is an industrial chemical compound. For itshigh nitrogen content (66%by mass), it has been illegally added into food, feed andeven milk to increase the apparent protein content. As a result, its illegal addition hasled to the pet melamine poisoning in USA,2007and infant renal calculus cases inChina,2008. Although, its acute toxicity is well known, its long-term toxicityespecially genetic toxicity is not clear and needs to be investigated urgently toappease the public panic. Thus, it is very important to control the use of melamine.Nowadays, main methods for detection of melamine in milk and dairy products are asthe following: HPLC, HPLC-MS, GC, HPLC-MS/MS. Additionally, some newmethods are also developed for melamine monitoring, such as SERS, fluorescence,spectrophotometric absorption and chemiluminescence. Although these methods arehighly sensitive, most of them are either time-consuming due to the exhaustivepretreatment or high cost due to the expensive instrumentation. Therefore, simple,rapid, low-cost, easy operated methods are required for detecting melamine in milkand dairy products.The major contents of this thesis are given in the following.In this research paper, the effects of melamine on mutagenesis in prokaryotes andeukaryotes were tested by Ames test, in vitro mammalian chromosome aberration testand mouse micronucleus test; the effect of melamine on DNA damage in sperm cellswere observed by single cell gel electrophoresis. The results show that melamine hasno mutagenic function in prokaryotes and eukaryotes in vitro and in vivo, but it hasability to increase DNA damage of sperm cells.In this paper, we report a rapid, visual, facile colorimetric detection of melaminein raw milk by unmodified gold nanoparticles (AuNPs). AuNPs can be induced by melamine from dispersion to aggregation rapidly, along with the color change fromred to blue (or purple). After the optimization of reaction conditions, the wholeanalysis only needs about20min including the simple pretreatment we designed. Theanalysis can be observed by the naked eye, and simple to operate withoutsophisticated instruments. In the raw milk, the present limit of detection for melamineis1μM by naked eyes and down to375nM by the instument. Furthermore, weexplore the interaction principle between melamine and citrate-stabilized AuNPs inthis work; establish the foundation for modifying the AuNPs and optimizing thesystem of AuNPs-melamine in the future.In this paper, we also report a rapid and sensitive colorimetric sensor formelamine detection in milk by the aptamer based nanoparticles (AuNPs). Aptamercan absorb on the surface of AuNPs and electrostatically interacts with Poly(diallyldimethylammonium chloride)(PDDA), which protects AuNPs fromaggregating. The introduction of melamine would form a melamine-aptamer complexby hydrogen bonds, thus the following cationic polymer could aggregate AuNPs andcause a remarkable change in color. According to this, melamine can be determinedby naked eyes and means of absorbance. This sensor is selective for detection ofmelamine in milk samples and has a limit of detection of34nM. Sinceaptamer-modified AuNPs is more stabilized and selective than unmodified AuNPs inthe sensor of melamine, we hope that this detection method-building process will behelpful for the detection of other small molecules.