| Melamine, with a1,3,5-triazine skeleton, is an organic compound and a trimer of cyanamide, which is widely used in the production of plastics, dyes, fertilizers, manufacture tableware, and fabrics. Melamine is combined with formaldehyde to produce melamine resin which is a very durable thermosetting plastic used in formica. If it is mixed with resins, melamine has fire retardant properties due to its nitrogen gas releasing capacity when burned. Because of melamine’s very high nitrogen content, it can cause false assay results for protein content monitoring of food. So melamine was sometimes illegally added to food products in order to increase the apparent protein content. Animal feeding with excessive melamine concentration can induce renal failure and even death. The residue of melamine in edible animal products also threatens human health.Melamine is used as food additives which has a rather poor biodegradability. The possibility of water resources and soils being contaminated by melamine discharge arouse more and more concern. Due to high prevalence of epidemic cases of renal failure among Chinese infants in2008, resulting from melamine contaminated milk, raised concerns about food safety and also the international interest to studying the melamine toxicity mechanism was established.This study was designed to test the melamine toxicity effects on aquatic ecosystem. S.obliquus was exposed to series melamine concentrations (0,50,200,750mg-L"1). Five parameters were measured after7days exposure, which were growth rate, superoxide dismutase(SOD), photosynthetic pigment, free malondialdehyde(MDA) and soluble sugar contents. Melamine concentrations of50,200mg·L-1caused a significant increase in growth and photosynthetic pigments contents. SOD activities of S.obliquus were stimulated first, then inhibited with the increasing of melamine concentrations, and reached its peak in200mg·L-1(compared with the control, P<0.05), reduced by43.6%in750mg·L-1. The contents of MDA and soluble sugar were inhibited significantly under moderate and high concentrations (50,200,750mg·L-1) of melamine.This study indicated that, SOD was sensitive to melamine exposure and could be used as a potential biomarker for risk assessment of aquatic ecosystem safety. Melamine, as a kind of hapten, the molecular weight is only126.12. Glutaraldehyde method was used to conjugate melamine with the carrier protein BSA and OVA. Coupling ratios of the melamine to BSA and OVA were3:1and4:1respectively.Melamine-BSA was used to immunize8-week BALB/c female mouse by multi-point injection immunization method. The serum titer had reached1:1600. Blood sample was obtained by mouse eyeballs removing method and a large number of monoclonal antibody was purifed through serum with caprylic acid-ammonium sulfate. The optimized reaction conditions were:hapten coat concentration is4μg/ml, blocking reagent on ELISA for ME is3%skimmed milk and the reaction time is15min. Under the optimun experimental condition, high ELISA cross-reactivity rates for CAAT and artidicial antigen, were193%and146%, respectively.The specificity of antibody was obtained by glutaraldehyde method is not high. This study is aimed to develop a rapid, sensitive detection method of melamine using ELISA. It will provide foundations for the development of melamine assay kit. |
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