Study On Rapid Detection Of Cadmium Based On Aptamer

Cadmium is a toxic metal element.Cadmium has a long toxic time and a long half-life,is not easy to eliminate,showing toxic damage 20-30years after poisoning.The rapid development of economy has brought great environmental pollution problems to China.The excessive content of heavy metals in soil contaminated grain plants,leading to food safety problems,especially cadmium contamination.The traditional detection methods of cadmium include graphite furnace atomic absorption spectrometry,atomic fluorescence spectrometry,inductively coupled plasma mass spectrometry,and high performance liquid chromatography.These methods are classic and sensitive,but well-equipped laboratory is needed and the assay time is long.A lot of efforts have been done for the development of rapid detection technology of metal cadmium,including immunoassay,biochemical sensor,lateral flow strip test paper,etc.,but these methods have low sensitivity,poor stability and other shortcomings.In this work,two detection methods based on aptamer for cadmium ion were constructed by using aptamer as recognition element and its specific recognition ability for cadmium ion.The specific work is as follows:1.A gold nanoparticles labeled aptamer based lateral flow strip test assay for rapid detection of Cd²⁺was established.The preparation conditions of gold nanoparticles labeled aptamer were optimized.The optimal concentration of NaCl was 50 mmol/L,the optimal concentration of aptamer was 600 nmol/L,the optimal incubation temperature was44℃,and the optimal incubation time 2 hours.The influences of aptamer sequences and complementary probes on the analytical performance were investigated.Under the optimal test conditions,the response signal of the lateral flow strip and the concentration of Cd²⁺showed a good linear relationship at 10～100 ng/mL,the linear equation was y=-6.6355 x+706.71 R²=0.9865.and the detection limit of this method was 3.79ng/mL.2.A new method of non-labeled fluorescence assay was established based on aptamer for cadmium ion detection.The p H of the system,the molar ratio of thiazole orange to aptamer,the binding time of thiazole orange with aptamer,and the binding time of aptamer with Cd²⁺were optimized.Under the optimal conditions,the difference of fluorescence intensity（F-F₀）showed a good linear relationship with the concentration of Cd²⁺,the linear equation was y=-2.3406x+284.73,R²=0.9911.The linear range was 2.00～80.00 ng/mL,and the detection limit was 0.23ng/mL.This method is simple,energy-saving and low cost,and does not need to modify aptamer.