Development Of Gold Nanoparticles Colorimetric Method Based On Aptamer For The Detection Of Chlorpyrifos And 17?-estradiol

Along with the frequent occurrence of food safety events,ensuring food safety has become an important question of our country and the world.Remains of pesticide and veterinary drugs in the food and environment is one of the important factors that threaten food safety and human health.As one of the most commonly used organophosphorus pesticides,Chlorpyrifos is very representative.Due to its widespread uses in the farmland,its residue has been discovered many times in the water and the soil.Research indicates that chlorpyrifos can damage on human nervous system by chronic toxicity.17?-estradiol is a natural endocrine-disrupting compound(EDC)excreted by humans and domestic animals,which can residues in animal products as well as water and enter human body through food chain.It mimics the hormone estrogen in the body and interferes with normal metabolic processes,which will make human body function disorders.Current detection methods for them are mainly limited to chromatography,enzyme-linked immunoassay and so on,and these methods are expensive in equipment,complicated to use and time-consuming in operation,which also limits their scope of application.Aptamers,in-vitro selected functional DNA or RNA structures,are superior to antibodies in specificity and affinity for their target molecules so that they become more and more popular in the analysis of food hazards detection as the sensitive recognition element.Gold nanoparticles is one of the metal nanoparticles that are widely used in the detection and identification of some materials due to its special properties,such as optical properties,molecular recognition performance and adsorption.In this paper,we use gold nanoparticles as colorimetric probes and combine the specific recognition of aptamers and target to established two highly sensitive,accurate and rapid colorimetric aptasensors for the detection of chlorpyrifos and 17?-estradiol.The detail research contents are as following:1.The mercaptoethylamine modified gold nanoparticles(CS-Au NPs)used traditional methods to prepared are positive charged,while the aptamer is negatively charged because of its phosphate skeleton.So that the aptamer of chlorpyrifos cancause the aggregation of CS-Au NPs,and change its color from red to purple,with the ultraviolet absorption spectrum changing.When chlorpyrifos exists,aptamers will first combine with chlorpyrifos,which does not cause the aggregation of gold nanoparticles.Four experimental conditions are optimized,including the concentration of gold nanoparticles and aptamers,the reaction time between CS-Au NPs and aptamers and the incubation time of chlorpyrifos and aptamers.Under the optimum conditions,the linear range of this method is 1-110 ng/m L and the detection limit is 0.83ng/mg.The spiked recovery rates are between 102.38% and107.29% in apple sample,and the RSD was between 1.02% and 3.40%.Therefore,this simple,low-cost and time-saved method also has excellent selectivity and good sensitivity.It is a promising candidate for rapid screening of chlorpyrifos.2.The citrate modified gold nanoparticles could be prepared using HAu Cl4 and sodiumcitrate.The appropriate amount of Na Cl could induce the aggregation of dispersed Au NPs.Single stranded DNA could adsorb on the surface of Au NPs,thus preventing Au NPs against the Na Cl-induced aggregation.While in the presence of17?-estradiol,aptamer could specifically bind with 17?-estradiol accompanied with configuration change,no longer protect Au NPs,leading to the subsequent aggregation of Au NPs.Through the Au NPs accumulation induced by Na Cl and the change of the absorption spectra and color,make it easy to detect the estradiol in water.Moreover,the whole detection process can complete within approximately 30 min.And the linear range of this method is 10-90 ng/m L,the detection limit of 17?-estradiol is 3ng/m L.The spiked recovery rates are between 199% and 115% in water sample,and the RSD was between 1.40% and 3.16%.The proposed method exhibits good reproducibility and accuracy,providing a rapid and simple method for the analysis of estradiol.Further,by developing this kind of colorimetric aptasensors,we suggested a new idea for the detection of small molecular in food.