Studies And Applications Of Gold Nanoparticjes-based Colorimetric Sensors For β-Agonists And Antibiotic

Gold nanoparticles, a typical representative of the metal nanoparticles, possessthe basic properties of metal nanoparticles. Besides, AuNPs also has many uniqueproperties, such as good optical properties, adsorption properties, molecularrecognition properties and so on. AuNPs has been widely applied in the fields ofbiology, medicine, etc. and widely concerned by more and more people. Recently,AuNPs has been also successfully applied in detection and recognition of DNA, metalions, protein and small molecules. Aptamer has high association constant andspecificity, easy production and modification, cost-effectiveness and stability. Thecolorimetric/visual sensing strategies based on aptamers and AuNPs have been widelyapplied in many fields. As the representative of β-agonists, the residues of clenbuteroland ractopamine in animal products are deemed as an important health hazard.Tetracycline (TET) is a member of the most common antibiotic. However, because ofextensive use and illegal addition, tetracycline residue in foods of animal origin is oneof the typical food safety issues. Therefore, detection for β-agonists and antibiotic infood became a key technology of food safety testing. In this article, with AuNPs asthe colorimetric probe, a colorimetric method using the interaction between citrate-stabilized AuNPs and clenbuterol/ractopamine is developed, and a colorimetricaptasensor based on the interaction between cysteamine-stabilized AuNPs, aptamerand taget is established. The detail content is as follows:1、Citrate-stabilized AuNPs was synthesized using the traditional method, andthe size is about13nm. The interaction mechanism between AuNPs andclenbuterol/ractopamine was systematacially esplored. The color of well-dispersedAuNPs was wine red. Howerve, after adding clenbuterol/ractopamine,clenbuterol/ractopamine could easily bind onto the surface of AuNPs via Au-N bonds,which resulted in the aggregation of the AuNPs. Thus an obvious color and spectrumchange of AuNPs could be observed. Based on this principle, a simple, rapidcolorimetric method for clenbuterol and ractopamine detection was developed. Underthe optimized conditions, the method was used for detecting clenbuterol/ractopaminein pig urine. The detection limit for clenbuterol is0.0158μg/mL and for ractopamine is0.0299μg/mL. The whole process could be accomplished within30min, and it ispromising for on-site screening of clenbuterol and ractopamine.2、Cysteamine-stabilized AuNPs was synthesized using the traditional method,and the size is about34nm. Through studying the mechanism between CS-AuNPs,tetracycline aptamer and tetracycline, the results indicate that TET aptamer couldcause the aggregation of CS-AuNPs, but with the presence of TET, the aptamers werefirstly exhausted due to the specific aptamer-TET binding, and could not induce theaggregation of CS-AuNPs. Based on this experimental phenomenon, colorimetricassay has been developed. The four experimental conditions were optimized,including CS-AuNPs concentration, the reaction time of CS-AuNPs and aptamers,aptamers concentration and the incubation time of TET and aptamers. Under theoptimum conditions, the linear coefficient R=0.9907, the detection limit0.039μg/mL.Which is lower than the permissible level in the European Union (EU)(225nM) andChina (100μg/kg). The established colorimetric method was successfully applied todetect TET in raw milk. Therefore, the method is simple, low-cost, time-saving andalso has excellent selectivity and good sensitivity. It appears to be a promisingcandidate for rapid screening of TET residue in raw milk.