| Food contaminants are closely related to food safety and human health, while the present researches on the quantitative detection of the small molecule contaminants in food are still inadequate. Hence, it is essential to establish rapid and cost-efficient sensors for the analysis of small molecule contaminants in food. Owing to the advantages of high affinity, excellent specificity, easy modification and so on, aptamers are commonly recognized as a molecular recognition component and widely applied in the construction of the sensors. Nanomaterials, which can be used as signal transduction components due to its unique physicochemical properties, are becoming a powerful tool to develop novel sensing methods and improve the existing detection methods. In this paper, utilizing the specific indentification of aptamer and the advantages of quantum dots-gold nanoparticles fluorescent nanoprobes, two kinds of universally applicable nanomaterial-based fluorescence aptasensors for rapid detection of bisphenol A(BPA) and 17β-estradiol were built based on the priciple of inner filter effect(IFE) and fluorescence resonance energy transfer(FRET). The main contents are as follows:(1) An aptamer-based IFE method for the analysis of BPA has been developed based on the specific recognition of aptamers employing the similarly charged gold nanoparticles(AuNPs) and CdTe quantum dots(CdTe QDs). The fluorescence of CdTe QDs could be significantly quenched by AuNPs via the IFE. The IFE efficiency can be adjusted by BPA in that the specific recognition between BPA and aptamers could show different influences on the salt-induced aggregation of AuNPs, and correspondingly modulate the IFE process. Under optimum conditions, a good linear correlation to BPA concentration was exhibited from 10 ng·mL-1 to 80 ng·mL-1(R2=0.99) with the detection limit of 1.86 ng·mL-1, which was lower than the Maximum Residue Limits of BPA in drinking water. This assay showed excellent selectivity towards BPA over other BPA analogues. The application of this method for tap water samples obtained satisfactory recoveries in accordance with those from HPLC method. The proposed fluorescent method exhibits excellent advantages of high sensitivity, excellent selectivity and simple operation procedure, thus it would be suitable for the on-site and real-time screening of target in real samples.(2) A novel aptamers-based FRET assay for the analysis of 17β-estradiol was developed based on the specific recognition of aptamers employing the oppositely charged thioglycolic acid-capped CdTe quantum dots(TGA-CdTe QDs) and cysteamine-stabilized gold nanoparticles(cysteamine-AuNPs). The fluorescence of TGA-CdTe QDs was significantly quenched with addition of cysteamine-AuNPs via the FRET. The FRET process can be modulated by 17β-estradiol in that the specific recognition between 17β-estradiol and aptamers could show different effects on the aptamers-mediated aggregation of cysteamine-AuNPs, and correspondingly adjust the FRET process. The feasibility of the method has been demonstrated by carrying out the detection of 17β-estradiol with the wide linear range from 0.5 ng·mL-1 to 150 ng·mL-1 and the low detection limit of 0.057 ng·mL-1. The established assay exhibited favorable selectivity towards 17β-estradiol over other endocrine disrupting compounds and probably coexisting chemicals in real samples. Furthermore, the assay has been successfully applied to detect 17β-estradiol in real tap water samples and feeds samples with good performance. The results were in full consistence with those from HPLC method, indicating the reliability of the detection system. The aptamers-based FRET assay is expected to offer a new opportunity for the rapid analysis of 17β-estradiol in real samples. |
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