Study On Systematic Identification Of Environmental Endocrine Disruptors In Waste Leachate Based On Colorimetric Paper-based Microfluidic Chip

The composition of waste leachate generated in the process of municipal solid waste treatment and disposal is complex,and contains a variety of environmental pollutants including endocrine disruptors,which will cause environmental pollution and threaten human health.And current detection techniques rely on large scale instruments,which it is complex to operate.Therefore,the development of rapid,simple and low-cost detection techniques,which can be applied to systematically identify and monitor the environmental endocrine disruptors in waste leachate is of great practical significance for pollution management and environmental safety assessment.The colorimetry is commonly used in detection region,which presents the features of simple operation and easy identification.At the same time,the colorimetry based on microfluidic paper-based analytical devices(μPADs)shows the advantages of low reagent consumption,short reaction time and green recycling treatment.In this paper,a novel visual sensing platform,combining the high specificity of aptamers and the unique optical properties of noble metal nanoparticles,was designed and developed to achieve rapid detection and systematic identification of three environmental endocrine disruptors(bisphenol A,17β-estradiol and malathion)in waste leachate.The details of this work are as follows.(1)The electrostatic binding between noble metal nanoparticles and nucleic acid aptamers helps to avoid aggregation of the probe in salt-induction.In the present of the target,the aptamer combines preferentially to it,which causes the surface of the probe losing the protection of the aptamer.Thus,affected by salt solution,the nanoparticles could be aggregated in the solution with distinct color change.Based on the above principle,Au/Ag NPs were successfully selected as the part of the colorimetric probe,which was finalized as Au/Ag NPs/Aptamer probes.After the experimental conditions of each reaction system optimized by the specificity of different analyte aptamers,the construction of the visual detection system for bisphenol A,17β-estradiol and malathion was completed.The limits of detection(LODs)of bisphenol A,17β-estradiol and malathion were 2.9 ng/m L,3.3 ng/m L and1.6 ng/m L in the ranges of 50-700 ng/m L,50-800 ng/m L and 10-250 ng/m L,respectively.In addition,due to the extremely complex composition of waste leachate,it is necessary to use the simple pretreatment of the samples by SAX solid-phase extraction columns.The contents of three endocrine disruptors in the five samples were detected by Au/Ag NPs/Aptamer probes in colorimetry,which was consistent with the results of high performance liquid chromatography,indicating the reliability of the method for detecting the actual samples.This study provides a new idea for detection of environmental endocrine disruptors in complex samples.(2)Based on the successful establishment of the above-mentioned colorimetry,a new folded multi-channel μPAD was designed and prepared by wax printing.By optimizing the printing specifications and post-processing conditions,the preparation of the μPAD was completed.And the hydrophobic characteristic of the μPAD was tested,as well as the initial attempt of the colorimetry.The results showed that the prepared μPAD had the basic properties of selective hydrophobicity,with the functions of carrying a certain volume of solution and guiding its directional flow.Besides,the feasibility verification of paper-based colorimetry was completed successfully.This work provides the applied basis for the construction of a colorimetric platform to detect environmental endocrine disruptor by μPADs.(3)After optimizing the reagent concentration and volume,a novel μPAD with Au/Ag NPs/Aptamer probes could be a visual sensing platform to achieve the systematic identification of bisphenol A,17β-estradiol and malathion.The results showed that the above sensing platform can achieve quantitative analysis of bisphenol A,17β-estradiol and malathion by smart phones and color recognition software,with detection ranges of 5-20 μg/m L,2-20 μg /m L and 1-50 μg /m L,and detection limits of0.6 μg /m L,1.6 μg /m L and 0.9 μg /m L,respectively.To further validate the performance of the visual colorimetry,the spiked recovery experiments of the samples were performed,with the recovery rate ranged from 90.2% to 100.3%,indicating that the method is accurate and reliable for the determination of endocrine disruptors in complex environmental samples(waste leachate).In summary,this study provides a new platform for the rapid and systematic identification of contaminants in waste leachate.The designed colorimetric paper-based microfluidic chip successfully achieved the detection and analysis of three endocrine disruptors in waste leachate,which not only provided a new method for colorimetric detection of endocrine disruptors,but also provided a new idea for on-site detection and systematic identification of waste leachate.