Sensors to Detect Sulfur Pesticide Residues & Biothiols


Supervisor:li bin


Degree Year:2019





Nanomaterials,as compared to the bulk materials,have their characteristic optical properties,including semiconductor quantum dots with extremely high fluorescence quantum yield that is vastly superior to traditional organic fluorescent dye,and noble metal(gold or silver)nanoparticles with excellent fluorescent quenching efficiency.All of those nanomaterials have been intensively used in the detection of environmental pollutants and biomolecules.Microbeads,as the core materials in commercial suspension microarray platform,has demonstrated its excellent performance in multiplexing biomolecules detection with high degree of automation,fast detection time and ultra-low sample volume.However,development of novel detection method with higher detection limit and by the combination of microbeads with nanomaterials was rarely reported so far.In this work,we focused on the construction of nanohybrid by the use of microbeads,gold nanoparticles and quantum dots for the detection of various targets including biothiols and pesticide.For the detection of biothiols,flow cytometry-based method was realized,and the detect limit of 0.1 μmol/L could be achieved in a fluorescence “turn on” manner.Moreover,pesticides and heavy metal ion was also adopted as the potential targets to interrogate the generality of our nanohybrid,and the results demonstrated that our system has the potential for the detection of various target by changing the corresponding probe molecules modified on the surface of our nanohybrid.These results are summarized briefly as follows:1.In this section,a direct "turn on" fluorescence sensor was developed here for the first time to detect sulfur pesticide.Our probe “Polystyrene/Gold Nanoparticles/ Rhodamine B” or(PS/Au NPs/Rh B)was constructed by attaching Au NPs onto the surface of PS microbeads,followed by attaching Rh B as the source of fluorescence onto the surface of PS/Au NPs with electrostatic interaction.Initially,the fluorescence of Rh B was quenched by the effect of Au NPs.After mixing our probe with tap water containing sulfur pesticide thiram,the fluorescence of the probe not only “turned on” but also enhanced in 1 min with the detection limit of 1 nmol/L.Also,the probe was successfully applied to Thiram detection in tap water as a spiked sample with high sensitivity and selectivity.The recovery for our probe detection for thiram in tap water with different spiking concentrations(10 μmol/L,20 μmol/L and 30 μmol/L)were(130.9% ± 2.05,78.80% ± 2.22 and 101.43% ± 0.90),respectively.2.In this section,flow cytometry-based fluorescent sensor was for the first time developed for the detection of biothiols in a fluorescence “turn on” manner.The probe which we name “Polystyrene/Quantum Dots/Gold Nanoparticles” or(PS/QDs/Au)was constructed by immobilizing QDs onto the surface of PS microbeads to obtain fluorescent microbeads,followed by gold NPs absorption through electrostatic interaction to quench their fluorescence.In the presence of biothiols,the fluorescence of our probe can be restored in less than 5 min,and the detection limits for GSH,Cys and Hcy were 0.5 μmol/L,0.1 μmol/L and 0.3 μmol/L,respectively.Most importantly,the fluorescence signal of each of our probe microbeads can be collected individually by flow cytometry,realizing single microbead-based biothiols detection for the first time.Moreover,the probe was successfully applied to imaging of intracellular biothiols in A549 cells,demonstrating its potential in biological application.3.In the last section,several other probes by the use of QDs,Au NPs and microbeads for the detection of both biothiols and sulfur pesticide were investigated.The first one was constructed by sequentially immobilizing red-and green-emission QDs onto the surface of microbeads,and Cu2+ ion could quench both the fluorescence of red and green QDs.Interesting,the fluorescence of red QDs in this dual-emission probe could be selectively turned on in the presence of biothiols.In addition,Au NPs-based colorimetric method was developed for the detection of biothiols.Initially,due to the interaction between poly-ethylenimine(PEI)or poly(diallydimethyl)ammonium chloride(PDAMAC)and Au NPs,the color of probe solution was blue due to the aggregation of Au NPs.In the presence of biothiols,the color of probe solution changed into red because of the stronger interaction of biothiols to Au NPs than that of PEI or PDAMAC.