Development Of New Methods For BPA And Silver Ions Based On Enhancing Effect Of Nanoparticles

With the applications of the sensitizing effects of functional nanomaterials in food safetyanalytical fields, the unique magnetic separation, nuclear magnetic resonance properties（NMR） and surface plasmon resonance （SPR） of functional nanomaterials were fully utilizedfor developing a series of novel, rapid and sensitive BPA and silver ions detection methods,combining the traditional and advanced detection methods, All the studies were shown in thefollowing steps:1. Molecularly imprinted polymer （MIP） coated Fe₃O₄nanoparticles （Fe₃O₄@MIP） weresynthesized by atom transfer radical polymerization （ATRP） and used as highly selectivemagnetic solid-phase extraction （MSPE） sorbents for trace bisphenol A （BPA） of packedfood. The morphological and polymeric characteristics of the Fe₃O₄@MIP were characterizedby transmission electron microscopy and Fourier transform infrared spectroscopy. In thiswork, competitive recognition compounds （4-noctylphenol and bisphenol A diglycidyl ether）exhibited lower binding capability to the Fe₃O₄@MIP than BPA. A high performance liquidchromatography with fluorescence detection （HPLC-FLD） method was developed for thedetermination of BPA in canned orange and milk samples. The main factors influencing theextraction efficiency, high specificity, the amount of surfactant, the shaking time and thedesorption ability of complex food matrices were investigated and optimized. Various ofparameters such as the pH of the sample, the amount of Fe₃O₄@MIP sorbent, the extractiontime, and the desorption conditions were optimized. Notably, the extraction can be carried outquickly, and the extraction time for BPA onto Fe₃O₄@MIP sorbents can be clearly shortenedto5min. Good linearity （r²>0.9965） for all calibration curves were obtained, and the limit ofdetection （LOD） for BPA was0.1and0.3ng/mL in canned orange and milk samplesrespectively. To the best of our knowledge, this is the first time that surface molecularlyimprinted polymer nanoparticles have been used for the pretreatment of packed food.2. In order to develop facile, fast and sensitive detection methods for BPA, we describeda sensitive biosensing system involving magnetic relaxation switch, based on the assembly ofcross-linked superparamagnetic iron oxide （CLIO） nanoparticles induced by theantigen–antibody biorecognition. The design of smart CLIO-based superparamagnetic ironoxide nanoparticles and antigen-OVA was described for the detection of bisphenol A [2,2-bis（4-hydroxyphenol） propane （BPA）]. The addition of BPA to the rapid magnetic relaxationswitch immunosensor led to transverse relaxation time （T2） shortening compared to a blankcontrol as shown by NMR relaxometry measurements. This process was also applied to therapid and facile determination of concentrations of BPA in drinking water （tap water）. Goodlinearity for all calibration curves was obtained, and the limit of detection （LOD） for BPA was0.4ng/mL in tap water.3. The antibodies and coating antigen were adhered to the10nm Au NPs and20nm AuNPs respectively through electrostatic interaction. A smart chirality detection for BPA basedon immunorecognition-driven nanoparticle assembly has been fabricated for the first time.The structure characteristics of the assembly were characterized by transmission electron microscopy, UV/Vis spectroscopy and Dynamic Light Scattering （DLS）．A strong shiftedchiral signal was produced by asymmetric plasmonic nanoparticle dimers. The results showedthat the standard curve in the range of0.01-10ng/mL had good linear relation, reclaimationefficience was86.5%-96.7%, and LOD for BPA was0.02ng/mL in drink water.4. We report the formation of chiroptically active plasmonic heterodimers through DNArecognition mediated by silver ions, based on the assembly of cross-linked gold nanoparticlesinduced by the C-Ag+-C biorecognition. The different assembly by13bp,26bp and39bpDNA was studied and the structure characteristics of the assembly were characterized bytransmission electron microscopy, X-ray energy dispersive spectroscopy （XEDS）, UV/Visspectroscopy and Dynamic Light Scattering （DLS）．The results showed that the standardcurve in the range of0.005-10ng/mL had good linear relation, and LOD for Ag+was2pM indrink water, significantly better than those of fluorescence assays and electrochemicalmethods.