Preparation Of Rod-shaped And Cross-shaped Gold Nanoparticles And The Application In Food Analysis

The Longitudinal surface Plasmon resonance (LSPR) peak of gold nanorods waschanging with aspect ratios and highly sensitive to changes in the local environment.Moreover, the gold nanorods and gold nanocross can significantly enhance the fluorescenceof fluorophores localized in the vicinity of gold nanoparticles surface. In this paper, seriesrapid, simultaneous, sensitive UV-vis and fluorescence detection methods for the detection ofMicrocystins-LR, Pefoxacin and E.coli O157:H7eae Agene was mainly prapared.1. Optimal growth conditions of gold nanorods were determined: the concentration ratioof5-bromosalicylic acid with CTAB was1:20; the volume of silver nitrate, seed and ascorbicacid was1.8mL,800μL,350μL, respectively. Furthermore, gold nanorods with differentaspect ratios were prepared under acid condition. The prepared methods not only improvedthe biological safety but also simplify the washing steps of gold nanorods due to the lowconcentration of CTAB in growth solution.2. A simple UV-vis assay for the simultaneous detection of Microcystin-LR andPefloxacin in seafoods has been developed based on the fact that gold nanorods absorptionpeak is adjustable and is sensitive to dielectric surroundings. Under optimal conditions,magnetosome-enhanced UV-vis assays showed a good linear response over the range1ng·mL-1-20ng·mL-1(R2=0.9950and R2=0.9968) to MC-LR and Pefloxacin, the detectionlimit was0.33ng·mL-1, the specificity of this methods were good. Furthermore, UV-vis assaywas successful in the analysis of Microcystin-LR and Pefloxacin in naturally contaminatedfish samples and high recoveries were achieved.3. Gold nanocross was one-step prepared by seed-mediated synthesis methods. Then thesurface enhanced fluorescence effects of cy5in the proximity of gold nanorods and goldnanocross was investigated, fluorescence measurements indicated that the enhancement factorof gold nanocross was highest. Under optimal conditions, the surface enhanced fluorescenceassay exhibited a good linear response at Microcystin-LR concentrations of0.02ng·mL-1-16ng·mL-1(R2=0.9981), the detection limit was low to0.007ng·mL-1, meanwhile, thespecificity of this methods were good. Recoveries were obtained from naturally contaminatedfish samples, ranging from98.0%-102.2%.4. The fluorescence quenching or fluorescence enhancing was dependent on the distancebetween the gold nanocross and cy5molecules，two different fluorescence detection methodswere prepared based on a specific and conservative sequence of E.coli O157: H7eae A. The“turn-on” fluorescence quenching assay showed a good linear response over the target DNAconcentration of1×10-10mol·L-1-1×10-15mol·L-1(R2=0.9983), the detection limit was0.3×10-15mol·L-1; the surface enhanced fluorescence assay exhibited a good linear response at target DNA concentration of1×10-11mol·L-1-1×10-16mol·L-1(R2=0.9904) with a detectionlimit0.3×10-16mol·L-1. Both of these two prepared methods showed a good specificity for thedetection of complementary target sequence.