Novel Luminescent Nanomaterials Labeling Based Detection Method For Salmonella

With the increasing attention paid on food safety, higher standards are required for food detection technology with the requirements of simplicity, rapidity, sensitivity and efficiency. Nanotechnology and biotechnology are quickly growing in 21st century. Nanomaterials have been introduced into bio-sensing probe, and be parts of nano probes and sensors, which could improve the sensitivity of the determination and stability of analysis. The commonly used biological markers are enzymes or substrates, fluorescent dyes and some other fluorescent substances. However, these traditional markers of biological analysis are limited in developments and applications by their inherent defects.Upconvertion nanomaterial is a unique luminescent material with the characteristics of excitation by infrared light (long-wave) and emission with visible light (short-wave). At the same time upconvertion nanomaterials also have low toxicity, high chemical stability, stable light intensity and high Stokes shift. Those advantages attract a lot of attention from researcher. The upconvertion nanoparticles therefore become a processing nanomaterial in biological application.Firstly, ~50 nm upconvertion nanoparticles with high hydrophilic property and light stability were synthesized using Y2O3, Yb2O3 and Er2O3 as substrates in mild conditions. It was characterized by TEM image, XRD, FT-IR and fluorescence spectrum. And the amino groups were then successfully modified on the surface of upconvertion nanoparticles. Meanwhile, magnetic nanomaterials with the characteristics of uniform size, amino-functionalized and good crystallinity and dispersibility were also prepared and used as magnetic bioseparation and concentration substrate of trace nucleic acid.Secondly, the as prepared upconvertion nanoparticles were used as luminescent label, while the as-prepared magnetic nanoparticles were used as highly efficient bioseparation substance. Based on the nano-probe, DNA hybridization and fluorescent analytical technology, a rapid and sensitive method was developed for the detection of gram-negative bacterium Salmonella sequences-specific DNA. Under the selected conditions, it was found that the fluorescent intensity is proportional to the concentration of Salmonella target oligonucleotides over the range of 0.01-10 pmol/L with a detection limit of 3 fmol/L (3S/N), and the relative standard deviation is 2.6 % (1 pmol/L, n=11). The method has been successfully applied to the detection of Salmonella in the real samples.Thirdly, a novel detection method based on fluorescent resonance energy transfer (FRET) was developed to measure Salmonella sequences-specific DNA in homogeneous liquid samples using the as prepared upconvertion nanoparticles as fluorescent donor and gold nanoparticles as quenchers. Under the optimal conditions, it was found that the fluorescent intensity is proportional to the concentration of Salmonella target oligonucleotides over the range of 0.001-1 pmol/L with a detection limit of 1 fmol/L (3S/N), and the relative standard deviation is 3.7 % (0.01 pmol/L, n=11). The method has been successfully applied to the detection of Salmonella samples.