The Study On Detections Of Salmonella Based On AuNPs

In recent years, bacterial food poisoning has occurred frequently around the world. Anddiseases caused by food have become a hazard to human health seriously, and even causedproblem of death. As the most common and one of the highest incidence of food bornebacteria, Salmonella has received widespread attention, and has become one of the targetbacteria in the field of inspection of food hygiene. This paper constructed three methods ofdifferent Salmonella detection system, which were all based on the excellent properties ofAuNPs and took Salmonella as a model analyte, aiming to extend AuNPs amplication andprovide technical support to rich methods in the field of detection of Salmonella.Firstly, we established a new method to detect Salmonella by electrochemical methodbased on SiO2/Au signal amplification. We chose the complementary oligonucleotidesequences of bases which Salmonella can recognized specifically according to the principle ofcomplementary base pairing, then modified the surfaces of ITO and SiO2/Au with them. Itwould form a special "sandwich" structure at the time we added Salmonella target DNA intothe system. As SiO2/Au was positively correlated with the concentration of the target DNA,the peak current value of fully modified ITO would change when the concentration of thetarget DNA changed, so as to achieve the purpose of detection. Under the optimal conditions,it showed a good linear relationship when the concentrations of target DNA were in the rangeof10-11mol/L~10-7mol/L(y=-0.0003x+0.0001，R2=0.9989), the lowest detection limit was6×10-12mol/L(3S/N). And it showed a good linear relationship when the concentrations ofSalmonella was in the range of50cfu/mL~7900cfu/mL(y=-1.6×10-7x+0.0032，R2=0.9940),the lowest detection limit was35cfu/mL(3S/N).Secondly, we established a novel method for visual detection of Salmonella based onFe3O4magnetic beads and AuNPs. Compared with the former, this method could achievevisually detection, witnout depending electrochemical workstation. We chose thecomplementary oligonucleotide sequences of bases which Salmonella can recognizedspecifically, then modified the surfaces of Fe3O4magnetic beads and AuNPs with them. Itwould form a special "sandwich" structure at the time we added Salmonella target DNA intothe system according to the principle of complementary base pairing. As the color of AuNPschanges according to the degree of aggregation of AuNPs, if we added more target DNA,more and more AuNPs aggregated, the color of AuNPs would vary from red to blue. So thatwe realized the visual detection of Salmonella. Under the optimal conditions, it showed agood linear relationship when the concentrations of target DNA was in the range of1×10-12mol/L~1.5×10-9mol/L(y=0.007x+0.2535，R2=0.9983), the lowest detection limit was8×10-13mol/L(3S/N). And it showed a good linear relationship when the concentrations of Salmonella were in the range of30cfu/mL to8600cfu/mL(y=0.0001x+0.3083，R2=0.9962), the lowestdetection limit was23cfu/mL(3S/N).Thirdly, This method established another visual method of AuNPs on the basis of theprevious study. When adding the dilution of Salmonella liquids into the AuNPs-aptamersystem, aptamers would leave AuNPs and bine to Salmonella specifically. After that, weadded NaCl solution, AuNPs would get together and the color of it changed. So that, weachieved the purpose of visual detection. Under the optimal conditions, it showed a goodlinear relationship when the concentrations of Salmonella liquids were in the range of102cfu/mL~107cfu/mL(y=0.1946x[lgSalmonella(cfu/mL)]-0.2800，R2=0.9939), and the lowestdetection limit was56cfu/mL(3S/N).