Basic Application Research Of Near Infrared Laser In Rapid Detection Of Foodborne Pathogens

Foodborne pathogens are the leading cause of foodborne diseases. The existing detection methods either have complex preprocessing steps and high rate of false positive results, or have bulky and expensive instruments, and high environmental requirements, which are not suitable for rapid and real-time detection. Near infrared laser technique has the advantages of rapidity, deep penetrability, non-invasiveness and no pollution. Thus we attempt to combine this technique with the existing methods in order to realize rapid and sensitive detection of foodborne pathogens, and details are as follows:1. Classification of food borne pathogens based on near infrared laser imaging technology. Firstly, near infrared laser imaging system was developed for texture images collection of four bacteria, including E.coli, S.aureus, S.typhimurium and bacterial mixture. Then normalization and Zernike moments extraction were performed, and the resultant translation, scale and rotation invariances were applied as the characteristic variables. Both linear (LDA, KNN and PLSDA) and nonlinear (BPANN, SVM and ELM) pattern recognition methods were employed comparatively for modeling. Experimental results showed that the performances of nonlinear tools were superior to those of linear tools, especially for ELM model with 95% discrimination rate in the prediction set. The overall results showed that it is extremely feasible for rapid and noninvasive classifying foodborne pathogens using this developed system combined with appropriate multivariate calibration.2. Quantitative detection of single foodborne pathogen using near infrared excited upconversion fluorescence spectrum (for example, E.coli). Upconversion nanoparticles (NaYF4: Yb3+, Er3+) were fabricated and conjugated with antibodies against E.coli for use as fluorescent probes. After the captured E.coli cell samples were pelleted, the differences in the fluorescence intensities between sample supernatants and the control were observed to increase linearly with E.coli concentration from 42 to 42 × 106 cfu ml-1 (R2=0.9802), resulting in a relatively low limit of detection of 10 cfu ml-1. Furthermore, the ability of the bioassay to detect E.coli was also confirmed in adulterated meat and milk samples. In order to highlight this bioassay, other immune-labelled methods of recent researches were also listed for comparison.3. Quantitative detection of multiple foodborne pathogens using near infrared excited upconversion fluorescent spectrum (for example, E.coli and S.aureus). Upconversion nanoparticles (NaYF4:Yb3+, Er3+ and NaYF4:Yb3+, Tm3+) were fabricated and conjugated with respective antibodies against E.coli and S.aureus, and then mixed equally as multi-labelled fluorescent probes. After the captured E.coli and S.aureus cell samples were pelleted, the differences in the fluorescence intensities between sample supernatants and the control were observed to increase linearly with bacteria concentration; ranging from 47 to 47 × 106 cfu ml-1 (R2=0.9800) for E.coli, and 64 to 64 × 106 cfu ml-1 (R2=0.9657) for S.aureus, resulting in a relatively low limit of detection of 13 cfu ml-1 for E.coli, and 15 cfu ml-1 for S.aureus. Furthermore, the ability of the bioassay to simultaneously detect E.coli and S.aureus was also confirmed in adulterated meat and milk samples, indicating the feasibility of simultaneous detection of multiple pathogens.