Non-contact bacterial identification and decontamination based on laser-induced breakdown spectroscopy.

As a new kind of modern military biological weapon, bacterial agents pose a serious threat to the public health security of human beings. Existing bacterial identification requires manual sampling and testing, which is time-consuming, and may also introduce secondary contamination or radioactive hazards during decontamination. In this paper, a non-contact, nondestructive and "green" bacterial identification and decontamination technology based on laser-induced breakdown spectroscopy (LIBS) is proposed. The principal component analysis (PCA) combined with support vector machine (SVM) based on radial basis kernel function is used to establish the classification model of bacteria, and the two-dimensional decontamination test of bacteria is carried out using laser-induced low-temperature plasma combined with a vibration mirror. The experimental results show that the average identification rate of the seven types of bacteria, including Escherichia coli, Bacillus subtilis, Pseudomonas fluorescens, Bacillus megatherium, Pseudomonas aeruginosa, Bacillus thuringiensis and Enterococcus faecalis reaches 98.93%, and the corresponding true positive rate, precision, recall and F1-score reaches 0.9714, 0.9718, 0.9714 and 0.9716, respectively. The optimal decontamination parameters are laser defocusing amount of -50 mm, laser repetition rate of 15-20 kHz, scanning speed of 150 mm/s and number of scans of 10. In this way, the decontamination speed can reach 25.6 mm2/min, and the inactivation rates for both Escherichia coli and Bacillus subtilis are higher than 98%. In addition, it is confirmed that the inactivation rate of plasma is 4 times higher than that of thermal ablation, meaning that the decontamination ability of LIBS mainly relies on the plasma rather than the thermal ablation effect. The new non-contact bacterial identification and decontamination technology does not require sample pretreatment, and can quickly identify bacteria in situ and decontaminate the surfaces of precision instruments, sensitive materials, etc., which has potential application value in modern military, medical and public health fields.

Study on direct identification of bacteria by laser-induced breakdown spectroscopy.

Bacteria are everywhere in the natural environment. Although most of them are harmless, there are still some hazardous bacteria that will harm human health, so it is particularly important to identify bacteria quickly. Compared with traditional time-consuming and complicated identification methods, laser-induced breakdown spectroscopy (LIBS) is one of the potential technologies for rapid identification of bacteria. In this paper, six weakly active bacteria, including Escherichia coli, Enterococcus faecalis, Bacillus megaterium, Bacillus thuringiensis, Pseudomonas aeruginosa and Bacillus subtilis, are taken as analysis samples. The thawed bacteria are placed in deionized water, and then uniformly smeared on five kinds of substrates to verify the feasibility of using LIBS to identify these bacteria. Spectrum filtering, normalization and principal component analysis (PCA) are used to preprocess the spectra, and a multi-class identification method based on the one-against-all linear kernel function of support vector machine (SVM) is proposed to establish the prediction model. The identification performance is evaluated by using precision and recall. The experimental results show that high-purity graphite is the best substrate with the least interference to the LIBS spectrum of bacteria. The prediction precision of these six bacteria is 77.27%, 92.86%, 84.21%, 94.12%, 81.82% and 76.92%, respectively, recall is 85%, 100%, 94.12%, 80%, 81.82% and 75% respectively, and the identification rate is 84.17%. It can be seen that the direct identification of bacteria can be preliminarily realized by smearing bacteria on the graphite substrate and analyzing its LIBS spectra, which provides a feasible way for simple, rapid and on-site bacterial identification.

[Activation of anti-tumor cytotoxic T lymphocytes by fusion of human dendritic cells and melanoma cells].

OBJECTIVE: To determine the effect of activation of specific anti-tumor cytotoxic T lymphocytes (CTL) and the ability of cross-presentation in vitro by fusion of HLA-A2+ human dendritic cells (DCs) with HLA-A2- melanoma cells. METHODS: The HLA-A2+ human dendritic cells and HLA-A2- melanoma cells were fused by PEG and were cultivated in complete RPMI1640 media containing FCS (10%) and GM-CSF for 24-48 h, and then co-cultured fusion cells with Melan-A specific T cells. HLA-A2- melanoma cells were negative control,While T2 cells and DC+Pts were positive control. The activation of anti-tumor CTL elicited by the fusion cells was detected by intracellular cytokine staining. RESULTS: The immature DC could express CD80, CD83, CD86, HLA-DR, and HLA-ABC,but the mature DC induced by TNF-alpha, PGE-2, and CD40L further highly expressed above molecules. The rate of specific CTL cells primed by the fusion cells was 16.72%+/-4.26%, negative control was 0.21%+/-1.84%,and positive control was 28.60%+/-5.67%. The CTL from vaccine by fusing DC and LAR6 induced lysis of HLA-A2+ LAR1 cells. CONCLUSION: The HLA-A2 restricted specific anti-tumor CTL can be induced in vitro by fusion of HLA-A2+ human dendritic cells with HLA-A2- melanoma cells.