Detection And Discrimination Of Pathogenic Microorganisms In The Environment Using SERS

Surface-enhanced Raman scattering (SERS) is a special surface optical phenol-menon. It shows high sensitivity, selectivity and specificity for detecting the molecules absorbed on the surface of the metal substrates and presents plentiful Raman information of the molecule structures. Therefore, SERS has been widely used in medicine, biochemistry, microbiology, environment, archaeology and other fields. With the development of biotechnology and microbial contamination, detection and discrimination of pathogenic microorganisms using SERS is also increasing. The main results and conclusions are summarized as follows:1.According to a modified Lee and Meisel method, the influence of reducing agent’s dosage on the size and distribution of colloidal silver was investigated.Then added gold chaloride acid and hydroxylamine hydrochloride solution to prepare Ag/Au core-shell nanoparticles; And using two different reduction method of crystal seed to prepare gold nanoparticles. Moreover, transmission electron microscopy are used to check the size and stability of these three nanoparticles. We choose4-merca-ptobenzoic acid as the probe molecules. SERS activities of these three nanoparticles were studied. The results showed that the Raman signal of Ag/Au core-shell nano-particles was strong than the Raman signal of silver colloid and gold colloid. Two different gold nanoparticles had different size and SERS signal.2.Ag/Au core-shell nanoparticle SERS gene probe was prepared and4-mercap-tobenzoic acid was used as Raman reporter. The core-shell nanoparticle SERS gene probe was used for the detection of mip gene of Legionella pneumophilas using sand-wiched-type. The experimental results showed that obvious Raman signal can be obs-erved in the presence of target probe using Ag/Au core-shell nanoparticle SERS as detection probe. However, no signal can be found in the absence of target probe. Therefore, gene probe labeled by Ag/Au core-shell nanoparticle SERS tags in this study provided a potential method for detection of Legionella pneumophilas.3. Colloidal silver nanoparticles were prepared using sodium citrate as reducing agent. According to a modified Lee and Meisel method, the influence of reducing agent’s dosage on the size and distribution of colloidal silver was investigated. SERS was used to detect and discriminate E.coli and Shigella spp. based on the "whole organism fingerprinting" technology. The results showed that Escherichia coli and Shigella spp. themselves had no obvious Raman spectra, but the mixture of two bacteria and silver colloid had obvious Raman spectra. And the Raman spectra of two mixtures were so different that Escherichia coli and Shigella spp. can be easily discriminated. Then reproducible experiments were performed and the reproducibility of experiments was good. This study can detect and discriminate Escherichia coli and Shigella spp. So it provides the basis for pathogens detection.