Detection Of Six Foodborne Pathogenic Bacteria Based On Surface Enhanced Raman Spectroscopy

Directly bacteria detecting strategies without time-consuming culture processes are urgently desired by clinical diagnoses and biosecurity area.The development of fast,sensitive and accurate diagnostic methods for bacteria thus appears as a major goal for public health.Traditionally,detection of bacteria includes staining,light microscopic examination,microbial culture and amplification techniques such as immunoassays(enzyme-linked immune absorbent assay(ELISA)),nucleic acid identification(polymerase chain reaction,PCR).However,staining culture only discriminate Gram+(G+)and Gram-(G-),and microbial culture requires 24-72 hours to identify the pathogenic bacteria.Although the amplification strategies can approach high specific and sensitivity,they all need tediously sample preparation and the manual procedure is sophisticated.The high-throughput sequencing and microarray can achieve simultaneous detection of multiple pathogenic bacteria,however,these technologies also require prior isolation of bacterial DNA,preparation of enzyme reaction mix,and expensive instruments for nucleic acid amplification.The direct detection technique has been extensively developed.Laser for the flight mass spectrometry detection can bombard the bacteria,but the fingerprint difference is too little for different species and the instrument is too heavy for on-site detection.Optical elastic scattering is also could be used to analysis bacterial micro colony on agar,however,It only could discriminate microbiology by clone morphology.Vibrational spectroscopy that vibrational infrared(IR)and Raman spectroscopy could be obtained can differ the vibrational spectra of molecule fingerprints of bacteria.However,infrared spectroscopy is sensitive to water,which makes it not able to give full play to advantages of biological samples.Raman spectra can provide complementary microbial structure information to infrared spectroscopy and have weak effect from water,which makes Raman spectroscopy,can detect biological samples in water.(1)Apply surface enhanced Raman spectroscopy(SERS)to quickly detect Brucellasuis vaccine strain 2(B.suis S2),Salmonella typhimurium(S.typhimurium),Staphylococcus aureus(S.aureus),Escherichia coli O157: H7(E.coli O157: H7)and Shigellaflexneri(S.flexneri),respectively.According to the enhancement effect of SERS,the method of in Situ Coating with Ag Nanoparticles was used to enhance the bacteria Raman signal,so that the purpose of detecting bacteria by SERS was achieved.Within the range of 400-2000 cm-1,B.suis S2 has 10 distinct Raman peaks,S.typhimurium has 9 distinct Raman peaks,S.aureus has 5 distinct Raman peaks,E.coli O157: H7 has 9 distinct Raman peaks,S.flexneri has 7 distinct Raman peaks.And the position and intensity of Raman spectra of the five-foodborne bacteria were different.In this study,we can rapidly detect five foodborne pathogens within 10 minutes using SERS technique,which provides a basis for clinical diagnosis.(2)The characteristic of an ideal detection of bacteria method should have highly sensitivity and specificity,easy to operate,and without using time-consuming culture.In this study,we report a new bacteria detection strategy that can recognize bacteria quickly and directly with the formation of well-defined Bacteria-aptamer@AgNP by surface-enhanced Raman scattering(SERS).SERS signals generated by Bacteria-aptamer@AgNP exhibited a linear dependence on aptamer(R~2=0.9773)and bacteria(R~2=0.9671)concentration,and limit of detection is sensitive down to 10 cfu/mL.Meanwhile,the method own a SERS dramatically enhancement effect for bacteria by its recognized aptamers alone and the bacteria can be directly visually identified through the Raman spectrum.This strategy eliminates the puzzling data analysis of previous studies and has offered significant advantages over existing approaches,getting a critical step towards the creation of SERS-based biochips for rapid in situ detection bacteria in mixture samples.