Study On Preparation Of Sugar QDs And Detection Of Escherichia Coli

Incident of food poisoning coused by pathogenic Escherichia coli occurs frequently in recent years.The use of existing detection methods is limited by there fussy operaton. Therefore, searching for new testing method of E. coli is very significant. In this work, the specific recognition on different oligosaccharides of some E. coli strains was studied in order that rapid, simple and novel method was constructed to detect E. coli strains using unique spectral characteristics of quantum dot.Firstly,two kings of glycoconjugates named Mannose-PEG3-SH and Fucose-PEG3-SH were synthesized and their strucure were characterized by mass spectrometry and ’HNMR.Secondly,we gained two different load sugar amount of mannose quantum dots by ligand exchange method.Finally,These Man-QDs induce luminescent aggregates of Escherichia coli which can be used to detect bacteria in cell suspensions. The aggregation process is dependent on the E. coli cell surface FimH mannose-specific lectin.The TEM analysis and fluorescent characteristics of bacteria treated with Man-QDs. Under the same working conditions, we set out to change concentrations of sugar which capped with QD from300to1000,made different sugar mannose containing quantum dots combined with E.coli ORN178. Man-QDs(1000:1) provides a detection limit as few as625E. coli cells perml were determined by spectral absorption features. The simplicity of the method make the proposed approach useful as quick bacteria screening system.