title: An aptamer-based biosensor for colorimetric detection of Escherichia coli O157:H7.
abstract: BACKGROUND
  An aptamer based biosensor (aptasensor) was developed and evaluated for rapid colorimetric detection of Escherichia coli (E. coli) O157:H7.
  
  
  RESULTS
  The aptasensor was assembled by modifying the truncated lipopolysaccharides (LPS)-binding aptamer on the surface of nanoscale polydiacetylene (PDA) vesicle using peptide bonding between the carboxyl group of the vesicle and the amine group of the aptamer. Molecular recognition between E. coli O157:H7 and aptamer at the interface of the vesicle lead to blue-red transition of PDA which was readily visible to the naked eyes and could be quantified by colorimetric responses (CR). Confocal laser scanning microscope (CLSM) and transmission electron microscopy (TEM) was used to confirm the specific interactions between the truncated aptamer and E. coli O157:H7. The aptasensor could detect cellular concentrations in a range of 10(4)~ 10(8) colony-forming units (CFU)/ml within 2 hours and its specificity was 100% for detection of E. coli O157:H7. Compared with the standard culture method, the correspondent rate was 98.5% for the detection of E. coli O157:H7 on 203 clinical fecal specimens with our aptasensor.
  
  
  CONCLUSIONS
  The new aptasensor represents a significant advancement in detection capabilities based on the combination of nucleic acid aptamer with PDA vesicle, and offers a specific and convenient screening method for the detection of pathogenic bacteria. This technic could also be applied in areas from clinical analysis to biological terrorism defense, especially in low-resource settings.
authors.affiliation: Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, Wenzhou Medical College, Wenzhou, Zhejiang, People's Republic of China.
authors.forename: Wenhe
authors.initials: W
authors.lastname: Wu
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Meiqin
authors.initials: M
authors.lastname: Zheng
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Zhong
authors.forename: Jie
authors.initials: J
authors.lastname: Yang
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Zhao
authors.forename: Wenping
authors.initials: W
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Ye
authors.forename: Jie
authors.initials: J
authors.lastname: Wen
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Jianxin
authors.initials: J
authors.lastname: Lu
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D003124:Colorimetry / Q000295:instrumentation* / Q000379:methods; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D012680:Sensitivity and Specificity; D013234:Stem Cells