3 years ago

Orientation selection of broad-spectrum aptamers against lipopolysaccharides based on capture-SELEX by using magnetic nanoparticles

Huajie Gu, Hua Ye, Shijia Wu, Jinghong Li, Zhouping Wang, Guiliang Tan, Haitao Wang, Nuo Duan

Abstract

The authors describe a new kind of selection method (referred to as orientation selection) for improved screening for broad-spectrum lipopolysaccharides (LPSs) using unlabeled ssDNA aptamers. The method is based on the capture-SELEX technique using magnetic nanoparticles. LPS from Salmonella enterica serotype typhimurium was chosen as an exemplary target. Once the ssDNA library is preconcentrated to a certain degree, two Gram-negative bacteria were used as orientation molecules in the subsequent selection process. Using this strategy, one optimal aptamer ('EA7') was captured that has a high affinity (Kd = 102 ± 17 nM) for LPS and it was also confirmed that it can recognize three other bacterial LPSs. It is presumed that EA7 binds to the lipid A region of LPS. When using carboxyfluorescein labeled EA7, the observed fluorescence intensity and concentrations of four types of LPSs in drinking water are linearly correlated. The lower detection limit of the LPS is 3 ng·mL−1. Compared to multi-target mixed selection and conventional SELEX methods, the new orientation selection strategy produces results that are less uncertain.

Graphical abstract

An improved orientation selection strategy in capture-SELEX procedures was developed to screen broad-spectrum aptamers against lipopolysaccharides by using magnetic nanoparticles. Two Gram-negative bacteria were used as orientation molecules after library preconcentrated to a certain degree.

Publisher URL: https://link.springer.com/article/10.1007/s00604-017-2453-3

DOI: 10.1007/s00604-017-2453-3

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