Abstract
In this work, a novel sandwich-type impedimetric biosensor was fabricated for highly sensitive and selective detection of lipopolysaccharide (LPS) from E. coli O55:B5. LPS aptamer I was immobilized onto electrodeposited gold nanoparticles (Au) modified electrode for capturing LPS in buffer and serum. LPS aptamer II and rolling circle amplification (RCA) primer were conjugated with gold nanoparticles (AuNPs) to use as signal tags. LPS was sandwiched between AuNPs/primer/aptamer II bioconjugates and aptamer I. This was followed by extension of RCA, which resulted in long poly-thymine (T) single strand (ssDNA) sequences to adsorb copper ions (Cu2+) into the skeleton of poly-T sequences. Thus, poly-T ssDNA directly served as the specific template for copper nanoparticles (CuNPs) formation with the aid of ascorbic acid (VC). Finally, the formed CuNPs@ssDNA complex promoted the oxidation of pyrocatechol violet (PCV) to insoluble bulky oligomer (precipitation) in the presence of H2O2. The reaction significantly enhanced the resistance signal of LPS quantitative determination. The impedimetric aptasensor exhibited a wide dynamic working range of 0.01 pg/mL ˜ 100 ng/mL with a detection limit of 4.8 fg/mL. This method also showed good selectivity and reproducibility, and demonstrated the applicability of LPS detection in human serum samples, offering a promising avenue for sensitive LPS detection.
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