Microchip electrophoretic detection of bacterial lipopolysaccharide based on aptamer-modified magnetic beads and polymerase chain amplification

Bacterial lipopolysaccharides (LPS) are endotoxins, which can cause fever, inflammation, cell and tissue damage, irreversible septic shock and death in mammals as well as other organisms. Herein, a highly sensitive and selective strategy was proposed for detecting LPS using microchip electrophoresis (MCE) based on aptamer-modified magnetic beads and polymerase chain amplification. In this strategy, the biotinylated aptamer for the LPS (LBA) was hybridized partially with the complementary DNA (cDNA), then the double-stranded DNA obtained was immobilized onto the magnetic beads. In the presence of target LPS, the target-aptamer complex was formed and the cDNA would be freed. After a magnetic separation, the cDNA was released into the supernatant and subsequently triggered the polymerase chain amplification. This process eventually generated a large number of output DNA, which could be quantitatively detected by MCE. With the polymerase chain amplification, this designed protocol provided an ultrasensitive detection of LPS down to the 1.1 × 10^{− 14} g/mL with a linear range of 5 orders of magnitude. The proposed method also exhibited a high specificity toward LPS in the presence of other common interfering substances. Moreover, the assay showed a good practical application for LPS determination in serum samples.