Simple and Label-Free Liquid Crystal-based Optical Sensor for Highly Sensitive and Selective Endotoxin Detection by Aptamer Binding and Separation

Lipopolysaccharides (LPS), also commonly known as lipoglycans and endotoxins, can often accidentally contaminate recombinant protein therapeutics and bacteria-derived plasmid DNA vaccines. Since LPS can induce fever, hypotension, shock, and even death, their early and sensitive detection is necessary in relevant bioassays and for parenteral drug administration and/or biotherapeutics. In this study, an optical biosensor was developed using LPS-specific single-stranded DNA aptamers as LPS-selective probes. (3-Aminopropyl) triethoxysilane and glutaraldehyde were used as linkers to immobilize the LPS high-affinity aptamer on glass. Subsequently, each modification step was characterized by the optical responses obtained from liquid crystals using a polarized optical microscope. The sensor's ability to detect LPS was confirmed using a broad LPS detection range (5.5 pg/mL - 100 ng/mL). Despite the presence of plasmid DNA, RNA, and bovine serum albumin, the aptamer sensor showed high selectivity for LPS and could be regenerated for reuse at a low pH, thus, providing a promising option for detecting LPS in complex, low pH environments.