Determination of endotoxin through an aptamer-based impedance biosensor

► An aptamer-based impedance biosensor was developed to detect endotoxin in the range of 0.001–1 ng/ml. ► This aptamer-based biosensor showed high sensitivity and excellent selectivity in the present of pDNA, RNA and BSA. ► This developed biosensor was able to regenerate in low pH environment. Lipopolysaccharide (LPS) often referred to endotoxin is an undesirable impurity frequently entrained with various recombinant protein therapeutics and plasmid DNA (pDNA) vaccines of bacterial origin. The inherent toxicities (e.g. fever, hypotension, shock and death) of LPS render its early and sensitive detection essential for several biological assays and/or parenteral administrations of biotherapeutics. In this study, an electrochemical biosensor using an LPS specific single stranded DNA (ssDNA) aptamer as a probe was developed. Amine-terminated aptamer exhibiting high affinity ( K d = 11.9 nM) to LPS was immobilized on a gold electrode using 3-mercaptopropionic acid (MPA) as a linker. Each step of the modification process was characterized by cyclic voltammetry (CV) and electrochemical impendence spectroscopy (EIS). A good linear relationship of the changes in the charge-transfer resistance (Δ R et) and the logarithmic value of LPS concentration was demonstrated in a broad dynamic detection range of 0.001–1 ng/ml. Furthermore, the aptasensor showed a high selectivity to LPS despite the presence of pDNA, RNA and bovine serum albumin (BSA) and could be regenerated in low pH condition, offering a promising option for detecting LPS often present in a complex milieu.