A new electrochemical aptasensor for ultrasensitive detection of endotoxin using Fe-MOF and AgNPs decorated P-N-CNTs as signal enhanced indicator

Sensitive detection of endotoxin is especially critical in the fields of food security, therapeutics and medical science. In this work, a new sandwich-type electrochemical aptasensor was designed for ultrasensitive detection of endotoxin. For the first time, nitrogen-doped carbon nanotubes (N-CNTs) was functionalized with polydiallyldimethylammonium chloride (PDDA), forming P-N-CNTs nanocomposite. Then, Fe-based metal–organic framework (Fe-MOF) and silver nanoparticles (AgNPs) was decorated with P-N-CNTs to form the MOF/Ag-P-N-CNTs nanohybrid, which was employed as an enhanced signal indicator, not only exhibited outstanding electrochemical activity, but also could directly label with thiol-modified signal probes (TSPs) to form tracer label. Additionally, the avidin–biotin recognition system was introduced to increase the amount of biotin-modified capture probes (BCPs). Differential pulse voltammetry (DPV) was utilized to investigate the detection performances of the proposed aptasensor, which suggested a wide linear range from 1 fg/mL to 100 ng/mL with a low detection limit of 0.55 fg/mL toward endotoxin.