Highly Sensitive Electrochemical Endotoxin Sensor Based on Redox Cycling Using an Interdigitated Array Electrode Device

The Limulus amebocyte lysate (LAL) reaction-based assay, the most commonly used endotoxin detection method, requires a skilled technician. In this study, to develop an easy-to-use and highly sensitive endotoxin sensor, we created an electrochemical endotoxin sensor by using an interdigitated array electrode (IDAE) device with advantages of amplifiable signals via redox cycling and portability. We added Boc-Leu-Gly-Arg-p-aminophenol (LGR-pAP) as an electrochemical substrate for an LAL reaction and detected p-aminophenol (pAP) released from LGR-pAP as a product of an endotoxin-induced LAL reaction via an IDAE device. The IDAE device showed a great redox cycling efficiency of 79.8%, and a 4.79-fold signal amplification rate. Then, we confirmed that pAP was detectable in the presence of LGR-pAP through chronoamperometry with the potential of the anode stepped from -0.3 to 0.5 V vs. Ag/AgCl while the cathode was biased at -0.3 V vs. Ag/AgCl. Then, we performed an endotoxin assay by using the IDAE device. Our endotoxin sensor detected as low as 0.7 and 1.0 endotoxin unit/L after the LAL reaction for 1 h and 45 min, respectively, and these data were within the cut-off value for ultrapure dialysis fluid. Therefore, our highly sensitive endotoxin sensor is useful for ensuring medical safety.

Automated summary

In this study, we developed an electrochemical endotoxin sensor using an interdigitated array electrode (IDAE) device. The IDAE device showed high redox cycling efficiency and signal amplification rate. The sensor successfully detected p-aminophenol (pAP) released from Boc-Leu-Gly-Arg-p-aminophenol (LGR-pAP) as a product of an endotoxin-induced LAL reaction. The sensor could detect as low as 0.7 and 1.0 endotoxin unit/L after the LAL reaction for 1 h and 45 min, respectively, and these values were within the cut-off range for ultrapure dialysis fluid. Therefore, the highly sensitive endotoxin sensor is useful for ensuring medical safety.