Endotoxin is a component of the cell wall in the outer membrane of gram-negative bacteria that causes fever or shock when it enters the human blood stream.
In Japan, the concentration of endotoxins in both pharmaceutical and dialysis solutions have been regulated as shown in the following Table 1.
Limulus amebocyte lysate (LAL) is a coagulation system that is introduced by endotoxins. There are several endotoxin detection methods employing the so-called Limulus reaction using LAL. In conventional endotoxin analyzers, endotoxin detection methods using turbidimetric and chromogenic end-points as well as turbidimetric and chromogenic kinetic methods have been using. However, the two end-point methods have problems with their sensitivities (detection limits are 0.01-0.1EU/mL), and the kinetic methods have a problem with the measurement time (over 60 min).
Bioluminescence detection method has a high S/N ratio compared with other optical detection methods, such as fluorescence or chromogenic detection methods. The rapid and highly sensitive endotoxin detection method based on the bioluminescence test using mutant firefly luciferase1) with Limulus reaction was developed.2)
DKK-TOA developed the new endotoxin analyzer based on this bioluminescence detection method with Limulus reaction. The detection limit and measurement time is 0.0003 EU/mL and 20 minutes, respectively. The good performances including rapid and highly sensitive measurements were observed in the new endotoxin analyzer.
The ability of endotoxin measurement in dialysis solution was also tested by a third party and reported to be in compliance with the regulation in Japan.3) This analyzer has been used in many dialysate measurement sites in Japan.
1) H. Fujii, K. Noda, Y. Asami, A. Kuroda, M. Sakata, A. Tokida, “Increase in Bioluminescence Intensity of Firefly Luciferase using Genetic Modification”, Anal. Biochem., 366, 131 (2007).
2) K. Noda, H. Goto, Y. Murakami, A. B. F. Ahmed, A. Kuroda, “Endotoxin Assay by Bioluminescence using Mutant Firefly Luciferase”, Anal. Biochem., 397, 152 (2010).
3) M. Kondo, J. Uchino, J. Murakami, T. Hoshino, Y. Yamashita, T. Naramura, T. Shibamoto, “Multi-Institutional Study of a Newly Developed Bioluminescent Endotoxin Measurement Method based on the Limulus Amebocyte Lysate Reaction”, Nihon Toseki Igakkai Zasshi, 51, 591 (2018). < in Japanese >