Novel endotoxin assay by laser light‐scattering particle‐counting method

Abstract

Exposure of Limulus amoebocyte lysate to endotoxin under stirring produced light-reflective particles that appeared to be coagulin polymers. A laser light-scattering particle counter, the PA-200, detected these particles sensitively. The PA-200 detected endotoxin at a concentration as low as 0.00015 EU/ml in 71 min, whereas the minimum endotoxin concentration measured by a turbidimeter, ET-2000, was 0.0005 EU/ml in 138 min. Moreover, PA-200 was much less affected by the presence of colored substances and refractive materials than was ET-2000. We propose that the high sensitivity, speed, and high interference tolerance of the laser light-scattering particle-counting method make it more useful than the widely used turbidimetric method for quantitative endotoxin assay.

Endotoxin assay by bioluminescence using mutant firefly luciferase

“…In the pharmaceut ical industry, the current requirement is for a highly sensitive measurement method that is able to detect 0.1 pg/ml (equivalent to 0.0007 EU/ml) endotoxin for human health [8]. [6,7,13]. Therefore, the end-point methods are mainly used as primary tests for endotoxin contamination in products and the kinetic methods are used for the detection of low levels of endotoxin, for example in clinical treatments [14][15][16].…”

“…Recent ly, a laser light-scattering particle-counting method was reported as a new turbidimetric kinetic method for detecting endotoxin with high sensitivity [13,17]. The bioluminescence method using mutant luciferase was effective for rapid and highly sensitive endotoxin detection.…”