Specific assay for endotoxin using immobilized histidine and Limulus amebocyte lysate

Area of Science:

• Biochemistry
• Analytical Chemistry
• Biotechnology

Background:

• The Limulus Amebocyte Lysate (LAL) test is a standard method for endotoxin detection.
• Many biological and pharmaceutical samples contain substances that inhibit or enhance the LAL reaction, compromising test accuracy.
• Existing methods often require sample pretreatment or are unsuitable for complex matrices.

Purpose of the Study:

• To develop a novel, specific endotoxin assay method.
• To overcome the limitations of traditional LAL tests caused by interfering substances.
• To provide a reliable method for endotoxin determination in challenging sample types.

Main Methods:

• A two-step assay combining ultrafiltration, immobilized histidine as a specific endotoxin adsorbent, and a fluorometric LAL reagent.
• Step 1: Quantitative adsorption of endotoxins onto immobilized histidine, followed by separation from inhibitors/enhancers via ultrafiltration.
• Step 2: Direct reaction of adsorbed endotoxins with the fluorometric LAL reagent for sensitive detection.

Main Results:

• The developed method demonstrates high reproducibility and accuracy.
• Endotoxin recovery from sample solutions exceeds 95%.
• The assay effectively quantifies endotoxins in the presence of common LAL inhibitors/enhancers like amino acids and antibiotics.

Conclusions:

• Immobilized histidine-based endotoxin assay offers a specific and robust alternative to the conventional gel-clot LAL technique.
• This method is suitable for determining endotoxin levels in complex samples that interfere with standard LAL assays.
• The ultrafiltration and immobilized histidine approach enhances assay reliability and applicability in pharmaceutical and biological analyses.