Refinement of an open-microcavity optical biosensor for bacterial endotoxin test

The Limulus Amebocyte Lysate (LAL) test is an in vitro assay widely used in the pharmaceutical and biotechnology industries to detect bacterial endotoxins. Endotoxin is a structural component of the cell wall of Gram-negative bacteria, which has serious pathogenic effects in the body and may cause dysfunction of multiple organ systems and increased risk of mortality. To address the growing need for LAL assays due to the increased demand from drug and vaccine manufacturers, we have developed a new LAL assay approach. Our detection mechanism is different and improved from those currently used in the industry, leading to increased test sensitivity and reduced assay time. Our study utilizes an open-microcavity photonic-crystal biosensor to quantify endotoxin concentrations. It has demonstrated an improved LAL assay sensitivity by 10 fold compared to the commercial standard methods and reduced the time needed for the assay by more than half. In addition, this approach requires as little as 5 μL of LAL reagent per test, thereby decreasing costs and conserving horseshoe crabs. The results reported in this paper indicate the possibility of using the photonic-crystal biosensor based approach for significant enhancements of endotoxin testing.