*2.13. Assessment of Endotoxin Contamination*

The HEK-BlueTM hTLR4 assay system was used to test IP and HPP for LPS contamination. HEK-blue cells (5 × 105 cells/mL) expressing TLR4 were stimulated with LPS (0.1–100 ng/mL; positive control), or HPP or IP (both 1000 μM) for 24 h. Supernatants from the HEK-blue cells were incubated with HEK-blue detection medium, to measure SEAP expression, for 30 min at 37 ◦C and absorbance was read at 650 nm.
