Cytotoxicity testing (USP or ISO 10993-5) uses L929 mouse fibroblast cells. Medical seal extracts must show no cell lysis or growth inhibition. MEM elution with 37°C/72h extraction is standard. Only non-reactive grades receive approval for patient-contacting applications. Results are graded 0–4; medical seals must achieve grade 0 or 1 for acceptance. https://globalsealstech.com/medical/