Cytotoxicity

Cytotoxicity

Cytotoxicity testing is an essential procedure used to assess the general toxicity of medical tools and substances. Materials are extracted in a cell culture medium called MEM, and mouse fibroblast cells (L-929) are then exposed to the extracted fluid. The cells are then observed under a microscope or tested using a tetrazolium dye to measure the metabolic activity of the cells. A cytotoxic grade is assigned (0-4) based on the morphology and estimated percentage of lysis (death). Extracts are also applied to a monolayer of L-929 cells with a layer of agarose and incubated for 24 to 26 hours at 37°C with 5°% CO2. The zone of cell death is then measured and graded according to the AAMI/ANSI/ISO 10993-5 scale. If the cytotoxic response does not exceed grade 2, the substance meets the ISO criteria.

In rare cases, a device or substance will display a level of cytotoxicity beyond what is allowed by the ANSI/AAMI/ISO 10993-5 standard, leading to a failed test. This doesn’t necessarily mean that the technology or substance is dangerous to use in a clinical setting, but it does mean that the cause of the failure must be determined and any potential toxic hazards must be weighed. All medical equipment, raw materials, and devices undergoing cleaning validation or residual production should be subjected to the test.