[boldfacebutton7 (OP)]

Hello there,
I am working on a project which requires testing of specimen for various biological characteristics, one of them being cytotoxicity test.
I read through the reprints of the test carried so far and also the various ASM/ISO standards.
I am a mechanical Engineer and I could not catch even a single word.
Can anyone kindly explain the test in some simple words.

[evan_au]

Cytotoxicity is when a chemical substance is lethal to cells.

Two common ways that a cell can die include:

• Puncturing the cell membrane: If there are holes in the cell wall, dye surrounding a cell will enter the cell, causing a change in color under a microscope.
  
• Causing the cell to shred its DNA (apoptosis): This causes visible changes in the cell nucleus under a microscope.

Both of these modes of cell death eventually result in biological chemicals from within the cell leaking into the surrounding fluid, which can then be detected by indicator chemicals.

Other tests use changes in electrical conductivity or changes in refractive index to tell whether cells are alive or dead.

See: https://en.wikipedia.org/wiki/Cytotoxicity#Measuring_cytotoxicity

This is a much cheaper process (in a lab dish) than the next stage of testing, which has traditionally been with animals like mice. Often a substance is not cytotoxic itself, but can be transformed into a toxic chemical by enzymes on the liver, for example. You will not discover this from testing with single cells in a dish (unless you specifically test with liver cells).

If this is a new chemical that is to be used in food or in food packaging, it will need to go through a battery of tests. In contrast, there are many chemicals that have been used for 50 years which have never been officially tested, and are on a list of chemicals which are "Generally Recognized as Safe".

[evan_au]

Cell death can also occur through purely mechanical processes.

For example, artificial heart valves directly crush cells when they close, and cause shock waves, rupturing the cell membranes of nearby red blood cells. This potentially causes lethal blood clots. Patients with artificial heart valves are put on "blood thinners" (anticoagulant) medication for life.

Performing a cytotoxicity test after passing cells through an artificial heart valve could tell if cell membranes have been damaged, and thus the risk to patients.