Before revision: Methods Direct contact method A near confluent layer of fibroblasts are prepared in a culture plate Old cell culture media ( agar generally) is removed Fresh media is added Material being tested is placed onto the cultures, which are incubated for 24 hours at 37 degrees Celsius The material is removed The culture media is removed The remaining cells are fixed and stained, dead cells are lost during fixation and only the live cells are stained The toxicity of the material is indicated by the absence of stained cells around the material.
After revision:  generally) is removed Fresh media is added Material being tested is placed onto the cultures, which are incubated for 24 hours at 37 degrees Celsius The material is removed The culture media is removed The remaining cells are fixed and stained, dead cells are lost during fixation and only the live cells are stained The toxicity of the material is indicated by the absence of stained cells around the material.