XTT Cytotoxicity

The purpose of the study is to determine the potential biological reactivity of a mammalian cell culture (L929 cell line) in response to the medical device extract. The test item is extracted in MEM with 10% FBS (Fetal Bovine Serum) for usually 24 hours at 37 °C or 72 hours at 37 °C (permanent implants or prolonged exposure medical device). The cells are allowed to grow to sub-confluency in tissue culture plates and exposed to the test item extract at least 4 concentrations (100% always included) in 6 replicates. The plates are incubated for 24 hours at 37 °C after which the viability is assessed via the reduction of the yellow water-soluble XTT by the mitochondrial reductases enzymes into orange water-soluble formazan. The number of viable cells correlates to the color intensity determined by photometric measurements. The medical device is considered non-cytotoxic if the percentage of viable cells is equal to or greater than 70% of the untreated control.