Fetal Bovine Serum (FBS), 2 mM L-glutamine, 100 U/mL penicillin and 100 µg/mL streptomycin for 24 hours in a CO 2 incubator for cell culture at 37°C. The following controls were used: 1) negative control: commercial, non-toxic poly(e-caprolactone) (PCL, Capa™ 6430), 2) positive (toxic) control: nitrile glove (Mercator Nitrylex Classic, Kraków, Poland), 3) sham: media in an empty well. In parallel, 10×10 3 L929 cells (passage 10-25) were plated per well in a 96-well plate in complete growth medium. After incubation for 24 hours in a CO 2 incubator for cell culture at 37 °C, the medium in the plate with cells was aspirated and replaced with 100 µL of extract medium from a given sample (5-6 technical replicates, 2 samples per material). The plates were then returned to the cell culture incubator for another 24 hours of culture. Cell viability was then assessed using light microscopy (Delta Optical IB-100, Mińsk Mazowiecki, Poland) and the resazurin viability assay. Briefly, 20 μl of resazurin stock (0.15 mg/mL in phosphate-buffered saline) was added to each well (as well as to blank wells with media but no cells) and then incubated for 4 hours in the cell culture incubator at 37 °C.