To screen for any potential cytotoxicity of copolymers, a direct cytotoxicity study was performed according to ISO 10993-5, after the modification of the procedure using films and using L929 murine fibroblast cell line . Commercial medical-grade poly(ε-caprolactone) (PCL, Capa™ 6430) and nitrile gloves (Mercator Nitrylex Classic, Kraków, Poland) were used as non-toxic and cytotoxic controls, respectively. The direct contact method was followed, with a 24-hour sample-cell layer contact time and an area of one-tenth of the cell layer surface (according to . The copolymers films were sterilized using ultraviolet light and placed in a 24-well plate. Then, 1 mL of L292 cell suspension, with a concentration of 5x10 4 cells/ml, were seeded onto copolymers in the 24-well plate, using complete growth medium and incubated for 24 hours at 37 °C (according to the ISO, the direct contact assay involves placing the sample on a monolayer of cells). The experiment was repeated 5 times, with 3 samples per material. Cell viability was determined using light microscopy (Delta Optical IB-100, Mińsk Mazowiecki, Poland) and the resazurin viability assay. 200 μL of 0.15 mg/mL resazurin stock in phosphate-buffered saline was added to each well after 24h, including blank wells with media but no cells, and incubated for 4 hours at 37 °C. Fluorescence intensity was measured using a multi-functional plate reader (Biotek Synergy HTX, Winooski, VT, USA) with an excitation wavelength of 540 nm and emission wavelength of 590 nm.