The cytotoxicity of polymers was measured using the MTT assay protocol described previously [17 (link), 18 (link)]. Briefly, ScN2a cells were plated in a 24-well culture container and incubated for 6 days with polymers to be tested. The cells were incubated for additional 2 h with DMEM containing 0.5 mg/ml MTT. Purple MTT formazan products extracted in 0.05 N HCl-isopropanol were quantified by colorimetric readouts at 570 nm with background subtraction at 650 nm using Infinite M200Pro Multimode Reader (Tecan, Männedorf, Switzerland).