In this work, the copolymer-based synthesized Cysteine-loaded nanocarriers prepared by a routine protocol, coprecipitation method. It is the first report to investigate the neuroprotective potential and biocompatibility of Cysteine derivatives loaded into poly(ethylene glycol)-block-poly(e−caprolactone) methyl ether (PEG-b-PCL). The average size of the polymeric/empty NCs was 89 nm and for polymeric/Synthesized derivative of Cysteine was 126 nm. The Drug Loading efficiency was 81%. The concentration of Polymeric NCs was 2.1 x 10 10 particles/ml and the zeta potential of polymeric/empty and polymeric/ Synthesized derivative of Cysteine NCs -5 mV and -11 mV respectively. Biological part of this work were investigated in the SH-SY5Y human neuroblastoma cell line using cell viability and toxicity assays. The concentration of polymeric NCs below 1 x 10 10 particles/ml described as a zero-point damageable for the cell line. Also the Synthesized derivative of Cysteine encapsulated into polymeric NCs have more neuroprotective effect compared to free Cysteine at lower concentration, and therefore, have a significant neuroprotective potential against Z-VAD-fmk and St-evoked SH-SY5Y cell damage.