Tunable environmental sensitivity and degradability of nanogels based on derivatives of cystine and poly(ethylene glycols) of various length for biocompatible drug carrier

•New nanogel based on derivatives of cystine and poly(ethylene glycols) was obtained.•The nanogel loaded with DOX appeared to be stable in the physiological environment.•The highest cumulative release of DOX was observed in conditions typical for cancer cells.•The DOX loaded nanogels were found to be cytotoxic against the examined cancer cells.•The unloaded nanogel nanoparticles did not inhibit proliferation of the cells.