Antioxidant action of L-cysteine anchored on the surface of magnetite nanoparticles

This study addresses the synthesis, characterization, and evaluation of L-Cysteine (L-Cys) molecules anchored on superparamagnetic iron oxide nanoparticles (SPIONs), mainly magnetite (Fe₃O₄), for potential drug delivery applications. Fe₃O₄ nanoparticles are obtained via co-precipitation and functionalized with L-Cys to improve biocompatibility and antioxidant activity. To optimize the functionalization process, the dimerization of cysteine to cystine is investigated by varying the reaction time and mass proportions. The samples are characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and Raman spectroscopies, transmission electron microscopy (TEM), and magnetic curves. These results confirm that L-Cys molecules are anchored on the nanoparticle surface through their carboxylate groups, with free SH groups present in the dispersed nanoparticles. However, in the solid state, L-Cys dimerization leads to a cystine crystal structure, resulting in no free SH groups. The nanoparticles have a magnetite structure with an average crystallite size of (8.7±0.8) nm and superparamagnetic behavior. In vitro biological assays show the antioxidant effect of L-Cysteine on the surface of the nanoparticles.