Multimodal characterization of newly synthesized Schiff base PEI CA/ N-GQDs nanomaterial and its anticancer effects on human neuroblastoma cells

In this study, we synthesized a new material, Schiff base PEI-CA/N-GQDs, from the reaction of 4-hydroxy-3-methoxy-cinnamaldehyde (CA) with polyethyleneimine-functionalized N-doped graphene quantum dots (PEI N-GQDs). The synthesized material was experimentally characterized by FT-IR, UV-Vis, SEM, EDX, AFM, XRD, and TGA, as well as theoretically by the DFT method. In addition to their biological activities, their cytotoxic, apoptotic, and cell cycle-arresting effects were investigated in human epithelial neuroblastoma (SH-SY5Y) cells. According to the UV-Vis data, we observed that the material exhibits phenol-imine/keto-amine tautomerism, a phenomenon common in 2-hydroxy Schiff bases that helps to explain the various properties of the material. Furthermore, this material predominantly exists in the keto-amine form. The material demonstrated favorable electron transfer properties, making it suitable for electrochemical applications. We showed that it binds to DNA through an electrostatic interaction and causes oxidative and hydrolytic cleavage in DNA, which results in an increase in ROS in the cell, an activation of the CASPASE-3, leading the cells to undergo apoptosis, and inhibiting cell division in the G1/S phase. We believe that the chemical properties of the Schiff-based PEI N-GQDs make them a superior carrier molecule for cancer treatment. Furthermore, the anticancer properties of the Schiff-based PEI-CA/N-GQDs suggest their potential as a therapeutic agent for neuroblastoma.