Fe3O4-citrate-curcumin: Promising conjugates for superoxide scavenging, tumor suppression and cancer hyperthermia

Abstract

Fe3O4 nanoparticles have been conjugated to curcumin (CU) molecules via a citrate (CA) linker (Fe-CA-CU) and have been explored for superoxide scavenging, tumor suppression, and cancer hyperthermia. The conjugation chemistry reveals that Fe3+ ions on the nanoparticle surface readily conjugates to the available carboxyl sites on the CA molecule, which further conjugates to CU at its central enol -OH group. As seen from the UV-vis spectroscopy, the therapeutically active chromophore group of CU, which is seen at 423 nm, was intact, ensuring the activity the molecule. Magnetization measurements showed good hysteresis curves of Fe3O4 and Fe-CA-CU, indicating the presence of magnetism after conjugation. The loading percentage of citrate-curcumin was seen to be ∼10% from the thermo-gravimetric analysis. The systems when subjected to radio-frequency fields of 240 KHz, were seen to get heated up. The Fe3O4 heating exhibited better slope (1 °C/s) as compared to the Fe-CA-CU system (∼0.7 °C/s) for a sample of concentration 10 mg/ml in average time of ∼20 s to reach the required hyperthermia threshold temperature of ∼45 °C. Tumor suppression studies were done using potato assay, which showed that while only CU showed 100% suppression in 7 days, it was about 89% by the Fe-CA-CU. Upon subjecting these systems to the superoxide anion scavenging assay and superoxide radical scavenging assay (riboflavin), it was observed that the activity was enhanced in the Fe-CA-CU to 40% (from 38% in only CU) and 100% (from 5.75% in only CU). These studies promise Fe-CA-CU as a good cancer hyperthermia-cum-tumor suppressant and antioxidant agent.