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

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.