Ghaitsa Najma Zahira Shofa, Adhistinka Jiananda, Dyah Ayu Larasati, Mercuryta Dewi Noviastuti, Siti Fatimah Azzahro, Mahardika Yoga Darmawan, Emi Kurnia Sari, Nurul Imani Istiqomah, Larissa Jestha Mahardhika, Nugraheni Puspita Rini, Julia Angel, Hasniah Aliah, Edi Suharyadi
Magnetic hyperthermia is a minimally invasive cancer therapy based on heat generation through nanoparticle relaxation under an alternating magnetic field (AMF). However, the efficiency of this therapy critically depends on nanoparticle dispersibility, as aggregation suppresses Brownian relaxation and reduces the specific absorption rate (SAR). Other major barriers include limited colloidal stability, magnetic tunability, and biocompatibility of conventional magnetic nanoparticles (MNPs). Therefore, this study aimed to evaluate the green synthesis of a magnetite/carbon dots (Fe3O4/CDots) ferrofluid derived from watermelon peel waste and Moringa oleifera (MO) leaf extract, integrating magnetic responsiveness, structural stability, and cytocompatibility within a single platform. Fe3O4 nanoparticles were synthesized by coprecipitation, CDots through hydrothermal treatment, and both components were integrated through sonication to obtain a stable ferrofluid system. The results showed that Fourier Transform Infrared spectroscopy confirmed Fe−O vibrations together with C=C,C−O, and C−O−C functional groups, verifying successful CDots surface attachment. Ultraviolet–visible spectra showed absorption peaks at 282 nm (CDots) and 400 nm (Fe3O4), while photoluminescence had a red shift from 408 to 450 nm, indicating interfacial electronic interaction. X-ray diffraction confirmed a cubic spinel Fe3O4 structure with crystallite sizes of 8.2–8.4 nm, which remained stable across varying CDots concentrations. Furthermore, scanning electron microscopy (SME) showed uniform distribution on Fe3O4 surfaces, and high-resolution transmission electron microscopy indicated approximately spherical particles with diameters of 7-10 nm. Magnetic measurements showed superparamagnetic behavior, with saturation magnetization reducing from 55.3 to 29.2 emu/g after CDots incorporation. The magnetic anisotropy constant decreased with increasing CDots concentration, enabling controlled modulation of magnetic energy barriers. The ferrofluids showed high colloidal stability (zeta potential > +30 mV) and acceptable cytocompatibility (IC50 = 1567 μg/L). Under AMF (10–20 kHz; 100–150 Oe), therapeutic temperatures of 43−46°C were achieved. The SAR decreased with rising CDots concentration but increased with higher frequency and field strength, showing that heating efficiency was governed by the interplay between intrinsic magnetic properties and external field parameters. These results showed that biomass-derived CDots incorporation offered a sustainable strategy to simultaneously regulate magnetic performance, dispersion stability, and biological compatibility, thereby mitigating key material limitations in magnetic hyperthermia applications. © 2026 Elsevier B.V.
Departement of Physics, Universitas Gadjah Mada, Yogyakarta, Indonesia; Departement of Physics, Institut Teknologi Sumatera, Lampung, Indonesia; Research Centre for Nanotechnology System, National Research and Innovation Agency (BRIN), Tangerang Selatan, Indonesia; Department of Physics, UIN Sunan Gunung Djati, Bandung, Indonesia