New insight on optical and magnetic Fe3O4 nanoclusters promising for near infrared theranostic applications

Abstract

Extensive efforts have been devoted to the development of a new biophotonic system using near infrared (NIR) nano-agents for non-invasive cancer diagnosis and therapy. Here, we developed a simple synthesis reaction of ligands, hydrazine, and iron(II) chloride to fabricate Fe₃O₄ cluster-structured nanoparticles (CNPs) with interesting NIR photonics and high magnetization (M_s: 98.3 emu g⁻¹ and proton relaxivity r₂: 234.6 mM⁻¹ s⁻¹). These Fe₃O₄ CNPs exhibited optical absorption and reflection over all wavelengths, showing a U-shape absorption band with a low absorbance at a range of 750–950 nm and a progressive evolution in the second near infrared region. Strengthening of the scattering effect by incubating Fe₃O₄ CNPs with HeLa cells was observed when optical contrast enhancement was performed in an optical coherence tomography (OCT) microscope system with a laser light source at 860 nm. Using a 1064 nm laser at a low power density (380 mW cm⁻²) to excite the Fe₃O₄ CNPs (375 ppm_[Fe]) led to a rise in the water temperature from 25 °C to 58 °C within 10 min. Finally, we present the first example of magnetomotive OCT cellular imaging combined with enhanced photothermal therapy using Fe₃O₄ CNPs and applying a magnetic field, which is promising for preclinical and clinical trials in the future.