PEGylated Opto-Magnetic Gold and Silver Sulfide Iron Oxide Nanoprobes for Synergistic Photothermal Therapy

Abstract

There is a continuous vivid search for biocompatible hybrid magneto-optical nanoprobes with high heating and photoluminescence efficiencies for photothermal theranostics. Herein, two tailored multipurpose hybrid PEGylated gold (Au) and silver sulfide (Ag₂S) magnetic iron oxide nanoparticle formulations (Au-PEG-MNPs and Ag₂S-PEG-MNPs) with unique opto-magnetic properties for simultaneous photothermal therapy were prepared. The physiochemical properties of the hybrid MNPs were fully characterized using various electronic and spectroscopic techniques, showing colloidal stabilized small-sized nanoparticles (core sizes = 10 nm, D_H = 200 nm) with high saturation magnetizations (M_s up to 85 emu/g) and superparamagnetic behavior. Thermal effects in response to an alternating magnetic field (AMF) at different frequencies (f = 25–300 kHz) and field intensities (H = 12 and 24 kA/m) were assessed using an ultrafast magnetometric method, revealing high heating efficiencies with distinctive heating responses. The “optothermal” efficacies were then evaluated using a unique experimental setup equipped with a highly sensitive thermal camera for recording temperatures in real time, along with a simultaneous clinically safe near-infrared (NIR) laser (λ = 808 nm and power = 0.5 W cm^–2) and AMF (H = 12 kA/m, f = 180 kHz) dual effect. Remarkably, when irradiated with an NIR laser and AMF, both hybrid Au- and Ag₂S-PEG-MNPs displayed superior heat induction power (SAR = 384 and 441 W/g), rapidly reaching hyperthermia temperatures of 42 °C in only a few seconds. Temperatures could reach up to 75 °C for Au-PEG-MNPs and 90 °C for Ag₂S-PEG-MNPs in only 5 min. Such superior heating efficiencies for the hybrid MNPs increased ∼1.5–2 times under concurrent irradiation compared to the action by laser alone. Finally, cytotoxicity assays against cancerous and normal cells confirmed the safety profiles and low toxicities of the hybrid nanoformulations. This unique synergistic platform has great potential to be utilized for multimodal photothermal therapy with reduced field strengths, laser intensities, and short irradiation times in the unceasing search for tangible hyperthermal clinical nanoprobes.