Fe3O4 nanorods for photothermal applications within NIR-I bio-window: Photothermal performance and preliminary biological evaluations

Photothermal therapy (PTT) has recently become one of the focal points of therapeutic research. Hence, finding new nanomaterials being able to offer improved photothermal performance due to their specific morphology and/or composition is of great importance. In this study, polyethylenimine-coated magnetite (Fe 3 O 4 ) nanorods (Fe 3 O 4 @PEI NRs) were prepared through a multi-step procedure, using the intermediate phase of β-FeOOH. Photothermal evaluations on the samples containing Fe 3 O 4 @PEI NRs dispersed in water with different concentrations ( c = 2, 5, 10 mg/ml) were performed under various NIR laser power densities ( PD = 0.33, 0.63, 0.91 W/cm 2 ) within first near-infrared bio-window (NIR-I BW; λ = 850 nm). The results revealed that even under conditions of the lowest concentration and power density ( c = 2 mg/ml and PD = 0.33 W/cm 2 ), which is of significant importance in terms of biological safety considerations, Fe 3 O 4 @PEI NRs present considerable heating efficiency ( SAR = 503 ± 25 W/g) and photothermal transduction efficiency ( η = 42.2 ± 1.8 %). Moreover, in vitro cellular assays were performed to evaluate the cytotoxicity and cellular uptake of Fe 3 O 4 @PEI NRs on Raw 264.7 cell line (macrophage-like cells). The experiments indicated that Fe 3 O 4 @PEI NRs show low toxicity on Raw 264.7 cell line and they are well able to be taken up by these cells. The results of this research can open up potential avenues towards future in vitro / in vivo photothermal trials on Raw 264.7 macrophage-like cells using Fe 3 O 4 @PEI NRs.