Investigation of the factors affecting the photothermal therapy potential of small iron oxide nanoparticles over the 730–840 nm spectral region

Abstract

The use of superparamagnetic iron oxide nanoparticles (SPIONs) as a sensitizer in photothermal therapy (PTT) is relatively new and the origin of such a phenomenon is not known. Usually, large crystals and aggregated particles are preferred in the literature, suggesting that these increase the absorbance of particles at the irradiation wavelength, and hence, provide a larger temperature increase. This study has two major goals: identification of the key factors that affect the photo-induced temperature increase in well-controlled experiments and the influence of laser irradiation on nanoparticle properties. Small, biocompatible poly(acrylic acid) coated SPIONs (PAA/SPIONs) were used since they are more practical for future medical use than large aggregates. We studied the impact of three major laser-dependent variables, namely the wavelength (between 728 and 838 nm), intensity (1.85-9.76 W cm) and power (105-800 mW) as well as attenuation at the irradiation wavelength, on photothermal heating achieved with PAA/SPIONs. Within the studied range of these variables, only the laser power plays a critical role on the magnitude of photothermal heating in solutions. There is no strong correlation between the attenuation at the excitation wavelength and the temperature increase. In addition, extensive characterization of SPIONs before and after irradiation revealed no significant difference, which supports the re-usability of SPIONs. Lastly, the PTT potential of these small PAA/SPIONs was demonstrated in vitro on HeLa cells. At these low laser powers no temperature increase in SPION-free water or cell death in SPION-free cells was detected. Hence, this study provides a new insight into the photothermal effect of SPIONs, provides a clear and repeatable experimental procedure and demonstrates great potential for small SPIONs to be exploited in PTT.

Recent Advances in Cyanine-Based Phototherapy Agents

“…It is well established that thermal ablation triggers necrosis ( Jaque et al, 2014 ). Although some organic molecules can be used as a PS for PTT ( Lv et al, 2020 ), recently metal nanoparticles ( Ke et al, 2011 ; He et al, 2014 ), metal oxide nanoparticles ( Chu et al, 2013 ; Bilici et al, 2018 ), and quantum dots ( Liang et al, 2018 ; Hashemkhani et al, 2020 ), especially with significant absorbance at near-infrared (NIR) for both better tissue penetration and safety due to its nonionizing nature ( Jaque et al, 2014 ), are preferred. Light-to-heat conversion efficiency, dark toxicity, selective tumor accumulation, photostability, and effective heating of the whole tumor are factors to consider for PTT.…”

Applications of superparamagnetic iron oxide nanoparticles in drug and therapeutic delivery, and biotechnological advancements

“…Studies show that hyperthermia increases the efficacy of standard cancer treatments. When used in combination with chemotherapy, radiotherapy or radiofrequency ablation, or photothermal therapy, the final outcome of the combined therapy would be more beneficial to the patient, although in clinical practice, physicians are reluctant to use these methods [ 136 , 153 ].…”

“…Recently, SPIONs were observed to be good candidates for photothermal and photodynamic therapy, using near-infrared (700–2000 nm) laser excitation of the nanomaterial. For these therapies, SPIONs are theoretically preferred in larger clusters, although studies have shown that they can yield up to 12 °C temperature increase even in the ultrasmall range (4–5 nm SPIONs at 785 nm laser wavelength, 800 mW power for 20 min) [ 136 ]. The study concluded that ultrasmall SPIONs can also produce heat by excitation with wavelengths smaller than near infrared and that the heating efficacy depends on the laser power.…”

“…Also, there are increasingly more studies reporting on combinations with in vivo fluorescence imaging, sensing and detection. SPIONs have gained a lot of interest in theranostics, which combines diagnostics and treatment by a single intervention, where they show a lot of promise [64,[134][135][136][137][138].…”

Biomedical Applications of Hyaluronic Acid-Based Nanomaterials in Hyperthermic Cancer Therapy

“…The CoFe 2 O 4 NPs could be efficient and desirable nanomaterials for combined MHT. SPION, which have been recognized as MHT agents, have been recently utilized as photothermal agents as well [109,110]. One group [111] designed multi-functional polymeric micelles using HA, docetaxel (DTX), and SPION (HA–SPION–DTX) for combined photothermal chemotherapy.…”