Abstract
Photothermally-heated polymer-based superparamagnetic nanocomposite (SNC) implants have the potential to overcome limitations of the conventional inductively-heated ferromagnetic metallic alloy implants for interstitial thermotherapy (IT). This paper presents an assessment of a model SNC—poly-dimethylsiloxane (PDMS) and FeO nanoparticles (MNP)—implant for IT. First, we performed structural and optical characterization of the commercially purchased MNPs, which were added to the PDMS to prepare the SNCs (MNP weight fraction wt.%) that were used to fabricate cubic implants. We studied the structural properties of SNC and characterized the photothermal heating capabilities of the implants in three different media: aqueous solution, cell (in-vitro) suspensions and agarose gel. Our results showed that the spherical MNPs, whose optical absorbance increased with concentration, were uniformly distributed within the SNC with no new bond formed with the PDMS matrix and the SNC implants generated photothermal heat that increased the temperature of deionized water to different levels at different rates, decreased the viability of MDA-MB-231 cells and regulated the lesion size in agarose gel as a function of laser power only, laser power or exposure time and the number of implants, respectively. We discussed the opportunities it offers for the development of a smart and efficient strategy that can enhance the efficacy of conventional interstitial thermotherapy. Collectively, this proof-of-concept study shows the feasibility of a photothermally-heated polymer-based SNC implant technique.
Highlights
The ferromagnetic implant technique is a minimally invasive modality for interstitial thermotherapy (IT) involving two main steps
We explored the properties of superparamagnetic polymer nanocomposites in terms of their structural, optical and photothermal capabilities
The resulting nanocomposite implant had no new bond formed between the NP fillers and PDMS
Summary
The ferromagnetic implant (thermoseed) technique is a minimally invasive modality for interstitial thermotherapy (IT) involving two main steps. The feasibility and effectiveness of the technique have been explored in several studies ranging from fundamental research through to clinical studies [1–7]. The technique has been described as having features that are desirable for interstitial therapy including the thermal self-regulating capability of the thermoseeds coupled with the elimination of the need for physical contact between thermoseeds and the excitation field [1–3]. Issues related to biocompatibility and corrosiveness of the metallic alloy implants as well as the need to use a high number of implants to achieve therapeutic temperatures have affected effectiveness and precluded their full clinical use [8,9]. There is a need for novel strategies that can overcome the issues associated with the thermoseed technique
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