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Radio frequency radiation-induced hyperthermia using Si nanoparticle-based sensitizers for mild cancer therapy

View Article: PubMed Central - PubMed

ABSTRACT

Offering mild, non-invasive and deep cancer therapy modality, radio frequency (RF) radiation-induced hyperthermia lacks for efficient biodegradable RF sensitizers to selectively target cancer cells and thus avoid side effects. Here, we assess crystalline silicon (Si) based nanomaterials as sensitizers for the RF-induced therapy. Using nanoparticles produced by mechanical grinding of porous silicon and ultraclean laser-ablative synthesis, we report efficient RF-induced heating of aqueous suspensions of the nanoparticles to temperatures above 45-50°C under relatively low nanoparticle concentrations (<1 mg/mL) and RF radiation intensities (1–5 W/cm2). For both types of nanoparticles the heating rate was linearly dependent on nanoparticle concentration, while laser-ablated nanoparticles demonstrated a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations from 0.01 to 0.4 mg/mL. The observed effect is explained by the Joule heating due to the generation of electrical currents at the nanoparticle/water interface. Profiting from the nanoparticle-based hyperthermia, we demonstrate an efficient treatment of Lewis lung carcinoma in vivo. Combined with the possibility of involvement of parallel imaging and treatment channels based on unique optical properties of Si-based nanomaterials, the proposed method promises a new landmark in the development of new modalities for mild cancer therapy.

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Si nanoparticles as nanosensitizers for RF radiation-induced hyperthermia.(a) TEM image (inset), electron diffraction pattern obtained in the “transmission” geometry (inset) and corresponding size distribution of porous silicon (PSi) nanoparticles prepared by mechanical milling of electrochemically prepared porous silicon; (b) TEM image (inset), electron diffraction pattern (inset) and corresponding size distribution of NPs prepared by laser ablation from a Si target in deionized water; (c) Temperature growth of an aqueous suspension of PSi NPs with concentration of 1 mg/mL (red curve) and distilled water (black) under RF irradiation with intensity of 5 W/cm2 versus the RF irradiation time; (d) the same dependence for laser-ablated Si-based NPs with concentration of 0.015 mg/mL (open green circles) and 0.05 mg/mL (closed green circles). Insets in panels (c) and (d) show glass cuvettes with the NP suspensions of PSi and LA-Si, respectively.
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f2: Si nanoparticles as nanosensitizers for RF radiation-induced hyperthermia.(a) TEM image (inset), electron diffraction pattern obtained in the “transmission” geometry (inset) and corresponding size distribution of porous silicon (PSi) nanoparticles prepared by mechanical milling of electrochemically prepared porous silicon; (b) TEM image (inset), electron diffraction pattern (inset) and corresponding size distribution of NPs prepared by laser ablation from a Si target in deionized water; (c) Temperature growth of an aqueous suspension of PSi NPs with concentration of 1 mg/mL (red curve) and distilled water (black) under RF irradiation with intensity of 5 W/cm2 versus the RF irradiation time; (d) the same dependence for laser-ablated Si-based NPs with concentration of 0.015 mg/mL (open green circles) and 0.05 mg/mL (closed green circles). Insets in panels (c) and (d) show glass cuvettes with the NP suspensions of PSi and LA-Si, respectively.

Mentions: In our experiments, we tested two different types of Si-based nanostructures. First, we used NPs produced by mechanical milling of electrochemically-prepared porous silicon (see details in the Methods section). The advantage of the electrochemistry fabrication pathway consists in a fast and cost-efficient production of a large quantity of porous silicon-based (PSi) NPs having promising optical properties12, although the surface of PSi NPs should be properly cleaned to remove residual contaminants after the fabrication procedure. As shown in Fig. 2a, the electrochemically-prepared PSi NPs have a wide dispersion in size and shape: the size distribution contains a broad spectrum with the peak value at about 50 nm and a considerable portion of larger (several hundreds of nm) NPs. Second, we used Si-based NPs prepared by methods of femtosecond laser ablation in deionized water212223 (see details in the Methods section). The latter laser-ablative approach is unique in avoiding any residual contamination of the NP surface as a result of the synthesis in a clean aqueous environment in the absence of any toxic by-products. As shown in Fig. 2b, the laser-ablated Si NPs (LA-Si NPs) have nearly ideal round shape with a much smaller mean size (25–30 nm) and a low size dispersion (less than 15 nm full width at half maximum). Electron diffraction patterns (insets of Fig. 2a,b) show a periodic arrangement of reflections, evidencing the presence of crystalline structure of Si-based NPs. According to the FTIR spectroscopy data (Figure S2 of Suppl. Information (SI)) and XPS data23, the surface of freshly prepared PSi and LA-Si NPs is predominantly oxidized, with a certain amount of hydrogen still remaining on the PSi NPs surface. Such silicon oxide-related coverage of NPs is supposed to condition hydrophilic properties of their surface. The surface area of PSi NPs was found to be 450 m2/g, while the average pore diameter was about 4 nm (Fig. S1a,b of SI). LA-Si NPs are obviously oxidized due to their interaction with water, although the level of oxidation can be controlled by dosing the amount of dissolved oxygen in deionized water environment during laser synthesis procedure23. For comparison, we also used Au NPs prepared by fs laser ablation in deionized water (LA-Au NPs) according to the recipe described in Refs. 21, 22 (see details of the fabrication procedure in the Methods section).


Radio frequency radiation-induced hyperthermia using Si nanoparticle-based sensitizers for mild cancer therapy
Si nanoparticles as nanosensitizers for RF radiation-induced hyperthermia.(a) TEM image (inset), electron diffraction pattern obtained in the “transmission” geometry (inset) and corresponding size distribution of porous silicon (PSi) nanoparticles prepared by mechanical milling of electrochemically prepared porous silicon; (b) TEM image (inset), electron diffraction pattern (inset) and corresponding size distribution of NPs prepared by laser ablation from a Si target in deionized water; (c) Temperature growth of an aqueous suspension of PSi NPs with concentration of 1 mg/mL (red curve) and distilled water (black) under RF irradiation with intensity of 5 W/cm2 versus the RF irradiation time; (d) the same dependence for laser-ablated Si-based NPs with concentration of 0.015 mg/mL (open green circles) and 0.05 mg/mL (closed green circles). Insets in panels (c) and (d) show glass cuvettes with the NP suspensions of PSi and LA-Si, respectively.
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Related In: Results  -  Collection

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f2: Si nanoparticles as nanosensitizers for RF radiation-induced hyperthermia.(a) TEM image (inset), electron diffraction pattern obtained in the “transmission” geometry (inset) and corresponding size distribution of porous silicon (PSi) nanoparticles prepared by mechanical milling of electrochemically prepared porous silicon; (b) TEM image (inset), electron diffraction pattern (inset) and corresponding size distribution of NPs prepared by laser ablation from a Si target in deionized water; (c) Temperature growth of an aqueous suspension of PSi NPs with concentration of 1 mg/mL (red curve) and distilled water (black) under RF irradiation with intensity of 5 W/cm2 versus the RF irradiation time; (d) the same dependence for laser-ablated Si-based NPs with concentration of 0.015 mg/mL (open green circles) and 0.05 mg/mL (closed green circles). Insets in panels (c) and (d) show glass cuvettes with the NP suspensions of PSi and LA-Si, respectively.
Mentions: In our experiments, we tested two different types of Si-based nanostructures. First, we used NPs produced by mechanical milling of electrochemically-prepared porous silicon (see details in the Methods section). The advantage of the electrochemistry fabrication pathway consists in a fast and cost-efficient production of a large quantity of porous silicon-based (PSi) NPs having promising optical properties12, although the surface of PSi NPs should be properly cleaned to remove residual contaminants after the fabrication procedure. As shown in Fig. 2a, the electrochemically-prepared PSi NPs have a wide dispersion in size and shape: the size distribution contains a broad spectrum with the peak value at about 50 nm and a considerable portion of larger (several hundreds of nm) NPs. Second, we used Si-based NPs prepared by methods of femtosecond laser ablation in deionized water212223 (see details in the Methods section). The latter laser-ablative approach is unique in avoiding any residual contamination of the NP surface as a result of the synthesis in a clean aqueous environment in the absence of any toxic by-products. As shown in Fig. 2b, the laser-ablated Si NPs (LA-Si NPs) have nearly ideal round shape with a much smaller mean size (25–30 nm) and a low size dispersion (less than 15 nm full width at half maximum). Electron diffraction patterns (insets of Fig. 2a,b) show a periodic arrangement of reflections, evidencing the presence of crystalline structure of Si-based NPs. According to the FTIR spectroscopy data (Figure S2 of Suppl. Information (SI)) and XPS data23, the surface of freshly prepared PSi and LA-Si NPs is predominantly oxidized, with a certain amount of hydrogen still remaining on the PSi NPs surface. Such silicon oxide-related coverage of NPs is supposed to condition hydrophilic properties of their surface. The surface area of PSi NPs was found to be 450 m2/g, while the average pore diameter was about 4 nm (Fig. S1a,b of SI). LA-Si NPs are obviously oxidized due to their interaction with water, although the level of oxidation can be controlled by dosing the amount of dissolved oxygen in deionized water environment during laser synthesis procedure23. For comparison, we also used Au NPs prepared by fs laser ablation in deionized water (LA-Au NPs) according to the recipe described in Refs. 21, 22 (see details of the fabrication procedure in the Methods section).

View Article: PubMed Central - PubMed

ABSTRACT

Offering mild, non-invasive and deep cancer therapy modality, radio frequency (RF) radiation-induced hyperthermia lacks for efficient biodegradable RF sensitizers to selectively target cancer cells and thus avoid side effects. Here, we assess crystalline silicon (Si) based nanomaterials as sensitizers for the RF-induced therapy. Using nanoparticles produced by mechanical grinding of porous silicon and ultraclean laser-ablative synthesis, we report efficient RF-induced heating of aqueous suspensions of the nanoparticles to temperatures above 45-50°C under relatively low nanoparticle concentrations (<1 mg/mL) and RF radiation intensities (1–5 W/cm2). For both types of nanoparticles the heating rate was linearly dependent on nanoparticle concentration, while laser-ablated nanoparticles demonstrated a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations from 0.01 to 0.4 mg/mL. The observed effect is explained by the Joule heating due to the generation of electrical currents at the nanoparticle/water interface. Profiting from the nanoparticle-based hyperthermia, we demonstrate an efficient treatment of Lewis lung carcinoma in vivo. Combined with the possibility of involvement of parallel imaging and treatment channels based on unique optical properties of Si-based nanomaterials, the proposed method promises a new landmark in the development of new modalities for mild cancer therapy.

No MeSH data available.


Related in: MedlinePlus