Limits...
Carbon-covered magnetic nanomaterials and their application for the thermolysis of cancer cells.

Xu Y, Mahmood M, Fejleh A, Li Z, Watanabe F, Trigwell S, Little RB, Kunets VP, Dervishi E, Biris AR, Salamo GJ, Biris AS - Int J Nanomedicine (2010)

Bottom Line: X-ray diffraction and X-ray photoelectron spectroscopy analysis revealed that the cores inside the carbon shells of these NPs were preserved in their metallic states.Low RF radiation of 350 kHz induced localized heating of the magnetic NPs, which triggered cell death.Apoptosis inducement was found to be dependent on the RF irradiation time and NP concentration.

View Article: PubMed Central - PubMed

Affiliation: Nanotechnology Center and Applied Science Department, University of Arkansas at Little Rock, Little Rock, AR, USA. yxxu@ualr.edu; asbiris@ualr.edu

ABSTRACT
Three types of graphitic shelled-magnetic core (Fe, Fe/Co, and Co) nanoparticles (named as C-Fe, C-Fe/Co, and C-Co NPs) were synthesized by radio frequency-catalytic chemical vapor deposition (RF-cCVD). X-ray diffraction and X-ray photoelectron spectroscopy analysis revealed that the cores inside the carbon shells of these NPs were preserved in their metallic states. Fluorescence microscopy images indicated effective penetrations of the NPs through the cellular membranes of cultured cancer HeLa cells, both inside the cytoplasm and the nucleus. Low RF radiation of 350 kHz induced localized heating of the magnetic NPs, which triggered cell death. Apoptosis inducement was found to be dependent on the RF irradiation time and NP concentration. It was showed that the Fe-C NPs had a much higher ability of killing the cancer cells (over 99%) compared with the other types of NPs (C-Co or C-Fe/Co), even at a very low concentration of 0.83 microg/mL. The localized heating of NPs inside the cancer cells comes from the hysteresis heating and resistive heating through eddy currents generated under the RF radiation. The RF thermal ablation properties of the magnetic NPs were correlated with the analysis provided by a superconducting quantum interference device (SQUID).

Show MeSH

Related in: MedlinePlus

A) Cytotoxicity effects of the low concentration (0.83 μg/mL) C-Co, C-Fe/Co, and C-Fe NPs on the HeLa cancer cells after 2 to 30 minutes of RF exposure. B) Effect of different concentrations of the C-Fe, C-Fe/Co, and C-Co NPs on the HeLa cells that died from 350 kHz RF heating after two minutes of exposure time. C) Comparative RF-induced temperature variations as the function of different C-Fe, C-Fe/Co, and C-Co NP concentrations. Insert figure shows the temperature-rising characteristics of different magnetic NPs with the same amount under 350 kHz RF exposure.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2865011&req=5

f3-ijn-5-167: A) Cytotoxicity effects of the low concentration (0.83 μg/mL) C-Co, C-Fe/Co, and C-Fe NPs on the HeLa cancer cells after 2 to 30 minutes of RF exposure. B) Effect of different concentrations of the C-Fe, C-Fe/Co, and C-Co NPs on the HeLa cells that died from 350 kHz RF heating after two minutes of exposure time. C) Comparative RF-induced temperature variations as the function of different C-Fe, C-Fe/Co, and C-Co NP concentrations. Insert figure shows the temperature-rising characteristics of different magnetic NPs with the same amount under 350 kHz RF exposure.

Mentions: HeLa Cells cultured with various concentrations of magnetic NPs were introduced inside a water-cooled coil coupled to a radiofrequency generator with the frequency of 350 kHz, which is far lower than the 10 MHz to 300 GHz that is commonly used.17 The depth of penetration of RF radiation in human tissue decreases as the frequency increases. Current clinical microwave radiometers operate in the GHz frequency range. The effective depth of the RF penetration drops from 17 cm at 85 MHz to 7 cm at 220 MHz. Thus, RF below 200 MHz are more desirable for the thermal ablation of cells or tissues located 1–20 cm deep into the body. Such low frequency radiation has the ability to penetrate the biological tissues efficiently and present a path for cancer treatment deep inside the body (for example, at 400 kHz, field penetration into 15 cm of tissue is >99%).18 At frequencies below 100 MHz, the RF power deposition in patients is more evenly distributed over the exposed body volume than currently assumed.19 The frequency of the AC electromagnetic field should be chosen based on a compromise; namely, it must be higher than the frequency capable of provoking neuromuscular response and lower than the frequencies causing overheating of healthy tissues. It is believed that the frequency should be in the range 100–1000 kHz; in this case, correctly chosen frequencies and electromagnetic field strengths produce no notable side effects of the AC magnetic field in vivo.20 The schematic diagram of this setup was shown in our previous work.10 After the RF irradiation, the total number of live and dead cells was immediately counted through visualization by fluorescence microscopy. Figure 3a shows the results of the influence of the RF exposure for time periods of 2 to 30 minutes on the induction of apoptosis in the cells. If the concentration of the NPs was kept constant, the number of dead cells gradually increased after extending the RF-heating time. The three types of NPs were kept at the same low concentration (about 0.83 μg/mL) and were incubated with the HeLa Cells. After the RF heating, C-Fe NPs exhibited the highest killing rate of the HeLa Cells, as presented in Figure 3a. During only two minutes of RF exposure, 67.0% of cells were observed to have died. Increasing the heating time to 30 minutes caused the percentage of dead cells to reach about 74.5%, which is 2.14 times and 2.69 times higher than that induced by the C-Fe/Co NPs and C-Fe NPs, respectively. The results indicated that the C-Fe NPs were the best RF absorbers and induced cellular death in the shortest time and at the lowest concentrations. Moreover, for RF exposure times longer than 10 minutes, the percentage of dead cells increased rather slowly (around 10% or less) depending on the type of NPs used in the experiment. As a result, if the exposure time was kept constant, the percentage of dead cells was found to be highly dependent on the NP concentration. As shown in Figure 3b, when the NP concentration was increased to 3.33 μg/mL, C-Fe NPs killed almost 98.88%–100% of the exposed cells with only two minutes of RF exposure. However, for the C-Co NPs, a significantly higher concentration (∼20 μg/mL) was required to cause the same effect.10


Carbon-covered magnetic nanomaterials and their application for the thermolysis of cancer cells.

Xu Y, Mahmood M, Fejleh A, Li Z, Watanabe F, Trigwell S, Little RB, Kunets VP, Dervishi E, Biris AR, Salamo GJ, Biris AS - Int J Nanomedicine (2010)

A) Cytotoxicity effects of the low concentration (0.83 μg/mL) C-Co, C-Fe/Co, and C-Fe NPs on the HeLa cancer cells after 2 to 30 minutes of RF exposure. B) Effect of different concentrations of the C-Fe, C-Fe/Co, and C-Co NPs on the HeLa cells that died from 350 kHz RF heating after two minutes of exposure time. C) Comparative RF-induced temperature variations as the function of different C-Fe, C-Fe/Co, and C-Co NP concentrations. Insert figure shows the temperature-rising characteristics of different magnetic NPs with the same amount under 350 kHz RF exposure.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2865011&req=5

f3-ijn-5-167: A) Cytotoxicity effects of the low concentration (0.83 μg/mL) C-Co, C-Fe/Co, and C-Fe NPs on the HeLa cancer cells after 2 to 30 minutes of RF exposure. B) Effect of different concentrations of the C-Fe, C-Fe/Co, and C-Co NPs on the HeLa cells that died from 350 kHz RF heating after two minutes of exposure time. C) Comparative RF-induced temperature variations as the function of different C-Fe, C-Fe/Co, and C-Co NP concentrations. Insert figure shows the temperature-rising characteristics of different magnetic NPs with the same amount under 350 kHz RF exposure.
Mentions: HeLa Cells cultured with various concentrations of magnetic NPs were introduced inside a water-cooled coil coupled to a radiofrequency generator with the frequency of 350 kHz, which is far lower than the 10 MHz to 300 GHz that is commonly used.17 The depth of penetration of RF radiation in human tissue decreases as the frequency increases. Current clinical microwave radiometers operate in the GHz frequency range. The effective depth of the RF penetration drops from 17 cm at 85 MHz to 7 cm at 220 MHz. Thus, RF below 200 MHz are more desirable for the thermal ablation of cells or tissues located 1–20 cm deep into the body. Such low frequency radiation has the ability to penetrate the biological tissues efficiently and present a path for cancer treatment deep inside the body (for example, at 400 kHz, field penetration into 15 cm of tissue is >99%).18 At frequencies below 100 MHz, the RF power deposition in patients is more evenly distributed over the exposed body volume than currently assumed.19 The frequency of the AC electromagnetic field should be chosen based on a compromise; namely, it must be higher than the frequency capable of provoking neuromuscular response and lower than the frequencies causing overheating of healthy tissues. It is believed that the frequency should be in the range 100–1000 kHz; in this case, correctly chosen frequencies and electromagnetic field strengths produce no notable side effects of the AC magnetic field in vivo.20 The schematic diagram of this setup was shown in our previous work.10 After the RF irradiation, the total number of live and dead cells was immediately counted through visualization by fluorescence microscopy. Figure 3a shows the results of the influence of the RF exposure for time periods of 2 to 30 minutes on the induction of apoptosis in the cells. If the concentration of the NPs was kept constant, the number of dead cells gradually increased after extending the RF-heating time. The three types of NPs were kept at the same low concentration (about 0.83 μg/mL) and were incubated with the HeLa Cells. After the RF heating, C-Fe NPs exhibited the highest killing rate of the HeLa Cells, as presented in Figure 3a. During only two minutes of RF exposure, 67.0% of cells were observed to have died. Increasing the heating time to 30 minutes caused the percentage of dead cells to reach about 74.5%, which is 2.14 times and 2.69 times higher than that induced by the C-Fe/Co NPs and C-Fe NPs, respectively. The results indicated that the C-Fe NPs were the best RF absorbers and induced cellular death in the shortest time and at the lowest concentrations. Moreover, for RF exposure times longer than 10 minutes, the percentage of dead cells increased rather slowly (around 10% or less) depending on the type of NPs used in the experiment. As a result, if the exposure time was kept constant, the percentage of dead cells was found to be highly dependent on the NP concentration. As shown in Figure 3b, when the NP concentration was increased to 3.33 μg/mL, C-Fe NPs killed almost 98.88%–100% of the exposed cells with only two minutes of RF exposure. However, for the C-Co NPs, a significantly higher concentration (∼20 μg/mL) was required to cause the same effect.10

Bottom Line: X-ray diffraction and X-ray photoelectron spectroscopy analysis revealed that the cores inside the carbon shells of these NPs were preserved in their metallic states.Low RF radiation of 350 kHz induced localized heating of the magnetic NPs, which triggered cell death.Apoptosis inducement was found to be dependent on the RF irradiation time and NP concentration.

View Article: PubMed Central - PubMed

Affiliation: Nanotechnology Center and Applied Science Department, University of Arkansas at Little Rock, Little Rock, AR, USA. yxxu@ualr.edu; asbiris@ualr.edu

ABSTRACT
Three types of graphitic shelled-magnetic core (Fe, Fe/Co, and Co) nanoparticles (named as C-Fe, C-Fe/Co, and C-Co NPs) were synthesized by radio frequency-catalytic chemical vapor deposition (RF-cCVD). X-ray diffraction and X-ray photoelectron spectroscopy analysis revealed that the cores inside the carbon shells of these NPs were preserved in their metallic states. Fluorescence microscopy images indicated effective penetrations of the NPs through the cellular membranes of cultured cancer HeLa cells, both inside the cytoplasm and the nucleus. Low RF radiation of 350 kHz induced localized heating of the magnetic NPs, which triggered cell death. Apoptosis inducement was found to be dependent on the RF irradiation time and NP concentration. It was showed that the Fe-C NPs had a much higher ability of killing the cancer cells (over 99%) compared with the other types of NPs (C-Co or C-Fe/Co), even at a very low concentration of 0.83 microg/mL. The localized heating of NPs inside the cancer cells comes from the hysteresis heating and resistive heating through eddy currents generated under the RF radiation. The RF thermal ablation properties of the magnetic NPs were correlated with the analysis provided by a superconducting quantum interference device (SQUID).

Show MeSH
Related in: MedlinePlus