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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).

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Magnetization curves of different magnetic NPs at 300 K A) and 5 K B); C) Temperature dependence of ZFC and FC measurements recorded at a magnetic field of 30 Oe for these magnetic NPs.Abbreviations:
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f5-ijn-5-167: Magnetization curves of different magnetic NPs at 300 K A) and 5 K B); C) Temperature dependence of ZFC and FC measurements recorded at a magnetic field of 30 Oe for these magnetic NPs.Abbreviations:

Mentions: Magnetism of biological objects is negligibly small, so biologically compatible nontoxic magnetic NPs are used to strengthen the influence of an external magnetic field. Carbon-shelled magnetic NP heating happens under RF radiation and it is possible that the NPs undergo an “auto-heating” event whereby the NPs generate their own heat energy based on molecular rotation. After heating for 60 to 90 seconds, the NP powders were found to reach the heating equilibrium (as shown in the insert in Figure 3c). This relaxation corresponds either to the physical rotation of particles directly inside the liquid or to the rotation of nuclear magnetic moments inside each particle. Rotation of particles is usually referred to as Brownian rotation, and rotation of the magnetic moment inside each particle is called Néel relaxation. This “auto-heating” was attributed to the Néel relaxation21 of the spin of the NPs under low frequency (350 kHz) RF radiation. The Néel relaxation time, TN, of the magnetic NPs under an external magnetic field is expressed by following formula22:TN=π2T0Exp(KVm/kBT)(KVm/kBT)1/2where T0 is the relaxation time constant and has the order of 10−9 s, K is the anisotropy constant, and VM is the magnetic volume of particles. The Néel relaxation time, TN, was determined as the ratio of the energy of magnetic anisotropy of superparamagnetic particles to the thermal energy. The temperature of the three NPs increased rapidly in the initial stage (from 0–60 s) which can be seen from the curves in Figure 3c inset. After about 200 seconds, the final temperatures of 65 °C, 70 °C, and 90 °C were reached for Co, Fe/Co, and Co NPs, respectively. This is due to the thermally stable spin rotation of the ferromagnetic NPs caused by the RF induced hysteresis loss. These spin properties are attributed to the particle size for the C-Fe, C-Fe/Co, or C-Co NPs with diameters <10 nm as shown in Figure 5a.


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)

Magnetization curves of different magnetic NPs at 300 K A) and 5 K B); C) Temperature dependence of ZFC and FC measurements recorded at a magnetic field of 30 Oe for these magnetic NPs.Abbreviations:
© Copyright Policy
Related In: Results  -  Collection

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

f5-ijn-5-167: Magnetization curves of different magnetic NPs at 300 K A) and 5 K B); C) Temperature dependence of ZFC and FC measurements recorded at a magnetic field of 30 Oe for these magnetic NPs.Abbreviations:
Mentions: Magnetism of biological objects is negligibly small, so biologically compatible nontoxic magnetic NPs are used to strengthen the influence of an external magnetic field. Carbon-shelled magnetic NP heating happens under RF radiation and it is possible that the NPs undergo an “auto-heating” event whereby the NPs generate their own heat energy based on molecular rotation. After heating for 60 to 90 seconds, the NP powders were found to reach the heating equilibrium (as shown in the insert in Figure 3c). This relaxation corresponds either to the physical rotation of particles directly inside the liquid or to the rotation of nuclear magnetic moments inside each particle. Rotation of particles is usually referred to as Brownian rotation, and rotation of the magnetic moment inside each particle is called Néel relaxation. This “auto-heating” was attributed to the Néel relaxation21 of the spin of the NPs under low frequency (350 kHz) RF radiation. The Néel relaxation time, TN, of the magnetic NPs under an external magnetic field is expressed by following formula22:TN=π2T0Exp(KVm/kBT)(KVm/kBT)1/2where T0 is the relaxation time constant and has the order of 10−9 s, K is the anisotropy constant, and VM is the magnetic volume of particles. The Néel relaxation time, TN, was determined as the ratio of the energy of magnetic anisotropy of superparamagnetic particles to the thermal energy. The temperature of the three NPs increased rapidly in the initial stage (from 0–60 s) which can be seen from the curves in Figure 3c inset. After about 200 seconds, the final temperatures of 65 °C, 70 °C, and 90 °C were reached for Co, Fe/Co, and Co NPs, respectively. This is due to the thermally stable spin rotation of the ferromagnetic NPs caused by the RF induced hysteresis loss. These spin properties are attributed to the particle size for the C-Fe, C-Fe/Co, or C-Co NPs with diameters <10 nm as shown in Figure 5a.

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