- Email: [email protected]
Proposal of a magnetohyperthermia system: preliminary biological tests
ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 272–276 (2004) 2406–2407
Proposal of a magnetohyperthermia system: preliminary biological tests M.H.A. Guedesa, M.E.A. Guedesa, P.C. Moraisb, M.F. Da Silvab, T.S. Santosb, J.P. Alves Jra, C.E. Bertellia, R.B. Azevedoa, Z.G.M. Lacavaa,* a
! Depto de Gen!etica e Morfologia, Universidade de Bras!ılia, Instituto de Ci#encias Biologicas, Bras!ılia-DF 70910-900, Brazil b ! Universidade de Bras!ılia, Instituto de F!ısica, Nucleo de F!ısica Aplicada, Bras!ılia-DF 70919-970, Brazil
Abstract Magnetohyperthermia (MHT) has been proposed as an alternative therapy for cancer treatment. In order to perform MHT tests we have developed an apparatus operating at 1 MHz with AC magnetic field of 40 Oe in amplitude. Biological tests were performed after exposing the peritoneum region of mice to the AC field. Significative alterations were observed only when peritoneum was exposed by 10 min. The data allowed to conclude that: (1) the damage induced by the AC field to normal cells is related to the exposure time and (2) the equipment developed is adequate to perform MHT experiments. r 2003 Elsevier B.V. All rights reserved. PACS: 87.50.a; 87.50.Mn Keywords: Alternating magnetic field; Magnetothermocytolysis; Genotoxicity; Hyperthermia; Inflammation
In the last years hyperthermia has been used as alternative cancer therapy to minimize severe adverse effects of conventional treatments. Hyperthermia of tumors can be achieved using different strategies, such as application of microwave and radio frequency fields or introduction of ferromagnetic needles in the cancer site. Although hyperthermia has been shown to be an extremely powerful anti-cancer agent and a potent radiation sensitizer, the full potential of this therapy is hindered by a number of limitations, as for instance the non-homogeneous distribution of temperature over the cancer site, low specificity, patient discomfort, and thermo-tolerance development [1]. More recently, in order to overcome the above-mentioned limitations, biocompatible magnetic nanoparticles have been proposed as a material basis to support the development of hyperthermia [2]. Magnetic fluids (MFs) are stable colloidal suspensions usually containing ferrite-based (MFe2O4) magnetic nanoparticles dispersed in organic *Corresponding author. Tel.:/fax: +55-61-307-2963. E-mail address: [email protected] (Z.G.M. Lacava).
or inorganic liquid carriers. Biocompatible MFs, highly stable in water medium at neutral pH and physiological salinity, may present good thermal potential [3]. In the magnetohyperthermia (MHT) process (also known as magnetothermocytolysis [4]), the tumor cells lysis are obtained by thermal dissipation. In order to perform MHT experiments we have developed an equipment. One important question concerning the use of the MHT technology is the possible adverse effects of magnetic field exposure to the organism [5]. Thus, the purpose of this work is to investigate the in vivo action of the AC magnetic field produced by the apparatus on normal cells. The MHT system proposed is based on a portable apparatus operating at 1 MHz with 40 Oe of field amplitude. Briefly, a metallic core with a cylindrical (10.7 mm diameter) cross-section closely wound by a coil of wire concentrates the alternating magnetic flux. The solenoid core is linked to an adjustable support to apply the magnetic field in the targeted region. Swiss anesthetized mice were exposed to the magnetic field during 1, 2, 3, 4, 5, and 10 min (N ¼ 5). Biological tests
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.709
ARTICLE IN PRESS
Frequency (%)
100 80
*
60 40
*
Lym
**
20
Neu Mon
0
MN (frequency)
M.H.A. Guedes et al. / Journal of Magnetism and Magnetic Materials 272–276 (2004) 2406–2407
40 30 20
employed are detailed elsewhere [6,7]. Blood and peritoneum cytometry were performed 12; 1, 2, 24, and 48 h after exposing the animals to the AC field focused on the peritoneal region. The control group was not submitted to any treatment. Cytometry data were analyzed by the statistical test of Scheffe (ANOVA). The micronucleus (MN) assay was performed in bone marrow cells 24 and 48 h after magnetic field exposure to evaluate the cytotoxic and genotoxic effects. Differences in MN frequencies were evaluated by the Mann– Whitney test. Clinical observations did not reveal any adherence of peritoneal organs, inflammatory reaction, or tissue burn in the peritoneum. The animals did not present any apathy or irritability at any exposure time. Blood cytometry (data not shown) and peritoneal cytometry revealed significative alterations only when the peritoneum is exposed during 10 min to the magnetic field (See Fig. 1). In this case, it was observed an increase in the lymphocytes, simultaneously to a decrease in the monocyte frequency, 12 and 24 h after the AC field exposure. Nevertheless, alterations in the neutrophil frequency, an important signature of inflammatory reaction, were not observed at any time after AC field exposure. MN frequency was investigated in polychromatic (PCE) and normochromatic erytrocytes (NCE) from bone marrow. In our experiment, there was no induction of MN (See Fig. 2), from 1 to 5 min of AC field exposure, suggesting that the AC field does not present a genotoxic activity. Nevertheless, 10 min of AC field exposure increased the MN frequency to the level observed in the animals treated with cyclophosphamide, a potent clastogenic agent. This MN increase was observed 24 h (See Fig. 2) and also 48 h after AC field
*
PCE
*
NCE
10 0 CG CP 1 2 3 4 5 10 Exposure time (min)
CG ½ 1 2 24 48 Time after exposure (hours) Fig. 1. Effects of alternating magnetic field (10 min) exposure on peritoneal lymphocyte (Lym), neutrophil (Neu), and monocyte (Mon) populations. =statistically different from the control group (CG) (po0:05).
2407
Fig. 2. Effects of the alternating magnetic field exposure on the MN frequency observed in PCE or NCE; CP=cyclophosphamide treated group; =statistically different from the control group (CG) (po0:05).
exposure. Similarly, deviation from the 1:1 rate expected for PCE:NCE proportion was observed only in the animals exposed during 10 min to the AC field, indicating that interference on bone marrow cells and cytotoxic activity is being unchained (data not shown). DNA damage is the primary lesion mediating many cytotoxic and mutagenic events [8] and it has been observed in cells or organisms exposed to magnetic field [5]. In summary, the data allowed to conclude that: (1) the damage induced by the AC field to normal cells is related to the exposure time and (2) the equipment developed is adequate to perform MHT experiments. The authors acknowledge the financial support from the Brazilian agencies CNPq/PIBIC, CAPES, and FINATEC.
References [1] S.K. Calderwood, A. Asea, Int. Hyperthermia 18 (2002) 597. [2] A. Jordan, et al., J. Magn. Magn. Mater. 201 (1999) 413. [3] A. Jordan, et al., J. Magn. Magn. Mater. 225 (2001) 118. [4] J.C. Bacri, et al., in: U. H.afeli et al. (Eds.), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 44. [5] J. McCann, et al., Mutat. Res. 411 (1998) 45. [6] M.L.L. Freitas, et al., J. Magn. Magn. Mater. 252 (2002) 396. [7] V.A.P. Garcia, et al., Eur. Cell. Mat. 3 (Suppl. 2) (2002) 154. [8] Z.G.M. Lacava, et al., J. Magn. Magn. Mater. 201 (1999) 431.
Journal of Magnetism and Magnetic Materials 272–276 (2004) 2406–2407
Proposal of a magnetohyperthermia system: preliminary biological tests M.H.A. Guedesa, M.E.A. Guedesa, P.C. Moraisb, M.F. Da Silvab, T.S. Santosb, J.P. Alves Jra, C.E. Bertellia, R.B. Azevedoa, Z.G.M. Lacavaa,* a
! Depto de Gen!etica e Morfologia, Universidade de Bras!ılia, Instituto de Ci#encias Biologicas, Bras!ılia-DF 70910-900, Brazil b ! Universidade de Bras!ılia, Instituto de F!ısica, Nucleo de F!ısica Aplicada, Bras!ılia-DF 70919-970, Brazil
Abstract Magnetohyperthermia (MHT) has been proposed as an alternative therapy for cancer treatment. In order to perform MHT tests we have developed an apparatus operating at 1 MHz with AC magnetic field of 40 Oe in amplitude. Biological tests were performed after exposing the peritoneum region of mice to the AC field. Significative alterations were observed only when peritoneum was exposed by 10 min. The data allowed to conclude that: (1) the damage induced by the AC field to normal cells is related to the exposure time and (2) the equipment developed is adequate to perform MHT experiments. r 2003 Elsevier B.V. All rights reserved. PACS: 87.50.a; 87.50.Mn Keywords: Alternating magnetic field; Magnetothermocytolysis; Genotoxicity; Hyperthermia; Inflammation
In the last years hyperthermia has been used as alternative cancer therapy to minimize severe adverse effects of conventional treatments. Hyperthermia of tumors can be achieved using different strategies, such as application of microwave and radio frequency fields or introduction of ferromagnetic needles in the cancer site. Although hyperthermia has been shown to be an extremely powerful anti-cancer agent and a potent radiation sensitizer, the full potential of this therapy is hindered by a number of limitations, as for instance the non-homogeneous distribution of temperature over the cancer site, low specificity, patient discomfort, and thermo-tolerance development [1]. More recently, in order to overcome the above-mentioned limitations, biocompatible magnetic nanoparticles have been proposed as a material basis to support the development of hyperthermia [2]. Magnetic fluids (MFs) are stable colloidal suspensions usually containing ferrite-based (MFe2O4) magnetic nanoparticles dispersed in organic *Corresponding author. Tel.:/fax: +55-61-307-2963. E-mail address: [email protected] (Z.G.M. Lacava).
or inorganic liquid carriers. Biocompatible MFs, highly stable in water medium at neutral pH and physiological salinity, may present good thermal potential [3]. In the magnetohyperthermia (MHT) process (also known as magnetothermocytolysis [4]), the tumor cells lysis are obtained by thermal dissipation. In order to perform MHT experiments we have developed an equipment. One important question concerning the use of the MHT technology is the possible adverse effects of magnetic field exposure to the organism [5]. Thus, the purpose of this work is to investigate the in vivo action of the AC magnetic field produced by the apparatus on normal cells. The MHT system proposed is based on a portable apparatus operating at 1 MHz with 40 Oe of field amplitude. Briefly, a metallic core with a cylindrical (10.7 mm diameter) cross-section closely wound by a coil of wire concentrates the alternating magnetic flux. The solenoid core is linked to an adjustable support to apply the magnetic field in the targeted region. Swiss anesthetized mice were exposed to the magnetic field during 1, 2, 3, 4, 5, and 10 min (N ¼ 5). Biological tests
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.709
ARTICLE IN PRESS
Frequency (%)
100 80
*
60 40
*
Lym
**
20
Neu Mon
0
MN (frequency)
M.H.A. Guedes et al. / Journal of Magnetism and Magnetic Materials 272–276 (2004) 2406–2407
40 30 20
employed are detailed elsewhere [6,7]. Blood and peritoneum cytometry were performed 12; 1, 2, 24, and 48 h after exposing the animals to the AC field focused on the peritoneal region. The control group was not submitted to any treatment. Cytometry data were analyzed by the statistical test of Scheffe (ANOVA). The micronucleus (MN) assay was performed in bone marrow cells 24 and 48 h after magnetic field exposure to evaluate the cytotoxic and genotoxic effects. Differences in MN frequencies were evaluated by the Mann– Whitney test. Clinical observations did not reveal any adherence of peritoneal organs, inflammatory reaction, or tissue burn in the peritoneum. The animals did not present any apathy or irritability at any exposure time. Blood cytometry (data not shown) and peritoneal cytometry revealed significative alterations only when the peritoneum is exposed during 10 min to the magnetic field (See Fig. 1). In this case, it was observed an increase in the lymphocytes, simultaneously to a decrease in the monocyte frequency, 12 and 24 h after the AC field exposure. Nevertheless, alterations in the neutrophil frequency, an important signature of inflammatory reaction, were not observed at any time after AC field exposure. MN frequency was investigated in polychromatic (PCE) and normochromatic erytrocytes (NCE) from bone marrow. In our experiment, there was no induction of MN (See Fig. 2), from 1 to 5 min of AC field exposure, suggesting that the AC field does not present a genotoxic activity. Nevertheless, 10 min of AC field exposure increased the MN frequency to the level observed in the animals treated with cyclophosphamide, a potent clastogenic agent. This MN increase was observed 24 h (See Fig. 2) and also 48 h after AC field
*
PCE
*
NCE
10 0 CG CP 1 2 3 4 5 10 Exposure time (min)
CG ½ 1 2 24 48 Time after exposure (hours) Fig. 1. Effects of alternating magnetic field (10 min) exposure on peritoneal lymphocyte (Lym), neutrophil (Neu), and monocyte (Mon) populations. =statistically different from the control group (CG) (po0:05).
2407
Fig. 2. Effects of the alternating magnetic field exposure on the MN frequency observed in PCE or NCE; CP=cyclophosphamide treated group; =statistically different from the control group (CG) (po0:05).
exposure. Similarly, deviation from the 1:1 rate expected for PCE:NCE proportion was observed only in the animals exposed during 10 min to the AC field, indicating that interference on bone marrow cells and cytotoxic activity is being unchained (data not shown). DNA damage is the primary lesion mediating many cytotoxic and mutagenic events [8] and it has been observed in cells or organisms exposed to magnetic field [5]. In summary, the data allowed to conclude that: (1) the damage induced by the AC field to normal cells is related to the exposure time and (2) the equipment developed is adequate to perform MHT experiments. The authors acknowledge the financial support from the Brazilian agencies CNPq/PIBIC, CAPES, and FINATEC.
References [1] S.K. Calderwood, A. Asea, Int. Hyperthermia 18 (2002) 597. [2] A. Jordan, et al., J. Magn. Magn. Mater. 201 (1999) 413. [3] A. Jordan, et al., J. Magn. Magn. Mater. 225 (2001) 118. [4] J.C. Bacri, et al., in: U. H.afeli et al. (Eds.), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 44. [5] J. McCann, et al., Mutat. Res. 411 (1998) 45. [6] M.L.L. Freitas, et al., J. Magn. Magn. Mater. 252 (2002) 396. [7] V.A.P. Garcia, et al., Eur. Cell. Mat. 3 (Suppl. 2) (2002) 154. [8] Z.G.M. Lacava, et al., J. Magn. Magn. Mater. 201 (1999) 431.