Magnetic fluid hyperthermia is a promising cancer treatment that essentially ”fries” cells inside tumors. The procedure has been used successfully in prostate, liver, and breast tumors. Magnetic nanoparticles (each billionths of a meter in size) are injected into the body intravenously and diffuse selectively into cancerous tissues. Add a high-frequency magnetic field, and the particles heat up, raising the temperature of the tumor cells.
Thermal transfer plays an important role in many environmental, industrial, and biological processes. The knowledge of heat transfer can be applied to our everyday life, e.g., electrical power generation, energy conversion and storage, combustion processes, thermal insulation, refrigeration, material processing, and biological systems. A heat transfer analysis typically provides the rates of heat transfer and/or the temperature distributions for steady or transient states for specified boundary conditions, initial conditions, geometries, and materials. The transfer of heat in a stationary medium such as a solid, a liquid, or a gas is called heat conduction, but when the medium moved there is heat convection.
Temperature is a key factor in the normal biological development of the stem cell, determining the sex of an amphibian, and developing immune therapies . The human body has the ability to increase its basal temperature to fight diseases. When the body is infected by viruses and bacteria, it instinctively defends itself by increasing its temperature to slow or halt the rapid growth of the pathogens. It leads to what we call fever, which is another form of hyperthermia, i.e., by elevating in body temperature for therapeutic reasons. The normal body naturally maintains a temperature of 37 ◦C, and healthy cells can survive up to 42 ◦C. The elevation of body temperature enhances host defense. For this reason, thermal therapy is useful in clinical applications, such as the treatment of cancer. It is another way to induce therapy by elevating the temperature to a therapeutic temperature range of 42-45 ◦C to kill cancerous cells.
Thermal stress leads to the denaturation of proteins within cells which causes cell damage . Thermally induced stress proteins or heat shock proteins (HSP) were described about forty years ago. HSP occurs when temperatures are elevated in the nonlethal regions of tumor to help refold and repair denatured proteins. It synthesizes new proteins by inducing a wide variety of cellular functions and defense, including chaperoning functions. HSP levels can be triggered by environmental stresses (for example chemicals, heat shock, heavy metals), a pathophysiological state (fever, viral infection, inflammation), and non-stressful conditions (cell cycle) . HSPs are reported to be useful to increase the effectiveness of cancer vaccines. Different ranges of body temperatures can induce an immune response against tumors, i.e.,
Fever-range temperature: activities of immune cells
Heat shock temperature: increase of immunogenicity of tumor cells
Cytotoxic temperature: creation of an antigen source for induction of an anti-tumor immune response.
In the fever and heat shock ranges, although the temperature is not high enough to kill cancer cells, it is sufficient to modify the tumor and immune cells. This mild hyperthermia can significantly potentiate the effects of radiotherapy and chemotherapy. Thus, combinations with hyperthermia can lower doses of chemotherapeutic agents or radioactivity, leading to a lower toxicity to achieve a patient effective treatment. In the cytotoxic range, the sustained temperature above 42 ◦C causes necrosis of cancerous cells.
Since hyperthermia can be used in combination with radiotherapy and chemotherapy, one may not need to apply a thermal dose at a cytotoxic level. Also it can be used alone to treat the entire tumor or only specific locations. There are several techniques that have been proposed to achieve the hyperthermia as follows ,
|Whole body hyperthermia||Warm-water blankets, Inductive coils, Thermal chambers|
|Regional hyperthermia||Regional perfusion, Continuous hyperthermia, Peritoneal perfusion|
|Local hyperthermia||Radio waves, Laser ablation, Microwaves, Ultrasound waves|
The above hyperthermia techniques can treat tumors, whereas local hyperthermia (with radio waves, laser ablation, ultrasound waves, microwaves) can be applied externally to treat tumors near the skin and to reach the deep cancerous cells by using probes. However, treatment is also limited by the ability of the hyperthermia source to penetrate body tissues that surround tumors. Care should be taken to not harm the healthy tissues that lie between the external source and the cancer. Temperatures above 42 ◦C in healthy tissues bring discomfort, burns, and blisters. Magnetic fluid hyperthermia (MFH) can help overcome these probl