Magnetic hyperthermia Flashcards
How is cancer cell growth slowed or stopped?
by heating to 42-45 degrees between 30 mins and half an hour
How do magnetic materials inside the body generate heat?
In the presence of an alternating magnetic field due to movement of magnetc domain walls/phase lag between magnetization vector and field or eddy currents
What do nanoparticles enable?
uniform heating and multiple treatments
What is frequency and strength of magnetic field limited by?
physiological response and non-specific tissue heating
What is generaration of heat caused by in larger particled with domains larger than critical domain?
losses in magnetic energy during hysterisis cycle
What is heating power proportional to?
Applied frequency multiplied by area of hysteresis loop
What do limitations on applied field strength mean?
we cannot saturate sample, only obtain minor hysteresis loop
How does magnetization reversal occur when domains are present?
requires the reversal of the mangetic field to reduce M to zero - making hysteresis
How does generation of heat occur for smaller particles of single domains?
by a phase lag between the applied frequency and the particle magnetizaton vector. Most efficient method of generating heat in mag nans
What must the nans be to avoid aggregation probs in vivo?
superparamagnetic
What are two ways of relaxations that produce heat?
1)physical rotation of particles within the fluid 2)internal fluctuations of the particle magnetic movement. BOTH depend on particle size, and #2 depends on magnetic material properties
What is the relaxation time dominated by?
The mechanism with the shortest relaxation time
Which method of relaxation is possible if the particles are not free to move?
2, internal fluctuations of the particles magnetic moment
When is the phase lag (the heating effect) at a max?
When the applied frequency is matched to the relaxation time
What is the SLP/SAR
Specific Loss Power also known as Specific Absorption
How do we calculate the SLP for a nanoparticle fluid?
by measuring the initial temp rise
What is biogenic magnetite?
A common biological magnet found in animals that know north
What are magnetite nans formed by?
bacteria, intracellular or extracellularly
How can MNPs be produced externally?
in a biologically induced reaction through which Fe3 compounds are reduced outside of the cell wall
How did the in-vivo experiments with hyperthermia nanoparticles go?
Monocytes/macrophages loaded with MNPs, intreperitoneal injection - tumor migration, alternatime magnetic field exposure 20 mins 3 times, survival time increase of 31%
What temperature is it possible to kill cells with?
39-42 is hyperthermia and 42-45 thermal ablation
Whys tumour tissue more thermally sensitive than normal tissue?
bc of the tumour vasculature - lower nutrients, lower pO2 and more acidic
What can hyperthermia reverse?
Chemoresistance
What does hyperthermia increse?
tumour oxygenation
