School of Chemical and Physical Sciences

Research project - Magnetic nanoparticles

Magnetic nanoparticles are currently the subject of intense research worldwide and hold a strong interest in the field of nanoscience for their numerous applications including drug delivery, magnetic hyperthermia, contrast enhancement in magnetic resonance imaging and bioseparation. These applications can be enhanced by using materials that have large magnetizations, include iron, which has the highest magnetization out of all the elements.

However for successful application, strict control on nanoparticle size needs to be achieved, in order to obtain magnetic nanoparticles that are superparamagnetic; that is they do not retain magnetization once an applied field is removed and hence do not aggregate. Our group focuses on synthesizing these strongly magnetic nanoparticles for use in the following three areas:


Contrast enhancement for magnetic resonance imaging (MRI)

Contrast agents for MRI have been in use for the past ten years and are chemical substances that are introduced to the part of the body being imaged. These agents improve the resolution of MRI by increasing the brightness between different tissues or between normal and abnormal tissue. Through the use of MRI contrast agents it is possible to detect smaller tumours leading to earlier cancer detection and more enhanced treatment, and avoiding potential invasive therapeutic methods. Magnetic nanoparticles are excellent candidates for MRI contrast enhancement. Due to their size, they can be easily transported and diffused around the body, and do not require extensive chelating to render them biocompatible such as gadolinium based contrast agents currently used today. Currently iron oxide nanoparticles are the only commercial T2 or negative contrast agents due to their ease of synthesis and biocompatibility. T2 contrast is where healthy tissues/cells take up the nanoparticles while tumour tissue/cells do not. When subjected to MRI, as a result of the presence of iron oxide nanoparticles the healthy tissue darkens while leaving the tumour tissue white resulting in detection of the cancer. However, iron oxides are weakly magnetic, and as a result their contrast enhancement for MRI is limited, and are contained to superficial tumours just under the skin.


contrast enhancement

Contrast in medical imaging is of great importance. The top row shows core/shell particles compared with conventional particles in the lower row. The columns show different concentrations of particles. One can clearly see darker images due to the core/shell particles. This contrast enhancement enables doctors to detect tumours more efficiently.


Materials that possess larger magnetization could result in a greater image enhancement and a more efficient darkening of the tissue, thus allowing for a clearer and early detection of cancerous tumours. These magnetic nanoparticles enhance the visibility of tumours deep in the body which results in better quality MRI images and can lead to earlier detection of cancers. These magnetic nanoparticles are less toxic that current gadolinium based contrast agents and provide greater contrast compared to iron oxide nanoparticles currently in use now. Currently our group have developed T2 contrast agents which can provide images of cancer tumours 1-3 mm in size.

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Magnetic hyperthermia


contrast-enhancement

TEM picture of core/shell particles. Clearly visible is the difference in contrast between the iron core (darker contrast) and the iron-oxide shell (lighter contrast).


This is a new research focus of our group and will evolve into a major area of the magnetic nanoparticle research focus within the group. Magnetic hyperthermia is the process by which a tumour his heated up by magnetic nanoparticles in when they are subjected to an alternating magnetic field (AMF). The "flipping" of the magnetic nanoparticles results in the production of heat, and the temperature obtained is high enough to kill tumour cells. Currently iron oxides are the only nanoparticles being clinically used for magnetic hyperthermia. Their weaker magnetization mean a stronger magnetic frequency and longer duration is required for efficient treatment of tumours however this results in damaging of healthy tissue surrounding the tumour. Also iron oxides are only effective for tumours just below the skin and not for deep tissue targeting. Our magnetic nanoparticles are being investigated to see if their superior magnetic properties will result in a more efficient treatment and deeper targeting of tumours compared to iron oxides. We have a strong collaboration with Dr. Ian Hermans of the Malaghan Institute for Medical Research where we are looking at the therapeutic capabilities of the magnetic nanoparticles synthesized with our group when subjected to magnetic hyperthermia conditions.


Drug delivery systems

The silicon quantum dots synthesized by our group can be attached to magnetic nanoparticles along with various drug molecules. These then can be guided by antibodies or a magnetic field directly to the site of disease or cancer in the body. The magnetic particles can then be subsequently used to monitor the size of the tumour via MRI as it is attacked by the drug and/or subjected to magnetic hyperthermia conditions to provide a multifunctional disease therapeutic.


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