Magnetic Resonance Imaging (MRI) is an attractive platform for medical imaging because it uses neither harmful radiation nor expensive radio-tracers;however, MRI, even with the aid of suitable contrast agents, is plagued by background noise from the host tissue and lacks the ability to quantify exactly how much contrast agent is present at a given location. Despite the fact that contrast agents are useful in imaging and differentiating abnormal tissues (tumors) from healthy tissues at much larger scales, early detection of a few-thousand cancer cells is difficult due to the lack of contrast differentiating the tumor from surrounding healthy tissue. Additionally, quantification of cells at the disease site is crucial for development of more site-specific contrast agents that will enable future developments in image-guided therapeutics. Thus, there is a critical need to develop magnetic molecular probes that, unlike contrast agents, can be directly imaged, irrespective of the surrounding tissue, and can be simultaneously targeted to disease sites for early diagnostic imaging. Our goal is to use Magnetic Particle Imaging (MPI), a new medical imaging technology recently introduced by Philips that uses the magnetic relaxation of magnetite nanoparticles in alternating fields, to produce three-dimensional images of the distribution of the nanoparticles in the tissue. The magnetic nanoparticles will have a million times more signal in MPI compared to the nuclear paramagnetism of protons used in MRI. Royal Philips and Bruker Biospin, have jointly announced the development of a preclinical MPI hardware and imaging system, to be marketed in 2011/12. However, commercially available magnetite formulations are grossly inadequate for MPI, both in terms of signal intensity and spatial resolution. In fact, if this critical component, i.e. appropriate magnetite nanoparticle-based molecular probes, that are biocompatible and surface functionalized for facile bioconjugation, and tailored for optimal, performance, are not developed now the enormous potential of MPI may never be realized. Based on our knowhow, we propose to develop the technology of the molecular probes crucially required for the success of MPI in a most timely manner. Our three specific aims (SA) will focus on (SA1) development of monodispersed and biocompatible magnetic nanoparticles (MNPs) as molecular probes optimized for any specific driving frequency used in MPI, (SA2) functionalize the MNPs for specific targeting to tumor cells and the surrounding vasculature and determine the targeting effectiveness in vitro, and (SA3) demonstrate MPI's ability to detect and quantify our targeted MNPs in vitro using a home-built magnetic spectrometer, thereby setting the stage for Phase II work involving in vivo imaging and quantification.
Public Health Relevance: Medical imaging, in its many forms, is a crucial technique used by clinicians for diagnosing diseases and determining the correct treatment options for patients. Diagnosis of cancer, a disease that has resulted in over 550,000 deaths in the United States in 2010 alone (National Cancer Institute;www.cancer.gov), is especially difficult and often detected at much later stages when patient survival chances are low. For early detection of a few-thousand cells, it is important to use nanometer-scale probes (1 nanometer = 1 billionth of a meter) that can specifically target cancer cells and be directly imaged, without any interference or noise from the patient's body. In this project, we will develop functionalized magnetic nanoparticle-based molecular probes, with a million times more signal than nuclear paramagnetism used in MRI, for early detection of cancer using a new and emerging technique called Magnetic Particle Imaging (MPI). Our technology will complement the hardware being developed by Philips, the inventors of MPI. This technology, if successful, will be superior to current imaging techniques such as Magnetic Resonance Imaging (MRI) and has the potential to enable early diagnosis, giving patients a head start in the fight against cancer.
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