As we near the end of the 2011 Breast Cancer Awareness Month, it is fitting to continue our coverage of new developments related to breast cancer diagnostics and treatments. We recently reported on GE Healthcare‘s newly FDA-approved SenoBright system that promises to greatly improve imaging of breast tissue over traditional mammograms. Though mammographies have tremendously enhanced patient care – in some cases detecting pre-cancerous lesions three years prior to any problems arising – they are not perfect. Mammograms currently are incapable of distinguishing between benign and malignant lesions and are estimated to miss detecting 10-25 percent of breast cancers.
In the latest issue of Breast Cancer Research, a collaborative team of oncologists and nanotechnology researchers report using targeted magnetic nanoparticles and ultra-sensitive magnetic field sensors to accurately detect relatively small numbers of breast cancer cells. By conjugating iron-oxide nanoparticles (diameter < 30 nm) with antibodies for the aggressive breast cancer cell surface receptor, Her2, the team was able to attach hundreds of magnetic nanoparticles to each individual cancer cell. Then, using superconducting quantum interference device (SQUID) sensors, they could differentially distinguish cancerous cells from normal tissue. The authors refer to this as magnetic relaxometry, which they describe as:
… fast and theoretically is more specific than magnetic resonance imaging detection since only particles bound to their targets are detected, eliminating the problems associated with signals from unbound particles. The magnetic moments observed by magnetic relaxometry are also linear with the number of nanoparticles bound to the tumor and may be used to determine the number of cancer cells in the tumor. In magnetic relaxometry, magnetic nanoparticles that have been conjugated to antibodies or other agents are incubated with live cells. After a brief period, the nanoparticles attach to the targeted cells in large numbers, typically on the order of 100,000 nanoparticles per cell. A magnetizing pulse of less than 1 second is applied with a set of Helmholtz coils to achieve a uniform magnetizing field over the sample. A field of 40 gauss is adequate to appreciably polarize these nanoparticles, which are typically 25 nm in diameter, resulting in an induced collective magnetic moment. After the magnetizing field is removed, the magnetic moment decays through the Néel mechanism with a time constant on the order of 1 second. This decaying field is measured by an array of second-order gradiometer SQUID sensors. Our long-term goal is to develop magnetic nanoparticle-based magnetic imaging to detect in vivo malignancies with high sensitivity and specificity.
Flashback: Researchers examine bio-magnetic sensors
Image credit:: Wellcome Images: Breast cancer cells