Detection of breast cancer cells using targeted magnetic nanoparticles and ultra-sensitive magnetic field sensors.
BACKGROUND
Breast cancer detection using mammography has improved clinical outcomes for many women, because mammography can detect very small (5 mm) tumors early in the course of the disease. However, mammography fails to detect 10 - 25% of tumors, and the results do not distinguish benign and malignant tumors. Reducing the false positive rate, even by a modest 10%, while improving the sensitivity, will lead to improved screening, and is a desirable and attainable goal. The emerging application of magnetic relaxometry, in particular using superconducting quantum interference device (SQUID) sensors, is fast and potentially more specific than mammography because it is designed to detect tumor-targeted iron oxide magnetic nanoparticles. Furthermore, magnetic relaxometry is theoretically more specific than MRI detection, because only target-bound nanoparticles are detected. Our group is developing antibody-conjugated magnetic nanoparticles targeted to breast cancer cells that can be detected using magnetic relaxometry.


METHODS
To accomplish this, we identified a series of breast cancer cell lines expressing varying levels of the plasma membrane-expressed human epidermal growth factor-like receptor 2 (Her2) by flow cytometry. Anti-Her2 antibody was then conjugated to superparamagnetic iron oxide nanoparticles using the carbodiimide method. Labeled nanoparticles were incubated with breast cancer cell lines and visualized by confocal microscopy, Prussian blue histochemistry, and magnetic relaxometry.


RESULTS
We demonstrated a time- and antigen concentration-dependent increase in the number of antibody-conjugated nanoparticles bound to cells. Next, anti Her2-conjugated nanoparticles injected into highly Her2-expressing tumor xenograft explants yielded a significantly higher SQUID relaxometry signal relative to unconjugated nanoparticles. Finally, labeled cells introduced into breast phantoms were measured by magnetic relaxometry, and as few as 1 million labeled cells were detected at a distance of 4.5 cm using our early prototype system.


CONCLUSIONS
These results suggest that the antibody-conjugated magnetic nanoparticles are promising reagents to apply to in vivo breast tumor cell detection, and that SQUID-detected magnetic relaxometry is a viable, rapid, and highly sensitive method for in vitro nanoparticle development and eventual in vivo tumor detection.
Department of Cell Biology & Physiology, University of New Mexico School of Medicine, MSC08 4750, 1 University of New Mexico, Albuquerque, NM 87131, USA. hhathaway@salud.unm.edu
Helen J
HJ
Hathaway
Kimberly S
KS
Butler
Natalie L
NL
Adolphi
Debbie M
DM
Lovato
Robert
R
Belfon
Danielle
D
Fegan
Todd C
TC
Monson
Jason E
JE
Trujillo
Trace E
TE
Tessier
Howard C
HC
Bryant
Dale L
DL
Huber
Richard S
RS
Larson
Edward R
ER
Flynn
D000818:Animals; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D005260:Female; D005290:Ferric Compounds; D006801:Humans; D018796:Immunoconjugates; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D058185:Magnetite Nanoparticles; D051379:Mice; D008819:Mice, Nude; D019047:Phantoms, Imaging; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology / Q000378:metabolism; D012680:Sensitivity and Specificity; D023041:Xenograft Model Antitumor Assays
D005290:Ferric Compounds; D018796:Immunoconjugates; D058185:Magnetite Nanoparticles; D018719:Erb-b2 Receptor Tyrosine Kinases; C000499:ferric oxide; C508053:ERBB2 protein, human