Open Access Highly Accessed Research article

Detection of breast cancer cells using targeted magnetic nanoparticles and ultra-sensitive magnetic field sensors

Helen J Hathaway12*, Kimberly S Butler3, Natalie L Adolphi24, Debbie M Lovato3, Robert Belfon1, Danielle Fegan5, Todd C Monson6, Jason E Trujillo35, Trace E Tessier5, Howard C Bryant5, Dale L Huber7, Richard S Larson23 and Edward R Flynn25

Author Affiliations

1 Department of Cell Biology & Physiology, University of New Mexico School of Medicine, MSC08 4750, 1 University of New Mexico, Albuquerque, NM 87131, USA

2 Cancer Research & Treatment Center, University of New Mexico School of Medicine, MSC07 4025, 1 University of New Mexico, Albuquerque, NM 87131, USA

3 Department of Pathology, University of New Mexico School of Medicine, MSC08 46401 University of New Mexico, Albuquerque, NM 87131, USA

4 Department of Biochemistry & Molecular Biology, University of New Mexico School of Medicine, MSC08 4670, 1 University of New Mexico, Albuquerque, NM 87131, USA

5 Senior Scientific LLC, 800 Bradbury SE, Albuquerque, NM 87106, USA

6 Nanomaterials Sciences Department, Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185, USA

7 Center for Integrated Nanotechnologies, Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185, USA

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Breast Cancer Research 2011, 13:R108  doi:10.1186/bcr3050

Published: 3 November 2011

Abstract

Introduction

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.