Magnetic Quantum Dots and Magnetic Microarrays for Cell and Molecular Detection

Biomarker detection, whether of soluble biomolecules or surface expressed proteins, is critical to disease diagnosis and treatment. Nanotechnology has made a tremendous impact in ultrasensitive detection because of its size similarity to biomolecules and the unique properties conferred at the nanoscale. However, the majority of nanodetection schemes fail to isolate the molecules of interest in a non-destructive method that permits their subsequent downstream use. Here, we describe a lab-on-a-chip nanomagnetic conveyer belt scheme for the detection, quantification, and isolation of cells and biomolecules. This platform consists of magnetic quantum dots targeted to the molecules of interest that are manipulated by mobile magnetic disk or nanowire trap arrays controlled with external electromagnetic fields. We have used this technology to isolate single leucocytes via their CD45 receptors and have also quantified the number of expressed CD45 receptors in situ via quantum dot fluorescence. Additionally, we have detected and isolated avidin and short sequence p53 DNA from 10^-10 M solutions both individually and in multiplexed configurations. This corresponds to the ability to isolate ~60 copies of RNA/DNA per cell from samples of as few as 100 cells without the use of the polymerase chain reaction (PCR). Further, all of these experiments were accomplished using extremely small samples volumes (~ 5 µl). We are currently adapting this technology for the isolation of circulating tumor cells and PCR-less detection of their miRNA profiles. This technology thus has tremendous potential for clinical diagnostic applications.