(346c) Magnetic Quantum Dots Coupled with Magnetic Microarrays for Molecular Detection and Separation

Analysis of biomarker molecules is important not only in diagnostics, but also in monitoring disease progression, and response to therapy. Nanotechnology is revolutionalizing the field of biomarker detection with the development of ultrasensitive detection techniques. However, nanomaterials developed thus far have primarily been targeted towards molecular detection. An ideal chemical analysis scheme would also include separation of targeted molecules from the original location to permit further analysis and manipulation.

Here we describe a proof of principle study of the use of magnetic quantum dot nanoparticles for molecular detection and separation of biomarkers on the same microchip. A range of biomarkers: proteins, mutated DNAs, RNAs, circulating tumor cells can be detected with this assay. We have already demonstrated detection and separation of avidin from a 10^-10 M solution; we have also successfully manipulated human leucocytes on the microchip.  The assay is performed on a magnetic platform consisting of an array of magnetic discs or nanowires coupled to electromagnets that apply an external magnetic field. The target is detected by coalescence of magnetic and fluorescent nanoparticles to yield a composite nanoparticle with magnetic and fluorescent functionalities, whereas in the absence of the target these signals are not present. The response of a fluorescent probe to the external magnetic field constitutes a detection signal, and by controlling the direction of the external magnetic field the captured target is transported to the desired location on the array for further analysis. Detection and separation can be performed on the same platform. Further, because quantum dots are used as fluorescent probes, their size tunable and narrow emission spectra properties impart multiplexing capability. Ultimately this platform will be constructed in a lab on chip design incorporating nonmaterial-biomolecules mixing, detection, and magnetic separation. This technology could have tremendous impact on a number of fields including healthcare diagnostics, small-scale chemical synthesis, and molecular chromatography.