Superparamagnetic Fe2O3 Beads−CdSe/ZnS Quantum Dots Core−Shell Nanocomposite Particles for Cell Separation

This paper describes the synthesis of new nanocomposite nanoparticles that consist of polymer coated γ-Fe 2 O 3 superparamagnetic cores and CdSe/ZnS quantum dots (QDs) shell. A single layer of QDs was bound to the surface of thiol-modified magnetic beads through the formation of thiol−metal bonds to form luminescent/magnetic nanocomposite particles. Transmission electron microscopy (TEM) and energy disperse spectroscopy (EDS) were used to characterize the size, size distribution, and composition of the luminescent/magnetic nanoparticles. Their average diameter was 30 nm with a size variation of ±15%. The nanoparticles were modified with carboxylic groups to increase their miscibility in aqueous solution. A 3-fold decrease in the luminescence quantum yield of the luminescent/magnetic particles and a slight blue shift in their emission peaks compared to individual luminescent QDs were observed. However, the particles were bright and were easily observed using a conventional fluorescence microscope. Additionally, no apparent broadening of the luminescence peak of the QDs could be seen. The luminescent/magnetic nanoparticles were easily separated from solution by magnetic decantation using a permanent magnet. The new particles could be used in a variety of bioanalytical assays involving luminescence detection and magnetic separation. To demonstrate their utility we immobilized anticycline E antibodies on their surface and used the antibody coated particles to separate MCF-7 breast cancer cells from serum solutions. Anticycline E antibodies bind specifically to cycline, a protein which is specifically expressed on the surface of breast cancer cells. The separated breast cells were easily observed by fluorescence imaging microscopy due to the strong luminescence of the luminescent/magnetic nanocomposite particles.