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

Abstract

This paper describes the synthesis of new nanocomposite nanoparticles that consist of polymer coated γ-Fe2O3 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.

Development of a novel conductance-based technology for environmental bacterial sensing

“…On the other hand, filtration might be applied to removing those chemical pollutants, but the sample process afterwards requires the extraction step, which could result in damages of bacterial cells. A magnetic nanoparticle based method has been shown successful in separating cancer cells from serum samples, and it was suggested that such a method could be used in separating bacteria from complex system as well [28]. Use of antibody-coated magnetic particles could extract bacteria from the liquid suspensions, thus concentrating the species and minimizing the influence of the dissolved chemical ions on the technology developed here.…”

Co nanoparticles inserted into a porous carbon amorphous matrix: the role of cooling field and temperature on the exchange bias effect

“…The extended x-ray absorption fine structure (EXAFS) spectra were analyzed according to standard procedures and the spectra were normalized to the absorption coefficient averaged at high energy in order to eliminate the dependence of absorption with the sample thickness. 5 Two kind of magnetic measurements were performed combining SQUID and a Quantum Design PPMS magnetometer with the vibrating-sample (VSM) option: (i) after a zero field cooling (ZFC) from 300 K down to 10 K, it was measured the variation of the magnetization as a function 10 of the temperature between 10 and 340 K, M ZFC (T), and after field cooling (FC), M FC (T). In both cases the applied magnetic field was fixed to H = 10 Oe.…”

Multimodal Biomedical Imaging with Asymmetric Single-Walled Carbon Nanotube/Iron Oxide Nanoparticle Complexes

“…We attempted to magnetically modulate the complexes with a 0.02 T solenoid system, but the magnetic force was not sufficient to overcome Brownian motion, as the magnetic force exerted on a particle is proportional to the volume of the magnetic component. 26 Recent reports showed that CdSe quantum dots encapsulating a ∼10 nm magnetic core had a ∼70% lower emission quantum yield 46 and a ∼90% shorter lifetime 45 than the original quantum dots. In contrast, the optical properties of SWNT in this study are not significantly affected by the presence of the iron oxide nanoparticles.…”