Silica-coated Superparamagnetic Nanoparticles Research Articles

Increased endocytosis rate and enhanced lysosomal pathway of silica-coated superparamagnetic nanoparticles into M-HeLa cells compared with cultured primary motor neurons.

The unique properties of superparamagnetic iron oxide nanoparticles (SPIONs) enable their use as magnetic biosensors, targeted drug delivery, magnetothermia, magnetic resonance imaging, etc. Today, SPIONs are the only type of metal oxide nanoparticles approved for biomedical application. In this work, we analyzed the cellular response to the previously reported luminescent silica coated SPIONs of the two cell types: M-HeLa cells and primary motor neuron culture. Both internalization pathways and intracellular fate of SPIONs have been compared for these cell lines using fluorescence and transmission electron microscopy. We also applied a pharmacological approach to analyze the endocytosis pathways of SPIONs into the investigated cell lines. The penetration of SPIONs into M-HeLa cells is already noticeable within 30s of incubation through both caveolin-dependent endocytosis and micropinocytosis. However, incubation for a longer time (1h at least) is required for the internalization of SPIONs into motor neuron culture cells provided by dynamin-dependent endocytosis and macropinocytosis. The intracellular colocalization assay reveals that the lysosomal internalization pathway of SPIONs is also dependent on the cell type. The lysosomal pathway is much more pronounced for M-HeLa cells compared with motor neurons. The emphasized differences in cellular responses of the two cell lines open up new opportunities in the application of SPIONs in the diagnostics and therapy of cancer cells.

Combined antitumor effect of surface-modified superparamagnetic maghemite nanoparticles and a vitamin E derivative on experimental Walker-256 mammary gland carcinosarcoma

In a search for efficient anti-tumor agent, silica-coated superparamagnetic nanoparticles were designed and used in combination with vitamin E derivative as a potential new tool for anticancer treatment. The particles were characterized by numerous techniques, such as transmission electron microscopy and dynamic light scattering to determine the particle morphology and size both in dry state and water, atomic absorption spectroscopy to analyze the iron content, Fourier-transform infrared spectroscopy to confirm the presence of the functional groups, and vibrating sample magnetometry to determine the magnetic properties and content of maghemite. The next aim was to assess effect of the nanoparticles on suppression of experimental mammary gland carcinosarcoma W-256. Strong antitumor effect was achieved only with combined application of γ-Fe2O3@SiO2 and acetate derivative of α-tocopherol (Toc-6-Ac) resulting in 58% of tumor volume reduction. The results were compared with those obtained with poly(N,N-dimethylacrylamide)-coated iron oxide particles described earlier.

Synthesis, properties, and application in peptide chemistry of a magnetically separable and reusable biocatalyst

Enzyme-catalyzed chemical processes are selective, very productive, and generate little waste. Nevertheless, they may be optimized using enzymes bound to solid supports, which are particularly important for protease-mediated reactions since proteases undergo fast autolysis in solution. Magnetic nanoparticles are suitable supports for this purpose owing to their high specific surface area and to be easily separated from reaction media. Here we describe the immobilization of bovine α-chymotrypsin (αCT) on silica-coated superparamagnetic nanoparticles (Fe3O4@silica) and the characterization of the enzyme-nanoparticle hybrid (Fe3O4@silica-αCT) in terms of protein content, properties, recovery from reaction media, application, and reuse in enzyme-catalyzed peptide synthesis. The results revealed that (i) full acid hydrolysis of the immobilized protease followed by amino acid analysis of the hydrolyzate is a reliable method to determine immobilization yield; (ii) despite showing lower amidase activity and a lower K cat/K m value for a specific substrate than free αCT, the immobilized enzyme is chemically and thermally more stable, magnetically recoverable from reaction media, and can be consecutively reused for ten cycles to catalyze the amide bond hydrolysis and ester hydrolysis of the protected dipeptide Z-Ala-Phe-OMe. Altogether, these properties indicate the potential of Fe3O4@silica-αCT to act as an efficient, suitably stable, and reusable catalyst in amino acid, peptide, and protein chemistry as well as in proteomic studies.

Microfluidic continuous magnetophoretic protein separation using nanoparticle aggregates

We demonstrate a microfluidic continuous-flow protein separation process in which silica-coated superparamagnetic nanoparticles interact preferentially with hemoglobin in a mixture with bovine serum albumin, and the resulting hemoglobin-nanoparticle aggregates are recovered online using magnetophoresis. We present detailed modeling and analysis of this process yielding quantitative estimates of the recovery of both proteins, validated by experiments. While several previous studies utilize an average particle size in modeling magnetophoretic particle trajectories or process design, in this study we emphasize the importance of accounting for particle size distributions in calculating particle recovery, and therefore in estimating separation efficiency. We combine experimentally measured size distributions of protein-nanoparticle aggregates with simulations of particle trajectories and provide a simple analytical method to calculate the efficiency of separation at various flow speeds, which fully accounts for heterogeneity in particle sizes. Our method can potentially be used for affinity based biomolecular separations at both analytical and preparative scales by exploiting well-established techniques to functionalize nanoparticle surfaces with selective ligands. Further, the modeling methodology presented here may be applied to provide better estimates of particle recovery in a broad range of magnetophoretic separation processes involving heterogeneity in particle sizes.

Synthesis of magnetic and fluorescent bifunctional nanocomposites and their applications in detection of lung cancer cells in humans

We developed a novel strategy to detect lung cancer cells by utilizing magnetic and fluorescent bifunctional nanocomposites (BNPs) in combination with monoclonal anti-carcinoembryonic antigen (CEA) antibodies. The BNPs, consisting of silica-coated superparamagnetic nanoparticles and quantum dots (QDs), exhibited high luminescence and were easily separated in an external magnetic field. The binding specificity of the antibody-conjugated BNPs (immunonanoparticles) were confirmed via incubating with human lung adenocarcinoma SPCA-1 cells, human leukemic K562 cells and human embryonic lung fibroblasts MRC-5 cells. Further experiments demonstrated that the as-prepared immunonanoparticles can efficiently capture and detect cancer cells in pleural effusion from lung cancer patients. These results suggest that this method, of which the detection procedures are completed within 1h, could be applied to the rapid and cost-effective monitoring of cancer cells in clinical samples.

Synthesis of immunomagnetic nanoparticles and their application in the separation and purification of CD34+ hematopoietic stem cells

The silica-coated superparamagnetic nanoparticles with the uniform diameter of about 60nm were synthesized by reverse microemulsions method. And the magnetic nanoparticles were modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS). The immunomagnetic nanoparticles were then successfully prepared by covalently immobilizing anti-CD34+ monoclonal antibodies to the surface of amino silane modified magnetic particles. The cell separation results showed that the synthesized immunomagnetic nanoparticles could rapidly and conveniently separate the CD34+ cells with high efficiency and specificity than normal ones. The surface morphology of separated target cells was examined by scanning electron microscope (SEM). Atomic force microscope (AFM) also characterized the magnetic materials on the surface of the separated target cells for the first time, which further confirmed that the target cells were separated by the immunomagnetic nanoparticles. The viability of the separated cells was studied by culturing method and Beckman Vi-cell viability analyst. Therefore, our experiments provided a new, direct, rapid mode to separate target cells.