[Show abstract][Hide abstract] ABSTRACT: Circulating tumour cells are a key challenge in tumour therapy. Numerous approaches are on the way to achieving the elimination of these potential sources of metastasis formation. Antibody-directed magnetic cell sorting is supposed to enrich tumour cells with high selectivity, but low efficiency. The short term application of carboxymethyl dextran (CMD) coated magnetit/maghemit nanoparticles allows the discrimination of tumour cells from leukocytes. In the present work we show that the interaction of CMD nanoparticles is cell-type specific and time dependent. The breast cancer cell line MCF-7 and the CML cell line K-562 are characterized by a rapid and high interaction rate, whereas leukocytes exhibit a decelerated behaviour. The addition of carboxymethyl dextran or glucose stimulated the magnetic labelling of leukocytes. The variation of the degree of substitution of dextran with carboxymethyl groups did not affect the labelling profile of leukocytes and MCF-7 cells. In order to verify the in vitro results, whole blood samples from 13 cancer patients were analysed ex vivo. Incubation of the purified leukocyte fraction with CMD nanoparticles in the presence of low amounts of plasma reduced the overall cell content in the positive fraction. In contrast, the absolute number of residual tumour cells in the positive fraction was 90% of the initial amount.
[Show abstract][Hide abstract] ABSTRACT: The separation of tumor cells from healthy cells is a vital problem in oncology and hematology, especially from peripheral blood. Magnetic assisted cell sorting (MACS) is a possibility to fulfill these needs.
Tumor cell lines and leukocytes from peripheral blood were incubated with carboxymethyl dextran-coated magnetic nanoparticles under various conditions and separated by MACS.
We studied the interaction of magnetic nanoparticles devoid of antibodies with healthy and tumor cells. The magnetic nanoparticles interact with tumor cells and leukocytes and are located predominantly within the cell cytoplasm. Incubation of cell culture cells with magnetic nanoparticles led to a labeling of these cells without reduced biological properties for at least 14 days. The interaction of the magnetic nanoparticles with cells depends on several factors. The ionic strength (osmolality) of the solvent plays an important role. We could show that an increase in osmolality led to a dramatic reduction of labeled leukocytes. Tumor cells, however, are mildly affected. This could be detected not only in pure cultures of tumor cells or leukocytes but also in mixed cell populations.
This observation gives us the opportunity to selectively label and separate tumor cells but not leukocytes from the peripheral blood.
Journal of Cancer Research and Clinical Oncology 06/2006; 132(5):287-92. DOI:10.1007/s00432-006-0076-x · 3.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In oncology and hematology the separation of tumor cells from healthy cells in peripheral blood is a vital problem. We could show previously, that enrichment of tumor cells from peripheral blood is possible by using magnetic nanoparticles with a carboxymethyl dextran (CMD) shell. Long-term storage of CMD nanoparticles eliminated the differential labeling of tumor cells and leukocytes which might be due to an alteration of the carboxymethyl dextran shell. Incubation of stored CMD nanoparticles with freshly prepared carboxymethyl dextran restored the differential labeling. In contrast, enzymatic degradation of the carboxymethyl dextran shell with dextranase abolished the cell-type specific labeling. Thus, an intact carboxymethyl dextran shell is crucial for the cell-type specific interaction of the CMD nanoparticles and living cells.