The method of activated swelling of polymer particles developed by the authors allows the preparation of monodisperse spherical beads of predictable size from 1 to 100 µm in diameter. The polymer particles may be prepared from a number of different monomeric materials and with various morphologies including macroporous structures. The porous beads form the basis for magnetizable monodisperse polymer particles which have magnetic iron oxides distributed as small grains all through the volume of the beads. The magnetic particles are being used extensively for selective cell separation and for immunomagnetic separation within microbiology and molecular biology. A review of recent work within these fields is given. New methods for positive cell separation are announced.

Lipopolysaccharide (LPS), a glycolipid present in the outer membrane of gram-negative bacteria, is a potent inducer of proinflammatory responses from cells of the monocytic lineage. LPS stimulation of monocytes results in cytokine production, one of the key events in the pathogenesis of gram-negative sepsis (4). The cell surface glycoprotein CD14 (membrane CD14 [mCD14]) has been identified as the principal LPS receptor on phagocytic leukocytes, enabeling them to be stimulated with picogram amounts of LPS (42,47). This process is facilitated by the catalytic activity of the blood protein LPS binding protein (LBP), which accelerates the binding of LPS to mCD14 (20). CD14 exists in two forms; in myeloid cells it is expressed as a glycosylphosphatidylinositol (GPI)-anchored glycoprotein (21), whereas a soluble form of CD14 (sCD14) lacking a GPI tail is present in blood (2). We have previously reported that uronic acid polymers with a ␤ (134) glycosidic linkage are able to stimulate monocytes to produce tumor necrosis factor (TNF) in an mCD14-dependent manner; polymers of high mannuronic acid content (M-polymers) were found to be the most potent (14). Several reports subsequently implicated CD14 in responses to a variety of bacterial compounds (36,37,44), suggesting that the role of CD14 is not limited to LPS recognition.In addition to CD14, other proteins described as LPS receptors include the ␤2-integrins CR3 (CD11b/CD18, Mac-1) and CR4 (CD11c/CD18, p150,95) (46). Wright and coworkers reported that CR3 and CR4 function in the recognition of Escherichia coli by binding to the lipid A portion of LPS (46). However, cells from patients genetically deficient in CD18 expression responded normally to LPS (45), suggesting that CD18 is not essential for cellular responses to LPS. On the other hand, Ingalls et al. found that Chinese hamster ovary (CHO)-K1 cells transfected with CR3 or CR4 acquire LPS responsiveness, as evidenced by inducible NF-B translocation (24,25). Furthermore, components from group B streptococcus (GBS) type III can activate human monocytes to TNF production through a CD18-dependent mechanism (8, 31), suggesting that under certain defined conditions, engagement of the ␤2-integrins by bacterial ligands is proinflammatory. Previously we have reported that covalently linking detoxified LPS (DLPS) and M-polymers to particles increased their TNF-inducing potency 2,000 to 60,000 times compared to that of the polymers in soluble form (3). In the present work we have investigated the mechanisms by which soluble LPS, DLPS, and M-polymers (350 kDa) stimulate monocytes to produce TNF compared to DLPS covalently attached to particles (DLPS-particles) or M-polymers (ϳ3 kDa) covalently attached to particles (M-particles). The data suggest that phagocytes utilize membrane CD14 for LPS-, DLPS-, and Mpolymer-induced TNF production, both in solution and attached to particles. In contrast, the ␤2-integrin CR3 only participates in the response to the particulate form of the polymers. These data suggest that different membr...

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The principle of activated swelling has made available polymer particles in the range of 1–100 μm, highly uniform in size, and with great variations in morphology and chemical composition. A short description of the method is given. On the basis of monosized porous macroreticular particles, monosized magnetic polymer particles (MMP) are prepared which are uniform in size as well as in content of magnetic oxides. These particles have found applications in a number of selective cell separation procedures. Special types of MMP have been developed for isolation of organelles and viruses. The use of MMP as contrast agent in magnetic resonance imaging is shortly described.

Particles like barite and cuttings influence the friction properties of a mud. The standard API lubricity tester, however, cannot measure friction of fluids containing particles, and to overcome this problem it was modified with a cam setup. It was found that particles indeed alter the friction. Large beads are being used to reduce friction. They are, however, filtered out in the solids control equipment and to avoid this, we have investigated smaller polymer microbeads which will pass unhindered. The microbeads reduce the friction in water based muds with around 40% which is significantly better than four commercial lubricants.