Effects of surface modification of materials on human neutrophil activation

Neural differentiation of midbrain cells on various protein-immobilized polyethylene films

The effect of surface modification of polyethylene (PE) film on differentiation of midbrain (MB) cells obtained from rat embryos was determined by their micromass culture system. When cultured on untreated PE film, cell differentiation was suppressed to approximately two-thirds of that observed in a control culture dish. On the contrary, type I collagen-immobilized PE film increased differentiated foci of the MB cells more than did the untreated PE film. RGDS (Arg-Gly-Asp-Ser) peptide immobilization onto PE film resulted in almost the same differentiation activity as the collagen immobilized PE film. Bovine serum albumin (BSA) immobilization onto PE film enhance the differentiation activity more than did the untreated PE film, but not up to the levels of collagen- and RGDS-immobilized PE. The number of differentiated foci of the MB cells on untreated PE film were increased by the addition of the condition medium prepared from the collagen-immobilized PE film. However, the number of foci was not increased by the addition of other condition media obtained from control dish, untreated, BSA-, and RGDS-immobilized PE. On the other hand, none of these condition media enhanced a differentiation of the neuronal cell line of PC12 cells, suggesting that some factors effectively differentiate midbrain cells, composed of neuronal epithelial and mesenchymal cells, but not the PC12 cells secreted in the condition media prepared from collagen-immobilized PE. In addition, it is probable that neural growth factor was not secreted in these condition media, which could not induce the differentiation of PC12 cells.

C1q-independent activation of neutrophils by immunoglobulin M-coated surfaces

Neutrophil granulocytes are known to rapidly adhere and undergo frustrated phagocytosis upon contact with immunoglobulin and/or complement protein opsonized artificial surfaces. In this study, we examined the relation between serum protein deposition and human neutrophil activation on hydrophobic glass and silicon model surfaces that were coated with immunoglobulin G or M (IgG/IgM), both initiators of the classical complement pathway. Protein adsorption from normal human serum (NHS) was quantified with null-ellipsometry combined with antibody techniques. The neutrophil oxygen radical production was registered by luminol-amplified chemiluminescence (CL) and the morphology, as well as changes in the content of filamentous actin (F-actin), were documented by fluorescence microscopy. Complement factor 3 (C3) bound to both IgG- and IgM-coated surfaces, but surprisingly C1q was found only on IgG-coated surfaces. Both immunoglobulins triggered complement dependent neutrophil activation. However, CL and F-actin accumulation were found sensitive to the presence of C1q in the serum only at the IgG-coated surface. We suggest that spontaneously adsorbed IgM activates the complement system and interacts with neutrophils by C1q-independent mechanisms.

Simultaneous measurement of biopolymer-mediated Mac-1 up-regulation and adherence of neutrophils: a novel flow cytometric approach for predicting initial inflammatory interaction with foreign materials

Implantation of any medical device normally causes an inflammatory cell interaction with the foreign material. In vitro cell activation of human neutrophils (Mac-1 upregulation) has been taken as one measure to assess the attributable risk of inflammation due to biopolymers before their clinical application. Mac-1 expression has generally been measured by flow cytometric assays, whereas quantification of neutrophil adhesion to the biopolymer surfaces has been performed by separate and time-consuming assays, e.g. microscopically by differential cell counting. However, due to an increasing number of surface-modified novel biopolymers entering clinical usage, effective testing of their inflammatory potential is now mandatory. To facilitate these analyses, we have developed a novel flow cytometric assay permitting simultaneous measurement of biopolymer-mediated neutrophil activation and adhesion. The biopolymers were used as beads (diameter 25+/-10 microm), and were demonstrated to be non-phagocytosable and non-fluorescent before being co-incubated with whole human blood (range of ratio granulocytes/beads from 5:1 to 1:1). Besides flow cytometric measurement of Mac-1 up-regulated neutrophils as fluorescing events, a fluorescence of the bead population indicates the adherence of activated neutrophils to the biopolymer surface.After establishing this assay, we evaluated it by comparing six different biopolymers. We observed high levels of Mac-1 expression (>70% of positive control) accompanied by increased adhesiveness (>60% of neutrophils) for polyurethane (PUR), polymethylmetacrylate (PMMA), and poly-DL-lactide (PDLLA) beads. Low Mac-1 expression levels (<10%) accompanied by a low percentage of adhering neutrophils (<10%) were observed for polyethylene (PE), polyisoprene (PI), and silicone (SI) beads.

Cell activation by the micropatterned surface with settling particles

Surface topography plays an important role in cell orientation and morphogenesis. In this study, we prepared a micropatterned surface with settling particles to obtain more detailed information about the cell recognition against the microstructured surface. Core-shell type particles having a poly-(N-isopropylacrylamide) (polyNIPAM) shell were prepared by seeded polymerization. Particles were settled on a polystyrene (PSt) flat dish by the spinner to prepare a micropatterned surface with settling particles. It could be seen that the polyNIPAM shell shrunk above and swelled below the LCST. For comparison, a thermosensitive flat surface was prepared by the graft polymerization of NIPAM. No morphologic change of cells contacting the both surfaces was observed with either an optical or a scanning electron microscope. Moreover, particles could move or roll on these surfaces when shaking the dishes. The weak interaction between neutrophil-like cells and the micropatterned surface with settling particles or the polyNIPAM-grafted surface was estimated by measurement of active oxygen released by cells. A little release could be observed at both 25 and 35 degrees C. The amount of released active oxygen at 35 degrees C was slightly larger than at 25 degrees C. When the temperature was suddenly changed, the dynamic changes of particle shape and size resulted in the excess release of active oxygen from cells contacting the micropatterned surface with settling particles. Meanwhile no stimulation could be observed in the polyNIPAM-grafted surface even if the temperature is suddenly changed. These results indicate that the micropatterned surface with settling particles can induce the dynamic stimulus at a patterned input mode.

Hydrophilicity of polymers and soft tissue responses: a quantitative analysis

This study investigates the effect of changing the hydrophilicity of polyurethane on the soft tissue inflammatory response after implantation into rats. A series of five polyurethanes were made from the macrodiols poly(ethylene oxide) (PEO), poly(tetramethylene oxide) (PTMO), poly (hexamethylene oxide) (PHMO), poly(octamethylene oxide) (POMO), and poly(decamethylene oxide) (PDMO). In the sequence the macrodiols become less polar and phase separation in the polymer increases, creating a range of hydrophilicity. These five polyurethanes were studied along with commercial Pellethane 2363-80A. The materials were implanted intramuscularly into rats for 7 days, 1 month, and 3 months. The inflammatory response was analyzed using a combination of immunohistochemistry, enzyme histochemistry, and image analysis to determine the specific cell types involved in the response and to quantify these cellular responses. The presence of three cytokines also was investigated. The cell types targeted were neutrophils, monocytes, macrophages, and T and B lymphocytes. The cytokines target were tumor necrosis factor alpha (TNF alpha), interleukin 6 (IL-6), and monocyte chemotactic protein 1 (MCP-1). All samples were positive for macrophages and activated macrophages, TNF alpha, and MCP-1, and negative for all other antibodies. The response was sustained throughout the implantation period with no significant difference among the samples except at the 7-day time point. The study demonstrated an absence of lymphocytes and neutrophils in a response that was sustained in terms of macrophages with the presence of TNF alpha and MCP-1 and the absence of IL-6. The position of subsets of macrophages with respect to increasing distance from the implants was demonstrated to be significant and consistent within this series of polyurethanes.