Controlled adhesion of human lymphocytes on electrically charged polymer surface having phosphorylcholine moiety

The human lymphocytes were interacted with polymer surfaces whose surface potential was controlled by the formation of a polyion complex (PIC) having a phosphorylcholine moiety. 3-(Methacryloyloxypropyl)-trimethyl ammonium iodide as the cationic unit or potassium 3-methacryloyloxypropyl sulfonate as the anionic unit was copolymerized with 2-methacryloyloxyethyl phosphorylcholine (MPC) and n-butyl methacrylate. PIC was made at the solid–liquid interface, that is, an aqueous solution containing an anionic polymer with different concentrations was contacted with a cationic polymer coated polymer membrane. The formation process of PIC was followed using a quartz crystal microbalance, and the PIC surfaces were analyzed by ζ-potential and X-ray photoelectron spectroscopy. The surface potential on the PIC was controllable from +20 to −16 mV, which increased in the amount of adsorbed anionic copolymer as the ζ-potential decreased toward the negative charge. The PIC surface in contact with human lymphocyte for 5 h was observed using a scanning electron microscopy and the density of the adherent human lymphocyte was determined by the lactate dehydrogenase method. The lymphocyte adhesion on the surface was gradually reduced with an increase in the negative value of the ζ-potential. The morphological change in the adherent lymphocytes was not observed on the polymer surfaces with MPC units. The adherent lymphocytes were not activated on the PIC surface. The lymphocyte adhesion with reduced activation could be controlled by changing the surface potential on the polymer with the MPC unit.     

Domain-controlled polymer alloy composed of segmented polyurethane and phospholipid polymer for biomedical applications

Segmented polyurethane(SPU)s are block polymers which have a good elastic property and thermoplasticity. However, the biocompatibility of SPU is not sufficient, and a living organism rejects the SPU as a foreign material. Thus, some modification is needed to provide excellent biocompatibility and retain the good physical characteristics of the SPUs. In this study, we blended the 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer with SPU to prepare an SPU/MPC polymer alloy. We investigated the effects of the molecular weight (M_w) of the MPC polymer on the microdomain structure and mechanical property of the polymer alloy. When the MPC polymer with a higher M_w was blended with SPU, the polymer alloy underwent a reduction in mechanical strength. On the other hand, even when the lower M_w of the MPC polymer was blended with SPU, differential scanning calorimetric analysis revealed that the MPC polymer chains did not disrupt the crystallinity of the hard segments of SPU and the polymer alloy could maintain its physical properties the same as that of the original SPU. We investigated the adsorption of immunoglobulin (IgG) on the surface of the polymer alloy for evaluation of its fundamental biocompatibility. The SPU/MPC polymer alloy lowered the amount of adsorbed IgG compared to that on SPU. This means that the blending of the MPC polymer significantly improved the biocompatibility of the SPU. We succeeded in preparing an SPU/MPC polymer alloy that possesses both the good mechanical property of SPU and the improved biocompatibility using MPC polymers.     

Domain-controlled polymer alloy composed of segmented polyurethane and phospholipid polymer for biomedical applications

Segmented polyurethane(SPU)s are block polymers which have a good elastic property and thermoplasticity. However, the biocompatibility of SPU is not sufficient, and a living organism rejects the SPU as a foreign material. Thus, some modification is needed to provide excellent biocompatibility and retain the good physical characteristics of the SPUs. In this study, we blended the 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer with SPU to prepare an SPU/MPC polymer alloy. We investigated the effects of the molecular weight (M_w) of the MPC polymer on the microdomain structure and mechanical property of the polymer alloy. When the MPC polymer with a higher M_w was blended with SPU, the polymer alloy underwent a reduction in mechanical strength. On the other hand, even when the lower M_w of the MPC polymer was blended with SPU, differential scanning calorimetric analysis revealed that the MPC polymer chains did not disrupt the crystallinity of the hard segments of SPU and the polymer alloy could maintain its physical properties the same as that of the original SPU. We investigated the adsorption of immunoglobulin (IgG) on the surface of the polymer alloy for evaluation of its fundamental biocompatibility. The SPU/MPC polymer alloy lowered the amount of adsorbed IgG compared to that on SPU. This means that the blending of the MPC polymer significantly improved the biocompatibility of the SPU. We succeeded in preparing an SPU/MPC polymer alloy that possesses both the good mechanical property of SPU and the improved biocompatibility using MPC polymers.     

Effect of surface modification on laser direct joining of cyclic olefin polymer and stainless steel

Surface modification pretreatment on the laser-bonded joint between a cyclic olefin polymer (COP) and stainless steel (SUS304) was studied to determine its effect on improving the laser-bonded joint strength. The joint strength between the surface-modified COP and SUS304 was significantly improved compared with that of an equivalent un-treated joint. This improvement is caused by the generation of oxygen functional groups on the COP surface resulting in the improved adhesion of these groups with the oxide film formed on the SUS304 surface.As for the surface pretreatment of COP, the generation of bubbles in ultraviolet (UV)–ozone processing due to thermal degradation of the COP was more noticeable than with plasma pretreatment. Excessive surface modification of the COP, causing a decrease in joint strength was found to correlate with the surface energies of COP and SUS304.     

New perspectives on the roles of nanoscale surface topography in modulating intracellular signaling

The physical properties of biomaterials, such as elasticity, stiffness, and surface nanotopography, are mechanical cues that regulate a broad spectrum of cell behaviors, including migration, differentiation, proliferation, and reprogramming. Among them, nanoscale surface topography, i.e., nanotopography, defines the nanoscale shape and spatial arrangement of surface elements, which directly interact with the cell membranes and stimulate changes in the cell signaling pathways. In biological systems, the effects of nanotopography are often entangled with those of other mechanical and biochemical factors. Precise engineering of 2D nanopatterns and 3D nanostructures with well-defined features has provided a powerful means to study the cellular responses to specific topographic features. In this Review, we discuss efforts in the last three years to understand how nanotopography affects membrane receptor activation, curvature-induced cell signaling, and stem cell differentiation.