Microspheres surface charge

Tabata, Y. and Ikada, Y. (1988). Effect of the size and surface-charge of polymer microspheres on their phagocytosis by macrophage. Biomaterials, 9, 356-362. 

A stirred cell equipped with a 0.22iuni membrane filter was charged with 30 mL of latex, the dispersion of microsphere. The specific surfrice area was adjusted to 0.19 m per ImL and the ionic strength was calibrated to 0.01. At the constant stirrer speed, buffer solution was introduced into the stirred ceil until steady state flux was attained. Protein solutions were introduced with step of pulse injection. The permeate flux was measured continuously with an electronic balance (Precision plus, Ohaus Co., USA) by a data acquisition system. The electronic balance was connected to a PC through a RS 232C interfece. The surface charge density of microspheres was varied as 0.45, S.94, 9.14 and 10.25, and the stirrer speed was varied as 300,400 and 600rpm. 

Fig. 1. shows the steady-state permeate flux with respect to various stirrer speeds and surface charge densities. As the stirrer speed was faster, the higher permeate flux was observed because of the higher shear stress at the surface of a cake layer. The permeate flux was proportional to the surface charge density of microspheres, in the case of the higher surface charge density, the repulsive force became larger and the cake resistance decreased. 

The cake porosity, obtained from the steady-state flux, is shown with the surface charge density in Fig. 2. It was observed that the porosity of a cake layer tended to increase as the surface charge density increased. The stirring effect was investigated with monodisperse microspheres of different surface charge density. It was observed that the stirrer speed was proportional to the porosity of a cake layer. 

Phagocytosis of microspheres by Mphysicochemical properties of the microsphere surface, especially by the surface charge and the hydro-... 

The microspheres mentioned above are all spherical and no change of the diameter and aggregation of the microspheres takes place during the reaction of surface modification. The surface charge of every microsphere can be determined by electrophoresis. For instance, the zeta potentials of our cellulose triacetate, Cell-OH, crosslinked Cell-OH, Cell-CM, Cell-SE, Cell-NHa, Cell-DEAE, Cell-DEAE(Me), and benzyl cellulose microspheres were —19.9, —2.1, —2.7, —17.1, —20.9, +4.6, +14.2, +15.1, and —65.2 mV, respectively. This result indicates that anionic and cationic microspheres with the same average diameter but different surface charges can be prepared by this method. 

Hg. 11. Effect of the surface charge on phagocytosis of modified cellulosic microspheres (1) Cell-OH. (2) crc s-linked Cell-OH, (3) CeU-CM. (4) CeU-SE, (5) Cell-NH, (6) CeU-DEAE, (7) Cell-DEAE (Me), (8) lhilo triacetate, and (9) benzyl cellulose micro-spheres... 

Norris D, Sinko P. Effect of size, surface charge, and hydrophobicity on the translocation of polystyrene microspheres through gastrointestinal mucin. J Appl Polym Sci 1996, 63, 1481-1492. 

As one example, the force-versus-distance between a sUica particle and a titania flat is shovra in Fig. 7. Like in many publications, the force is scaled by division through the radius of the silica microsphere. According to Eq. (7), the scaled force, F/R, is equal to 2tiVa. Force curves were recorded at different pH values ranging from pH 8.8 for the top curve to pH 3.0 for the bottom curve. The surface charges of both materials are mainly determined by the pH. Sihca has... 

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