Kinetically caused saturation in the deposition of particles or cells

Sedimentation adsorption of a charge-regulated colloidal particle onto a large charged disk

The sedimentation adsorption of a charge-regulated colloidal particle, which simulates biocolloids such as cells, onto a large, charged disk is modeled theoretically. The influences of the parameters' key to the present problem, including the particle size, the nature of the acidic and basic functional groups on the particle surface, the initial particle-disk distance, and the surface potential of the disk, on the dynamic sedimentation behavior of the particle are investigated. The loci of a particle under various conditions are simulated to justify the specific behaviors of the phenomenon under consideration. In general, the smaller the fraction of the acidic functional groups and/or the lower the surface potential of the disk, the shorter the sedimentation time is. It is interesting to observe that the larger the particle and/or the longer the initial particle-disk distance do not necessarily lead to a longer sedimentation time.

Effect of ionic size on the deposition of charge-regulated particles to a charged surface

The deposition of charge-regulated particles to a rigid, planar charged surface is modeled theoretically, taking the effects of the excluded area arising from deposited particles and finite ionic sizes into account. Here, a particle comprises a rigid core and an ion-penetrable charged membrane layer, which represents a general type of particle. If the membrane layer has a negligible thickness, the particle simulates a regular inorganic particle, and if the membrane layer has a finite thickness, it simulates biocolloids such as cells. The results of numerical simulation reveal that the rate of particle deposition is faster under the following conditions: (1) lower potential of the planar surface, (2) thicker membrane, (3) higher counterion valance, (4) lower fixed charge density, (5) smaller counterions, (6) larger co-ions, (7) larger functional group, and (8) lower pH. Neglecting the sizes of ionic species may lead to an appreciable deviation in both the electrical repulsive force between particle and surface and the rate of deposition. Typical deviation for the former is approximately 20%, and that for the latter is approximately -75%.

Mathematical model of static platelet adhesion on a solid surface

The scheme of platelet/surface interaction and a kinetic model of platelet adhesion on a solid surface are suggested. The elaborated approach takes into account the platelet activation by the surface and accumulation of free activated cells in the bulk of the liquid phase. This effect has an especially important role in static experimental conditions. The suggested model explains three types of adhesion kinetic curves, obtained in experiments in vitro: sigmoid curves with or without saturation and an exponential curve with saturation. According to the model, the curve shape is determined by material surface properties, platelet functionality, and experimental conditions of the platelet/surface interaction. The data of static platelet adhesion from platelet rich plasma on glass, siliconized glass, hexadecyltrichlorosilane monolayers, and low-density polyethylene are described mathematically with the proposed model. Numerical parameters are calculated from approximation of experimental data by the model. These parameters allow quantitative characterization of platelet interaction with the material surface.

Short-term cell-attachment rates: a surface-sensitive test of cell-substrate compatibility

Mechanisms of cell deposition from a sessile liquid phase and adherence to various plastic substrates have been investigated by measurement of short-term (less than 120 min) cell-attachment rates. Sigmoidal attachment-rate curves were fit with a three-parameter variant of a logistic equation to quantify parameters related to initial rate and equilibrium-adherence. For substrates on which cell adhesion was low, initial rates were estimated from slopes of linear best-fit equations. Average variations in adherence parameters for three cell lines, MDCK (epithelioid), VERO, and AHL-1 (fibroblastic) to tissue-culture grade polystyrene dishes were less than 10% (standard-error-of-mean/mean X 100) over extended periods of more than two months, so that attachment measurements could be repetitively applied with the same cell stocks continuously subcultured in the laboratory. Developed techniques were applied to a variety of plastics and the results tabulated. Comparison of adherence parameters for ionomer and polyethylene films, both with and without adsorbed fetal-bovine-serum proteins, demonstrated that surface carboxyl groups were important in protein adsorption and cellular adherence. Attachment rates of MDCK to polystyrene were dependent on starting cell number whereas equilibrium adherence did not vary significantly over a wide range of inoculum concentrations. It was concluded from theoretical considerations that initial rates of MDCK attachment were sensitive to and dependent on electrostatic barriers to formation of close substrate contacts whereas equilibrium-adherence levels were controlled by short-range forces such as interfacial energies and formation of receptor-ligand complexes.