Adsorption Kinetics Model And Adsorption Mechanism Of Phospholipids Into Lung Surfactant Monolayers

Adsorption kinetics and adsorption mechanism of phospholipids into lung surfactant monolayers was investigated in this paper. The typical surface pressure (π)-time (t) isotherm of lung surfactant monolayer was divided into three regions:induction region, fast raise region and meso-equilibrium region. On the basis of the above description, an adsorption kinetics model was proposed by introducing two parameters, equilibrium half-time, t1/2, and adsorption rate constant, k, to describe z-t isotherms of phospholipids into monolayers. The model was used to correlate the dynamic surface pressure data reported in literature and the maximum absolute average error was 6.5%. In addition, it also has been discussed in this paper that the effect of initial surface pressure, temperature, and the concentration of DPPG in vesicles on characteristic parameters. The adsorption mechanism of phospholipids into monolayers was discussed. The adsorption of phospholipids to the interface was carried out by two steps. The first step is diffusion of phospholipids from bulk phase to sub-surface layer and the second step is the embedded of phospholipids into the surface. The second step is a transition process of phospholipid molecules in order from disorder state to order state. In the initial stage of adsorption, the second step is the controlling step of adsorption rate. When the adsorption amount reaches half of the total amount, the first step became the controlling step of adsorption rate.Surfactant protein C (SP-C) was separated by gel filtration chromatography, from fresh lung lavage. Theπ-t isotherms of lung surfactant monolayer under different temperature or different initial surface pressure were obtained using a self-made film balance. The experimental data was compared with model prediction values. The maximum error was 1.8% and the absolute average error was 0.8%. The results show that the model values agree with the experimental data and the model can be used to describe the adsorption kinetics behavior of phospholipids into lung surfactant monolayers.