Protein membrane composition adsorbed

These results show that without any optimization of membrane composition, measurement of lysozyme in concentrations ranging from 3E-7 to 3E-4 M is possible with the pH step titration method. In order to lower the detection limit and to improve the device-to-device reproducibility, other membrane materials may have to be investigated. Especially for selective protein detection, requiring specific receptor molecules deposited in the membrane, more hydrophilic membrane materials are probably necessary, since the hydrophobic polystyrene beads are known to adsorb easily proteins aspecifically. 

As an example of a membrane model, phospholipid monolayers with negative charge of different density were used. It had already been found ( ) and discussed O) that the physical and biological behavior of phospholipid monolayers at air-water interfaces and of suspensions of liposomes are comparable if the monolayer is in a condensed state. Two complementary methods of surface measurements (using radioactivity and electrochemical measurements), were used to investigate the adsorption and the dynamic properties of the adsorbed prothrombin on the phospholipid monolayers. Two different interfaces, air-water and mercury-water, were examined. In this review, the behavior of prothrombin at these interfaces, in the presence of phospholipid monolayers, is presented as compared with its behavior in the absence of phospholipids. An excess of lipid of different compositions of phos-phatidylserine (PS) and phosphatidylcholine (PC) was spread over an aqueous phase so as to form a condensed monolayer, then the proteins were inject underneath the monolayer in the presence or in the absence of Ca. The adsorption occurs in situ and under static conditions. The excess of lipid ensured a fully compressed monolayer in equilibrium with the collapsed excess lipid layers. The contribution of this excess of lipid to protein adsorption was negligible and there was no effect at all on the electrode measurements. 

The surface properties of the biomaterials will determine the type, amount and conformation of the adsorbed proteins [2]. The composition of this protein layer can be different, depending on the fluid composition and adsorption time [25], Besides the composition of the protein layer, the conformation and the orientation of the protein can also change with time [8]. This conditioning protein layer will increase the cell adhesiveness, since the cells have receptors in their membranes that specifically bind to the adhesion proteins. Moreover, the protein layer also increases the cell spreading at the biomaterial surface [6,10]. 

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