Three PLL/PLGA bilayers deposited on the alkane thiol-covered gold surface gave a dry thickness of approximately 40 ± 3.4Å. A QCM-D study gave a thickness of the wet (PLL/PLGA)3 film of 100±10Å [9]. Hence one may conclude that about

60% of the wet layer consisted of water. This is reasonable and agrees with previously reported values in the literature. It has been claimed that the large amount of bound water in the film is due to the polypeptides adsorbing in loops and tails, which favors storage of water in the film [20]. It is interesting that roughly the same dry content of the film is obtained in this work, in which no primer was used in the LbL process, as in earlier Inhibitors,research,lifescience,medical work with a primer present. Thus, the primer seems not to be needed on Inhibitors,research,lifescience,medical the alkane thiol surface used in the present systems, which, as discussed above, is a considerable advantage from an application point of view. Figure 1 Measured data for X (related to the real part) and Y (related to the imaginary part) fitted well with the calculated Inhibitors,research,lifescience,medical data using TFCompanion. The filmstack consists of (Au-SAM)-(PLL/PLGA)3, including an air content of 10% in the polypeptide layers. The … 3.2. Ellipsometry Study and Data Analysis of the PI3K activation Enzymatic Degradation of the PLL/PLGA Multilayers After the ellipsometry measurement the (Au-SAM)-(PLL/PLGA)3 substrate was immersed in Inhibitors,research,lifescience,medical buffer solution and allowed

to swell for at least 30 minutes before use. The samples were then moved to a new container and a solution of either trypsin (bovine) or V8 glutamyl endopeptidase (Staphylococcus aureus) was added. Two different degradation times were chosen for each enzyme solution, 3 hours and 16 hours. The enzymes were either added at one time or up to three times during the degradation period. The samples were then rinsed with Milli-Q water and dried

in nitrogen gas before ellipsometry measurements were performed. The assumed n value was 1.48 at 633nm for both enzymes [21] (k = 0), which is an appropriate value for proteins [22, 23]. As Inhibitors,research,lifescience,medical can be seen from Figure 2, trypsin adsorbed readily to the polypeptide surface and increased the thickness up to 5 times. This indicates that the overall positively charged trypsin (pH 7.4) adsorbs readily on top of the thin polypeptide film (negatively charged surface) Dichloromethane dehalogenase but the adsorption evidently does not result in any visible enzymatic degradation. This is similar to what was seen in a QCM-D study of the same system [9]. Despite a large increase in thickness it was difficult to rule out any catalytic activity; however, as trypsin prefers to catalyze positively charged substrates, the polypeptide film ending with negatively charged PLGA would not be ideal for catalysis. When modeling the adsorbed trypsin, a five-layer model was used; however, only the thicknesses of the trypsin and trypsin_EMA layers were variable.