Absorption of light and heavy water vapours in polyelectrolyte multilayer films

We studied the swelling and the uptake of water (H(2)O or D(2)O) vapours in polyelectrolyte (PE) multilayer (PEM) samples deposited on solid support (Si wafers) as a function of the isotope nature of the vapour and the charge of the last polymer layer. The samples were prepared with deuterated poly(sodium 4-styrenesulfonate) (dPSS) and poly(allylamine hydrochloride) (PAH). Two types of samples were studied. The sample with a structure Si/PEI/(dPSS/PAH)(6)/dPSS was negatively charged. A positively charged sample was PAH terminated and had the structure Si/PEI/(dPSS/PAH)(6). The film thickness and scattering length density were estimated from neutron reflectometry (NR) experiments and the results were complemented with in-situ QCM measurements. We demonstrate that the swelling of PEM in H(2)O and D(2)O vapours is similar. However, the amount of adsorbed D(2)O is around 10% more than the adsorbed H(2)O. Such isotope effect correlates well with the rough estimation that the isotope effect usually scales with the difference in the mass density of the different isotope forms of the substances. For precise analysis of the NR data we assumed existence of empty voids in the structure of the PEM. These voids might be filled with "condensed" water when the samples are exposed to water vapors. We show that the layers we studied consist of up to 25% of such voids. We showed that the amount of sorbed water depends on the nature of the last layer which builds the PEM thus confirming the "odd-even effect" already shown in the literature

Formation of polyelectrolyte multilayer architectures with embedded DMPC studied in situ by neutron reflectometry

The coupling of lipid molecules to polymer components in a planar biomimetic model membrane made of a lipid bilayer dimyristoylphosphatidylcholine supported by polyelectrolyte multilayers is studied. The polyelectrolyte support was prepared by layer by layer deposition of positively charged poly allylamine hydrochloride PAH and negatively charged poly sodium 4 styrenesulfonate PSS . Two polymer sample terminations were considered positively charged PAH terminated and negatively charged PSS terminated . Neutron reflectometry studies showed that, whereas positively charged samples did not favor the deposition of lipid, negatively charged samples allowed the deposition of a lipid bilayer with a thickness of ?5 nm. In the latter case, formation of polyelectrolyte layers after the deposition of the lipid layer was also possible. 2005 American Chemical Societ

Formation of polyelectrolyte multilayer architectures with embedded DMPC studied in situ by neutron reflectometry

The coupling of lipid molecules to polymer components in a planar biomimetic model membrane made of a lipid bilayer dimyristoylphosphatidylcholine supported by polyelectrolyte multilayers is studied. The polyelectrolyte support was prepared by layer by layer deposition of positively charged poly allylamine hydrochloride PAH and negatively charged poly sodium 4 styrenesulfonate PSS . Two polymer sample terminations were considered positively charged PAH terminated and negatively charged PSS terminated . Neutron reflectometry studies showed that, whereas positively charged samples did not favor the deposition of lipid, negatively charged samples allowed the deposition of a lipid bilayer with a thickness of ?5 nm. In the latter case, formation of polyelectrolyte layers after the deposition of the lipid layer was also possible. 2005 American Chemical Societ

Characterization of PAH/DPPG layer-by-layer films by VUV spectroscopy

The spectroscopic characterization of layer-by-layer (LbL) films containing liposomes is essential not only for determining the precise film architecture but also to guide the design of drug delivery systems. In this study we provide the first report of vacuum ultraviolet spectroscopy (VUV) characterization of LbL films made with liposomes from 1.2-dipalmitoyl-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (Sodium Salt) (DPPG) alternated with poly(allylamine hydrochloride) (PAH). Measurements in the 6.0–9.5 eV range allowed us to identify the electronic transitions responsible for the spectra, which were assigned to carboxyl, hydroxyl and phosphate groups in DPPG while the PAH spectra were governed by electronic transitions in the amino groups. The surface mass density of the LbL films could be determined, from which the formation of a DPPG bilayer was inferred. This rupture of the liposomes into bilayers was confirmed with atomic force microscopy measurements. In subsidiary experiments we ensured that the UV irradiation in vacuum had negligible damage in the DPPG liposomes during the course of the VUV measurements. In addition to demonstrating the usefulness of VUV spectroscopy, the results presented here may be exploited in biological applications of liposome-containing films