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The evaluation of the radial electron density profile of a drug containing a sterically stabilized liposomal system is described. Using synchrotron small-angle X-ray scattering, we were able to characterize the hydrophilic shell of the polyethylene glycol chains. Using a Gaussian model for describing the electron density profile along the normal of the bilayer, we got an asymmetric distribution of PEGylated lipids in accordance with theoretical considerations. Moreover, we used anomalous X-ray scattering to study the localization of a hydrophobic drug (a kinase inhibitor), which revealed that these molecules are mainly located in the hydrocarbon chain region of the phospholipid bilayer.

The effect of 5 th generation polyamidoamine (PAMAM G5) dendrimers on multilamellar dipalmitoylphosphocholine (DPPC) vesicles was investigated. PAMAM was added in two different concentration to the lipids (10 -3 and 10 -2 dendrimer/lipid molar ratios). The thermal behavior of the evolved systems was characterized by DSC; while the structure and the morphology were investigated with small-and wide-angel X-ray scattering (SWAXS), freeze-fracture electron microscopy (FFTEM) and phosphorus-31 nuclear magnetic resonance ( 31 P-NMR) spectroscopy, respectively. IR spectroscopy was used to study the molecular interactions between PAMAM and DPPC. The obtained results show that the dendrimers added in 10 -3 molar ratio to the lipids generate minor perturbations in the multilamellar structure and thermal character of liposomes, while added in 10 -2 molar ratio dendrimers cause major disturbance in the vesicular system. The terminal amino groups of the dendrimers are in strong interaction with the phosphate headgroups and through this binding dendrimers disrupt the regular multilamellar structure of DPPC. Besides highly swollen, fragmented bilayers, small vesicles are formed.

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The thermotropic and structural effects of low molecular weight poly(malic acid) (PMLA) on fully hydrated multilamellar dipalmitoylphosphatidylcholine (DPPC)-water systems were investigated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and freeze-fracture transmission electron microscopy (FFTEM). Systems of 20wt% DPPC concentration and 1 and 5wt% PMLA to lipid ratios were studied. The PMLA derivatives changed the thermal behavior of DPPC significantly and caused a drastic loss in correlation between lamellae in the three characteristic thermotropic states (i.e., in the gel, rippled gel and liquid crystalline phases). In the presence of PBS or NaCl, the perturbation was more moderate. The structural behavior on the atomic level was revealed by FTIR spectroscopy. The molecular interactions between DPPC and PMLA were simulated via modeling its measured infrared spectra, and their peculiar spectral features were interpreted. Through this interpretation, the poly(malic acid) is inferred to attach to the headgroups of the phospholipids through hydrogen bonds between the free hydroxil groups of PMLA and the phosphodiester groups of DPPC.

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One of the main challenges of sizing methods for nanoparticle (NP) suspensions is to distinguish between particles and particle populations with very small size differences. This would be especially important to follow various surface functionalization processes of nanoparticles resulting in small alterations of their size. In this respect, methods involving the detection of single particles, such as resistive pulse sensing (RPS) or nanoparticle tracking analysis, are generally considered superior to ensemble measuring methods such as dynamic light scattering. However, to compare the exact capabilities of these methodologies require systematic investigations in optimized conditions for each method. Here, such a study is presented for a narrow size range of spherical latex nanoparticles (60–200 nm). It is concluded that the RPS methodology based on quartz nanopipets as single nanopore counters, is the only sizing method among those studied capable to fully resolve a ternary mixture of 70, 110, and 140 nm average diameter NPs. The practical usefulness of this size resolution is demonstrated by following the increase in diameter of latex nanoparticles after their surface modification with antibodies.