Paramagnetic relaxation enhancement experiments: a valuable tool for the characterization of micellar nanodevices

Specific Binding of Primary Ammoniums in Aqueous Media by Homooxacalixarenes Incorporated into Micelles

The development of artificial receptors for efficient recognition of analytes in water is a challenging task. Homooxacalix[3]arene-based receptor 1, which is selective toward primary ammoniums in organic solvents, was transferred into water following two different strategies: direct solubilization and micellar incorporation. Extensive ¹H NMR studies showed that recognition of ammoniums is only observed in the case of micellar incorporation, highlighting the beneficial effect of the microenvironment of the micellar core. The selectivity of the system for primary ammoniums over secondary and tertiary ones was also maintained. The hydrophobic effect plays an important role in the recognition properties, which are counterion-dependent due to the energy penalty for the dissociation of certain ammonium salts in the apolar micellar core. This study shows that the straightforward self-assembly process used for the encapsulation of artificial receptors in micelles is an efficient strategy for developing water-soluble nanosized supramolecular recognition systems.

1H NMR study of the interaction of trans-resveratrol with soybean phosphatidylcholine liposomes

Resveratrol (RSV) is a well-known natural derivative with a wide range of biological and pharmacological activities. Despite of these demonstrated properties, it exhibits low both aqueous solubility and chemical stability and therefore low bioavailability. Consequently, the major concern of the technological research is to exploit delivery systems able to overcome bioavailability problems. In the recent past liposomes have been successfully studied for these purposes. In this paper, 1H-NMR spectroscopy, Nuclear Overhauser Spectroscopy (NOESY) as well as Paramagnetic Relaxation Enhancements (PRE) experiments have been carried out to quantitatively investigate the incorporation of resveratrol, at both the liposome preparation stage and by preformed liposomes, also with the aim to characterize resveratrol- soybean phosphatidylcholine (P90G) lipid bilayer interactions. Overall results of 1H NMR spectroscopy analysis suggest that RSV is located nearby the phosphocholine headgroups and also provide quantitative data on the incorporation of RSV (5% w/w), which corresponds to a 150-fold increase with respect to the solubility of RSV in water. Beside, considering that the same level of RSV incorporation was obtained via spontaneous uptake by preformed P90G liposomes, it can be concluded that RSV easily diffuses through the lipid bilayer.

Fluoride binding in water with the use of micellar nanodevices based on salophen complexes

Uranyl-salophen complexes incorporated into micelles are evaluated as supramolecular nanosystems for the binding of fluoride in water.

Primary amine recognition in water by a calix[6]aza-cryptand incorporated in dodecylphosphocholine micelles

A zinc calix[6]azacryptand complex was incorporated into dodecylphosphocholine micelles. This complex can strongly and selectively bind linear primary amines in an aqueous medium.

Tuning micelle dimensions and properties with binary surfactant mixtures

Detergent micelles are used in many areas of research and technology, in particular, as mimics of the cellular membranes in the purification and biochemical and structural characterization of membrane proteins. Applications of detergent micelles are often hindered by the limited set of properties of commercially available detergents. Mixtures of micelle-forming detergents provide a means to systematically obtain additional micellar properties and expand the repertoire of micelle features available; however, our understanding of the properties of detergent mixtures is still limited. In this study, the shape and size of binary mixtures of seven different detergents commonly used in molecular host-guest systems and membrane protein research were investigated. The data suggests that the detergents form ideally mixed micelles with sizes and shapes different from those of pure individual micelles. For most measurements of size, the mixtures varied linearly with detergent mole fraction and therefore can be calculated from the values of the pure detergents. We propose that properties such as the geometry, size, and surface charge can be systematically and predictably tuned for specific applications.