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Patrick Shahgaldian

Publications and source records attributed to Patrick Shahgaldian.

11 recordsLinked to original sources
PubMed2005

Enantioselective recognition of phenylalanine by a chiral amphiphilic macrocycle at the air-water interface: a copper-mediated mechanism.

The synthesis of a new chiral amphiphilic calix[4]resorcinarene, tetrakis(N-methylprolyl)tetraundecylcalix[4]resorcinarene (L-RA-Pro), bearing four L-prolyl moieties at the macrocyclic upper rim and four undecyl chains at the lower rim is described. This synthesis has been carried out via a Mannich-type reaction of L-proline and formaldehyde. It has been shown by means of Langmuir balance technique that L-RA-Pro self-assemble as well-defined monomolecular layers at the air-water interface. The effect of various cations on the stability of these monolayers has been studied. The experiments reveal that while there is a slight stabilization effect of K+, Cd2+, Co2+, Mg2+, and Ni2+, there is a high decrease in the collapse pressure in the presence of Cu(II) cation, showing that monolayers of L-RA-Pro, formed at the air-water interface, have a certain selectivity for copper(II) ions with regard to other cations tested. This supramolecular complex exhibits enantioselective recognition properties vs phenylalanine; the mechanism of this interaction is discussed.

Air↗
PubMed2004

Distribution and modification of sorption sites in amphiphilic calixarene-based solid lipid nanoparticles from hyperpolarized 129Xe NMR spectroscopy.

The site distribution and accessibility in amphiphilic calixarenes-based solid lipid nanoparticles were determined as a function of lipid chain length using in situ 129Xe NMR spectroscopy with flowing hyperpolarized Xe gas. The study illustrates that host cavities in as-prepared materials are increasingly occluded by the lipid chain for compounds with chain lengths from C6 to C12 and are almost completely occluded for C14 and C16 chain lengths. Host cavities present at the surface of the particles are still accessible to small atoms (xenon) and organic molecules (methylene chloride, etc). The Xe spectra show that the accessible void space can be increased remarkably by exposure of the particle surface to suitably sized guest molecules that appear to displace the occluding hydrocarbon chains from the host cavities by competitive adsorption. This postsynthesis treatment thus modifies the state of self-assembly and improves sorption capability. The HP Xe NMR approach presented is suitable for small samples (a few milligrams) of SLNs, likely also for other biomaterials such as vesicles, model membranes, etc.

Journal Article↗
PubMed2004

Haemolytic properties of some water-soluble para-sulphonato-calix-[n]-arenes.

In this paper, we describe the haemolytic effect of parent para-sulphonato-calix-[n]-arenes and their derivatives bearing one pendant group at the lower rim of calix-arene towards human erythrocytes. A maximum of 30% of haemolysis has been observed for para-sulphonato-calix-[8]-arene for a concentration of 200 mM representing 300 g of calix-arene per liter of human blood, para-sulphonato-calix-[4]-arene and para-sulphonato-calix-[6]-arene show much lower haemolytic effects, 0.5 and 8%, respectively at 200 mM concentration. Coupling of a methoxy-carboxylate function at the phenolic group reduces haemolytic effects in all cases. The presence of an ethoxy-amine function increases the haemolytic behaviour for the calix-[4]-arene and calix-[6]-arene systems, but reduces the effect for the calix-[8]-arene derivatives.

Arylsulfonates↗
PubMed2003

Interactions of amphiphilic calix[4]arene-based Solid Lipid Nanoparticles with bovine serum albumin.

The interaction of Solid Lipid Nanoparticles (SLN) based on amphiphilic calix[4]arene with one of the major circulatory protein, serum albumin, has been investigated by Photon Correlation Spectroscopy (PCS) and Atomic Force Microscopy (AFM). The carrier systems have shown the ability to interact with bovine serum albumin (BSA), which forms a capping layer up to 17nm in depth. AFM imaging revealed that the SLNs are protected by this layer against flattening on surfaces.

Adsorption↗
PubMed2003

Para-acyl-calix-arene based solid lipid nanoparticles (SLNs): a detailed study of preparation and stability parameters.

The preparation and stability parameters of para-acyl-calix[4]arene based solid lipid nanoparticles (SLNs) have been investigated. Atomic force microscopy (AFM) and photon correlation spectroscopy (PCS) show a mean particle size of 130 nm. In terms of preparation parameters, using the solvent displacement method, the nature and the volume of the organic solvent, the concentration of the amphiphile and the presence of a co-surfactant in the organic phase have been shown to affect significantly the size of the produced SLNs. In contrast, the stirring speed, the viscosity and the acidity of the aqueous phase and the amphiphile hydrophobic chain length have been shown to have no effect. In terms of stability parameters, the ionic strength has been shown to affect the short-time SLN stability depending on both the anion and the cation studied, with sodium sulphate causing precipitation. Ultrasonic, ultraviolet or microwave treatments of the SLN suspensions have no effect on the size of the SLNs. The study of the effects of short time thermal treatment revealed that the SLNs are not affected by one freezing-defreezing cycle and are stable at 100 degrees C in suspension. It is difficult to reconstitute the SLN suspensions after freeze-drying. Finally, the temporal stability of these suspensions in water has been shown to be superior to 1 year. The long-term temporal stability of suspensions stored in saline solution has been investigated. It has been demonstrated that the most destabilising effects arise from the presence in the storage suspension of sulphate ions.1H NMR, X-ray powder diffraction (XPD) and AFM have also been carried out on the calix-arene based SLNs and demonstrate the presence of a semi-organised matrix structure for the SLNs.

Calixarenes↗
PubMed2003

Interfacial interactions between amphiphilic cyclodextrins and physiologically relevant cations.

The compression isotherms of a series of amphiphilic cyclodextrins, formed (a) by acylation at the secondary hydroxyl face and (b) by acylation accompanied by varying degrees of sulfatation (DS) at the primary hydroxyl face (DS=0, 4, and 7), have been studied on subphases of pure water and of water containing NaCl, KCl, MgCl(2), and CaCl(2) at inter- and extracellular concentrations. The formation of solid lipid nanoparticles (SLNs) by two of the molecules has been observed, while these do not aggregate at concentrations of monovalent salts up to 150 mM for the sulfated derivative. In the presence of divalent salts one of these with a DS=0 for sulfatation degree flocculates at divalent salt concentrations below 0.1 mM while the other with a DS=4 flocculates at Mg(2+) concentration above 5 mM and a Ca(2+) concentration above 3 mM. AFM noncontact mode imaging has been carried out, in air, for the SLNs deposited on mica.

Cations↗
PubMed2003

AFM imaging of calixarene based solid lipid nanoparticles in gel matrices.

Contact mode atomic force microscopy has been carried out on gels of four current polymers, carbopol 980, carbopol 2020, hyaluronic acid and xanthan containing dispersions of solid lipid nanoparticles (SLNs) of amphiphilic calixarenes. Imaging shows that the SLNs are dispersed within the gels as discrete particles of 150nm in diameter and show little or no aggregation. The simultaneous use of lateral force, topographic and force modulation mode imaging allows a clear interpretation of the observed images, showing the presence of nanoparticles in the sub-surface region and that the SLNs affect the local mechanical properties of the gels. Photon correlation spectroscopy similarly demonstrates a lack of interaction in suspensions.

Bridged-Ring Compounds↗
PubMed2003

A study of the freeze-drying conditions of calixarene based solid lipid nanoparticles.

In this note, we report a study of cryoprotectant carbohydrate (glucose, fructose, mannose and maltose) effects on the reconstitution of calixarene based solid lipid nanoparticle (SLN) suspensions after freeze-drying, studied by atomic force microscopy and photon correlation spectroscopy. All carbohydrates tested showed excellent cryoprotection and redispersion properties with the calixarene based SLNs.

Absorptiometry, Photon↗
PubMed2003

Scanning electron microscopy and atomic force microscopy imaging of solid lipid nanoparticles derived from amphiphilic cyclodextrins.

Scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been applied to the imagery of solid lipid nanoparticles (SLNs) formulated from an amphiphilic cyclodextrin, 2,3-di-o-alkanoyl-beta-cyclodextrin, beta-CD21C6. Comparison of the results shows that the vacuum drying technique used in sample preparation for SEM causes shrinkage in the size of the SLNs, whereas the deposition method used for AFM causes the SLNs to form small clusters. The hydrodynamic diameter determined from photon correlation spectroscopy (PCS) is 359+/-15 nm and the zeta potential is -25 mV.

Cyclodextrins↗