Patrick Shahgaldian

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.

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.

A synthetic nanomaterial for virus recognition produced by surface imprinting

Major stumbling blocks in the production of fully synthetic materials designed to feature virus recognition properties are that the target is large and its self-assembled architecture is fragile. Here we describe a synthetic strategy to produce organic/inorganic nanoparticulate hybrids that recognize non-enveloped icosahedral viruses in water at concentrations down to the picomolar range. We demonstrate that these systems bind a virus that, in turn, acts as a template during the nanomaterial synthesis. These virus imprinted particles then display remarkable selectivity and affinity. The reported method, which is based on surface imprinting using silica nanoparticles that act as a carrier material and organosilanes serving as biomimetic building blocks, goes beyond simple shape imprinting. We demonstrate the formation of a chemical imprint, comparable to the formation of biosilica, due to the template effect of the virion surface on the synthesis of the recognition material.

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.

Amino-substituted amphiphilic calixarenes: self-assembly and interactions with DNA.

The amphiphilic 5,11,17,23-tetramino-25,26,27,28-tetradodecyloxycalix[4]arene is shown to self-assemble as stable and well-defined Langmuir monolayers at the air-water interface. The effect of the presence of DNA in the subphase reveals interactions taking place at the interface between the positively charged surface and the negatively charged DNA, causing an expansion of the monolayers and a phase transition from a liquid-condensed to a liquid-expanded phase; a slight decrease in the stability of the monolayers is also observed. The title compound is shown to self-assemble, with the absence of a cosurfactant, as stable colloidal suspensions. Photon correlation spectroscopy, zeta-potential measurements, and atomic force microscopy reveal that these colloidal suspensions present a monodisperse size distribution and are composed of positively charged solid lipid nanoparticles (SLNs), with an average hydrodynamic diameter of 190 nm and a surface potential of +13.2 mV. The interaction of these SLNs with double-stranded DNA is demonstrated.

Synthesis and properties of novel amphiphilic calix-[4]-arene derivatives

Abstract A series of amphiphilic calix-[4]-arenes having four hydrophobic acyl chains (C6–C12) at the macrocyclic upper rim as well as two hydrophilic dihydroxyphosphoryloxy groups at the lower rim and analogous to the diacylphosphatidic acids lipids have been synthesised and characterised. The synthesis proceeds via regioselective 1,3 lower phosphorylation of the tetra-acyl calix-[4]-arene by diethylchlorophosphate in the presence of triethylamine. The ethyl groups are removed by consecutive treatment with trimethylbromosilane and methanol. All the new amphiphilic derivatives self-assemble at the air–water interface as stable Langmuir monolayers.

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.

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.

Para-acyl calix[4]arenes: amphiphilic self-assembly from the molecular to the mesoscopic level

Studies of the properties of a series of amphiphilic calixarenes show that they can form stable monolayers, Langmuir-Blodgett layers and solid lipid nanoparticles, the mesostructures were investigated by atomic force microscopy and the crystal structure of one compound shows a partially interdigitated tilted bilayer structure.

A First Approach to the Study of Calixarene Solid Lipid Nanoparticle (SLN) Toxicity

The haemolytic effects of a series of amphiphilic calix-arene derived Solid LipidNanoparticles (SLNs) have been measured on human erythrocytes. The effectsof both the hydrophobic chain length and the nature of the polar head-groups on theamphiphilic calix[4]arene have been investigated. For all systems, no haemolyticeffects are observed.