Sophie Franceschi-Messant

Functionalized Vesicles Based on Amphiphilic Boronic Acids: A System for Recognizing Biologically Important Polyols

We report on a new approach for creating water-soluble functionalized vesicles employing N-alkyl-3-boronopyridinium triflates (alkyl = Me, C12H25, C16H33) as sensors for monosaccharides. The nanoaggregate properties were studied by means of DLS, TEM, high-resolution (1)H NMR, and the solvatochromic dyes Reichardts betaine and Methyl Orange. The vesicles were shown to have 30-200 nm diameters depending on the amphiphile chain length. Diol binding to the vesicles was studied by steady-state fluorescence and UV-vis using Alizarin Red S as a probe in the solution at pH 7.4 in the presence and in the absence of D-glucose and D-fructose. Strong sensing ability of boronic acid functional moieties in the order D-fructose > D-glucose was demonstrated, and apparent binding constants were estimated.

Modulation of photo-oxidative DNA damage by cationic surfactant complexation.

The natural packaging of DNA in the cell by histones provides a particular environment affecting its sensitivity to oxidative damage. In this work, we used the complexation of DNA by cationic surfactants to modulate the conformation, the dynamics, and the environment of the double helix. Photo-oxidative damage initiated by benzophenone as the photosensitizer on a plasmid DNA complexed by dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium chloride (TTAC), cetyltrimethyammonium chloride (CTAC) and bromide (CTAB) was detected by agarose gel electrophoresis. By fluorescent titration in the presence of ethidium bromide (EB) and agarose gel electrophoresis, we experimentally confirmed the complexation diagrams with a critical aggregation concentration on DNA matrix (CAC DNA) delimiting two regions of complexation, according to the DNA-phosphate concentration. The study of the photo-oxidative damage shows, for the first time, a direct correlation between the DNA complexation by these surfactants and the efficiency of DNA cleavage, with a maximum corresponding to the CAC DNA for DTAC and CTAC, and to DNA neutralization for CTAC and CTAB. The localization of a photosensitizer having low water solubility, such as benzophenone, inside the hydrophobic domains formed by the surfactant aggregated on DNA, locally increases the photoinduced cleavage by the free radical oxygen species generated. The inefficiency of a water-soluble quencher of hydroxyl radicals, such as mannitol, confirmed this phenomenon. The detection of photo-oxidative damage constitutes a new tool for investigating DNA complexation by cationic surfactants. Moreover, highlighting the drastically increased sensitivity of a complexed DNA to photo-oxidative damage is of crucial importance for the biological use of surfactants as nonviral gene delivery systems.

Gelled oil particles: A new approach to encapsulate a hydrophobic metallophthalocyanine

Chloroaluminum phthalocyanine (ClAlPc) is a promising sensitizer molecule for photodynamic therapy, but its hydrophobicity makes it difficult to formulate. In this study, we have efficiently encapsulated ClAlPc into gelled soybean oil particles dispersed in water. 12-Hydroxystearic acid (HSA) and polyethyleneimine (PEI) were the gelling and stabilizing agents, respectively. The preparation process involved hot emulsification above the gelation temperature (Tgel), followed by cooling to room temperature, which gave a colloidal dispersion of gelled particles of oil in aqueous medium. The gelled particles containing ClAlPc had a medium diameter of 280 nm, homogeneous size distribution (polydispersity index ≈0.3) and large positive zeta potential (about +50 mV) and showed a spherical morphology. The gelled oil particle formulations exhibited good physical stability over a 6-month period. ClAlPc interfered with the HSA self-assembly only slightly, and decreased the gelation temperature to a small extent; however it did not affect gelation process of the oil droplets. The amounts of PEI and HSA employed during the preparation allowed us to control particle size and the dispersion stability, a phenomenon that results from complex electrostatic interactions between the positively charged PEI and the negatively charged HSA fibers present on the gelled particles surface. In summary, by using the right ClAlPc, HSA, and PEI proportions, we prepared very stable dispersions of gelled soybean oil particles with excellent ClAlPc encapsulation efficiency. The obtained colloidal formulation of gelled oil particles loaded with ClAlPc shall be very useful for photodynamic therapy protocols.

Preparation and evaluation of microporous organogel scaffolds for cell viability and proliferation

Various porous scaffolds utilizing an organogel were prepared by particulate-leaching method. The porous organogels were made of biodegradable, non-toxic ingredients like soybean oil or caprylic/capric triglyceride as the organic liquids and 12-hydroxystearic acid as the gelator. The scaffolds possessed an effective porosity of 56-65%, and good pore interconnectivity with an average pore size from 220 to 290mum. The biodegradability of such materials was evaluated and lipases were able to totally degrade the scaffolds. The porosity of the material associated with high draining led to suitable scaffolds which were evaluated for CHO cell viability and proliferation using the MTT test. This evaluation was performed over a period of 3 weeks and showed a greater ability to promote cell proliferation for the soybean oil based scaffold than for the caprylic/capric triglyceride one. The histological investigations revealed that this scaffold was able to promote cell colonization and attachment and could induce the production of collagen.

Soft Microporous Green Materials from Natural Soybean Oil

Rheological Study: The rheological properties of the organogels were studied by an advanced rheological expansion system (Advanced Rheometer AR-1000, TA Instruments, USA). The gel was first dissolved in an oven at 100°C and then 1 mL of this solution was dropped between the two parallel plates of the AR-1000. The upper plate (cone diameter = 60 mm, cone angle 2°) was lowered to form a gap of 61 μm between the two plates. To obtain the storage modulus G ́ (a measure of elasticity) of the gel, a dynamic temperature ramp test was carried out. The ramp rate was set at 1°C/min. The amplitude of the oscillation was controlled to obtain a strain of 1% and the frequency was set at 0.1 Hz. The T°gel was measured by following the variation of elastic modulus (G’) and viscous modulus (G”) with the temperature. The T°gel was determined when we observed an abrupt increase in the two moduli (gelation process). The accuracy of T°gel measurements was ±1°C.

Development of an extraction method based on new porous organogel materials coupled with liquid chromatography–mass spectrometry for the rapid quantification of bisphenol A in urine

A new method based on the use of porous organogel materials in combination with liquid chromatography-tandem mass spectrometry (LC-MS-MS) was assessed for the quantification of trace contaminants in complex matrices. As a demonstration of the use of these new materials, the contaminant chosen as a model was bisphenol A (BPA) and its extraction was investigated in urine. Organogel materials consist of an organic solvent immobilized by an organogelator. The composition of the organogel materials was optimized in terms of extraction efficiency and compatibility with LC-MS-MS. Porosity was introduced into the organogel by means of the particulate leaching method using sugar crystals. This new absorbing material is simple to use; the extraction method is reduced to a few steps. The originality of the method lies in the complete dissolution of the material for analysis by LC-MS-MS. The matrix effect of the organogel components was studied and was found to be minimal in atmospheric-pressure chemical ionization (APCI) compared to electrospray ionization (ESI) in negative mode. The influence of matrix components on the extraction was investigated by working with different media (acidified water, synthetic urine, horse urine and human urine). The partition coefficient was not affected within the margin of error (±0.1). After optimization, bisphenol A recoveries from urine samples reached 80%. The actual concentration factor was 10. The relative standard deviation (RSD, n=6) for the extraction and determination of BPA in horse urine spiked at 10ngmL(-1) was 9%. Tests with spiked human urine showed that the extraction performances were the same as with the solutions tested previously. The use of porous organogel allowed a fast, simple, sensitive, robust, green method to be developed for the determination of trace contaminants in complex matrices.

Evaluation of biocompatible stabilised gelled soya bean oil nanoparticles as new hydrophobic reservoirs.

Based on the organogel concept, in which an oil is trapped in a network of low-molecular-mass organic gelator fibres creating a gel, a formulation of gelled soya bean oil nanoparticles was evaluated for its capacity to form biocompatible hydrophobic reservoirs. The aqueous dispersions of nanoparticles were prepared by hot emulsification (T° > Tgel) and cooling at room temperature in the presence of polyethyleneimine (PEI). The dispersions were stabilised by the electrostatic interactions between the positively charged amino groups of the PEI and the negatively charged carboxylates of the gelator fibres present at the surface of the particles. The aqueous dispersions were highly stable (several months) and the gelled particles were able to entrap a hydrophobic fluorescent model molecule (Nile red), allowing testing in cells. The gelled oil nanoparticles were found to be biocompatible with the tested cells (keratinocytes) and had the ability to become rapidly internalised. Thus, organogel-based nanoparticles are a promising hydrophobic drug delivery system.

DNA Photo-oxidative Damage Hazard in Transfection Complexes

Complexes of DNA with various cationic vectors have been largely used for nonviral transfection, and yet the photochemical stability of DNA in such complexes has never been considered. We studied, for the first time, the influence of DNA complexation by a cationic lipid and polymers on the amount of damage induced by benzophenone photosensitization. The localization of benzophenone inside the hydrophobic domains formed by a cationic lipid, DOTAP (N‐[1‐(2,3‐dioleoyloxy)propyl]‐N,N,N‐trimethylammonium chloride), and close to DNA, locally increases the photoinduced cleavage by the reactive oxygen species generated. The same effect was found in the case of DNA complexation with an amphiphilic polymer (polynorbornenemethyleneammonium chloride). However, a decrease in DNA damage was observed in the case of complexation with a hydrophilic polymer (polyethylenimine). The DNA protection in this case was because of the absence of benzophenone hydrophobic incorporation into the complex, and to DNA compaction which decreased the probability of radical attack. These results underline the importance of the chemical structure of the nonviral transfection vector in limiting the risks of photo‐oxidative damage of the complexed DNA.

Factors influencing the erosion rate and the drug release kinetics from organogels designed as matrices for oral controlled release of a hydrophobic drug.

Abstract This article proposes solid-like systems from sunflower oil structured with a fibrillar network built by the assembly of 12-hydroxystearic acid (12-HSA), a gelator molecule for an oil phase. The resulting organogels were studied as oral controlled release formulations for a lipophilic drug, Efavirenz (EFV), dissolved in the oil. The effects of the gelator concentration on the thermal properties of the organogels were studied by Differential Scanning Calorimetry (DSC) and showed that drug incorporation did not change the sol–gel–sol transitions. The erosion and drug release kinetics from organogels under conventional (filling gelatin capsules) or multiparticulate (beads obtained by prilling) dosage forms were measured in simulated gastric and intestinal fluids. EFV release profiles were analyzed using model-dependent (curve-fitting) and independent approaches (Dissolution Efficiency DE). Korsmeyer–Peppas was the best fitting release kinetic model based on the goodness of fit, revealing a release mechanism from organogels loaded with EFV different from the simple drug diffusion release mechanism obtained from oily formulations. From organogels, EFV probably diffuses through an outer gel layer that erodes releasing oil droplets containing dissolved EFV into the aqueous medium.

Spontaneous Vesicle Formation by Caffeate Ion-Pair Surfactants: Antioxidant Properties and Application to DNA Protection

A new family of antioxidant ion-pair surfactants was developed by acid-base association of a fatty amine (C12 or C16) with caffeic acid, a natural antioxidant molecule. The amphiphilic molecules obtained, spontaneously formed stable vesicles in water with hydrodynamic diameters around 230 nm. Moreover, as shown by a surface tension study, they presented a phase transition from micelles to vesicles. The maintenance of the antioxidant properties of both caffeate ion-pair surfactants was confirmed by the DPPH test. The amphiphilic properties associated with the antioxidant ability of these new caffeates were used to protect complexed DNA by cationic surfactant (CTAB) from photooxidative cleavage induced by benzophenone photosensitization.