Alice Bejjani

Toward Cell Selective Surfaces: Cell Adhesion and Proliferation on Breath Figures with Antifouling Surface Chemistry

We report the preparation of microporous functional polymer surfaces that have been proven to be selective surfaces toward eukaryotic cells while maintaining antifouling properties against bacteria. The fabrication of functional porous films has been carried out by the breath figures approach that allowed us to create porous interfaces with either poly(ethylene glycol) methyl ether methacrylate (PEGMA) or 2,3,4,5,6-pentafluorostyrene (5FS). For this purpose, blends of block copolymers in a polystyrene homopolymer matrix have been employed. In contrast to the case of single functional polymer, using blends enables us to vary the chemical distribution of the functional groups inside and outside the formed pores. In particular, fluorinated groups were positioned at the edges while the hydrophilic PEGMA groups were selectively located inside the pores, as demonstrated by TOF-SIMS. More interestingly, studies of cell adhesion, growth, and proliferation on these surfaces confirmed that PEGMA functionalized interfaces are excellent candidates to selectively allow cell growth and proliferation while maintaining antifouling properties.

Ion beam analysis and PD-MS as new analytical tools for quality control of pharmaceuticals: comparative study from fluphenazine in solid dosage forms.

In order to evaluate the potential of accelerator based analytical techniques ((particle induced X-ray emission (PIXE), particle induced gamma-ray emission (PIGE), and particle desorption mass spectrometry (PD-MS)) for the analysis of commercial pharmaceutical products in their solid dosage form, the fluphenazine drug has been taken as a representative example. It is demonstrated that PIXE and PIGE are by far the best choice for quantification of the active ingredient (AI) (certification with 7% precision) from the reactions induced on its specific heteroatoms fluorine and sulfur using pellets made from original tablets. Since heteroatoms cannot be present in all types of drugs, the PD-MS technique, which makes easily the distinction between AI(s) and excipients, has been evaluated for the same material. It is shown that the quantification of AI is obtained via the detection of its protonated molecule. However, calibration curves have to be made from the secondary ion yield variations since matrix effects of various nature are characteristics of such mixtures of heterogeneous materials (including deposits from soluble components). From the analysis of solid tablets, (either transformed into pellets and even as received), it is strongly suggested that the physical state of the grains in the mixture is a crucial parameter in the ion emission and accordingly for the calibration curves. As a result of our specific (but not optimized) conditions the resulting precision is <17% with an almost linear range extending from 0.04 to 7.87 mg of AI in a tablet made under the manufacturer conditions (the commercial drug product is labeled at 5 mg).

Investigation of norflurazon pesticide photodegradation using plasma desorption time‐of‐flight mass spectrometry analysis

We have previously demonstrated that PD-TOFMS (plasma desorption time-of-flight mass spectrometry) analysis is a powerful technique for the in situ analysis of pesticides deposited or adsorbed on solid materials. With the aim of producing reproducible data on the modification of a pesticide under controlled photodegradation conditions, we have now undertaken a study where both the substrate and the pesticide are well characterized. This is the case for norflurazon deposited onto an aluminium substrate, in particular regarding the reproducibility of preparation of the samples and the change with time of their chemical composition. Degradation parameters have been derived from the variation in yield of ions representative of the molecule and of its breakdown products and, particularly, from the time required for 50% dissipation of their initial concentration (DT50). DT50 values ranging between 1 and 10 h have been found. An interpretation of the degradation process is proposed from the decay of other ions. As expected, the degradation is faster when the UV sunlight is unfiltered (a factor of 3.8 for the molecule, and around 5 for the breakdown products).

Surface initiated supplemental activator and reducing agent atom transfer radical polymerization (SI-SARA-ATRP) of 4-vinylpyridine on poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) substrates were modified by means of surface-initiated supplemental activator and reducing agent atom transfer radical polymerization (SI-SARA-ATRP) of 4-vinylpyridine (4VP). Substrates were pretreated in order to graft chloromethylbenzene (CMB) units capable of initiating the radical polymerization reaction of 4VP units. Surface characterization techniques, including Water Contact Angle (WCA), Attenuated Total Reflection (ATR), X-ray photoelectron spectroscopy (XPS), Atomic Force Microscopy (AFM) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) showed a successful grafting of a stable, smooth and homogenous layer of p4VP. This process offers the advantages of a rapid, simplified and low cost strategy to chemically modify polymer substrates with covalently bonded layer of the pH responsive p4VP for different applications. Moreover, by using TOF-SIMS profiling, we were able to track a density gradient along the z-axis generated by the interpenetrating phases of the different layers of the final modified surface. Fact that we correlated to the various positions of initiation sites within the polyethylenimine (PEI) used for PET aminolysis prior to CMB grafting. Our strategy will be used in future work to graft other polymers for different applications where industrial scale viable options are needed.

Swift Quantification of Fenofibrate and Tiemonium methylsulfate Active Ingredients in Solid Drugs Using Particle Induced X-Ray Emission

The quantification of active ingredients (AI) in drugs is a crucial and important step in the drug quality control process. This is usually performed by using wet chemical techniques like LC-MS, UV spectrophotometry and other appropriate organic analytical methods. However, if the active ingredient contains specific heteroatoms (F, S, Cl…), elemental IBA like PIXE and PIGE techniques, using small tandem accelerator of 1-2 MV, can be explored for molecular quantification. IBA techniques permit the analysis of the sample under solid form, without any laborious sample preparations. In this work, we demonstrate the ability of the Thick Target PIXE technique for rapid and accurate quantification of both low and high concentrations of active ingredients in different commercial drugs. Fenofibrate, a chlorinated active ingredient, is present in high amounts in two different commercial drugs, its quantification was done using the relative approach to an external standard. On the other hand, Tiemonium methylsulfate which exists in relatively low amount in commercial drugs, its quantification was done using GUPIX simulation code (absolute quantification) The experimental aspects related to the quantification validity (use of external standards, absolute quantification, matrix effect,...) are presented and discussed.

Hydrophobization of chitosan films by surface grafting with fluorinated polymer brushes

Chitosan with its surface-properties and biodegradability is a promising biomaterial for green packaging applications. Till now, this application is still limited due to chitosan high sensitivity to water. Some existing studies deal with the incorporation of hydrophobic additives to enhance water-proof performances of chitosan films. As these additives may impair the film properties, our study focuses on chitosan efficient hydrophobization by means of simple and successful surface grafting reactions. Chitosan films prepared by solvent casting were modified by means of surface-initiated activators regenerated by electron transfer atom radical polymerization (SI-ARGET-ATRP) of 2-hydroxyethyl methacrylate (HEMA) followed by esterification reaction with fluorinated acyl compound. X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) highlighted the surface chemical changes after each step. Surface properties were investigated by contact angle measurements and surface energy calculations. Hydrophobic surfaces with low surface energy and good water-repellent properties were obtained using a simple handling polymerization procedure. This is the first study in applying ARGET ATRP to prepare hydrophobic biopolymer films offering potential applications in packaging.