Dario Solinas

Study of the solid state of carbamazepine after processing with gas anti-solvent technique

The purpose of this study was to investigate the influence of supercritical CO2 processing on the physico-chemical properties of carbamazepine, a poorly soluble drug. The gas anti-solvent (GAS) technique was used to precipitate the drug from three different solvents (acetone, ethylacetate and dichloromethane) to study how they would affect the final product. The samples were analysed before and after treatment by scanning electron microscopy analysis and laser granulometry for possible changes in the habitus of the crystals. In addition, the solid state of the samples was studied by means of X-ray powder diffraction, differential scanning calorimetry, diffuse reflectance Fourier-transform infrared spectroscopy and hot stage microscopy. Finally, the in vitro dissolution tests were carried out. The solid state analysis of both samples untreated and treated with CO2, showed that the applied method caused a transition from the starting form III to the form I as well as determined a dramatic change of crystal morphology, resulting in needle-shaped crystals, regardless of the chosen solvent. In order to identify which process was responsible for the above results, carbamazepine was further precipitated from the same three solvents by traditional evaporation method (RV-samples). On the basis of this cross-testing, the solvents were found to be responsible for the reorganisation into a different polymorphic form, and the potential of the GAS process to produce micronic needle shaped particles, with an enhanced dissolution rate compared to the RV-carbamazepine, was ascertained.

Characterization of solid dispersions of itraconazole and vitamin E TPGS prepared by microwave technology

BACKGROUND This study describes the influence of microwave irradiation (MW) on the preparation and properties of solvent-free solid dispersions (SDs) employing vitamin E D-α-tocopheryl polyethylene glycol (TPGS) 1000 succinate, with itraconazole as a model drug. MATERIALS AND METHODS Itraconazole is characterized by low aqueous solubility and vitamin E TPGS was chosen as the surfactant carrier for the formulation of MW solid dispersions in different ratios. Their physicochemical characteristics were investigated by means of powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and hot-stage microscopy. Comparison with the corresponding physical mixtures and the drug alone allowed the relationship between influence of the technological process on physicochemical and morphological properties of the systems to be examined. RESULTS PXRD data confirmed the absence of phase transitions in the solid state of the drug subjected to MW alone. On the other hand, an amorphous form of the drug was obtained in the solid dispersion with the highest content of carrier investigated (1:3 w/w). All the SDs showed an improvement in the solubility and dissolution profile of the drug, with the best results obtained in the case of the 1:3 w/w SD. This was related to an interaction between the drug and the carrier with a complex that formed due to favorable H bonds, as demonstrated by DRIFT analysis. CONCLUSION It was demonstrated that the amorphization of the drug led to an increase in wettability and a significant improvement in bioavailability. Therefore, SDs obtained by MW technique using vitamin E TPGS as carrier provide a promising way to increase the dissolution rate and solubility of poorly bioavailable drugs.

Terminal sterilization of BisGMA-TEGDMA thermoset materials and their bioactive surfaces by supercritical CO2

The development of biomaterials endowed with bioactive features relies on a simultaneous insight into a proper terminal sterilization process. FDA recommendations on sterility of biomaterials are very strict: a sterility assurance level (SAL) of 10(-6) must be guaranteed for biomaterials to be used in human implants. In the present work, we have explored the potential of supercritical CO(2) (scCO(2)) in the presence of H(2)O(2) as a low-temperature sterilization process for thermoset materials and their bioactive surfaces. Different conditions allowing for terminal sterilization have been screened and a treatment time-amount of H(2)O(2) relationship proposed. The selected terminal sterilization conditions did not notably modify the mechanical properties of the thermoset nor of their fiber-reinforced composites. This was confirmed by μCT analyses performed prior to and after the treatment. On the contrary, terminal sterilization in the presence of H(2)O(2) induced a slight decrease in the surface hardness. The treatment of the thermoset material with scCO(2) led to a reduction in the residual unreacted monomers content, as determined by means of high performance liquid chromatography (HPLC) analyses. Finally, it was found that a thermoset coated with a polysaccharide layer containing silver nanoparticles maintained a very high antimicrobial efficacy even after the scCO(2)-based terminal sterilization.

The effect of acetylation on hybrid poplar after artificial weathering

ABSTRACT The effect of acetylation on weathering resistance of a hybrid poplar (Pacific Albus®) was studied by colour change evaluation, mechanical tests, FT-IR spectroscopy and moisture absorption measurements. The acetylation process was performed without any pre-treatment and it was verified by means of weight percentage gain and FT-IR spectroscopy: the average weight percentage gain was 14.4 ± 0.6% and the band areas at 1370 and 1740 cm−1 increased about 50% compared to unmodified wood. It was also demonstrated that acetylation process increased mechanical performance and reduced wood moisture absorption. Unmodified and acetylated wood samples were artificially weathered with a Xenon-arc lamp up to 400 h. The mechanical properties of both acetylated and untreated wood showed the same trend, but acetylated samples exhibited higher stiffness, strength and elongation at break. The outcomes demonstrated that acetylated samples were more stable to degradation mechanisms induced by artificial weathering.