Molecular mobility study of amorphous and crystalline phases of a pharmaceutical product by thermally stimulated current spectrometry.

Two crystalline forms and the amorphous state of irbesartan, a pharmaceutical drug chosen as a model, were analyzed by Thermally Stimulated Current (TSC) spectroscopy, a powerful technique currently used in polymer science to investigate the molecular dynamics of heterogeneous and complex materials. Whereas no specific dielectric response was noted for the B crystalline form, the A form of irbesartan exhibited molecular motions localized inside its channel structure. The dynamics involved in the dielectric glass transition of amorphous samples followed a compensation law characteristic of highly cooperative relaxation processes.

Alterations in the chain dynamics of insoluble elastin upon proteolysis by serine elastases.

The high temperature dielectric relaxations of purified and elastolized ligamentum nuchae elastin in the dry state have been investigated by thermally stimulated depolarization current spectrometry, with an equivalent frequency comprised between 10(-2) and 10(-3) Hz. A main relaxation mode, located close to 150 degrees C and attributed to the dielectric manifestation of a glass transition, is found for all samples. After decomposition by the fractional polarization method, the analysis of the high temperature mode shows the existence of two relaxation mechanisms: a cooperative one, associated with flexible zones of the protein, and an isoenthalpic one, corresponding to more ordered and constrained zones.

Dielectric characterization of collagen, elastin, and aortic valves in the low temperature range.

The low temperature dielectric relaxation of porcine aortic valves and its main macromolecular proteins. i.e.

Characterisation of elastin and collagen in aortic bioprostheses.

Porcine aortic valves used as cardiac valve bioprostheses are well adapted to physiological functions in the short term, but they lack long-term durability. Several multi-step extractions have been performed to obtain a perfectly acellular matrix. A new physical methodology is proposed to evaluate the resulting fibrous protein damage after biochemical extraction (TRI-COL and SDS).

Thermal analysis characterization of aortic tissues for cardiac valve bioprostheses.

Two multistep extractions were achieved on porcine aortic tissues to obtain acellular matrices used for cardiac bioprostheses. The evaluation of structural modifications and the possible damage of extracellular matrix fibrous proteins were investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Protein-water interactions and degradation temperatures were determined by TGA.