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We report in this paper the synthesis and characterization of a new class of biopolymer−clay nanocomposites based in the assembling of chitosan to sepiolite, which is a natural magnesium silicate showing a microfibrous texture. CHN and ICP/AES chemical analyses, XRD, FTIR spectroscopy, 13C solid-state NMR, LT-SEM, and thermal analysis have been employed in the characterization of the resulting nanocomposites. The adsorption isotherm of chitosan on sepiolite in acidic medium reveals a significant coverage of the biopolymer at high equilibrium concentration values indicating a multilayer adsorption. The arrangement of chitosan chains on the surface of the silicate microfibers is discussed on the basis of physicochemical data obtained by application of the different techniques. The potentiometric response of this new type of bio-nanocomposites incorporated in carbon paste electrodes toward aqueous salt solutions was employed for the first time as a valuable technique for a rapid assessment of the ion-exchange behaviors. Thermal behaviors and mechanical properties have been determined by DTA-TG and DMTA, respectively. As these materials are well-processed as self-supporting films, in view of their properties they show potential interest as membranes for different processes related to separation of ions and gases, as well as components in electrochemical devices (fuel-cell, potentiometric sensors).

Introduction: The aim of the study is to evaluate the improvement of arterial distensibility by means of: (1) decrease of pulse wave velocity (PWV); (2) decrease of SBP and PP; and (3) decrease of Blood Pressure (BP), using an Angiotensin-II receptor antagonist, Irbesartan. Material and Methods: 97 hypertensive patients, of which 43 (45.7%) were men, who attended their primary care centres two times. Mean age was 55 (SD ±10) in men and 62 (SD ±11) in women. All patients had their BP checked with a mercury sphygmomanometer, and their PWV measured with an automatic device, Complior, which registers in two different points (carotid and femoral arteries). Both measurements were taken at the initial appointment and at the six months follow up. Results: there was a decrease in SBP, Diastolic Blood Pressure (DBP), PP, and PWV. A significant relation between the decrease of PWV and the decrease of the SBP was found. Conclusions: (1) The PWV can be a valid indirect method to measure the arterial elasticity decrease in clinical practice, and (2) The use of drugs that act directly on the renin-angiotensin system (Irbesartan) can be useful in improving such elasticity.