Structural investigation of the confinement of finite amounts of trehalose in water-containing sodium Bis(2-ethylhexyl)sulfosuccinate reversed micelles.

The structural effect of trehalose confined in water-containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reversed micelles at water to AOT molar ratio W = 5 and 10 as a function of the trehalose to AOT molar ratio T (0 < T < 0.1) has been investigated by small-angle neutron scattering (SANS). SANS data analysis is consistent with the hypothesis that trehalose is encapsulated within the quite spherical hydrophilic micellar cores of water-containing reversed micelles, causing an increase of the aggregate size and a decrease of the polydispersion. Moreover, SANS results suggest that the trehalose confinement in water-containing reversed micelles involves marked changes on the molecular packing of the water-containing micellar cores. In particular, according to the obtained findings, we can hypothesize the intercalation of the trehalose molecules between the polar surfactant headgroups. The preferential solubilization in this specific nanodomain could explain the trehalose capability to prevent, upon dehydration, the transition to a gel phase, hindering serious damage to biostructures.

Interactions of alpha-tocopherol with biomembrane models: binding to dry lecithin reversed micelles.

The state of alpha-tocopherol (Vitamin E) in solutions of dry lecithin reversed micelles dispersed in an apolar medium has been investigated as a function of the Vitamin E to surfactant molar ratio (RVE) at fixed surfactant concentration by FT-IR, 1H NMR and SAXS with the aim to emphasize the role played by anisotropic intermolecular interactions and confinement effects as driving forces of its partitioning between apolar bulk solvent and polar nanodomains and of mutual Vitamin E/reversed micelle effects. It has been found that its binding strength to reversed micelles, triggered by steric and orientational constrains, is mainly regulated by specific interactions between the hydrophilic groups both of Vitamin E and surfactant. Moreover, the RVE dependence of the Vitamin E distribution constant and of the micellar size suggest that the inclusion of increasing amounts of Vitamin E in reversed micelles involves substantial changes in the structural and dynamical properties of the micellar aggregates. The occurrence of mutual effects and the partitioning of Vitamin E between hydrophilic/hydrophobic interfaces and apolar domains allow to infer some important biological implications concerning the capacity of Vitamin E to scavenge free radicals arising from hydrophilic and/or hydrophobic domains, possible variations of its local reactivity respect to that observed in bulk as well as its significant influence on the stability of biomembranes.

Surfactant self-assembling in gas phase: electrospray ionization- and matrix-assisted laser desorption/ionization-mass spectrometry of singly charged AOT clusters.

The self-assembling of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in gas phase has been investigated by electrospray ionization- and matrix-assisted laser desorption/ionization mass spectrometry. Large surfactant clusters with an aggregation number close to that found in apolar media have been observed either as positive or negative ions. Moreover, the marked predominance of singly charged species as well as preliminary theoretical calculations strongly suggest an aggregate structure characterized by an internal hydrophilic core hosting the extra charge surrounded by an apolar shell constituted by the surfactant alkyl chains. This structure is similar to that of the more familiar reversed micelles formed when an appropriate surfactant is solubilized in apolar solvents. Finally, similar trends are observed independently either on the ionization technique or the polarity of the solvent used. This, together with the large dependence of the aggregation number on the flow rates, strongly indicates that self-assembling of the surfactant molecules occurs during the evaporation step.

Physicochemical investigation of acrylamide solubilization in sodium bis(2-ethylhexyl)sulfosuccinate and lecithin reversed micelles.

The state of acrylamide confined within dry sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and lecithin reversed micelles dispersed in CCl(4) has been investigated by FTIR and (1)H NMR spectroscopy. Measurements have been performed at 25 degrees C as a function of the acrylamide-to-surfactant molar ratio (R) at a fixed surfactant concentration (0.1 mol kg(-1)). The analysis of experimental data, corroborated by the results of SAXS measurements, is consistent with the hypothesis that acrylamide is quite uniformly distributed among reversed micelles mainly located in proximity to the surfactant head-group region and that its presence induces significant unidimensional growth of micellar aggregates. Moreover, the confinement of acrylamide within reversed micelles involves some changes of the typical H-bonded structure of pure solid acrylamide attributable to the establishment of system-specific acrylamide/surfactant head group interactions. Preliminary experiments showed that, by exposure to X-rays, the polymerization of acrylamide can be induced in the confined space of dry AOT and lecithin reversed micelles.

[Antibiotic prophylaxis in prostate biopsy]. / La profilassi antibiotica nell'agobiopsia prostatica.

INTRODUCTION: Prostate biopsy is nowadays one of the most frequent diagnostic procedures in urology. The incidence of bacteraemia, bacteriuria and infective complications is higher after the transrectal procedure than after the transperineal one. A survey demonstrated that 98% of the urologists in USA use antibiotics to prevent infective complications. The transrectal prostate biopsy is the only diagnostic intervention procedure in urology for which an antibiotic prophylaxis is recommended, also for low-risk patients, by the guidelines of the European Association of Urology. If the perineal route is adopted, the antibiotic prophylaxis is recommended only in high-risk patients. MATERIALS AND METHODS: The patient should preferably receive an evacuative enema to achieve a rectal cleansing and to ameliorate the diagnostic accuracy of transrectal ultrasound. A survey in the US demonstrated that an evacuative enema with saline solution is adopted by more than 80% of urologists. Criteria for antibiotics choice. The majority of bacteraemias are transitory, asymptomatic and self-limiting. On the other side, bacteriuria can persist for several days. Antibiotics must achieve high drug concentrations not only in plasma and tissue but also in urine. Symptomatic infections are generally caused by E. Coli and less frequently by the Streptococcus faecalis. Nevertheless, other agents as Klebsiella and Chlostridium, although rare, might cause severe infections. Thus, prophylaxis needs antibiotics at large spectrum and a single agent may not be enough for high-risk patients. Risk determination and drug schedules. It is essential to point out the infective risk of the patient. The choice of the drug, the timing and schedule of antibiotic prophylaxis are still object of debate. Several randomized studies have been conducted with contradictory results. RESULTS: The antibiotic prophylaxis should be tailored according to patients? infective risk and to the procedure adopted. It is able to reduce infections rate after transrectal biopsy below 5%. The adoption of periprostatic anesthesia and the number of cores can influence the incidence of infective complications. Commonly, one-three days oral administration of fluoroquinolone is adopted. A single-dose prophylaxis can be also used with favorable results. Tolerability and route of administration should be taken into account, and also costs should be considered. CONCLUSIONS: Considering the low cost of antibiotics adopted as short-term prophylaxis and the high cost of the treatment of infective complications, it seems reasonable to provide antibiotics prophylaxis for all patients at high risk for infective complications and for all cases submitted to transrectal prostate biopsy.