The role of edible oils in low molecular weight organogels rheology and structure.

In this paper, the role of solvent characteristics on the rheological and physicochemical properties of organogels was investigated using different techniques. Vegetable oils, such as rice, sunflower and castor oil were used as solvents, for producing organogels with monoglycerides of fatty acids or a mixture of fatty alcohols (policosanol) as gelators. Moreover, two non-edible oils (silicon and paraffin oil) were also used for analysing the properties of solvents completely different in nature with respect to the edible ones, for a better interpretation of the given results. Organogels were investigated from a rheological point of view and through a microscopic analysis, given by polarised light (POM) and atomic force (AFM) microscopy, and X-rays to study the crystallinity of the system. The IR technique was used to analyse the intermolecular interactions, resulting in interesting information about the effect of oil polarity on the driving forces promoting structuration. This investigation showed that when solvents of a similar chemical nature are used, their physical properties, mainly oil polarity, are strictly related to the properties of the organogel, such as the onset of crystallisation temperature, the stiffness of the final material and its crystallinity. Anyway, these physical parameters seem insufficient to describe properly the role of solvents when oils of a different chemical nature are compared.

Effect of the monostearate/monopalmitate ratio on the oral release of active agents from monoacylglycerol organogels.

The delivery of active agents from organogels is becoming an important topic owing to the possibility of releasing, in a controlled way, lipophilic agents. Controlled release from foods is a topic with increasing relevance owing to the growing industrial interest towards functional or medical foods, i.e. foods containing nutraceutical agents or drugs. Anyway, release properties are related to the rheological properties of organogels, and, therefore, a deep knowledge of their microstructure and physical characteristics is necessary to design carriers with expected release properties. In this work, two low molecular weight gelators (i.e. glycerol monopalmitate, GMP, and glycerol monostearate, GMS) have been investigated using rheology, microscopy and infrared spectroscopy, IR, aiming at understanding the effects of different gelator ratios on organogel properties. It was observed that GMP, within the range of investigated compositions, seems to be more effective in yielding consistent organogels and this effect was related to differences in microstructure with respect to GMS. Their ability to control the oral release of active agents was investigated, in vitro, using a chemotherapeutic drug for adenocarcinoma of the gastrointestinal tract, 5 fluorouracil (5-FU). A physical model based on carrier erosion was used to describe the release data, evidencing a good agreement with experimental values. Among the tested samples it seems that the use of 90% of GMS (over total organogelator content) yields promising results allowing a good partition of the released drug between the gastric and intestinal tracts with the largest value (although lower than 40% of loaded amount) of the total released drug.

Olive oil and hyperthermal water bigels for cosmetic uses.

Bigels are biphasic systems produced with an organogel (or oleogel) and a hydrogel mixed together at high shear rates. These systems are promising for different uses, among them the formulation of new cosmetic matrices for cosmetic agents delivery is under investigation. In the present paper, a common cosmetic formulation for skin care was enriched with increasing fractions of monoglycerides of fatty acids/olive oil organogels, in order to understand the rheology and the microstructure of these systems. Small amplitude oscillation tests, NMR-self diffusion analysis, contrast phase microscopy and electric conductivity confirmed that the addition of the organogel caused a microstructural change of the starting material, which turned from O/W to a more complex system where, probably, a matrix-in-matrix structure is present at the highest fractions of added organogel.

Oxidation of human red blood cells by a free radical initiator: effects on rheological properties.

The main aim of this study was the investigation of the rheological properties of Red Blood Cells (RBCs) obtained from subjects admitted to blood donors, associated with the lipid profile of High-Density Lipoprotein Cholesterol (HDL-C), Low-Density Lipoprotein Cholesterol (LDL-C), Triglyceride (TG) and Total Cholesterol (TOT-C). The deformability index of RBCs was determined by using a Dynamic Stress Rheometer (DSR-500) under oxidative injury induced by 2.2'-azo-bis (2-amidinopropane) dihydrochloride (AAPH). An increased rigidity of RBCs in subjects with borderline level of hyperlipidemia was found, compared with the control group. In order to explain the reason for the reduced deformability, a borderline group was studied for the evaluation of anionic permeability on membrane, haemolysis and morphological changes induced by AAPH, as well as ThioBarbituric Acid Reactive Substances (TBARs) generation. Haemolysis by AAPH indicated a decrease of globular resistance in the borderline group, furthermore, the elevated values of TBARs suggested lipid peroxidative damage to the RBCs membrane associated with morphological changes and anion permeability alterations. Our study shows the correlation between biochemical and morphological parameters of RBCs and their rheological behavior during oxidative injury. Rheological studies might be useful as a clinical and diagnostic monitoring technique and provide support for further research.