Young adult gender differences in forearm skin-to-fat tissue dielectric constant values measured at 300 MHz.

BACKGROUND/PURPOSE: Skin-to-fat tissue dielectric constant (TDC) values depend on measurement depth and gender. Our goal was to assess male-female differences in TDC values associated with differing skin depths. METHODS: Bilateral forearm TDC measurements were made on young adult male and females with mean ages from 24.7 to 27.3 years. There were four measurement groups distinguished by the TDC measurement depth and include the following numbers of subjects for each gender; 30, 150, 60, and 50 for probe-measurement depths of 0.5, 1.5, 2.5, and 5.0 mm. Data were subsequently compared with values calculated with a simple two-layer model. RESULTS: For females and males, there was a significant difference in TDC values among depths (P < 0.001) with TDC values decreasing with increasing depth. Gender comparisons showed that TDC values of males were significantly (P < 0.001) greater than values for females at each depth. Male-female percentage differences ranged from 14.8% to 22.0%. Model calculations suggest that gender differences might be explained by skin thickness differences. CONCLUSION: Findings indicate that decisions with regard to skin water content among or between groups based on TDC measurements need to account for gender and are best made when corresponding skin thickness measurements are available. However, changes in TDC values assessed in individual patients and comparisons between corresponding skin areas in affected and non-affected sites are not limited. Thus, assessments of acute treatment effects and assessments of inter-arm or inter-leg TDC differences or ratios within genders are a useful and suitable method to characterize edema and lymphedema features.

ESR technique for noninvasive way to quantify cyclodextrins effect on cell membranes.

A new way to study the action of cyclodextrin was developed to quantify the damage caused on cell membrane and lipid bilayer. The Electron Spin Resonance (ESR) spectroscopy was used to study the action of Randomly methylated-beta-cyclodextrin (Rameb) on living cells (HCT-116). The relative anisotropy observed in ESR spectrum of nitroxide spin probe (5-DSA and cholestane) is directly related to the rotational mobility of the probe, which can be further correlated with the microviscosity. The use of ESR probes clearly shows a close correlation between cholesterol contained in cells and cellular membrane microviscosity. This study also demonstrates the Rameb ability to extract cholesterol and phospholipids in time- and dose-dependent ways. In addition, ESR spectra enabled to establish that cholesterol is extracted from lipid rafts to form stable aggregates. The present work supports that ESR is an easy, reproducible and noninvasive technique to study the effect of cyclodextrins on cell membranes.

Quantification of Randomly-methylated-beta-cyclodextrin effect on liposome: an ESR study.

In the present work, the effect of Randomly-methylated-beta-cyclodextrin (Rameb) on the microviscosity of dimyristoyl-l-alpha phosphatidylcholine (DMPC) bilayer was investigated using the electron spin resonance (ESR) technique. The ability of Rameb to extract membrane cholesterol was demonstrated. For the first time, the percentage of cholesterol extracted by Rameb from cholesterol doped DMPC bilayer was monitored and quantified throughout a wide Rameb concentration range. The effect of cholesterol on the inner part of the membrane was also investigated using 16-doxyl stearic acid spin label (16-DSA). 16-DSA seems to explore two different membrane domains and report their respective microviscosities. ESR experiments also establish that the presence of 30% of cholesterol in DMPC liposomes suppresses the jump in membrane fluidity at lipids phase-transition temperature (23.9 degrees C).

Development of a new topical system: drug-in-cyclodextrin-in-deformable liposome.

A new delivery system for cutaneous administration combining the advantages of cyclodextrin inclusion complexes and those of deformable liposomes was developed, leading to a new concept: drug-in-cyclodextrin-in-deformable liposomes. Deformable liposomes made of soybean phosphatidylcholine (PC) or dimyristoylphosphatidylcholine (DMPC) and sodium deoxycholate as edge activator were compared to classical non-deformable liposomes. Liposomes were prepared by the film evaporation method. Betamethasone, chosen as the model drug, was encapsulated in the aqueous cavity of liposomes by the use of cyclodextrins. Cyclodextrins allow an increase in the aqueous solubility of betamethasone and thus, the encapsulation efficiency in liposome vesicles. Liposome size, deformability and encapsulation efficiency were calculated. The best results were obtained with deformable liposomes made of PC in comparison with DMPC. The stability of PC vesicles was evaluated by measuring the leakage of encapsulated calcein on the one hand and the leakage of encapsulated betamethasone on the other hand. In vitro diffusion studies were carried out on Franz type diffusion cells through polycarbonate membranes. In comparison with non-deformable liposomes, these new vesicles showed improved encapsulation efficiency, good stability and higher in vitro diffusion percentages of encapsulated drug. They are therefore promising for future use in ex vivo and in vivo experiments.