Biomedical subjects

S E Friberg

Publications and source records attributed to S E Friberg.

11 recordsLinked to original sources

PubMed1998

Fragrance compounds and amphiphilic association structures.

Fragrance formulations have traditionally been based on alcohol as the solvent, but the recent legal restrictions on volatile organic solvents have prompted the industry to change to aqueous solubilized systems. The article reviews the fundamental factors in the application of such systems evaluating the influence by different amphiphilic association structures on the vapor pressure of fragrance compounds. This information is subsequently used to estimate the variation of fragrance compound vapor pressures during evaporation. The results reveal that the vapor pressure versus time variation is improved compared to solvent-based formulations.

Micelles↗

PubMed1995

Curcumin in a model skin lotion formulation.

A lamellar liquid crystalline region was identified in a typical skin lotion formulation system composed of a mixture of isostearic acid and triethanolamine (TEA) at 65:35 (w/w), decane, and water (the temperature was controlled at 30 degrees C). The interlayer spacings were determined by a small-angle X-ray diffraction technique. Incorporation of a natural dye, curcumin, resulted in lower interlayer spacings and higher penetration of water into the layered structure. However, the higher penetration of water was not apparent at all compositions of isostearic acid:TEA, decane, and water.

Chemistry, Pharmaceutical↗

PubMed1995

Surface and colloid chemical aspects of saliva particle interactions.

Sections of flash-frozen saliva particle mixture were examined by transmission electron microscopy. The saliva samples used consisted of 40% by volume parotid and 60% by volume submandibular sublingual fractions. One mL of the saliva was mixed with 0.1 mL of either hydrophilic or hydrophobic particles of 0.9 microns diameter. The micrographs of the saliva and hydrophilic particles mixes showed the multiple spherical particles in the salivary network structures. Micrographs of the saliva and hydrophilic particle mixes showed the presence of few such objects; when observed, the particles were located only in the electron dense part of the salivary structures.

Adult↗

PubMed1994

A lamellar liquid crystal with fosinopril sodium.

The location and conformation of fosinopril sodium (FS) in a lamellar liquid crystal of water, sodium dodecyl sulfate, and decanol was studied by low-angle X-ray diffraction. The result showed the FS molecule to be located within the amphiphilic part of the liquid crystalline structure with the polar parts anchored at the water/polar part interface. An area per molecule in the range of 95-100 A2 showed not only the polar groups but also the benzene ring to be located at this interface.

Chemical Phenomena↗

PubMed1991

Lyotropic liquid crystals and the structural lipids of the stratum corneum.

Lipids were extracted from human stratum corneum and the remaining corneocytes were reaggregated with different lyotropic liquid crystals. Water transport through the reaggregated stratum corneum was determined using a diffusion chamber according to Smith and Blank. The permeability constant for the reaggregated stratum corneum with natural lipids was 25-40% lower than that with the surfactant liquid crystals, but there was no significant difference between different liquid crystals.

Adult↗

PubMed1990

Water permeation of reaggregated stratum corneum with model lipids.

Corneocytes were prepared from stratum corneum after extraction of the lipids and then were reaggregated with model lipids to form a membrane. The transport of water through the membrane was found to be similar to earlier published values for reaggregated stratum corneum formed with the indigenous lipids. Similar values were also obtained when only partially saponified free fatty acids were present as lipids. These results support an earlier hypothesis, that the lipid barrier to water penetration of the stratum corneum is determined by the structural organization of the lipids, not by the exact chemical structure of individual species.

Biological Transport↗

PubMed1989

Water evaporation rates from a model of stratum corneum lipids.

Water evaporation rates were measured from thin samples of a model layered structure of stratum corneum lipids with 32% water. A model with only free fatty acids present gave the lowest evaporation rates, while a model with only oleic acid gave values approximately 50% higher. Using the total lipid spectrum of stratum corneum gave a structure with an evaporation rate between those mentioned above. The diffusion coefficients calculated were one to two orders of magnitude higher than those of stratum corneum, reflecting the influence of the proteinous part of the latter structure. A sample with only saturated fatty acids gave extremely high evaporation rates; in fact, they were of the same magnitude as those from an unprotected water surface.

Diffusion↗

PubMed1989

Thin-section transmission electron microscopy of human saliva.

Thin sections (90-100 nm) of flash-frozen human saliva fractions and whole saliva were examined by transmission electron microscopy. Inside the major filamentous structural components numerous ultrastructural details were observed, especially for whole saliva and submandibular/sublingual fractions. An outer reticulated zone believed to contain the major salivary glycoproteins surrounded an inner core consisting of a continuous, more electron dense phase with multiple vacuoles and granules of different sizes, shapes, and electron densities. The observed structures suggest a complex microarchitectural model for whole saliva.

Actin Cytoskeleton↗

PubMed1988

The effect of solvent extraction on the lipids of the stratum corneum in relation to observed immediate whitening of the skin.

Irritant contact dermatitis along with an increased transepidermal water loss can result from exposing the skin to solvents. A study of the interaction of various solvents with human stratum corneum was made using thin-layer chromatography. Comparison of 10 solvents (trichloroethylene, toluene, dimethylsulfoxide, n-hexane, 1,2-propanediol, carbon tetrachloride, methyl ethyl ketone, ethanol, acetone, distilled water) showed that 3 solvents (dimethylsulfoxide, 1,2 propanediol, distilled water) did not extract lipids from intact human stratum corneum. The findings are discussed in relation to the visual appearance of skin (whitening) after exposure to solvents.

Chromatography, Thin Layer↗

PubMed1985

The influence of solvent on nonaqueous lyotropic liquid crystalline phase formed by triethanolammonium oleate.

The geometry of a lyotropic lamellar liquid crystalline phase formed by triethanolamine (TEA) and oleic acid (OLA) with solubilized oligomers of polyethylene glycols and different types of oils was determined from small angle X-ray diffraction patterns. The region of stability of the lamellar liquid crystalline phase on addition of soluble glycols or oils was found to depend on the molar ratio of triethanolamine to oleic acid. A series of ethylene glycol oligomers, which were solubilized in the polar part of the structure, showed maximum solubilization at the OLA-TEA mole ratio of 1.6. The organic oils, on the other hand, which are solubilized into the hydrophobic part of the structure, exhibited maximum solubilization at the OLA-TEA mole ratio of 0.8.

Chemical Phenomena↗

PubMed1984

Liquid crystals as a potential ointment vehicle.

A lecithin-water lyotropic liquid crystal was used as an ointment vehicle for a hydrocortisone formulation. The hydrocortisone was soluble in the liquid crystalline phase up to 5% by weight. The diffusion coefficient determined for the hydrocortisone in the liquid crystalline phase was 5.5 X 10(-9) cm X s-1, which is four magnitudes higher than the corresponding value for skin.

Chemistry, Pharmaceutical↗