Limited information exists regarding the processing parameters and extent of reinforcing potential natural fibers have in polymer matrices. The five natural fiber mats studied were low shive flax, mid shive flax, high shive flax, hemp and kenaf. The parameters characterized were fiber size, wax content, surface contact angle, and shive content. The compressive force and unsaturated permeability was measured for each mat, and composites were constructed and tested using selected mats in a soy-based polyurethane (PU) matrix. All mats exhibited a viscoelastic behavior under compression, and an increase in shive content correlated with an increase in relaxation. The presence of shive and larger fiber size increased the permeability. Higher wax content and contact angle lowered the permeability. The mechanical properties for all composites performed better than the neat PU, showing there was matrix to fiber adhesion and load transfer. Hemp outperformed the other fibers studied in all mechanical tests.

The present work was done to determine the effect of temperature of the half-saturation constant (ø) and the maximum transport rate (K) of the facilitated diffusion of glycerol across the erythrocyte membrane of Peromyscus californicus.

Femetinide is a synthetic retinoid with chemotherapeutic activity against various malignancies. After oral administration to animals, femetinide was found to be incompletely absorbed and excreted primarily in feces. The purpose of this study was to investigate the mechanism(s) responsible for the transport of femetinide across Caco-2 cell monolayers with an aim to determine the possible reasons for poor oral absorption of fenretinide. Fenretinide was found to be highly lipophilic (log P = 7.4) and practically insoluble in water. The water solubility of fenretinide was enhanced by formulating it as a Povidone K 25 solid dispersion. The Transepithelial Electrical Resistance (TEER) and antipyrine permeability (transcellular marker) were not affected after treatment with 0.5% PVP K 25 on the apical side. The apparent permeability coefficient (Papp) of fenreti nide was extremely low [(8.8 ± 0.5) x 10-8 cm/sec] even in the presence of 4% bovine serum albumin (BSA) in the receiver. The apical to basolateral (AP-BL) transport appeared linearly related to the fenretinide concentration ( 125-640 μM), thereby indicating that femetinide penneates the Caco-2 monolayer by passive diffusion within the concentration range. Transport studies at different donor (apical) pH conditions (6.0 or 7.4) revealed that no pH-dependent transporters were involved in the apical to basolateral transport of fenretinide across the Caco-2 monolayer. Efflux transporters like P-glycoprotein (P-gp) and the paracellular pathway did not play a significant role on the permeability of fenretinide. The partitioning of highly lipophilic molecules like fenretinicle from the cell membrane into the receiver depends on the composition of the receiving medium. The permeability of fenretinide increased with an increase in the bovine serum albumin (BSA) concentration (0 to 4 %) in the receiver. The addition of RBP to the receiving medium containing 4 % BSA increased the permeability of femetinicle clue to a greater binding affinity of fenretinicle for RBP. Significant amount (13-15% of the initial amount) of drug was found to accumulate in the cell membrane. The permeation of femetinide in Caco-2 monolayers is limited due to extensive accumulation in the cell membrane and poor partitioning from the cell membrane into the receiver medium.

N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) has been shown to cause changes in cultured endothelial cells and smooth muscle function at concentrations from 5 to 25 mM. To determine whether HEPES also affects vascular permeability, the effects of two buffers, HEPES and phosphate, were compared in isolated perfused rabbit lungs. Hemodynamic parameters and vascular protein permeability-surface area products (PS) were measured after perfusion with the buffers. Endothelial permeability was measured for an anionic and a cationic albumin to assess the charge effects of the zwitterion buffer. With HEPES, there were no changes in vascular pressure or resistance but permeability was affected. Cationic albumin permeability increased with 12 mM HEPES (8.7(phosphate) → 30(12 mM HEPES) x ml · min-1 · g dry lung-1 x 10-2) as did the anionic albumin PS (2.7(phosphate) → 3.52(12 mM HEPES). The cationic PS returned to baseline (8.1(60 mM HEPES)) at 60 mM HEPES, but the anionic PS did not change from the 12 mM HEPES (4.01(60 mM HEPES)). In summary, we find that HEPES is not innocuous. Although hemodynamic parameters did not change, endothelial permeability was increased when HEPES was used at normal concentrations. Therefore, HEPES should be used with caution as a physiological buffer in perfused organ systems.

The gas transport and separation properties of polymers have been successfully exploited in commercial ventures. Industrial applications employing membrane processes range from production of pure gases to barrier coatings for protection against environmental elements. Membrane separations are simple, energy efficient processes, which can be economically competitive with traditional separation technologies. Membrane separation and permeation characteristics for a particular mixed gas system is typically calculated from single-component transport parameters, namely, diffusion coefficients and solubility constants. In certain gas systems involving gaseous or vapor mixtures, where mass transport is affected by coupling effects or competition between penetrants for unrelaxed free volume, such calculations can lead to erroneous estimates of the membrane separation efficiency. Attempts to study the true transport phenomena effective during mixed gas permeation through membranes have been restricted due to experimental limitations. Also, the absence of rigorous theoretical models hinders the complete understanding of the transport phenomena. The current research involved design and development of an experimental set-up for observing mixed gas permeation through non-porous membranes with real time resolution. The technique employs a gas chromatograph as the selective detector for monitoring the variation in gas concentration, as the gases permeate through the membrane. The same set-up can also be used for conducting single gas permeation experiments. The novelty in the experimental set-up is the In-line sampling interface, used for injection of permeate gases in the GC without introducing any leaks in the permeate volume. Also, a novel data cropping technique is used to elucidate the transport properties of gases through membranes under mixed gas permeation conditions. Mixed gas feed concentration studies performed on a rubbery polymer (PDMS: poly dimethyl siloxane) showed no coupling effects. However, with a glassy polymer (NEW TPI: thermoplastic polyimide), the synergistic effects of gases is observed to play a major role in altering the gas transport and separation properties of the membrane. / Ph. D.

Early qualitative erythrocyte permeability studies (Gryns, 1896; Hedin, 1897) revealed the wide range of non-electrolyte permeability rates across a cell membrane composed of lipid molecules. Theoretically, water-soluble non-electrolytes such as glycerol, ethylene glycol and erythritol would penetrate less rapidly than lipid-soluble non-electrolytes. It was thought that the rate of penetration of water-soluble non-electrolytes was inversely proportional to their molecular size and the penetration of lipid-soluble non-electrolytes was directly proportional to their lipid-solubility.

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Numerous studies have found certain unmethylated phytochemicals to possess anti-carcinogenic activity; however, they have been associated with poor oral bioavailability which is a major limiting factor in their usage in chemopreventative treatment. The purpose of this study was to investigate if methylation of a compound would affect bioavailability, in terms of transport and permeability, in a Caco-2 cell model as well as the effect of cell viability and cellular uptake in human colon cancer cell lines. Furthermore, a new analytic method using reversed-phase high performance liquid chromatography coupled with electrochemical detector (HPLC-EC) for the detection and quantification of resveratrol and pterostilbene was developed. This new method was simple, rapid, and more sensitive compared to other detection methods used to analyze resveratrol and pterostilbene. Linear range, limit of detection (LOD), precision and recovery were used to validate this new analytical method. There was a significant increase in intracellular uptake and stronger growth inhibitory of pterostilbene in human cancer cells lines in comparison to resveratrol. Resveratrol exhibited a higher and more rapid rate of transport than pterostilbene across the Caco-2 monolayer regardless of the concentration tested and direction. Pterostiblene exhibited little difference in the rate of transport from either direction. The HCT-116 colon cells had intracellular uptake of each of the polymethoxyflavones (PMFs) tested. Transport was observed by all the PMFs and each had different rates of transport. Overall, location and amount of methyl groups had an effect on bioavailablity of a compound and these compounds show promise as chemopreventative agents.