Papers by Keyword: Permeation

Abstract: Nanobubbles are gaseous vesicles under 1 micrometer in size, widely used in medical imaging and drug delivery. Their compressibility enhances ultrasound imaging, while their small size allows for extravasation into tumors via the enhanced permeation and retention effect. However, drug delivery remains challenging due to high interstitial pressure within tumors, which limits penetration to the core. To address this, nanobubbles can serve as drug delivery devices, with controlled release triggered by focused ultrasound. Understanding their transport behavior is crucial, particularly in the tumor microenvironment. This study investigates the effect of ultrasound and presence of shear on the permeation of nanobubbles through the tumor interstitium. Rhodamine-loaded nanobubbles, mimicking drug-loaded delivery device, were introduced into a membrane insert system containing an agarose-gel layer simulating the tumor interstitium. Nanobubble concentration in the receiver well was monitored via fluorescence intensity, assessing transport efficiency under different conditions. Comparisons with non-echogenic fluorescent dextrans provided insights into distinct nanoparticle behaviors. Results showed that ultrasound significantly enhanced nanobubble permeation, whereas the presence of shear primarily benefited dextran transport. These findings highlight the unique responsiveness of nanobubbles to ultrasound, offering a promising strategy for improving drug delivery in solid tumors.

Abstract: A physical model studying the diffusion of interstitial atoms has been used in the study of hydrogen redistribution, in order to predict the risk of hydrogen damage in a range of manufacturing processes. In this work, conditions representative of hydrogen storage and some scenarios in the nuclear or chemical industries are considered. A singular advantage of this model is that, contrary to some simplified commercial and academic models, it contemplates diffusion in its most comprehensive description, i.e., with the driving force for atom diffusion being the gradient in chemical activation instead of simply considering it occurs down a composition gradient. Because the model also incorporates thermal history, microstructure, matrix solubility, multiple trapping distributions, interaction with the atmosphere and others, it is ideally suited to study real industrial applications. In this work, several simulations of hydrogen permeation are considered. Hydrogen permeation in industrial applications may introduce damage within the metal structure, leading to delayed failure. In the cases studied hydrogen is transported through a metal wall separating one volume with high hydrogen pressure and/or high temperature from another volume with low hydrogen pressure and temperature. By using such comprehensive physical model, it is possible to study the effects of hydrogen pressure and temperature gradient, wall thickness, metal microstructure and trap distribution on the flux across the wall and on the accumulation of hydrogen within the metal. Furthermore, it makes possible to estimate the embrittlement risk and when necessary the time to fracture. Keywords: hydrogen, steel, permeation, physical model, hydrogen storage, nuclear industry

Abstract: Currently available diffusion constant and Sieverts constant experimental results are based on time dependent permeation experiments. The common principle is an analysis which is expecting that the permeating hydrogen is “transported” from the retentate chamber to the permeate chamber through the connecting membrane, with a vanishing hydrogen partial pressure on the permeate side. But reality shows a different behaviour caused by the fact that a nonzero hydrogen partial pressure in the permeate chamber is necessary for detection purposes. This nonzero pressure is mostly not considered by analysis. This issue is solved (approximatively) numerically by the procedure as described in this paper. This work is rooted in the field of fusion research, where so called purge gas with low partial pressure of tritium is contacting the structural materials (300-550°C) of the fusion reactor (blanket) and of process equipment, where the tritium losses are of interest. The developed algorithms are intended for the evaluation of an experiment termed “Q-PETE” (Q for any hydrogen isotope, PEermeation Transport Experiment), which abstracts the hydrogen transport conditions of the fusion blanket, and where the effect of nonzero hydrogen concentration on the permeate side is relevant. The algorithms are useful for all experiments, where the ratio of hydrogen pressures between retentate and peremeate side are far from infinite.

Abstract: Delivery of drug through topical route, delivers most convenient and novel approach. The Skin can offer several advantages as a route of drug administration although its barrier nature makes it difficult for most drugs to penetrate in to and permeate through it. During the past decades there has been a lot of interest in lipid vesicles as a tool to improve topical drug delivery. Vesicular system such as liposomes, niosomes, ethosomes and elastic deformable vesicles provide an alternative for improved skin drug delivery. In fact vesicles can act as drug carriers controlling drug release. The Research findings were intended to develop sustained release of aceclofenac niosomes formulations in order to reduce gastrointestinal disturbances and to provide better effect when applied topically. Niosomes of aceclofenac was prepared by modified ether injection method using different ratio of surfactants (Tween 20, 40, 60 & 80) with cholesterol and drug. The developed formulations were optimized based on the high entrapment efficiency and in-vitro release studies. Optimized batch was selected and made in to topical niosomal gel using gelling agents like carbopol and sodium carboxy methyl cellulose. Formulation were evaluated for various parameters like vesicle shape, vesicle size, entrapment efficiency, drug content, compatibility studies, in-vitro release studies and stability studies. Ether injection method was found to be most satisfactory in terms of niosome particle size, drug entrapment efficiency was found to be 88.68 ±0.64 % and in-vitro release studies showed 40% of sustain drug release at the end of 8 hrs of study when compared with marketed formulation. Hence, the formulated niosomal topical gel was found to be a better alternative when compared to the marketed formulation in terms of better efficacy, bioavailability and permeation.

Abstract: Membrane gas separation is a forthcoming technology that advertised a great commercial potential in diverse industrial applications. Consequently, membrane-based natural gas processing has been among the fastest growing segments of the economic growth. The turbostratic structure of carbon membranes has been affirmed to accommodate with good separation selectivity for permanent gases. With that, the most auspicious technique acquired is by controlling the carbonization temperature during the carbon membrane fabrication. In this study, polymer-based carbon tubular membranes have been fabricated and characterized in terms of its structural morphology and gas permeation properties. Polyimide (Matrimid 5218) was used as a precursor for carbon tubular membrane preparation to produce high quality of carbon membrane via carbonization process. The polymer solution was coated on TiO₂ –ZrO₂ tubular tubes (Tami) by using dip-coating method. The polymer tubular membrane was then carbonized under Nitrogen atmosphere at 600, 750, and 850 ◦C. The structural morphology of the resultant carbon membranes was analyzed by means of scanning electron microscope (SEM). Pure gas permeation tests were performed using CO₂ and N₂ gases at 8 bars and room temperature. Based on the results, the highest CO₂/ N₂ selectivity of 79.53 was obtained for carbon membrane prepared at 850 ^oC.

Abstract: Poly (ethylene-co-vinyl acetate) (EVA)/clay nanocomposites with different clay loadings were prepared. The transport of gases (oxygen and nitrogen) through the composite membranes was investigated. These studies revealed that the incorporation of nanoclays in the polymer increased the efficiency of the membranes toward barrier properties. It was also found that the barrier properties of the membranes decreased with clay loadings. This is mainly due to the aggregation of clay at higher loadings. The mechanical properties of the nanocomposites were analysed. Samples with 5 wt % Cloisite 15A clay showed superior performance in tensile strength and elongation at break.

Abstract: The aim of the present study was to develop a self nanoemulsifying drug delivery system (SNEDDS) for the improved oral delivery of Rosuvastatin, a lipid lowering agent. Captex 810D, based on the higher solubility of Rosuvastatin was selected as an oil phase. Mixture of permeation enhancers such as Solutol HS15 and Acconon MC8 was selected as surfactants for the formulation of SNEDDS. Formulated SNEDDS upon mixing with water, dispersed rapidly into fine droplets size ranging from 95-263nm. Further the SNEDDS was evaluated for self nanoemulsification time, precipitation, cloud point, morphology, in-vitro drug release and ex-vivo permeation. Formulation (F3) showed the globule size of 139nm, quick self nanoemulsifiation time (20 sec) and transparency (97%). Maximum drug release of 99.9% and higher drug permeation of 95% was observed with formulation F3 when compared with conventional tablet. The formulated SNEDDS can be used to improve the oral absorption and bioavailability of Rosuvastatin.

Abstract: Geopolymer is a binder that can act as an alternative of Portland cement. Geopolymers use by-product substances such as fly ash, and can help reduce carbon dioxide emission of concrete production. This paper presents the results of a study on the fly ash based geopolymer concrete suitable for curing at ambient temperature. To activate the fly ash, a combination of sodium hydroxide and sodium silicate solutions was used. The setting and hardening of geopolymer concrete were obtained by blending blast furnace slag with fly ash instead of using heat curing. Ground granulated blast furnace slag (GGBFS) was used at the rate of 10% or 20 % of the total binder. The tests conducted include compressive strength, tensile strength, flexure strength, sorptivity and volume of permeable voids (VPV) test. The geopolymer concrete compressive strength at 28 days varied from 27 to 47 MPa. Results indicated that the strength increased and water absorption decreased with the increase of the slag content in the geopolymer concrete. In general, blending of slag with fly ash in geopolymer concrete improved strength and permeation properties when cured in ambient temperature.

Abstract: Recently, poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) has drawn the attention of many researchers as an excellent material for polymer electrolytes. In this paper, the homogeneous P(VDF-co-HFP) films were prepared by volatilizing solvent method. The swelling behaviors of P(VDF-co-HFP) films in four kinds of carbonate esters (dimethyl carbonate, diethyl carbonate, propylene carbonate, and ethylene carbonate) and the permeation behaviors of the four carbonate esters in P(VDF-co-HFP) films were investigated at 10, 20, 30, 40 and 50°C under atmospheric pressure. It was found that the liquid content and degree of elongation of P(VDF-co-HFP) films in the carbonate esters increased with the increasing temperature, following the order of DMC > PC > DEC > EC. The order of permeation flux of the carbonate esters in the P(VDF-co-HFP) films was DMC > DEC > PC = EC = 0. The swelling behaviors of P(VDF-co-HFP) films were explained by Hansen Solubility Parameter (HSP) theory.

Abstract: To study the permeation mechanics during the impregnation of carbon graphite for mechanical applications, a permeation test with single-phase water saturated is conducted on carbon graphite porous medium, testing the permeability of the porous medium. The result of the test shows that the porosity of carbon graphite for mechanical applications is between 9.24% ~27.41% and the permeability of the samples is not a fixed value, averagely between 0.071mD and 9.953mD; and that the permeability of porous carbon graphite is resulted from the factors of pore structure properties of the porous medium, permeation force field and fluids properties. Based on the rules of permeability and permeation speed change, the permeability of carbon graphite porous medium can be classified into three categories: low-high-stable permeability, fluctuating permeability, and decreasing permeability.