Significant Differences In Permeability Research Articles

The Mechanism Study of Fracture Porosity in High-Water-Cut Reservoirs

Many onshore oil fields currently adopt water flooding as a means to supplement reservoir energy. However, due to reservoir heterogeneity, significant differences in permeability exist not only between different reservoirs but also within the same reservoir across different planar orientations. After prolonged fluid flushing in the near-wellbore zone of injection wells, the resulting increased flow resistance between layers exacerbates inefficient and ineffective circulation. A considerable amount of remaining oil is left unexploited in untouched areas, significantly impacting the overall recovery. To investigate the multiscale plugging mechanisms of fracture-dominated pore channels in high-water-cut oil reservoirs and achieve efficient management of fractured large channels, this study explores the formation of the fracture-flushing zone-low saturation oil zone. A physical experimental model with fractures and high-intensity flushing is established to analyze changes in pore structure, mineral composition, residual oil distribution, and other characteristics at different positions near the fractures. The research aims to clarify the mechanism behind the formation of large channels with fracture structures. The results indicate that under high-intensity water flushing, cementing materials are washed away by the flowing water, clay particles are carried to the surface with the injected fluid, and permeability significantly increases, forming high-permeability zones with fracture structures. In the rock interior away from the fracture end, channels, corners, and clustered oil content noticeably decrease, while the content of film-like oil substantially increases, and clay minerals are not significantly washed away. Under strong flushing conditions, the number of residual clay particles near the fracture end is mainly influenced by flow velocity and flushing time; thus, the greater the flushing intensity, the faster the water flow, and the longer the flushing time, the fewer residual clay particles near the fracture end.

Screening of Surfactants for Flooding at High-Mineralization Conditions: Two Production Zones of Carbonate Reservoir

The selection of effective surfactants potentially can mobilize oil up to 50% of residuals in mature carbonate oilfields. Surfactants’ screening for such oilfields usually is complicated by the high salinity of water, high lipophilicity of the rock surface, and the heterogeneous structure. A consideration of features of the oilfield properties, as well as separate production zones, can increase the deep insight of surfactants’ influence and increase the effectiveness of surfactant flooding. This article is devoted to the screening of surfactants for two production zones (Bashkirian and Vereian) of the Ivinskoe carbonate oilfield with high water salinity and heterogeneity. The standard core study of both production zones revealed no significant differences in permeability and porosity. On the other hand, an X-ray study of core samples showed differences in their structure and the presence of microporosity in the Bashkirian stage. The effectiveness of four different types of surfactants and surfactant blends were evaluated for both production zones by two different oil displacement mechanisms: spontaneous imbibition and filtration experiments. Results showed the higher effect of surfactants on wettability alteration and imbibition mechanisms for the Bashkirian cores with microporosity and a higher oil displacement factor in the flooding experiments for the Vereian homogeneous cores with lower oil viscosity.

Nonlinear regimes of binary mixture convection in a two-layer porous medium of different configurations

The results of modeling the convection of a binary mixture of liquid hydrocarbons in a two-layer porous medium are presented. The simulation area is a horizontally elongated rectangular cavity divided into two layers. In one of the considered cases, these sublayers are of equal height, and in the other case, the interface between the layers has the shape of a convex downward circular arc, which imitates a synclinal geological fold. The layers have different permeability. In the cavity, there is a geothermal temperature gradient with an average temperature characteristic of a depth of 2000 m, which corresponds to the average oil depth. The composition of the mixture, the thermal conditions and the geometry used make up the reservoir model of the hydrocarbon deposit. The problem is solved in terms of the Darcy–Boussinesq model with allowance for the effect of thermal diffusion. The emergence and establishment of nonlinear convection regimes, as well as the distribution of the concentration of mixture components for different values of the permeability of the layers and their dependence on which of these layers is more permeable, are considered in simulations. It is found that in the case of a small difference in the permeabilities of the layers, a stationary regime is established in the cavity of any of the considered configurations. With a significant difference in permeability of the layers in the cavity, either quasi-periodic oscillations of a complex shape or irregular oscillations can be observed. A "local" occurrence of convection is shown for a large permeability difference, followed by a weak penetration of the flow into a less permeable layer, as well as a "large-scale" occurrence of convection in the case of an insignificant permeability difference.

Elaboration and Characterization of Bioactive Films Obtained from the Incorporation of Cashew Nut Shell Liquid into a Matrix of Sodium Alginate.

The objective of this work was to obtain and characterize sodium alginate-based biopolymer films with the addition of cashew nut shell liquid (CNSL). The study employed a completely randomized design, including 0%, 0.5%, 1%, and 1.5% inclusion of CNSL. Uniform formation of the films was observed, and the addition of CNSL provided better thermal resistance than did the treatment without inclusion, while the addition of CNSL reduced the homogeneity of the microstructure, especially for the 1.5% inclusion level. The permeability of the film increased as the level of CNSL increased, especially in response to the concentrations of 1% and 1.5%, and no significant difference in permeability was observed between these treatments. The tensile strength decreased proportionally as a function of the addition of CNSL, as its inclusion increased the elasticity and elongation of the films. In addition, the films with CNSL demonstrated strong antioxidant activity and discrete antimicrobial activity, and ecotoxicity analysis showed that the levels of CNSL tested and the films produced were nontoxic. Thus, these films are promising and self-sustainable alternatives for the agrifood industry.

Lower Cretaceous Rodby and Palaeocene Lista Shales: Characterisation and Comparison of Top-Seal Mudstones at Two Planned CCS Sites, Offshore UK

Petroleum-rich basins at a mature stage of exploration and production offer many opportunities for large-scale Carbon Capture and Storage (CCS) since oil and gas were demonstrably contained by low-permeability top-sealing rocks, such as shales. For CCS to work, there must be effectively no leakage from the injection site, so the nature of the top-seal is an important aspect for consideration when appraising prospective CCS opportunities. The Lower Cretaceous Rodby Shale and the Palaeocene Lista Shale have acted as seals to oil and gas accumulations (e.g., the Atlantic and Balmoral fields) and may now play a critical role in sealing the Acorn and East Mey subsurface carbon storage sites. The characteristics of these important shales have been little addressed in the hydrocarbon extraction phase, with an understandable focus on reservoir properties and their influence on resource recovery rates. Here, we assess the characteristics of the Rodby and Lista Shales using wireline logs, geomechanical tests, special core analysis (mercury intrusion) and mineralogical and petrographic techniques, with the aim of highlighting key properties that identify them as suitable top-seals. The two shales, defined using the relative gamma log values (or Vshale), have similar mean pore throat radius (approximately 18 nm), splitting tensile strength (approximately 2.5 MPa) and anisotropic values of splitting tensile strength, but they display significant differences in terms of wireline log character, porosity and mineralogy. The Lower Cretaceous Rodby Shale has a mean porosity of approximately 14 %, a mean permeability of 263 nD (2.58 × 10−19 m2), and is calcite rich and has clay minerals that are relatively rich in non-radioactive phases such as kaolinite. The Palaeocene Lista Shale has a mean porosity of approximately 16% a mean permeability of 225 nD (2.21 × 10−19 m2), and is calcite free, but contains abundant quartz silt and is dominated by smectite. The 2% difference in porosity does not seem to equate to a significant difference in permeability. Elastic properties derived from wireline log data show that Young’s modulus, material stiffness, is very low (5 GPa) for the most shale (clay mineral)-rich Rodby intervals, with Young’s modulus increasing as shale content decreases and as cementation (e.g., calcite) increases. Our work has shown that Young’s modulus, which can be used to inform the likeliness of tensile failure, may be predictable based on routine gamma, density and compressive sonic logs in the majority of wells where the less common shear logs were not collected. The predictability of Young’s modulus from routine well log data could form a valuable element of CCS-site top-seal appraisals. This study has shown that the Rodby and Lista Shales represent good top-seals to the Acorn and East Mey CCS sites and they can hold CO2 column heights of approximately 380 m. The calcite-rich Rodby Shale may be susceptible to localised carbonate dissolution and increasing porosity and permeability but decreasing tendency to develop fracture permeability in the presence of injected CO2, as brittle calcite dissolves. In contrast, the calcite-free, locally quartz-rich, Lista Shale will be geochemically inert to injected CO2 but retain its innate tendency to develop fracture permeability (where quartz rich) in the presence of injected CO2.

Experimental study of impact of shearing velocity and effective normal stress on post-shearing permeability evolution of silica fault gouges

Fault permeability is an important parameter for understanding the occurrence of natural hazards and evaluation of natural gas and oil reservoirs. In this study, effects of shear velocity on the permeability perpendicular to the shear zone formed after large shear displacements are revealed for silica sand. To this end, ring-shear experiments were performed for four shearing velocities under conditions of high effective normal stress. As observed, post-shear permeability values under effective normal stresses of 1 and 2 MPa demonstrated a reduction of two and one order of magnitude, respectively, along with negative velocity dependence. However, no significant difference in permeability was observed under exceeding 3 MPa. In addition, the shear-zone structure under high shear velocity and higher effective normal stress demonstrated existence of a grain-crushed zone, which closely corresponds to reductions in pore-diameter and grain size. Findings of this study indicate the instability mechanism of landslides related to groundwater movement and facilitate understanding of resource systems controlled by natural faults.

Pore size distribution in the tight sandstone reservoir of the Ordos Basin, China and their differential origin

The micro-nano pore throat system widely developed in tight sandstone is the essential difference between tight sandstone reservoir and conventional sandstone reservoir; it is also the main factor affecting the seepage characteristics and development effect of tight sandstone reservoir. This thesis analyzed the pore-throat types and distributions of the Chang 6 and the Chang 7 reservoirs in the Jiyuan area of the Ordos Basin and discussed the original causes by cast section, SEM, and constant-rate mercury injection. The results showed that the pore type of the Chang 6 reservoir is predominantly residual intergranular pores wherein the throat is mostly compacted. The pore of Chang 6 is more developed than the throat. The pore type of the Chang 7 reservoir is mainly feldspar solution pores, whereas its throat is mostly dissolution. The throat of Chang 7 is more developed than pore. The pore radius distribution range and the average value of the Chang 6 reservoir are similar to those of the Chang 7 reservoir. The distribution range and average value of the throat radius of the Chang 6 reservoir are obviously larger than that of the Chang 7 reservoir. Meanwhile, the physical property of the Chang 6 reservoir is better than that of the Chang 7 reservoir. The Chang 6 reservoir is located in delta sedimentary with shallow burial depth. The high chlorite membrane content and low compaction strength of the Chang 6 reservoir make it more conducive to maintaining the original sedimentary pore space; the dissolution further enlarges the pore space. The Chang 7 reservoir is located in a semi-deep lake sedimentary with large burial depth. The compaction and cementation of the Chang 7 reservoir are strong, and the original sedimentary pore space is massively compressed. Although dissolution strongly occurs in the later stage, the connectivity and seepage capacity of the throat of dissolution origin are lower than those of compaction origin. Dissolution can increase reservoir space; nevertheless, it cannot significantly improve seepage capacity. Therefore, there is a significant difference in permeability of the two successive layers.

From algal cells to autofluorescent ghost plasma membrane vesicles

Plasma membrane vesicles can be effective, non-toxic carriers for microscale material transport, provide a convenient model for probing membrane-related processes, since intracellular biochemical processes are eliminated. We describe here a fine-tuned protocol for isolating ghost plasma membrane vesicles from the unicellular alga Dunaliella tertiolecta, and preliminary characterization of their structural features and permeability properties, with comparisons to giant unilamellar phospholipid vesicles. The complexity of the algal ghost membrane vesicles reconstructed from the native membrane material released after hypoosmotic stress lies between that of phospholipid vesicles and cells. AFM structural characterization of reconstructed vesicles shows a thick envelope and a nearly empty vesicle interior. The surface of the envelope contains a heterogeneous distribution of densely packed, nanometer-scale globules and pore-like structures which may be derived from surface coat proteins. Confocal fluorescence imaging reveals the highly pigmented photosynthetic apparatus located within the thylakoid membrane and retained in the vesicle membrane. Transport of the fluorescent dye calcein into ghost and giant unilamellar vesicles reveals significant differences in permeability. Expanded knowledge of this unique membrane system will contribute to the design of marine bio-inspired carriers for advanced biotechnological applications.

Quantitative analysis for lipophilic drug transport through a model lipid membrane with membrane retention

Drug absorption after oral administration mostly occurs in the intestine, and is controlled mainly by the aqueous solubility and the intestinal permeability of the drug. In modern drug discovery, the proportion of lipophilic drug candidates with poor water solubility has increased, and these lipophilic drugs are known to undergo membrane retention during transport across the cell membrane, depending on the hydrophobic interaction between the drug and lipid molecules. Hence, a precise and effective permeability assay for lipophilic drug compounds, which can also quantify membrane retention, is required. In this study, we developed a permeability assay for lipophilic drugs with poor water solubility using a freestanding lipid bilayer. The lipid bilayer was created within a UV cuvette, and the number of transported molecules through the bilayer was estimated by measuring the UV absorbance over time. We then measured the permeability of six tested compounds, and there was a significant difference in permeability between the Biopharmaceutics Classification System (BCS) class 2 and class 4 compounds. In addition, the fraction of molecules trapped in the lipid bilayer were estimated for each compound as well. As a result, the drugs with higher lipophilicity were found to undergo more membrane retention, which agrees with the previous reports, supporting that our model lipid membrane system could also be applied to investigate the drug-lipid interaction.

Comparison of the Effects of Cryotherapy and Thermotherapy on Permeability After Skeletal Muscle Injury

Skeletal muscle injuries are common in active individuals. The inflammatory process is a vital component of muscle healing beginning with enhanced permeability. As blood vessels dilate, inflammatory promoting proteins and white blood cells enter the damaged area to eliminate debris and initiate regeneration. The application of controlled temperature on the injured muscle remains the most common treatment. However, there is conflicting evidence on the advantages of cryotherapy, and there is a lack of evidence on benefits of thermotherapy. Therefore the purpose of our study was to compare the effects of cryotherapy and thermotherapy on muscle vascular permeability in both male and female mice. Barium chloride (BaCl2) was injected into the right tibialis anterior (TA) to cause a chemical injury and sodium chloride (NaCl) was injected into the left TA as a control. Therapy was started immediately after injury. The control group was anesthetized, the thermotherapy group received heat treatment (41°C) while anesthetized, and the cryotherapy group received cold therapy (10°C) while anesthetized, for 20 mins every 3 hours, during 2 consecutive 12 hr wake cycles. Evans Blue (EB) dye was injected through the lateral tail vein to assess vascular permeability in the TA muscles. There was no significant difference in permeability between the NaCl injected muscles regardless of treatment. Permeability 36 hours post‐injection was significantly elevated in the BaCl2 injected TA muscles in all groups. Cryotherapy significantly reduced permeability in the BaCl2 injured muscles as compared to thermotherapy (cryotherapy: 4.78±2.68 vs. thermotherapy: 11.1±2.32 ngEB/mgTA). Our data suggests that cryotherapy limits permeability 36 hrs post‐skeletal muscle injury. New data suggests inflammation is necessary for efficient muscle healing. Therefore new treatments for muscle injury should be considered.Support or Funding InformationUrsinus College Student Research FundingThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Reduced urothelial regeneration in rat bladders augmented with permeable porcine small intestinal submucosa assessed by magnetic resonance imaging.

Augmentation enterocystoplasty remains the gold standard surgical bladder reconstruction procedure to increase the capacity and compliance of dysfunctional bladders. Since the use of the patient's intestine has severe risks of complications, alternative biodegradable matrices have been explored. Porcine small intestinal submucosa (SIS) has gained immense interests in bladder reconstruction due to its favorable properties. However, trials have shown inconsistent regeneration with SIS, attributed to the heterogeneity in microstructures and mechanical properties. We hypothesize that uneven SIS permeability to urine is a factor responsible for the inconsistency. We measured permeability to urine in situ using a contrast enhanced-magnetic resonance imaging (MRI), and evaluated urothelium regeneration using immunohistochemical staining of urothelial cell markers in SIS-augmented rat bladders. Results showed significant differences in permeability among SIS-augmented rat bladders. Commercial SIS scaffolds were then categorized into nonleaky and leaky groups based on MRI results. Hematoxylin and eosin staining showed higher numbers of inflammatory cells in leaky SIS on day 14 relative to nonleaky SIS. In addition, trichrome staining showed major changes in the distribution of collagen on day 28 between SIS-augmented bladder groups. Furthermore, expressions of urothelium-associated markers (cytokeratins AE1/AE3, claudin 4, and uroplakin III) were completed in bladders augmented with nonleaky SIS, whereas limited urothelial differentiation was noticed in leaky SIS-augmented bladders at post-augmentative day 14. These results show that scaffold permeability to urine may be responsible for variations in regenerative capacity of porcine SIS. Applications of MRI technique will be helpful to understand a relationship between biomaterial property and regenerative capacity. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1778-1787, 2018.

An In‐tether Chiral Center Modulates the Helicity, Cell Permeability, and Target Binding Affinity of a Peptide

The addition of a precisely positioned chiral center in the tether of a constrained peptide is reported, yielding two separable peptide diastereomers with significantly different helicity, as supported by circular dichroism (CD) and NMR spectroscopy. Single crystal X-ray diffraction analysis suggests that the absolute configuration of the in-tether chiral center in helical form is R, which is in agreement with theoretical simulations. The relationship between the secondary structure of the short peptides and their biochemical/biophysical properties remains elusive, largely because of the lack of proper controls. The present strategy provides the only method for investigating the influence of solely conformational differences upon the biochemical/biophysical properties of peptides. The significant differences in permeability and target binding affinity between the peptide diastereomers demonstrate the importance of helical conformation.

Excised segments of rat small intestine in Ussing chamber studies: A comparison of native and stripped tissue viability and permeability to drugs

Excised rat intestinal tissue mounted in an Ussing chamber can be used for intestinal permeability assessments in drug development. The outer layer of the intestine, the serosa and part of the muscle layer, is traditionally removed since it is considered a barrier to the diffusion of nutrients and oxygen as well as to that of pharmaceutical substances. However, the procedure for removing the serosal-muscle layer, i.e. stripping, is a technically challenging process in the pre-experimental preparation of the tissue which may result in tissue damage and reduced viability of the segment. In this study, the viability of stripped and native (non-stripped) rat small intestine tissue segments mounted in Ussing chambers was monitored and the apparent permeability of the tissue to a set of test compounds across both tissue preparations was determined. Electrical measurements, in particular the potential difference (PD) across the intestinal membrane, were used to evaluate the viability. In this study, there were no differences in initial PD (health status of the tissue) or PD over time (viability throughout the experiment) between native and stripped rat jejunum segments. Overall, there were also no significant differences in permeability between stripped and native rat intestinal tissue for the compounds in this study. Based on these results, we propose that stripping can be excluded from the preparation procedures for rat jejunal tissue for permeability studies when using the Ussing chamber technique.

Gap junction mediated miRNA intercellular transfer and gene regulation: A novel mechanism for intercellular genetic communication.

Intercellular genetic communication is an essential requirement for coordination of cell proliferation and differentiation and has an important role in many cellular processes. Gap junction channels possess large pore allowing passage of ions and small molecules between cells. MicroRNAs (miRNAs) are small regulatory RNAs that can regulate gene expression broadly. Here, we report that miRNAs can pass through gap junction channels in a connexin-dependent manner. Connexin43 (Cx43) had higher permeability, whereas Cx30 showed little permeability to miRNAs. In the tested connexin cell lines, the permeability to miRNAs demonstrated: Cx43 > Cx26/30 > Cx26 > Cx31 > Cx30 = Cx-null. However, consistent with a uniform structure of miRNAs, there was no significant difference in permeability to different miRNAs. The passage is efficient; the miRNA level in the recipient cells could be up to 30% of the donor level. Moreover, the transferred miRNA is functional and could regulate gene expression in neighboring cells. Connexin mutation and gap junctional blockers could eliminate this miRNA intercellular transfer and gene regulation. These data reveal a novel mechanism for intercellular genetic communication. Given that connexin expression is cell-specific, this connexin-dependent, miRNA intercellular genetic communication may play an important role in synchronizing and coordinating proliferation and differentiation of specific cell types during multicellular organ development.

Monitoring of permeability of different analytes in human normal and cancerous bladder tissues in vitro using optical coherence tomography

We report our preliminary results on quantification of glucose and dimethyl sulfoxide (DMSO) diffusion in normal and cancerous human bladder tissues in vitro by using a spectral domain optical coherence tomography (SD-OCT). The permeability coefficients (PCs) of a 30 % aqueous solution of glucose are found to be and in normal and cancerous bladder tissues, respectively. The PCs of 50 % DMSO are calculated to be and in normal and cancerous bladder tissues, respectively. The obtained results show a statistically significant difference in permeability of normal and cancerous tissue and indicate that the PC of 50 % DMSO is about 1.13-and 1.21-fold higher than that of 30 % glucose in normal bladder and cancerous bladder tissues, respectively. Thus, the quantitative measurements with the help of PCs from OCT images can be a potentially powerful method for bladder cancer detection.

Effect of molecular weight of chitosan on microcapsules and hypatocytes in microcapsules

Objective To study the influence of molecular weight of chitosan on microcapsules and hepatocytes in microcapsules. Methods The mechanical strength, permeability to fluoresceine isothiocyanate-bovine serum albumin (FITC-BSA) and activity of hepatocytes in microcapsules were compared between two kinds of microcapsules made by low and middle molecular weight chitosan. Results After 100 min of stirring microcapsules, all middle molecular weight chitosan microcapsules were damaged, 5% low molecular weight chitosan microcapsules were damaged. There was significant difference in breakage rate of the mechanical strength between two microcapsules (P ＜ 0. 05). Fifteen min after addition of FITCBSA into microcapsule solution, fluorescence intensity in the low molecular weight chitosan microcapsules was 4 AU, and that in middle molecular weight of chitosan microcapsules was 1. 5 AU, suggesting there was significant difference in permeability to FITC-BSA between two kinds of microcapsules (P ＜ 0. 05).One week after culture of microencapsulated hepatocytes, staining test showed that 100% of liver cells in low molecular weight chitosan microcapsules were alive, while the number was about 40% in middle molecular weight chitosan microcapsules (P ＜ 0. 05). Conclusion Low molecular weight chitosan is more suitable as materials of microcapsules than molecular weight chitosan. Key words: Hepatocyte; Microcapsules; Chitosan

Assessment of functional oesophageal mucosal integrity in biopsies of patients with refractory gord

IntroductionPatients with non-erosive reflux disease (NERD) exhibit oesophageal mucosal epithelial dilated intercellular spaces (DIS), which can be reversed by PPI therapy and are not seen in patients with functional heartburn....

Systemic Administration of Lipopolysaccharide Induces Cyclooxygenase-2 Immunoreactivity in Endothelium and Increases Microglia in the Mouse Hippocampus

In this study, we observed the effects of lipopolysaccharide (LPS) on neurodegeneration and immune response in the hippocampus. LPS is a gram-negative bacterial cell surface proteoglycan and known as a bacterial endotoxin. For this, we investigated the optimal concentration of LPS influencing the ICR mouse hippocampus to measure the LPS receptor, e.g., toll-like receptor 4 (TLR4), expression in mouse hippocampal homogenates. TLR4 expression was significantly and prominently increased in the hippocampal homogenates of the LPS (1 mg/kg)-treated group. Next, we examined pro-inflammatory response in the hippocampus using cyclooxygenase-2 (COX-2, a marker for inflammatory response) immunohistochemistry after LPS treatment. COX-2 immunoreactivity was significantly increased in the endothelium of blood vessels in the hippocampus 6 h after LPS treatment, judging from double immunofluorescence study with platelet-derived endothelial cell adhesion molecule-1 (PECAM-1, a marker for endothelial cells): it decreased 12 h and disappeared 24 h after LPS treatment. In addition, the ionized calcium-binding adapter molecule 1 (Iba-1)-immunoreactive ((+)) microglia were morphologically activated in the mouse hippocampus after LPS treatment. At 24 h after LPS treatment, Iba-1(+) microglia of activated forms were abundant in the hippocampus. However, NeuN (a neuron-specific soluble nuclear antigen)(+) neurons were not significantly changed in the hippocampus after LPS treatment. Fluoro-jade B (a marker for neuronal degeneration)(+) cells were not detected in the hippocampus at any time after LPS treatment. In addition, there were no significant differences in permeability of blood-brain barriers at any time points after LPS treatment. In brief, our results indicate that intraperitoneal administration of 1 mg/kg LPS effectively induces LPS receptor (TLR4) expression in the hippocampus, and the treatment increases corticosterone levels, inflammation in the blood vessels, and microglial activation in the hippocampus without any neuronal damage.

Chitosan macroporous asymmetric membranes—Preparation, characterization and transport of drugs

Chitosan macroporous membranes with asymmetric morphology were obtained by using an inorganic porogen agent (SiO 2). Chitosan/silica ratios used were 1:1, 1:3, and 1:5 w/w. A methodology to obtain asymmetric membranes with control of porosity and average pore size was proposed. The porous membranes were obtained taking advantage of the opposite solubility characteristics of chitosan and silica (4–20 μm). The membranes were characterized by SEM and water sorption capacity. The porosity was calculated by the relationship between dense and macroporous membranes. The SEM images of both surfaces and cross-section of the membranes confirmed their asymmetric morphology. Using a double-cell method, the permeability coefficients of two model drugs (sodium sulfamerazine and sulfametoxipyridazine) were determined. The effects of porous layer, drug type, concentration and temperature were evaluated. The results revealed that the increase in porosity results in significant differences in permeability and that the effects of drug concentration and bath temperature become less pronounced as porosity increases. The mass transport was analyzed in terms of pore-flow mechanism and the solution-diffusion mechanism. The results showed that the methodology was very efficient to yield asymmetric membranes with good mechanical resistance, control of porous size and dense layer thickness and that these membranes can potentially be used to the transport of drugs.

AN EXAMINATION OF MECHANISMS UNDERLYING THE SURVIVAL BENEFIT CONFERRED BY INTESTINESPECIFIC OVEREXPRESSION OF INTERLEUKIN-10

Background: We have shown that transgenic (TG) mice overexpressing IL-10 in the intestine have a significant survival advantage over their wildtype (WT) counterparts when challenged with cecal ligation and puncture (CLP). The mechanism underlying this survival advantage is unknown. Objective: To determine mechanisms responsible for the survival advantage conferred by intestine-specific overexpression of IL- 10. Methods: Given the documented role of IL-10 on systemic inflammation, the gut, and the lungs, each was examined in detail in septic TG and WT mice. TG (n=13) and WT (n=14) mice were subjected to CLP with a 1 by 27 injury. The animals were sacrificed 24 hours later and intestines, lungs, serum, and bronchoalveolar lavage (BAL) fluid were collected. The serum and BAL were spun down and assayed for cytokines IL-12, TNFa, IFN, MCP-1, IL-10, and IL-6 using cytometric bead analysis. Intestines and lungs were sectioned and stained by H&E. Intestines were assessed for epithelial apoptosis in 100 intact crypt-villus units while the lungs were assessed qualitatively. A piece of the intestine was also used to evaluate permeability utilizing the everted gut sac model. Results: IL-12 levels were lower (p <.05) in the serum of transgenic mice (5.1 +/− 0.5 vs. 6.7 +/− 0.5) with no significant differences in the other serum or BAL cytokines measured. There was no statistically significant disparity in intestinal apoptosis, and lung histology was unremarkable. Evaluation of clearance in the intestine revealed no significant difference in permeability. Conclusions: Intestinal production of IL-10, an anti-inflammatory cytokine, induces a minor downstream block of systemic IL-12 expression in septic animals but has no effect on other serum or BAL cytokines, gut permeability and apoptosis, and lung histology. The main mechanisms underlying the survival advantage conferred by intestinal overexpression of IL-10 remain to be determined.