Penetration Of Acid Research Articles

Reactive-Dissolution Modeling and Experimental Comparison of Wormhole Formation in Carbonates With Gelled and Emulsified Acids

Summary Polymer-based (gelled or in-situ gelled) and emulsified acids have been used for matrix acidization of carbonate reservoirs for several years. Gelled and emulsified acids are typically used for acidization of high-temperature carbonate reservoirs because of their lower reaction rate as compared with nongelled/emulsified acids, resulting in deeper penetration of acid, whereas in-situ gelled acid is used for acid diversion. Literature review indicates that several laboratory-scale experimental studies have been performed to analyze the effect of acid gelation and emulsion on carbonate acidization as compared with nongelled/emulsified acids. However, there are very few modeling or quantitative theoretical studies regarding carbonate acidization with gelled and emulsified acids that can be tested at laboratory or field scale. More specifically, a theoretical analysis of the effect of transport and rheological properties (i.e., shear-thinning behavior) of gelled and emulsified acids on the acidization process is not available in the literature. Therefore, the primary objective of this study is to analyze the effect of transport and rheological properties of gelled and emulsified acids on carbonate acidization in three dimensions, which can help in terms of design of gelled- and emulsified-acid properties to achieve lower leakoff rate and deeper penetration of wormholes. The authors present 3D numerical simulations of carbonate acidization with hydrochloric acid (HCl), gelled acid, and emulsified acid by use of a two-scale-continuum model. By use of this model, the effect of transport and rheological properties of these non-Newtonian acids on the acidization curve and dissolution pattern is analyzed and compared with the available laboratory-scale experimental data. It has been observed from the numerical simulations that a lower amount of acid is necessary to breakthrough, and thinner wormholes are formed for both gelled and emulsified acids compared with neat HCl. Additionally, acidization remains in the optimum dissolution regime for a large variation in terms of acid-injection rate for both gelled and emulsified acids compared with neat HCl. Finally, the authors develop a wormholing criterion for acids, the rheological behavior of which can be described by the power law. This criterion can be used to estimate the optimum injection rate for vuggy and nonvuggy carbonates.

Fracture Mechanics and Testing of Interface Adhesion Strength in Multilayered Structures – Application in Advanced Solar PV Materials and Technology

Quantitative characterization techniques based on fracture mechanics were proposed and used to examine the interface strength in multilayered structures. Novel in situ micro-fracture testing for nanolayers inside a Scanning Electron Microscope (SEM) is developed to observe fracture evolution during bending deformation of nanolayered films. Other quantitative technique on interface fracture mechanics has been the 4-point bending or double cantilever beam bending methods. In this paper we will discuss about these two techniques and their applications. In particular, the Double Cantilever Beam bending test method using Delaminator v8.2 Adhesion testing system has been used to quantify the adhesion strength between the Solar PV backsheet and encapsulant. The environmental conditions in tropical countries makes the photovoltaics components vulnerable to salt mist and water vapour as well as acid penetration. Under moisture condition, the hydrolysis reaction of water vapour with backsheet materials release acetic acid, causing delamination and further corrosion of the encapsulant and inter-metallic connectors on solar cells by the salt mist leading to electrical shorts, heat accumulation and fire. Understanding the interface strength between these two materials and its degradation with typical environments in tropical and near-ocean regions is instrumental to enable robust and reliable solar PV technology for such regions.

Improved Delivery of Caffeic Acid through Liposomal Encapsulation

Photoageing resulting from long term exposure of the skin to UV light can be minimized by scavenging the reactive photochemical intermediates with antioxidants. For effective photoprotection, the antioxidant must overcome the barrier properties of the skin and reach the target site in significant amounts. The present study aims to improve the skin penetration of caffeic acid, a very effective free radical scavenger, by encapsulating in liposomes. Caffeic acid loaded liposomes prepared using the reverse phase evaporation technique showed 70% encapsulation efficiency and size around 100 nm with zeta potential of −55 mV.In vitrodiffusion through a dialysis membrane enabled 70% release of encapsulated caffeic acid within 7 h, whereas 95% of free caffeic acid diffused within 4 h in PBS solution (pH 7.4). Liposomal caffeic acid permeation through pig skin epidermis in a Franz cell apparatus was 45 % during 7 h. In contrast, free caffeic acid was almost nonpermeable (<5%) to pig skin during this time. The DPPH assay indicated that skin penetration did not destroy the antioxidant activity of liposomal caffeic acid or free caffeic acid. In conclusion, we confirm that liposomal caffeic acid may be successfully employed as an effective photoprotective agent against UV mediated skin damage.

Influence of acetic and lactic acids on cocoa flavan-3-ol degradation through fermentation-like incubations

Abstract The biochemical reactions occurring inside cocoa beans during fermentation are mostly due to penetration of lactic and acetic acids issued from microbial activities. In the present study, fresh, ripe cocoa beans were subjected to three fermentation-like incubation schemes: incubation for 2 days at pH 4 in a solution of acetic acid, lactic acid, or both, followed by a 3-days incubation at pH 5 in acetic acid solution. After each treatment applied, the fermentation index was above 1 and a cut test revealed a brown color, characteristic of well-fermented beans. As shown by RP-HPLC-ESI(−)-MS/MS analysis, the main flavan-3-ols found in German Cocoa (Amelonado group) and ICS 40 (Trinitario group) ranked as follows: epicatechin > C1 > B2 > catechin > B5 > dehydrodiepicatechin A. In both natural fermentations and fermentation-like incubations, these compounds showed a sharp decrease, this effect being strongest when acetic acid was present from the start. Lactic acid exhibited a somewhat polyphenol-protective effect. Two procyanidins with a molecular weight of 576, undetected before fermentation, were evidenced here for the first time in both incubated and naturally fermented cocoa beans.

Effects of soap-water wash on human epidermal penetration.

Skin decontamination is a primary interventional method used to decrease dermal absorption of hazardous contaminants, including chemical warfare agents, pesticides and industrial pollutants. Soap and water wash, the most common and readily available decontamination system, may enhance percutaneous absorption through the "wash-in effect." To understand better the effect of soap-water wash on percutaneous penetration, and provide insight to improving skin decontamination methods, in vitro human epidermal penetration rates of four C(14) -labeled model chemicals (hydroquinone, clonidine, benzoic acid and paraoxon) were assayed using flow-through diffusion cells. Stratum corneum (SC) absorption rates of these chemicals at various hydration levels (0-295% of the dry SC weights) were determined and compared with the results of the epidermal penetration study to clarify the effect of SC hydration on skin permeability. Results showed accelerated penetration curves of benzoic acid and paraoxon after surface wash at 30 min postdosing. Thirty minutes after washing (60 min postdosing), penetration rates of hydroquinone and benzoic acid decreased due to reduced amounts of chemical on the skin surface and in the SC. At the end of the experiment (90 min postdosing), a soap-water wash resulted in lower hydroquinone penetration, greater paraoxon penetration and similar levels of benzoic acid and clonidine penetration compared to penetration levels in the non-wash groups. The observed wash-in effect agrees with the enhancement effect of SC hydration on the SC chemical absorption rate. These results suggest SC hydration derived from surface wash to be one cause of the wash-in effect. Further, the occurrence of a wash-in effect is dependent on chemical identity and elapsed time between exposure and onset of decontamination. By reducing chemical residue quantity on skin surface and in the SC reservoir, the soap-water wash may decrease the total quantity of chemical absorbed in the long term; however, the more immediate accelerated absorption of chemical toxins, particularly chemical warfare agents, may be lethal. Copyright © 2015 John Wiley & Sons, Ltd.

Fractional radiofrequency combined with sonophoresis to facilitate skin penetration of 5-aminolevulinic acid.

Ablative fractional technology has been used to improve transdermal drug delivery. However, there have been few previous in vivo investigations of the relative potency and methodology of fractional radiofrequency (RF) combined with sonophoresis. The purpose of this study was to investigate the effects of fractional RF combined with sonophoresis on 5-aminolevulinic acid (ALA) penetration of the skin. Three male domestic swine were used. The skin of the pigs was exposed to fractional RF and/or sonophoresis, followed by topical ALA application. Fluorescence intensity (FI) of porphyrin fluorescence was measured. In both the epidermis and the dermis, FI increased after fractional RF and increased additionally with the addition of sonophoresis. Fractional RF with sonophoresis effectively enhanced ALA skin penetration. Pre-fractional RF followed by posttreatment with sonophoresis can be used for ALA-photodynamic therapy to achieve higher ALA uptake.

Capric Acid Absorption in the Presence of Hydroxypropyl-β-Cyclodextrin in the Rat Ileum using the In Situ Single-Pass Perfusion Technique

The purpose of the present study was to gain quantitative mechanistic insight into the role cyclodextrin carriers may play in the intestinal absorption of highly lipophilic molecules. The physical model approach was employed to investigate capric acid absorption in the rat ileum using the in situ single-pass method with 2-hydroxypropyl-β-cyclodextrin (HPB) present in the perfusate. Two physical models were examined: the flat surface model in which the intestinal wall was treated as a hollow, smooth, circular cylinder, and the villus model in which the intestinal surface allowed for the presence of villi. Capric acid absorption was found to be essentially 100% aqueous boundary layer controlled at low HPB concentrations and increasingly membrane controlled at the higher HPB concentrations. Theoretical calculations based on the experimental data and model parameters were found to be consistent with: at low HPB concentrations, capric acid was mainly absorbed at the villus tips and there was very little capric acid penetration into the intervillus space; in contrast, at 50 mM HPB, there was considerable capric acid penetration into the intervillus space, this corresponding to around a 4.5-fold increase in the accessible area for absorption when compared with 0 mM HPB.

Study of the protective effect on intestinal mucosa of the hydrosoluble fiber Plantago ovata husk.

BackgroundSeveral studies have indicated that dietary fiber may have a protective effect on gastrointestinal mucosa. The aim of this study was to evaluate the protective action of the soluble fiber Plantago ovata husk against intestinal damage.MethodsTo evaluate the anti-ulcerogenic effect on duodenal mucosa of the soluble fiber Plantago ovata husk, low-dose acetylsalicylic acid (10 mg/kg) was given orally to animals once daily for 14 or 28 days with and without Plantago ovata husk (100 mg/kg). 24 h after final dosing duodenal samples were removed for anatomopathological evaluation. Villi were examined by both light and scanning electron microscopy.ResultsAcetylsalicylic acid induced severe lesions in duodenal mucosa of rabbits, including erosions, epithelium disorganization, and cell vacuolization, increasing as well the amount of mononuclear and caliciform cells. Damage was much more severe in animals treated for 28 days. In groups receiving Plantago ovata husk, a significant attenuation of acetylsalicylic acid-induced lesions was already observed in group treated for 14 days, becoming more evident in those treated for 28 days, all of them with duodenal cytoarchitecture normal and similar to control animals.ConclusionsThese findings suggest that Plantago ovata husk may protect intestinal mucosa probably by limiting acetylsalicylic acid penetration into epithelial cells, although further studies are needed to confirm the same effect in other experimental models of induced mucosal damage and to elucidate the mechanisms of fiber protection.

Development and ex vivo evaluation of 5-aminolevulinic acid-loaded niosomal formulations for topical photodynamic therapy

The objective of this study was the development of a niosomal formulation for improving skin permeation and penetration of 5-aminolevulinic acid (ALA) in the treatment of skin malignancies by photodynamic therapy (PDT). Different niosomal dispersions were prepared, using two different preparation methods. The effect of addition to a classic formulation, consisting in an equimolar Span 60-cholesterol mixture, of two different edge activators, dicethyl-phosphate (DCP) and sodium cholate (SC), and of the presence of ethanol on the vesicle properties and stability was evaluated. Selected formulations were loaded with the drug and evaluated for physicochemical and stability properties and encapsulation efficiency. Classic and elastic DCP-containing niosomes were the only formulations able to effectively incorporate the drug without instability problems. Ex vivo permeation and penetration studies through excised human skin showed that both the niosomal formulations were significantly more effective in improving ALA skin delivery than the simple aqueous drug solution commonly used in clinical practice, allowing, respectively, an increase of about 80 and 40% of the drug permeated amount and of about 100 and 50% of the drug retained into the skin. These results lead to consider the developed formulations potentially useful for improving ALA bioavailability and therapeutic effectiveness in skin malignancies treatment by topical PDT.

LeciPlex, invasomes, and liposomes: A skin penetration study

The present study compares three vesicular systems, cationic LeciPlex, invasomes, and conventional liposomes for their ability to deliver drugs deep into the skin. Skin penetration ability of the three vesicular systems was studied for two drugs namely idebenone (antioxidant/anticancer) and azelaic acid (antiacne). All systems showed sizes in nanometer range with small polydispersity indices. Vesicular systems were characterized by CryoTEM studies to understand the differences in morphology of the vesicular systems. Ex vivo human skin penetration studies suggested a pattern in penetration of drugs in different layers of the skin: LeciPlex showed higher penetration for idebenone whereas invasomes showed higher penetration of azelaic acid. Ex vivo study using a fluorescent dye (DiI) was performed to understand the differences in the penetration behavior of the three vesicular systems on excised human skin. In vitro cytotoxicity studies on B16F10 melanoma cell lines revealed, when loaded with idebenone, LeciPlex formulations had the superior activity followed by invasomes and liposomes. In vitro antimicrobial study of azelaic acid loaded systems on Propionibacterium acne revealed high antimicrobial activity for DDAB leciplex followed by almost equal activity for invasomes and CTAB LeciPlex followed by liposomes. Whereas antiacne efficacy study in rats for azelaic acid loaded systems, invasomes exhibited the best antiacne efficacy followed by liposomes and LeciPlex.

Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy.

Topical delivery of molecules into the human skin is one of the main issues in dermatology and cosmetology. Several techniques were developed to study molecules penetration into the human skin. Although widely accepted, the conventional methods such as Franz diffusion cells are unable to provide the accurate localization of actives in the skin layers. A different approach based on Raman spectroscopy has been proposed to follow-up the permeation of actives. It presents a high molecular specificity to distinguish exogenous molecules from skin constituents. Raman micro-imaging was applied to monitor the skin penetration of hyaluronic acids (HA) of different molecular weights. The first step, was the spectral characterization of these HA. After, we have determined spectral features of HA by which they can be detected in the skin. In the second part, transverse skin sections were realized and spectral images were recorded. Our results show a difference of skin permeation of the three HA. Indeed, HA with low molecular weight (20-300 kDa) passes through the stratum corneum in contrast of the impermeability of high molecular weight HA (1000-1400 kDa). Raman spectroscopy represents an analytical, non-destructive, and dynamic method to evaluate the permeation of actives in the skin layers.

Comparison of Buffer Effect of Different Acids During Sandstone Acidizing

The most important concern of sandstone matrix acidizing is to increase the formation permeability by removing the silica particles. To accomplish this, the mud acid (HF: HCl) has been utilized successfully for many years to stimulate the sandstone formations, but still it has many complexities. This paper presents the results of laboratory investigations of different acid combinations (HF: HCl, HF: H3PO4 and HF: HCOOH). Hydrofluoric acid and fluoboric acid are used to dissolve clays and feldspar. Phosphoric and formic acids are added as a buffer to maintain the pH of the solution; also it allows the maximum penetration of acid into the core sample. Different tests have been performed on the core samples before and after the acidizing to do the comparative study on the buffer effect of these acids. The analysis consists of permeability, porosity, color change and pH value tests. There is more increase in permeability and porosity while less change in pH when phosphoric and formic acids were used compared to mud acid. From these results it has been found that the buffer effect of phosphoric acid and formic acid is better than hydrochloric acid.

Leak-Off Model Considering the Effect of CO2 in Acid Hydrofracking of Naturally Fractured Carbonate Reservoirs

Carbonate reservoirs are generally highly heterogeneous and fractured. Acid leak-off (infiltration) in acid hydrofracking is particularly serious because it reduces the acid efficiency and limits the fracture length from acid etching. As a result, a favorable reservoir away from the wellbore may fail to be connected, leading to poor results after acid hydrofracking. In this work, a new three-phase (oil—gas—acid) model of acid leak-off (infiltration) in acid hydrofracking of a reservoir that considers dissolution of rock by acid, changes in the width of natural fractures, and the effect of CO 2 was developed and a numerical calculation method was also given. The model allows precise description of the characteristics of acid leak-off in acid-fractured carbonate reservoirs. The results show that the mechanism of acid infiltration into fractured and porous (permeable) reservoirs differs widely. The acid penetrates deep into the reservoir mainly via wide natural fractures and only thereafter through microfissures and the matrix. The acid reacts most vigorously with the rock in wide fractures, leading to further widening of the natural fractures and increased infiltration of the acid into the fractures, which causes deeper penetration of the acid into the fractures. CO 2 reduces the acid leak-off rate, which is less at higher CO 2 concentrations.

Differential effects of some natural compounds on the transdermal absorption and penetration of caffeine and salicylic acid

Many natural products have the potential to modulate the dermal penetration of topically applied drugs and chemicals. We studied the effect of five natural compounds (hydroxycitronellal, limonene 1,2-epoxide, terpinyl acetate, p-coumaric acid, transferrulic acid) and ethanol on the transdermal penetration of two marker drugs (14C-caffeine and 14C-salicylic acid) in a flow through in vitro porcine skin diffusion system. The parameters of flux, permeability, diffusivity, and percent dose absorbed/retained were calculated and compared. The dermal absorption of 14C-caffeine was significantly higher with terpinyl acetate and limonene 1,2-epoxide as compared to ethanol; while dermal absorption of 14C-salicylic acid was significantly greater with hydroxycitronellal and limonene 1,2-epoxide as compared to ethanol. A 10-fold increase in flux and permeability of caffeine with terpinyl acetate was observed while limonene increased flux of caffeine by 4-fold and permeability by 3-fold. Hydroxycitronellal and limonene increased salicylic acid’s flux and permeability over 2-fold. The other natural compounds tested did not produce statistically significant effects on dermal penetration parameters for both caffeine and salicylic acid (p≥0.05). These results emphasize the differential effects of natural substances on the transdermal penetration of hydrophilic (caffeine) and hydrophobic (salicylic acid) drugs.

Emerging role for αB-crystallin as a therapeutic agent: pros and cons.

HSPB5 or αB-crystallin (αBC) is a major protein of the vertebrate eye lens belonging to the small heat-shock protein family of proteins that respond to various stressful conditions. αBC also is found outside the lens in various non-ocular tissues and acts as a molecular chaperone by preventing aggregation of proteins, inhibits apoptosis and inflammation, and maintains cytoskeletal architecture. The αBC protein is phosphorylated on three serine residues S59, S45, and S19, and several functions of αBC are modulated by phosphorylation. Numerous studies have revealed the upregulation of αBC in pathological conditions such as neurodegenerative diseases, cancers, diabetes, retinal diseases, cataracts, ischemia/repurfusion, aging, and others. However, it is unknown whether the up-regulation of αBC is causative or protective for these pathological conditions. Although αBC has been shown to provide a protective effect in neurodegenerative diseases, inflammation, diabetes, and retinal diseases, other studies have described a deleterious role of αBC in cancers and pulmonary fibrosis. The therapeutic potential of αBC alone or in combination with αA-crystallin has been reported. Acetylated αBC peptides have been shown to be more potent than native αBC for chaperone as well as therapeutic activities using both in vitro and in vivo models. Further, for efficient delivery of α BC into cells, carrier molecules such as polylacticcoglycolic acid, polycaprolactone and cell penetration peptides have been used. In this review, we have summarized current data from emerging and exciting studies of the therapeutic strategies of α BC and α BC peptides and the efficient delivery strategies of these proteins in various disease models, including neurodegenerative diseases, retinal diseases, platelet aggregation, inflammation, and ischemia.

Amperometric In Vitro Monitoring of Penetration through Skin Membrane

AbstractThe aim of this study was to demonstrate that penetration of quercetin, hydrogen peroxide and ascorbic acid through skin membranes can be monitored amperometrically. Skin membrane was fixed on the top of chemically modified electrodes and penetration of the appropriate compound was registered as electrode current. The methodology allows the study of penetration from solution as well as from pharmaceutical creams. From real‐time measurements of electrode current, fluxes and diffusion coefficients of mentioned compounds in skin membranes have been estimated.

Determination of in vitro usnic acid delivery into porcine skin using a HPLC method.

Usnic acid, a lichen metabolite, has been proposed as a potential topical treatment for microbial skin lesions, burn wounds as well as a sunscreen. An isocratic HPLC method was validated according to FDA's Guidance for Industry: Bioanalytical Method Validation to determine skin penetration and permeation of usnic acid. The penetration and permeation of usnic acid was evaluated using Franz cells and porcine skin. The method was valid according to selectivity, linearity, precision, accuracy and stability. Usnic acid was quantified in the skin surface (6.13 µg cm(2)), stratum corneum (34.4 µg cm(2)), viable epidermis (5.6 µg cm(2)), dermis (28.2 µg cm(2)) and receptor compartment (3.2 µg cm(2)). These results help us to understand the penetration profile of usnic acid and plan topical therapeutic approaches as well as new topical delivery systems to modulate this penetration profile.

Influence of the composition of monoacyl phosphatidylcholine based microemulsions on the dermal delivery of flufenamic acid

Although microemulsions are one of the most promising dermal carrier systems, their clinical use is limited due to their skin irritation potential. Therefore, microemulsions based on naturally derived monoacyl phosphatidylcholine (MAPL) were developed. The influence of the water, oil and surfactant content on dermal delivery of flufenamic acid was systematically investigated for the first time. A water-rich microemulsion led to significantly higher in vitro skin penetration of flufenamic acid compared to other microemulsions. The superiority of the water-rich microemulsion over a marketed flufenamic acid containing formulation was additionally confirmed. Differences in drug delivery could be explained by alterations of the microemulsions after application. Evaporation of isopropanol led to crystal-like structures of MAPL on the skin surface from the surfactant- or oleic acid-rich microemulsions. In contrast, the formation of this additional barrier was hindered in case of the water-rich microemulsion. The skin penetration of MAPL was additionally analyzed by combined ATR-FTIR and tape stripping experiments, where MAPL itself penetrated only into the initial layers of the stratum corneum, independent of the microemulsion composition. Since a surfactant must penetrate the skin to cause irritation, MAPL can be presumed as a skin-friendly emulsifier with the ability to stabilize pharmaceutically acceptable microemulsions.

Effects of Skin Penetration Enhancers in Topical Antiaging Products Containing α-HydroxyAcids and Hyaluronic Acid

Background: Transdermal drug delivery has several advantages and has been vastly investigated over the last decades. Chemical enhancers improve the quantity of drug penetration through the skin. Objectives: In this study, some conventional solvents and surfactants were used as enhancers to promote dermal penetration of α-hydroxyacids (AHA) and hyaluronic acid (HA). Materials and Methods: A total of 42 different formulations containing AHA or HA as the active ingredient and a solvent or surfactant as the enhancer were prepared. The experiments for determination of transdermal absorption of AHA or HA for each formulation were performed using a diffusion cell and a slice of chicken skin as model at 32℃. After 1.5 or 12 hours, samples from the medium were collected and analyzed for AHA or HA concentration. Results: After 1.5 and 12 hours, the maximum permeated amount of AHA were 89.8 and 342.5 mg, respectively, which related to the formulations with liquid paraffin. After 1.5 and 12 hours, the maximum permeated amount of HA were 57.3 and 70.6 mg, respectively, which related to the formulations with glycerol. Conclusions: The most effective enhancer for AHA and HA were liquid paraffin and glycerol, respectively. The most effective surfactant for both AHA and HA was Tween 80. The effects of the enhancers were increased by prolonging the exposure time.

A New Method for Measuring Acid Effective Consumption Time in Acid Fracturing

In acid fracturing, the fast acid-rock reaction limits live acid penetration distance. Many kinds of acids were developed to reduce the acid-rock reaction rate. Acid effective consumption time in the fracure is a key factor for accurate prediction of live acid penetraiton distance in acid fracturing designs. In this paper, we developed a new method for measuring acid effective consumption time in the fracture and did experimental result matching to obtain effective acid diffusion coefficient with a acid flow-reaction model. Firstly, we designed a apparatus and corresponding experimental procedure. Then used the new method to measure the effective consumption time for gel acid and crosslinked acid. The new method uses reservoir core samples and is convenient to heat all the fluid as well as pipe lines to the reservoir tempeature, which reflects in-situ conditions more reliably. In the experiment, the rock mass loss with time was measured, based on which the acid consumption time is predicted. Under the experiment conditoins, the gel acid has a effecive consumption time about 17-minute, and the crosslinked acid has about 22-minutes at 130°. Finally, a model of acid flow-reaction in a fracture was used to match experimental results to obtained the acid diffution coeffecient. The results from this study help improve accuracy in acid fracturing designs.