Cellophane Membrane Research Articles

Investigation of concentration profiles inside operating biocatalytic sensors with scanning electrochemical microscopy (SECM)

Scanning electrochemical microscopy (SECM) with amperometric or potentiometric measuring tips was used to investigate biocatalytic reactions inside the enzyme layer of a biosensor during its operation. The well known glucose oxidase catalyzed oxidation of glucose has been selected for the studies. Local, instantaneous concentration of dissolved oxygen and hydrogen peroxide was studied observing the amperometric current while miniaturized potentiometric tip served for local pH measurements. Liquid enzyme layer immobilized with Cellophane membrane or cross linked polyacrilamide gel membrane containing entrapped enzyme served for biocatalytic media in the SECM imaging. Local maximum of H 2O 2 and minimum of O 2 profiles were found at approximately 200 μm far from the substrate/enzyme layer boundary. From the experimental findings guidelines to design well functioning biocatalytic sensors could be concluded. The concentration profiles obtained with SECM techniques were compared with the results of simple model calculations carried out with the method of finite changes. Most of earlier made SECM studies dealing with enzyme reactions imaged the electrolyte being in contact with the immobilized enzyme. The data in our investigation, however, were collected inside the working catalytic layer.

Effect of polarisation layers on salt permeability across membranes with different structures

The influence of concentration-polarisation on salt transport across three membranes with different structures, an ultrafiltration (PPS), an asymmetric nanofiltration (PES-10) and a symmetric for dialysis (C-5), was studied. Salt diffusion measurements were carried out in a dead-end cell, at different stirring rates of the solutions at both sides of the membrane (0 ≤ n (rpm) ≤ 1100) under the same NaCl concentration gradient (Δ C ext = 5×10 −2 M). Salt permeability for the membrane system ( P s ) at each stirring rate, which includes both the membrane itself and the polarisation layers, was determined by the fitting of the corresponding concentration vs. time curves. The permeability of the solute in the membrane ( P s m ) and the thickness of the solution layers at a given stirring celerity, d, were estimated by the fit of P s as a function of the solution stirring rate. Differences found between P s and P s m for the studied samples clearly show the different influence of concentration-polarisation layers on salt diffusion depending on the membrane structure. In fact, salt permeability through the C-5 membrane was at least one order of magnitude higher than for the two other samples, while P s m is around 2.5 times higher for the ultrafiltration membrane than for the nanofiltration one. A comparison of the thickness of polarisation layers at a given stirring celerity shows the following values: d(C-5)=25 μm, d(PPS) = 1 mm and (PES-10) = 6 mm. On the other hand, a comparison of the membrane permeability obtained for the cellophane membrane in the dead-end cell (3×10 −6 m/s) and that obtained in a tangential flow cell (5×10 −6 m/s), shows rather good agreement, which can be considered as a proof of validity of the results.

Controle em pós-colheita de Monilinia fructicola em pêssegos

A podridão parda (Monilinia fructicola) causa danos relevantes nos pessegueiros (Prunus persicae) apesar das práticas de profilaxia e produtos químicos utilizados em pré e pós-colheita. O controle biológico vem sendo pesquisado como alternativa, e neste trabalho foram selecionados microrganismos antagônicos ao patógeno e avaliada a eficiência destes antagônicos, de fungicidas (iminoctadine tris albesilate e azoxystrobin) e de fosfitos (CaB e K) no controle da doença em pós-colheita. No laboratório, o antagonismo de fungos filamentosos obtidos de pêssegos da região da Lapa, PR, foi avaliado utilizando dois métodos: culturas pareadas e difusão de metabólitos por membrana. Em pós-colheita, dois ensaios foram realizados utilizando frutos da safra 1997 e 1999. Cada fruto foi imerso nas suspensões preparadas com os produtos químicos e com os fungos antagônicos e, em seguida, inoculado com o patógeno por aspersão. Avaliou-se a incidência da doença em ferimentos provocados e fora deles. Os fungos que mostraram produção de substâncias inibitórias foram Trichothecium spp. (isolados F1, F2 e F4), e Trichoderma spp. (F8 e F12) e, com crescimento sobre o patógeno foram Trichoderma spp. (F7, F8 e F12) e Penicillium sp (F9). Nos frutos, os antagonistas que exerceram maior controle da doença foram os isolados de Trichothecium spp. (F1 e F2), acima de 80% de controle, não diferindo estatisticamente dos fungicidas testados, iminoctadine e azoxystrobin. O fosfito de K proporcionou um controle superior a 85% de lesões latentes em ambos experimentos.

A Comparison of Electrochemical and Electrokinetic Parameters Determined for Cellophane Membranes in Contact with NaCl and NaNO3 Solutions

Electrochemical and electrokinetic characterizations of cellophane membrane samples have been carried out by measuring membrane potential, salt diffusion, and tangential streaming potential, which allow the determination of different characteristic membrane parameters. Experiments were made with the membrane samples in contact with NaCl and NaNO3 solutions at different concentrations and under different external conditions (concentration gradients), in order to obtain differences in transport and membrane characteristic parameters, depending on the electrolyte considered. Salt permeability across the membrane, which was obtained from diffusion measurements, is about twice as high for NaCl solutions as for NaNO3 solutions, which is attributed to the different sizes of the electrolytes. Membrane potential measurements keeping the concentration ratio constant (C1/C2=2) were used to determine both the effective fixed charge concentration in the membrane, Xf, and the average value of transport numbers, 〈ti〉; taking into account these values, concentration dependence of membrane potential under a different external condition (C1=cte=0.01 M, 5×10−3≤C(M)≤5×10−2) was predicted. Results show that cellophane membrane behaves as a weak cation-exchange membrane and its permselectivity to cations is practically independent of the electrolyte considered. From electrokinetic results, assuming a Langmuir-type adsorption of anions on the cellophane surface, the number of accessible sites per surface unit was obtained, which is higher for Cl− than for NO3−, in agreement with the small radii of chlorine ions; however, no significant differences in the specific adsorption free energy were found (ΔGNacl=−22.0×103 J/mol) and (ΔGNaNO3=−23.2×103 J/mol).

Cultured epidermal allografts: Quantitative evaluation of their healing effect in deep dermal burns.

This study summarizes the Brno Burn Centre experience with the application of cultured epidermal allografts (CEAl) in the treatment of deep dermal burns. In a prospective randomised trial on 30 patients with deep dermal burns CEAl obtained from young healthy and examined donors and fixed on tulle grass carrier (Grasolind) were compared with empty Grasolind as the lowest layer of dressing. All the other layers were identical.Both kinds of dressing were applied simultaneously on the same deep dermal burn wound between 6th and 10th day after burn. Six days later the non-healed wound areas were recorded through painting on cellophane membrane and scanned in the computer. The percentage of wound reduction was calculated and statistically evaluated.The reduction of the non-epithelialized wound area was 86.5% when covered through CEAl and only 71.2% when covered with tulle grass (Grasolind) only. This difference is statistically significant.In conclusion it can be stated that cultured epidermal allografts strongly stimulate reepithelialisation in deep dermal burns.

Cyclodextrins and drug permeability through semi-permeable cellophane membranes

Determinations of drug fluxes through semi-permeable cellophane membranes are used to evaluate cyclodextrin complexes and cyclodextrin containing drug formulations. In the present study we investigated how the cyclodextrin concentration, the membrane thickness and the molecular weight cut off (MWCO) of the membrane influence drug fluxes. The cyclodextrin used was 2-hydroxypropyl-β-cyclodextrin (HPβCD) and the sample drug was hydrocortisone. The MWCO of the membranes ranged from 500 to 14,000 and the HPβCD concentration ranged from 0 to 25% (w/v). The hydrocortisone flux from saturated solutions through the MWCO 500 membrane was unaffected by the cyclodextrin concentration. When MWCO of the membrane was greater than the molecular weight of the complex the flux from solutions saturated with hydrocortisone increased with increasing HPβCD concentration. This increase showed negative deviation from linearity. When the flux was corrected for the viscosity increase with increasing HPβCD concentration then the flux pattern could be described on the basis of Fick's first law and Stokes–Einstein equation. However, the flux did not correlate with the viscosity when it was increased by adding polymer to the saturated drug solutions. It was shown that the observed flux pattern was consistent with self-association of cyclodextrin complexes in the aqueous donor phase.

Topical Permeation Characteristics of Diclofenac Sodium from NaCMC Gels in Comparison with Conventional Gel Formulations

Topical gel formulations of diclofenac sodium were prepared by using sodium carboxymethylcellulose (NaCMC), a low-toxicity cellulose polymer as a gel-forming material that is biocompatible and biodegradable. The influence of various formulation variables, such as initial drug concentrations and NaCMC concentration, and certain skin permeation enhancers on release characteristics of the diclofenac sodium from the prepared gels through a standard cellophane membrane was studied in comparison with four commercially available gel formulations of diclofenac sodium. The cumulative amounts released and the apparent release rates were higher for the prepared gels in comparison with the commercial formulations. Skin permeation studies using abdominal rat skin revealed good improvement of skin permeation characteristics of diclofenac sodium using NaCMC gels as compared to the commercial gels. The cumulative amount permeated at 6h (μg/cm2), steady-state flux Jss (μg/cm2h), lag time tL (h), permeability coefficient kp (cm/s), partition coefficient k, and diffusion coefficient D (cm2/s) were determined for the prepared gels in comparison with the commercial gels. Skin permeation enhancers such as isopropyl alcohol (IPA), Tween 80, and α-tocopherol polyethylene glycol succinate (TPGS) exhibited little or no effect on the permeation characteristics of diclofenac sodium. Infrared (IR) spectrum and differential scanning calorimetry (DSC) studies on the pure diclofenac sodium, NaCMC, and their physical mixture at a 1:1 ratio revealed that there was no positive evidence for the interactions between the drug and NaCMC, indicating the compatibility of the drug and the vehicle. Based on experimental results, preparation of diclofenac sodium gels using NaCMC vehicle is promising.

TOPICAL OLEO-HYDROGEL PREPARATIONS OF PIROXICAM WITH ENHANCED SKIN PERMEABILITY AND ANTIINFLAMMATORY ACTIVITY

In an attempt to improve the skin permeation and anti-inflammatory activity of piroxicam, various topical formulations including oleo-hydrogels (oleo-gels) were prepared and their in vitro diffusion, skin permeation and in vivo anti-inflammatory activities were evaluated. In vitro diffusion and permeation through a standard cellophane membrane and hairless abdominal rat skin were studied using a modified diffusion cell. The diffusion and permeation parameters such as apparent release rate, cumulative amount permeated, steady-state flux, lag time, permeability coefficient, diffusion coefficient and partition coefficient were determined for the prepared formulations in comparison with a commercial piroxicam gel (Feldene gel, Pfizer). The topical anti-inflammatory activity of the prepared formulations were compared with the Feledene gel using croton oil-induced inflammation in mice. The results indicate that topical oleo-hydrogels under study improved the diffusion and skin permeation characteristics of piroxicam. In addition, the anti-inflammatory activity of piroxicam in the oleo-gel preparations was relatively higher as compared with the commercial piroxicam gel, Feldene-gel.

Effect of humidity and temperature on conidial germination and appressorium development of two Philippine isolates of the mango anthracnose pathogen Colletotrichum gloeosporioides

A comparison of rates of germination and appressorium formation by an isolate of Colletotrichum gloeosporioides on mango leaves, fruit surfaces and cellophane membranes showed that behaviour was broadly similar on all three substrates. Frequency of appressorium formation was slightly higher on cellophane membranes, and both hyaline and melanized appressoria were formed. Only melanized appressoria were formed on mango surfaces. In vitro experiments on membranes showed comparative differences in physiological behaviour with temperature for two Philippine isolates of C. gloeosporioides. The most stimulatory temperature for production of appressoria differed in isolates I‐2 and I‐4 (25 and 20°C, respectively). At 30°C more appressoria became melanized than at lower temperatures, but the frequency of formation of penetration pegs was highest at 25°C. Conidia of C. gloeosporioides germinated on cellophane membranes at relative humidities as low as 95%, but the percentage of conidia germinating and forming appressoria increased as the RH approached 100%. Approximately 18% of conidia of C. gloeosporioides I‐2 held at 62 and 86% RH for 4 weeks retained viability, and some were capable of forming appressoria when placed at 100% RH. These results have implications for epidemiological models for disease control.

Regulation of Controlled Release of Ibuprofen from Crosslinked Polymers Containing Cubane as a New Crosslinking Agent

The nonsteroidal anti-inflammatory drug 2-(4-isobutylphenyl)-propionic acid (ibuprofen) and cubane-1,4-dicarboxylic acid (CDA) were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The drug-linked HEMA (ibuprofen-linked HEMA) abbreviated as HI and cubane-1,4-dicarboxylic acid (CDA) linked to two HEMA groups as CA. A difunctional spacer group was introduced between the drug and acrylic moiety of the monomer through a hydrolyzable ester linkage. Free radical crosslinking polymerization of the monomer HI with the various ratios CA as crosslinking agent were carried out in DMF, DMSO or dioxane solution, using AIBN as initiator at the temperature range of 60-70°C. The structure of the monomers was confirmed by FTIR, 1 H NMR and 13 C NMR spectroscopy. The compositions of the crosslinked three-dimensional polymers were determined by FTIR spectroscopy. Glass transition temperature (T g ) of the network polymers was determined calorimetrically. The hydrolysis of drug-polymer conjugates was carried out in cellophane membrane dialysis bags containing an aqueous buffer solution (pH 8 and pH 1) at 37°C. Detection of the hydrolysis product by UV spectroscopy shows that the drug (ibuprofen) was released by the hydrolysis of the ester bond located between the drug and spacer group.

Enzyme diffusion from Trichoderma atroviride (= T. harzianum P1) to Rhizoctonia solani is a prerequisite for triggering of Trichoderma ech42 gene expression before mycoparasitic contact.

A plate confrontation experiment is commonly used to study the mechanism by which Trichoderma spp. antagonize and parasitize other fungi. Previous work with chitinase gene expression (ech42) during the precontact period of this process in which cellophane and dialysis membranes separated Trichoderma harzianum and its host Rhizoctonia solani resulted in essentially opposite results. Here, we show that cellophane membranes are permeable to proteins up to at least 90 kDa in size but that dialysis membranes are not. ech42 was expressed during the precontact stage of the confrontation between Trichoderma atroviride and its host only if the cellophane was placed between the two fungi. These results are consistent with enzyme diffusion from T. atroviride to R. solani generating the trigger of ech42 gene expression.

An experimental artificial liver utilizing extracorporeal metabolism with sliced or granulated canine liver. 1963.

Guest Editor's Introduction: This paper was originally presented at the 9th congress of ASAIO in April 1963. The original paper was printed in Volume IX of Trans. Soc. Artif. Int. Organs 1963, pages 358–362. It was reprinted with permission in Therapeutic Apheresis, Volume 4, Issue 1, 2000 as a millennium project of the International Society for Apheresis. This paper describes for the first time a hybrid artificial live and extracorporeal circulatory system composed of a specially developed high permeable gel type cellophane membrane. This membrane separated the patient's blood and the metabolic fluid in which freeze‐dried canine liver granules were contained. Carbohydrate metabolism and ammonia detoxification were maintained in this metabolic chamber, eventually helping the patient's metabolic functions. In addition to experimental studies, four clinical studies were briefly reported.

Dehydration of Glycerol–Water Mixtures Using Pervaporation: Influence of Process Parameters

Pervaporation, a membrane-based separation technique, is proposed as a potential replacement for the vacuum distillation process which is normally used for the dehydration of glycerol-water mixtures. Separation characteristics of glycerol-water mixtures containing a trace amount of water by using a water-selective cellophane membrane are studied. Experiments show that the membrane is selective toward water, and pure water is obtained as the permeant. Thus, the selectivity coefficient is infinite. However, the rate of permeation of water is solely controlled by the liquid-phase mass transfer boundary layer resistance due to the very high viscosity of glycerol. Accordingly, increased agitation and temperature cause considerable enhancement of flux. On the other hand, the presence of salt in the feed mixture significantly reduces the rate of permeation. An unsteady-state model, that includes various process parameters, has been developed for prediction of the process output. The model prediction fits satisfactorily with the experimental observations of the present study.

In Vitro Iontophoretic Release of Lithium Chloride and Lidocaine Hydrochloride from Polymer Electrolytes

Ionically conducting polymers, frequently known as polymer electrolytes, are potential candidates as hosts for drugs to be delivered iontophoretically. The iontophoretic delivery of lithium or lidocaine from polymer electrolyte films through a cellophane membrane was examined using different delivery current regimes. Thin, mechanically strong, polymer electrolyte films were fabricated from poly(ethylene oxide) (PEO) with lithium chloride or lidocaine hydrochloride. Experiments showed that iontophoretic transport of both lithium chloride and lidocaine hydrochloride might be achieved from these PEO-based films. Cation transport number determinations give values for PEO-based films of about 0.4 for lithium chloride systems and 0.12 for lidocaine hydrochloride systems. The mechanism of transport from these PEO-based polymer electrolyte films allows the delivery of ionic salts such as lithium chloride and lidocaine hydrochloride to be controlled solely by current, thus providing a system that can deliver precise amounts of drug.

Radiotracer analysis of cadmium speciation in soil solutions using electrophoresis, dialysis, centrifugation, and ultrafiltration.

Speciation of carrier-free 109Cd, added in cationic form to pre-filtered extracts obtained by leaching forest soil samples with distilled water, was analyzed using electrophoresis, dialysis, centrifugation, and ultrafiltration. Rapid establishment of isotopic equilibrium between the added 109Cd and stable cadmium present in the extracts was observed. All the data obtained indicated that 109Cd and also stable cadmium were present in the analyzed extracts in the form of neutral or negatively charged organic complexes or small colloids. The results of electrophoresis enabled the characterization, at least semiquantitative, of the abundance and electrophoretic mobility of the forms present. The incomplete dialysis of 109Cd from the soil extracts through cellophane membrane against water proved the presence of organic associates with molecular weights higher than 10(4). Dialysis against the same, but unlabeled extract was always complete, indicating the reversible (labile) nature of the organic forms of cadmium. Assessment of the stability constants of the organic forms using a simple discrete two-site model suggested that humate and/or fulvate complexes of cadmium were formed.

Determination of stability constant of β-cyclodextrin complexes using the membrane permeation technique and the permeation behavior of drug–competing agent–β-cyclodextrin ternary systems

The stability constants ( Kc) of β-cyclodextrin (β-CyD) complexes with phenacetin and various benzoic acids were determined using the membrane permeation technique using a cellophane membrane permeable for guest molecules which was impermeable for β-CyD molecules. The permeation rate equations of guests in the presence of β-CyD in the donor phase were derived and the permeation profiles were analyzed as a function of time to determine the Kc values. The Kc values determined using the membrane permeation technique were in close agreement with those determined by the conventional kinetic method and the solubility method. The membrane permeation technique is of greater advantage than the conventional methods, because in the former method the stability constant can be obtained from only one experimental run by analyzing the permeation data as a function of time. In the latter method, on the other hand, some property changes have to be measured at various CyD concentrations and in turn analyzed as a function of CyD concentration. The permeation profiles of phenacetin of the drug–competing agent–β-CyD ternary system were estimated by using the stability constants and the experimental curves closely matched the theoretically derived ones.

Cyclodextrins as permeation enhancers: some theoretical evaluations and in vitro testing

It is well known that cyclodextrins can enhance the permeation of poorly soluble drugs through biological membranes. However, the permeability will decrease if cyclodextrin is added in excess of the concentration needed to solvate the drug. The mechanism of cyclodextrin effect on drug permeability has not been fully explained. The effect of cyclodextrins can not be explained as solely due to increased solubility of the drug in the aqueous donor phase nor can it be explained by assuming that cyclodextrins act as classical permeation enhancers, i.e. by decreasing the barrier function of the lipophilic membrane. In the present work we have modeled the effect of cyclodextrins in terms of mixed barrier consisting of both diffusion and membrane controlled diffusion, where the diffusion of the drug in the aqueous diffusion layer is significantly slower than in the bulk of the donor. This diffusion model is described by simple mathematical equation where the properties of the system are expressed in terms of two constants P M/ K d and M 1/2. Data for the permeation of hydrocortisone through hairless mouse skin in the presence of various cyclodextrins, and cyclodextrin polymer mixtures, were fitted to obtain values for these two constants. The rise in flux with increased cyclodextrin complex concentration and fall with excess cyclodextrin was accurately predicted. Data for the permeation of drugs through semi-permeable cellophane membrane could also be fitted to the equation. It was concluded that cyclodextrins act as permeation enhancers carrying the drug through the aqueous barrier, from the bulk solution towards the lipophilic surface of biological membranes, where the drug molecules partition from the complex into the lipophilic membrane.

Effect of carpropamid on secondary infection by rice blast fungus

Carpropamid (WIN®, KTU 3616) provides good control of leaf and panicle blast by 'one-shot' nursery-box treatment. It inhibits melanin biosynthesis in appressorial cells of Pyricularia oryzae, making them hyaline. Penetration by infection hyphae from the hyaline appressoria into rice epidermal cells is substantially hindered. In addition, the spread of rice blast spores from primary lesions to the other parts of the plant leading to secondary infection is largely prevented when the plants are treated with carpropamid by spray or water surface application. Secondary infection was simulated in a glass chamber fitted with an ultrasonic humidifier. On treated plants, many blast spores formed in the lesions, but the number of air spora that were dispersed from the lesions decreased significantly. A similar suppression of the spore liberation was observed in vitro when lesions on rice leaf segments, or discs from Pyricularia cultures on oatmeal agar were treated with the chemical. Spores from treated lesions or from the cultures on oatmeal agar amended with the chemical germinated normally and produced well-melanized appressoria on cellophane membranes. In addition, the spores proved to be fully pathogenic towards rice seedlings, producing normal disease symptoms. These results strongly suggest that carpropamid reduces the secondary infection of rice by Pyricularia by specifically hindering spore liberation.

Experimental neodymium:YAG laser damage to acrylic, poly(methyl methacrylate), and silicone intraocular lens materials

Purpose: To compare neodymium: YAG (Nd:YAG) laser effects on acrylic, silicone and poly(methyl methacrylate) (PMMA) intraocular lens (IOL) polymers Methods: Ten Nd: YAG laser exposures were produced in each of 6 implantation quality acrylic (Alcon MA60BM), silicone (Staar AQ1016), and PMMA (Alcon MC60BM) IOLs under identical conditions. Each polymer type was irradiated at 6 power settings (0.3, 0.5, 1.0, 1.5, 2.0, and 3.0 mJ) and at 2 focal points (midpoint of lens optic and on the posterior surface to which a cellophane membrane was affixed). The linear extent of the damage was measured using light microscopy,. Specimens exposed to 1.0 mJ were processed for scanning electron microscopy. Results: The damage threshold (≥ μm depth) was 0.3 mJ for silicone and 10 mJ for acrylic and PMMA IOLs. At the clinically relevant power levels, 10 to 20 mJ the depth of damage in the acrylic polymer was 11.9 to 30.5 times less than the depth in the silicone polymer. Similarly, the depth of damage in the PMMA polymer was 5.4 to 52.6 times less than the depth in the silicone polymer. The morphologic pattern of damage in the silicone IOL showed a deep, irregularly configured trough with meandering tendrils. Acrylic IOL damage morphology consisted of an ameboid-shaped entry site without radiating fracture and mild posterior penetration. Poly(methyl methacrylate) IOL damage consisted of a shallow focal trough with radiating fractures. Conclusions: The silicone IOL polymer had the lowest threshold for laser-induced damage and greater linear extension of damage than the PMMA and acrylic IOL polymers. Poly(methyl methacrylate) and silicone polymers exhibited collateral damage or ejected particulates adjacent to the entry site, whereas the acrylic polymer showed a discrete locus of damage.

Histochemical detection of laccase in Pycnoporus cinnabarinus using microwave-enhanced colloidal gold microcrystallization

Laccase was detected histochemically in Pycnoporus cinnabarinus fungal hyphae by growing the organism on cellophane or microporous polycarbonate membranes overlaid on malt extract agar. Membrane sections were stained with a reagent of 2,6-dimethoxyphenol and colloidal gold for 30 min and irradiated for 24 s at maximum output in a microwave oven. Laccase was detected as purple-blue deposits at the apical tip region in high concentrations, and at lower levels on the exterior, sub-apical hyphal sheath.