Abstract  Electrode bodies and biosensors are engineered from membranes that often contain poly(vinyl chloride) (PVC) as the structural component. Citroflex B-6 (CF), dibutyl sebacate (DBS), dioctyl sebacate (DOS), epoxidized linseed oil (ELO), epoxidized soybean oil (ESO), ortho-nitrophenyl octyl ether (o-NPOE), and propylene glycol dioleate (PGDO) were used to plasticize the PVC membranes. After adding tridodecylamine (TDDA) and potassium tetrakis-4-chlorophenyl berate (KTpCIPB) as neutral charge carriers and negative sites, respectively, the dielectric properties of the plasticized PVC membranes were measured with a TA Instruments' DEA 2970. Using parallel plate sensors, the plasticizers were scanned at 3 degrees C min(-1) from -100 to + 100 degrees C at seven log frequencies: - 1, 0, 1, 2, 3, 4, and 5. Generally, increasing the amount of plasticizer in the membrane improved the ionic conductivity (sigma) and lowered the temperature of the tan delta peak. A positive linear correlation existed between the log sigma and the log(phr ratio) for a given temperature and frequency. The slopes and intercepts of the log sigma versus log(phr ratio) lines were linear functions of the log frequency but non-linear functions of temperature. The positive slope of the log sigma versus log(phr ratio) lines was greatest at about 0 degrees C and 10(-1) Hz, and the peak values of the slopes diminished as they shifted to higher temperatures and frequencies. The intercepts of the log sigma versus log(phr ratio) lines increased monotonously and tended to converge at the highest temperatures and frequencies. In the final analysis, the traditional phr ratios, which are associated with 200 parts of plasticizer per 100 parts of polymer, were not necessary since sufficient performance was achieved for all plasticizers at lower phr ratios.

Abstract  Initial attempts to measure K+ activity (a(k)) in vacuoles of barley leaf epidermal cells using triple-barrelled K+-Selective microelectrodes gave values that were only about one-third of those expected. This was due to high (c. 200 mM) NO3- concentrations in the vacuoles interfering with the K+-sensor, The effect of NO3- was on 1,2,-dimethyl-3-nitrobenzene (DNB) used as a plasticizer in the K+-sensor. Replacing DNB with dibutyl sebacate, but not with 2-nitrophenyl octyl ether, overcame this problem and the modified sensor gave acceptable calibration curves with no interference from physiological concentrations of other ions, These electrodes were used successfully to measure a mean a(k) of 235 mM in vacuoles of epidermal cells of K+-replete barley leaves.

Abstract  Ethyl cellulose films plasticized with 0, 10 and 20% of five different plasticizers were prepared. The films were cast into teflon molds from ethanol solution. The plasticizers used were: dibutyl sebacate, triethyl citrate, triacetin, Myvacet(R) (acetylated monoglycerides) and diethyl phthalate. The physical properties of the films were evaluated using thermal analysis, tensile testing, porosimetry, scanning electron microscopy and hot stage microscopy. The results reported are glass transition temperature, tensile stress, percentage elongation at break, elastic modulus, total volume of pores, total surface area of pores and mean and median diameters of pores. On the basis of tensile tests and thermal analysis, dibutyl sebacate and Myvacet(R) were found to be the two most efficient plasticizers for ethyl cellulose films cast from ethanol solution.

Abstract  IPA COPYRIGHT: ASHP Numerous batches of niacin (nicotinic acid) pellet formulations were coated to determine the levels of coating with Surelease, a combination of dibutyl sebacate, ethylcellulose, oleic acid, and silica, needed to exhibit in vitro release patterns suitable for twice daily dosing. Levels of 1.2% Surelease coating had an in vitro dissolution profile approximating that of a twice daily product. Scanning electron microscopy showed that the surface of the coating was smooth and uniform with a coating thickness of about 2mum. Dissolution profiles were not significantly changed by storage for 2 months. It was concluded that niacin pellets coated with 1.2% Surelease exhibited desirable release profiles and were stable for up to 2 months.

Abstract  IPA COPYRIGHT: ASHP To investigate the source of pH dependency of release from ethylcellulose (Aquacoat)-coated pellets, phenylpropanolamine hydrochloride pellets overcoated with ethylcellulose were examined. pH dependency of release was observed in all batches plasticized with dibutyl sebacate and column dried to an end-product temperature of 43-45DGC. However, when batches were heated for an additional 2 h in a forced air oven, or triethyl citrate was used as plasticizer, release was virtually independent of pH. Heating the product above the glass transition temperature (Tg) of the plasticized film was associated with more consistent release profiles. Contact angle measurements suggested that these effects were associated with changes in surface behavior upon heating; little change in titration data was seen. It was hypothesized that heating the product above the Tg of the plasticized film results in film relaxation, enabling even distribution of the surfactant throughout the film and thus minimizing surface effects that are associated with pH dependent release.

Abstract  HEEP COPYRIGHT: BIOL ABS. The toxicity to HeLa cells of 29 plasticizers was determined in the MIT(Metabolic Inhibition Test)-24 test system. The 7-day IC50 (median inhibitory concentration) for HeLa cells varied from 260 to 1.5 g/l. Phthalates, adipates, sebacates, azelates and phosphates with long carbon chain alcohols were very non-toxic to the cells, probably due to insolubility in water of the compounds, while the citrates, some phosphates and the 2 polymer plasticizers had a higher toxicity to the cells. A comparison of the HeLa cytotoxicity with the toxicity in vitro to other cells for 7 plasticizers showed a similarity of the cytotoxicity to all cell types. A comparison of the HeLa cytotoxicity for 20 plasticizers with i.p. lethal dosage in rodents demonstrated a rough similarity of values, suggesting a toxicity in rodents of the compounds by toxic interference of the agents with basal functions and structures of tissues (basal cytotoxicity). Tissue culture studies of the cytotoxic mechanisms of the plasticizers therefore could reveal modes of toxic action in vivo.

Abstract  The lipid fraction of larvae of the black soldier fly Hermetia illucens was shown to contain lauric acid (38.43 wt %) and its esters, azelaic and sebacic acids, and azelaic acid dibutyl ester. The dominant compound in the group of identified glycerides was lauric acid monoglyceride (0.70 wt %). Glycerides were also represented by triglycerides and diglycerides of lauric acid. Sterols were represented primarily by phytosterols (over 75%), the major of which was alpha-sitosterol (45%). The identified lipid complex composition is apparently determined by the biological characteristics of the fly Hermetia illucens and ensures antibacterial defence of larvae and stability of lipids at changing ambient temperature.

Abstract  A family of biodegradable poly(amine-co-esters) was synthesized in one step via enzymatic copolymerization of diesters with amino-substituted diols. Diesters of length C4-C12 (i.e., from succinate to dodecanedioate) were successfully copolymerized with diethanolamines with either an alkyl (methyl, ethyl, n-butyl, t-butyl) or an aryl (phenyl) substituent on the nitrogen. Upon protonation at slightly acidic conditions, these poly(amine-co-esters) readily turned to cationic polyelectrolytes, which were capable of condensing with polyanionic DNA to form nanometer-sized polyplexes. In vitro screening with pLucDNA revealed that two of the copolymers, poly(N-methyldiethyleneamine sebacate) (PMSC) and poly(N-ethyldiethyleneamine sebacate) (PESC), possessed comparable or higher transfection efficiencies compared with Lipofectamine 2000. PMSC/pLucDNA and PESC/pLucDNA nanoparticles had desirable particle sizes (40-70 nm) for cellular uptake and were capable of functioning as proton sponges to facilitate endosomal escape after cellular uptake. These polyplex nanoparticles exhibited extremely low cytotoxicity. Furthermore, in vivo gene transfection experiments revealed that PMSC is a substantially more effective gene carrier than PEI in delivering pLucDNA to cells in tumors in mice. All these properties suggest that poly(amine-co-esters) are promising nonviral vectors for safe and efficient DNA delivery in gene therapy. [copy 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2011.

Abstract  Derivatives of tetramethylpiperidines are extensively employed in polymers to prevent photooxidation, and their stabilizing effect is attributed to the activity of the nitroxide radical derived from the parent amine. In this study, we examined the photoprotective effect of a commercial polymer photostabilizer, HALS-1, its corresponding nitroxide, bis(2,2,6,6-tetramethyl-piperidine-1-oxyl-4-yl)sebacate (TINO), and two derivatives of the piperidine nitroxide TEMPOL, 2,2,6,6-tetramethyl-piperidin-4-acetyloxy-1-oxyl (TEMP2) and 2,2,6,6-tetramethyl-piperidin-4-octanoyloxy-1-oxyl (TEMP8) synthesized by us, in liposomes exposed to ultraviolet A (UVA) radiation. For comparison, the UVA-absorber, 4-tert-butyl-4'-methoxydibenzoylmethane (Parsol 1789) used in many suncream formulations, was also included. The nitroxide TINO resulted extremely efficient at inhibiting aldehydic breakdown products deriving from 30 min exposure of liposomes to UVA and the protection was dose-dependent (10-100 microM). The corresponding amine HALS-1 was the least efficient while protection increased in the order: TEMP2 < Parsol 1789 < TEMP 8. HALS-1, TINO, and the two TEMPOL derivatives were also tested in a simple protein system consisting of bovine serum albumin (BSA) exposed to UVA. In this case, these compounds did not inhibit nor enhance UVA-mediated protein carbonyl formation in BSA. The differences in protection between the compounds are discussed in relation to their chemical reactivity, UVA-absorbing capacities, and their molecular structure. Overall, the results obtained envisage the potential use of nitroxide compounds as topical antioxidants.

Abstract    A mathematical model of heat and mass transfer for the rotating evaporator surface on a centrifugal molecular still has been developed for binary mixtures. A numerical solution for the relationship between the rate of distillate and its composition and an approximate solution under a special condition are proposed, and effects of some dimensionless parameters on the evaporation phenomena are discussed. The validity of this mathematical model was demonstrated by evaporation experiments for two binary systems; DBP (dibutyl phthalate)-EHP (di-2-ethylhexyl phthalate) and EHP-EHS (di-2-ethylhexyl sebacate), using two centrifugal molecular stills. Experimental data agreed well with the numerical solution and the usefulness of the mathematical model was elucidated.

Abstract  Tumor cells exhibit drug resistant phenotypes that decrease the efficacy of chemotherapeutic treatments. The drug resistance has a genetic basis that is caused by an abnormal gene expression. There are several types of drug resistance: efflux pumps reducing the cellular concentration of the drug, alterations in membrane lipids that reduce cellular uptake, increased or altered drug targets, metabolic alteration of the drug, inhibition of apoptosis, repair of the damaged DNA, and alteration of the cell cycle checkpoints (Gottesman et al., 2002; Holohan et al., 2013). siRNA is used to silence the drug resistant phenotype and prevent this drug resistance response. Of the listed types of drug resistance, pump-type resistance (e.g., high expression of ATP-binding cassette transporter proteins such as P-glycoproteins (Pgp; also known as multi-drug resistance protein 1 or MDR1, encoded by the ATP-Binding Cassette Sub-Family B Member 1 (ABCB1) gene)) and apoptosis inhibition (e.g., expression of anti-apoptotic proteins such as Bcl-2) are the most frequently targeted for gene silencing. The co-delivery of siRNA and chemotherapeutic drugs has a synergistic effect, but many of the current projects do not control the drug release from the nanocarrier. This means that the drug payload is released before the drug resistance proteins have degraded and the drug resistance phenotype has been silenced. Current research focuses on cross-linking the carrier's polymers to prevent premature drug release, but these carriers still rely on environmental cues to release the drug payload, and the drug may be released too early. In this review, we studied the release kinetics of siRNA and chemotherapeutic drugs from a broad range of carriers. We also give examples of carriers used to co-deliver siRNA and drugs to drug-resistant tumor cells, and we examine how modifications to the carrier affect the delivery. Lastly, we give our recommendations for the future directions of the co-delivery of siRNA and chemotherapeutic drug treatments.

Abstract  The objectives of this study were to prepare push-pull osmotic tablets (PPOT) of felodipine using an interpolymer complex of chitosan (CS) and poly(acrylic acid) (PAA) as an osmopolymer, and to study the mechanisms of drug release from these tablets. The interpolymer complexes were prepared with different weight ratios of CS to PAA. Preparation of PPOT involved the fabrication of bilayered tablets with the drug layer, containing felodipine, polyethylene oxide, and the polymeric expansion layer, containing the CS-PAA complex. The effects of polymer ratios, type of plasticizers, and compression forces on release characteristics were investigated. It was found that drug release from PPOT exhibited zero-order kinetics and could be prolonged up to 12 or 24 h depending on the plasticizer used. PPOT using dibutyl sebacate showed a longer lag time and slower drug release than that using polyethylene glycol 400. In the case of polyethylene glycol 400, an increase in the CS proportion resulted in an increase in the drug release rate. The compression force had no effect on drug release from PPOT. Drug release was controlled by two consecutive mechanisms: an osmotic pump effect resulting in the extrusion of the drug layer from the tablet and subsequent erosion and dissolution of the extruded drug layer in the dissolution medium. The mathematical model (zero-order) related to extrusion and erosion rates for describing the mechanism of drug release showed a good correlation between predicted and observed values.

Abstract  AIM: In this work, we report the use of plasticized poly vinylchloride (PVC) as a potential antifouling coating material. The materials contain a variety of sebacic and succinic acid-derived plasticisers providing a variation in molecular shape and structure; diethyl succinate (DESn), di-(2-ethylhexyl sebacate) (DEHS), dibutyl sebacate (DBS), and diethyl sebacate (DES). Each plasticiser from the sebacate group possessed the same basic C10H16O4 moiety with varied dialkyl terminated groups, affording a different range of homologous series plasticisers. This work investigates whether branching of the side substituted alkyl chains on each plasticiser molecule affects microorganism attachment and subsequent fouling.

MATERIALS AND METHODS: The plasticized polymers are spin coated to create thin films for testing. In order to determine the antifouling capacity of the materials, the polymer coatings underwent a series of analyses for biomass determination, glycocalyx production, and protein and carbohydrate adsorption. Topological and morphological characterization was performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM).

RESULTS: After a 7 day laboratory biofouling study it was found that the plasticisers with increased alkyl branching, DESN, and DEHS revealed the greatest degree of prevention of microorganism colonization and attachment thus significantly reducing the initial formation of biofilms by up to 65% in some biofouling assays when compared to the uPVC blank.

Abstract  The aim of this study was to better understand the effects of the curing conditions on the resulting drug release patterns from pellets coated with aqueous polymer dispersions. Diltiazem HCl was used as model drug, ethylcellulose as polymer, triethyl citrate (TEC), dibutyl sebacate (DBS), and distilled acetylated monoglycerides (Myvacet) as plasticizers. Interestingly, the effects of the curing conditions strongly depended on the coating level and the type of plasticizer: in the case of TEC, the drug release rate monotonically decreased with increasing harshness of the curing conditions (time, temperature, and relative humidity), irrespective of the coating level. In contrast, in the case of DBS and Myvacet, this type of relationship was only observed at low coating levels (5%). At intermediate coating levels (around 7.5%), the curing conditions had virtually no effect on drug release. At high coating levels (10%), the release rate initially increased and then decreased with increasing harshness of the curing conditions. This more complex behavior might be attributable to the superposition of two competing phenomena: improved film formation and drug migration into the polymeric membrane. Furthermore, it could be shown that the type of plasticizer had a major effect on drug release in not fully coalesced and equilibrated film coatings, whereas the release profiles were similar for all plasticizers in the case of completely formed and equilibrated film coatings. Importantly, the latter systems were stable for long term even during storage under stress conditions.

Abstract  The activity of penicillin acylase has been studied in aqueous and organic solvents, as free enzyme as well as immobilized within the membrane of liquid-core capsules. The activity of the enzyme is inhibited by the accumulation of the products of the hydrolysis reaction, namely phenyl acetic acid (PAA). In order to overcome this inhibition a range of organic solvents were tested for use in in situ product recovery. Of these solvents dibutyl sebacate (DBS) was chosen due to the rapid extraction rate, the high logP and to facilitate capsule production. The extraction efficiency at pH 3.5 for PAA was >80% for phase ratios of >50% free solvent with partition coefficients of 8 and 0.7 for PAA and penicillin G (PenG), respectively, thereby showing that PAA could be selectively extracted at pH 3.5 and 25 degrees C. Liquid-core capsules containing DBS were shown to efficiently remove PAA selectively and the PAA could be effectively back-extracted and the capsules re-used in a three-stage process resulting in high product separation. Immobilization of penicillin acylase onto the capsule membranes resulted in increased operational stability of the enzyme and a very high enzyme activity. Over 53.3% of the PAA formed could be recovered in the capsule core with a concentration over sevenfold higher than in the aqueous phase. Higher extraction efficiencies could be obtained by varying the substrate concentration and number of capsules. The enzyme immobilized on capsules could be stored for over 4 months at pH 8 and 4 degrees C with no loss of activity. Over 80% of the initial activity could be recovered over five repeated batch cycles of the bioconversion process. The importance of capsular perstraction and reactive capsular perstraction has been clearly demonstrated.

Abstract  The purpose of this study was to determine the influence of plasticizer content on the tensile bond strength of heat-cured acrylic soft denture liners to a denture base resin. Differences among materials were significant, except for 100 wt% Dibutyl Sebacate (DBS) and 80 wt% DBS of tensile bond strength. The bond strength of all materials to the denture base increased with an increase in thermal cycles significantly except for 40 wt% DBS. The tensile bond strength of soft denture liners to the denture base resin significantly decreased with an increase of plasticizer contents. Differences were found among the difference plasticizer contents in failure types between the denture base resin and soft denture liners. The results suggest that the tensile bond strengths of heat-cured acrylic soft denture liners to the denture base resin were lower with an increase in plasticizer content.

Abstract  The development of a loading method of a water-soluble drug using aqueous binding solution to produce microgranules that were then coated with an aqueous ethylcellulose dispersion to sustain drug release is described. The results, in terms of drug used, showed that besides the fluidized bed parameters, the amount of drug dissolved in the binder solution plays an important role in obtaining a satisfying result during the spraying process. Thus, it seems necessary to determine the critical concentration above which the material started to adhere to the interior of the fluidization column, and the possibility of drug layering onto carrier material is aggravated. ANOVA of the time parameter for release of 63.2% of total drug (td) value showed significant influence of ethylcellulose (Aquacoat ECD-30) and dibutyl sebacate concentration on diphenhydramine hydrochloride (DPH) release. The dissolution rate decreased with an increase in polymer concentration. The diffusional exponent n of the Peppas equation indicated that the DPH release kinetic was non-Fickian but approached Fickian diffusion, particularly at higher coating levels.

Abstract  PVDF microporous membranes were prepared via thermally induced phase separation ( TIPS) method. gamma-Butyrolactone (gamma-BA), Propylene carbonate ( PC), Dibutyl phthalate (DBP) and Dibutyl sebacate (KD) were used as diluents, and ethanol as extractant. The melting temperatures and crystallization temperatures of different PVDF/diluent systems were determined using difference scanning calorimeter (DSC). Membrane cross-section morphologies from different systems were observed using scanning electron microscope (SEM). The effects of diluent, cooling rate, and polymer concentration on the polymer crystallization and membrane cross-section morphology were investigated in detail.